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Antioxidant capacity and total phenolic content of Malaysian underutilized fruits
Journal of Food Composition and Analysis 22 (2009) 388–393
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Original Article
Antioxidant capacity and total phenolic content of Malaysian underutilized fruits Emmy Hainida Khairul Ikram a, Khoo Hock Eng a, Abbe Maleyki Mhd Jalil a, Amin Ismail a,*, Salma Idris b, Azrina Azlan a, Halimatul Saadiah Mohd Nazri a, Norzatol Akmar Mat Diton a, Ruzaidi Azli Mohd Mokhtar a a b
Department of Nutrition and Dietetics, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia Botany Division, Strategic Resource Research Center, Malaysian Agricultural Research and Development Institute (MARDI), 43400 Serdang, Selangor, Malaysia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 1 November 2007 Received in revised form 16 February 2009 Accepted 2 April 2009
The purpose of this study was to evaluate the antioxidant capacity (AC) and total phenolic content (TPC) of selected Malaysian underutilized fruits. The 58 underutilized fruits of 32 different species from 21 genera were analyzed for AC and TPC. AC was measured using b-carotene bleaching, ferric reducing antioxidant potential (FRAP) and 2,2-diphenyl-1-picryl hydrazyl (DPPH) assays, and TPC was determined using the Folin–Ciocalteu reagent assay. Our findings showed that the fruits from genera of Pometia, Averrhoa, Syzygium, Sallacca, Phyllanthus, Garcinia, Sandoricum and Maipighia had higher AC compared to other studied genera. Among the underutilized fruits, Sandoricum and Phyllanthus fruits contained the highest TPC (>2000 mg/100 g edible portion). The correlation between AC and TPC varied. The study indicated that some of these underutilized fruits have the potential to be sources of antioxidant components. ß 2009 Elsevier Inc. All rights reserved.
Keywords: Underutilized fruit Inhibition of oxidation activity Antioxidant activity Scavenging activity Total phenolic content Food analysis Food composition
1. Introduction Epidemiological studies have shown that there is a positive association between intake of vegetables and fruits and reduced cardiovascular diseases (Hu, 2003) and certain cancers (Riboli and Norat, 2003). It is generally assumed that the main dietary constituents contributing to these protective effects are the antioxidant components (Agudo et al., 2007). Along with other antioxidant components, polyphenols (e.g. flavonoids) present in fruits and vegetables have been reported to be potential candidates in lowering cardiovascular diseases (Huxley and Neil, 2003; Joshipura et al., 2001). The protective effects could be due to their properties as free radical scavengers, hydrogen-donating compounds, singlet oxygen quenchers and/or metal ion chelators. Generally, Malaysians consume vegetables that are relatively abundant sources of antioxidant components with strong potential antioxidant activities (Amin and Lee, 2005; Amin et al., 2004, 2006). Similar to vegetables, tropical and subtropical fruits such as ciku, star fruits and guava have been reported to be rich in antioxidants (Leong and Shui, 2002). Besides the commonly consumed local fruits, some under-
* Corresponding author. Tel.: +60 3 8947 2435; fax: +60 3 8942 6769. E-mail address: [email protected] (A. Ismail). 0889-1575/$ – see front matter ß 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2009.04.001
utilized fruits are important in the Malaysian diet, especially in rural communities. Malaysia is one of the countries that has a rich diversity of underutilized fruits that grow wild in the region of Peninsular Malaysia, Sabah and Sarawak. Some of the underutilized fruits are rarely eaten, unknown and unfamiliar. Due to the broad spectrum of their flesh and skin color, these underutilized fruits may have potential benefits to human health. It is important to include these fruits in health promotion campaigns. In addition, some of these fruits have the potential to be used and processed as food products for local consumption. However, underutilized fruits have not received much attention as antioxidant sources compared to commercial fruits like guava, papaya and pineapple. This could be due to their lack of popularity among local communities, lack of information on nutritional compositions and physical qualities and the lack of promotional campaigns for these fruits. In Malaysia, many kinds of underutilized fruits are available, such as nam-nam (Cynometra sp.), bacang (Mangifera sp.), jambu bol (Psidium sp.), durian (Durio sp.), bidara (Ziziphus sp.), mertajam (Leppisanthes sp.), longan (Dimorcarpus sp.), lenggeng serawak (Pometia sp.), belimbing buloh (Averrhoa sp.), assam kelubi (Salacca sp.), buah melaka (Phyllanthus sp.), assam gelugor (Garcinia sp.), sentol (Sandoricum sp.), rambai Sarawak (Baccaurea sp.), remia (Bouea sp.), pulasan (Nephelium sp.) and others. These fruits are usually grown in orchards or fruit gardens around houses, and
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some grow wild in the rain-forest (Rukayah, 1992). These fruits are known by older folks to be associated with many nutritional and medicinal properties. There is a dearth of information on the antioxidant capacity (AC) and antioxidant components, including total phenolic content (TPC), of Malaysian underutilized fruits. Therefore, this work was initiated to determine AC and TPC of selected Malaysian underutilized fruits. In addition, the relationship between AC and TPC was determined. 2. Materials and methods 2.1. Preparation of sample and extract Two lines of research work consisting of 58 Malaysian underutilized fruits of 32 different species from 21 genera were conducted in this study. The first line of research work consisted of 51 underutilized fruits of 26 different species from 17 genera, while the second line of work consisted of 9 underutilized fruits of 9 different species from 8 genera. The fruits were sampled from different locations by the Strategic Resource Research Centre, Malaysian Agricultural Research and Development Institute, Malaysia. The fruits were grown wild and harvested at maturity at different time periods. Mature fruits for each sample were transported from the Centre directly to the analytical laboratory. The whole fruit was washed under running tap water to remove dirt and other foreign materials and wiped with tissue paper. The fruit was weighed for the whole and edible portions. The edible portion was then cut into small pieces and stored at 80 8C before lyophilization using a bench-top freeze dryer (Virtis, Gardiner, New York). The lyophilized fruits were ground into powder form, and kept at 20 8C prior to analysis. Methanolic extract was prepared by mixing 1 g of the lyophilized fruit powder with 80% methanol (v/v) at a ratio 1:4. The mixture was placed in a conical flask (wrapped with an aluminum foil) and agitated at 200 rpm, at 50 8C, with the aid of an orbital shaker (Heidolph Unimax 1010, Schwabach, Germany) for 2 h. The mixture was then filtered through a filter paper (Whatman No. 4) to obtain a clear solution. The extract was used for determination of AC and TPC. 2.2. b-Carotene bleaching method The inhibition activity of b-carotene oxidation by peroxide radicals of the fruit methanolic extract was determined according to a modified procedure, initially described by Velioglu et al. (1998). Briefly, 1.0 mL of b-carotene solution (0.2 mg/mL chloroform) was pipetted into a round-bottom flask containing 20 mL linoleic acid, 200 mL Tween 20 and 200 mL fruit extract. The mixture was then evaporated at 30 8C for 20 min using a rotary evaporator (Buchi Rotavor R-200, Switzerland) to remove chloroform. After evaporation, 50 mL of distilled water was immediately added to the mixture. The mixture was vigorous agitated for 5 min using an orbital shaker to form an emulsion. Aliquots (2.0 mL) of the emulsion were transferred into different test tubes. The mixture was then gently mixed and placed in a water bath at 50 8C for 2 h. Absorbance of the samples was recorded at 0 and 2 h at 470 nm using a Spectronic GenesysTM 5 spectrophotometer (Milton Roy Company, New York). All determinations were performed in triplicate. AC was calculated as percent of inhibition relative to control using the following equation from Al-Saikhan et al. (1995): Antioxidant capacity (%) = [(drcontrol–drsample)/drcontrol 100], where, drcontrol and drsample are the degradation bleaching rates of b-carotene in reactant mixed with fruit extracts at 0 and 2 h, respectively.
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2.3. Total phenolic content (TPC) The content of reducing components (expressed as TPC) was estimated using the Folin–Ciocalteu assay according to a method developed by Velioglu et al. (1998), with slight modification. Briefly, 0.75 mL of 10-fold diluted Folin–Ciocalteu reagent and 100 mL of methanolic extract were placed in a test tube. The mixture was mixed and allowed to stand at room temperature for 5 min. Then, 0.75 mL of 6% (w/v) sodium carbonate solution was added. The mixture was homogenized and allowed to stand at room temperature for 90 min. TPC was determined using a Spectronic GenesisTM spectrophotometer at 725 nm. The standard calibration curve was plotted using gallic acid at the concentrations of 0.02–0.1 mg/mL. The TPC was expressed as gallic acid equivalent (GAE) mg/100 g edible portion. 2.4. Determination of ferric reducing antioxidant potential (FRAP) FRAP assay was performed according to the method of Benzie and Strain (1996). The FRAP reagent was prepared by mixing 16.7 mM FeCl36H2O and 8.3 mM 2,4,6-tripyridyl-s-triazine (TPTZ) with 250 mM acetate buffer, pH 3.6. A total of 75 mL fruit extract and 225 mL of distilled water was added to 2.25 mL of freshly prepared FRAP reagent in a test tube. The mixture was incubated at 37 8C throughout the reaction. The absorbance was read at initial and after 4 min at 593 nm using a UV–vis spectrophotometer during the monitoring period. The antioxidant potential of the fruit extract was determined based on a calibration curve plotted using FeSO47H2O at a concentration ranging between 400 and 2000 mM. 2.5. Determination of free radical scavenging activity (DPPH) The scavenging activity of the extract was determined based on 2,2-diphenyl-1-picryl hydrazyl free radical (DPPH) scavenging assay described by Lai et al. (2001). The fruit extract (200 mL) was mixed with 800 mL of 100 mM Tris–HCl buffer, pH 7.4. The mixture was then added to 1.0 mL of 500 mM DPPH (previously prepared in methanol). This was made up to the DPPH final concentration of 250 mM. The control was performed by mixing 200 mL of methanol with 1.0 mL DPPH. The mixture was then shaken vigorously and left to stand for 20 min at room temperature in a dark room. The absorbance was read using a UV–vis spectrophotometer at 517 nm with methanol as the blank. Triplicate measurements were carried out and their activity was calculated based on the percentage of scavenged DPPH as follows: Scavenging activity ð%Þ ¼ ½1 ðAbsorbance of sample at 517 nm=Absorbance of control at 517 nmÞ 100 2.6. Statistical analysis Data were expressed as mean standard deviation of triplicate measurements. Data were statistically analyzed using statistical software, SPSS version 14.0 for windows (SPSS Inc, Chicago, IL, USA). One-way analysis of variance (ANOVA) and Pearson correlation coefficients, were determined and the significant difference was set at p < 0.05. 3. Results and discussion In the first line of the study, a total of 51 samples in 17 genera underutilized fruit were analyzed for their AA and TPC using bcarotene bleaching and Folin–Ciocalteu reagent methods, respectively (Table 1). AC of the underutilized fruits ranged from 45% to
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Table 1 Total phenolic content and antioxidant capacity (based on b-carotene bleaching assay) of 52 underutilized fruits from 17 genera. Scientific name
Common name
Total phenolic content (mg GAE/100 g edible portion)
Antioxidant capacity (%)
Averrhoa bilimbi L. Baccaurea motteyana Baccaurea polyneura Bouea microphylla Cynometra cauliflora Dimorcarpus longan Durio kutejensis Durio zibenthinus
Belimbing Buloh Rambai Sarawak Jentik-Jentik Remia Nam-Nam Isau Durian Isu Kuning Durian Isu Oren
1261.63 31.41 1160.14 20.56 546.25 15.70 1064.68 19.40 1868.94 11.68 203.92 14.35 183.07 6.23 168.26 9.92
91.89 0.00 71.17 5.63 81.98 3.12 76.58 1.56 45.95 2.70 52.25 3.12 54.05 2.70 64.86 2.70
Durian Tutong
79.93 13.40 68.41 1.90 64.57 3.43
68.47 4.12 73.87 1.56 54.05 2.70
Durio sp.
Durian Hutan
292.79 14.35 113.95 2.5 123.27 3.29
60.36 8.69 47.75 4.13 –
Garcinia atroviridis Garcinia parvifolia Garcinia prainiana
Assam Gelugor Kundung Sarawak Cerapu
68.41 0.95 95.84 3.43 1668.15 11.68
72.97 2.70 79.28 7.80 91.90 0.00
Leppisanthes rubiginosa
Mertajam
1110.21 38.99 1308.26 79.94
54.05 2.70 50.45 5.63
Phyllanthus emblica Pometia sp. Salacca conferta Syzygium jambos Psidium guajava Ziziphus mauritania Mangifera foetida
Buah Melaka Lengeng Sarawak Assam Kelubi Jambu Mawar Jambu Susu Bidara Bacang Gelok Bacang
Mangifera odorata
Kuini
Mangifera pajang
Bambangan Bambangan Masam Manis Mata Kucing Pulasan Hijau Pulasan Hitam Pulasan Kuning Sentol Tempatan Sentol Bangkok
2664.97 115.40 894.61 81.19 1455.29 62.14 555.57 28.33 1394.94 81.04 1321.98 4.14 763.49 11.52 491.94 8.55 815.61 24.26 579.71 5.29 763.50 11.52 849.63 27.06 663.10 8.55 487.00 8.23 523.21 16.21 388.80 9.93 245.06 15.87 372.89 4.14 2664.97 115.40 291.69 13.20 268.65 2.51 229.70 12.46 906.13 28.99 433.78 10.96 549.54 14.25 221.47 10.71 339.97 20.58 275.79 7.60 240.67 18.50 433.78 12.46 144.67 1.65 3185.05 59.00 1022.99 92.70
81.98 5.63 97.30 0.00 84.68 8.69 90.09 3.12 63.96 7.80 57.66 8.26 90.99 1.56 79.28 3.12 97.30 0.00 83.78 0.00 31.53 4.13 68.47 4.12 75.68 2.70 72.07 1.56 74.78 4.13 69.37 1.56 71.17 3.12 93.69 1.56 81.08 2.70 72.07 4.13 66.67 3.12 79.27 3.12 73.87 1.56 62.16 2.70 81.08 0.00 68.47 1.56 48.65 2.70 56.76 0.00 72.07 4.13 74.77 1.56 76.58 4.13 74.77 3.12 85.59 1.56
Nephelium malaiense Nephelium ramboutan-ake
Sandoricum macropodum
97%. Cynometra cauliflora contained the lowest AC compared to other studied fruits. The AC (>70%) of the studied genera was in the order of Pometia > Averrhoa > Syzygium > Salacca > Phyllanthus > Garcinia > Sandoricum > Baccaurea > Bouea > Nephelium (Fig. 1). High AC was observed in the studied fruits that had sour (e.g. Baccaurea, Garcinia, Mangifera and Pometia) and bitter tastes (e.g. Phyllanthus and Averrhoa). In the b-carotene bleaching assay, oxidation of linoleic acid releases linoleic acid peroxide as free radicals that oxidize b-carotene resulting in discoloration, thus decreasing the absorbance value (Talcott et al., 2000). A linear relationship was found between the ability of the sample extract to inhibit oxidation and antioxidant capacity. In this study, it was observed that the same
genera of fruits from different locations exhibited a variation in antioxidant capacity. These findings agree with those of Salunkhe and Desai (1988). Among 17 genera of the studied fruits, Sandoricum and Phyllanthus contained the highest TPC (>2000 mg/100 g edible portion), while other 7 genera contained a moderately high amount of TPC (Bouea < Leppisanthes < Averrhoa < Ziziphus < Psidium < Salacca < Cynometra), ranging from 1000 to 2000 mg GAE/100 g edible portion. Mangifera, Syzygium, Garcinia, Baccaurea and Pometia fruits contained 509, 556, 611, 853, and 894 mg GAE/ 100 g of TPC, respectively. The lowest values of TPC were found for Durio, Dimorcarpus and Nephelium fruits (<500 mg/100 g) (Table 1).
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Fig. 1. Total phenolic content and antioxidant capacity of 17 genera of underutilized fruits. Values are expressed as mean SD of triplicate measurements.
Mango (Mangifera indica) was previously reported to have a TPC in the range of 47 mg GAE/100 g (Brunswick Labs, 2002) to 209 mg GAE/100 g edible portion (Sonia et al., 2007). However, our findings showed a higher value of TPC in Mangifera foetida, Mangifera odorata and Mangifera pajang (221–2665 mg GAE/ 100 g). Mahatanatawee et al. (2005) reported lower values of TPC (159–232 mg GAE/100 g) for different species of Syzygium fruit compared to our findings. The presence of lypophilic compounds in the fruits may contribute to variation in TPC. Deepa et al. (2006) and George et al. (2005) reported that the Folin–Ciocalteu reagent method may overestimate TPC, because reducing agents, such as ascorbic acid, may interfere with the results. However, different phenolic compounds have different responses in the Folin– Ciocalteu method (Heinonen et al., 1998; Kahkonen et al., 1999). Underutilized fruits that contained high TPC may not have high AC, as shown in Fig. 1. Leppisanthes fruit had 46% of AC and 1869 mg GAE/100 g of TPC, while Pometia fruit had 97% of AC with moderate amount of TPC (895 mg GAE/100 g). Similar results were obtained for Garcinia, Nephelium and Syzygium fruits. Our findings are in agreement with Mahatanatawee et al. (2005). Moreover,
Table 2 Relationship between antioxidant capacity and total phenolic content. Genera
Correlation coefficient (r)
Bouea Garcinia Pometia Cynometra Averrhoa Nephelium Mangifera Leppisanthes Durio. Dimorcarpus Syzygium Psidium Phyllanthus Baccaurea Salacca Sandoricum Ziziphus
0.955 0.852** 0.410 0.352 0.333 0.062 0.072 0.148 0.382* 0.596 0.620 0.733 0.823 0.839* 0.887 0.923** 0.997*
Data were statistically analyzed using Pearson correlation coefficient test. * Indicates a significant difference at the level of p < 0.05. ** Indicates a significant difference at the level of p < 0.01.
Amarowicz et al. (1993) also reported that flaxseed with the lowest TPC had exhibited the highest AC. Pearson correlations coefficient showed that among 17 studied fruit genera, 5 genera showed positive correlations, while the other 12 genera showed negative correlations between AC and TPC (Table 2). There was a high and significant correlation (p < 0.01) between AC and TPC (r = 0.93). Sandoricum fruit exhibited the highest positive correlation (r = 0.852); Ziziphus fruit showed the highest negative correlation (r = 0.997). Previous studies suggested that there was a strong correlation between AC and TPC (Deighton et al., 2000; Soong and Barlow, 2004; Dykes et al., 2005). Similar studies on AC using b-carotene bleaching coupled with oxidation of linoleic acids and Folin assay had found a positive correlation between AC and TPC (Tsushida et al., 1994; Kaur and Kapoor, 2002). However, there are findings indicating that AC and TPC do not correlate with each other (Sun and Ho, 2004; Amin and Lee, 2005; Amin et al., 2006). The molecular antioxidant response of phenolic compounds in methyl linoleate varies remarkably depending on their chemical structure (Statue-Gracia et al., 1997). Thus, the AC of an extract cannot be predicted on the basis of its phenolic content, but also requires proper characterization of individual phenolic compounds. However, there are several reasons to explain the ambiguous relationship between AC and TPC found in published studies. The variations may be due to a high content of reducing agents such as ascorbic acid, minerals and carotenoids in the fruits (George et al., 2005; Deepa et al., 2006), high protein content or genetic, agronomic and environmental influences (Jagdish et al., 2007). There are several methodological limitations for antioxidant determinations, which were reported by Kaur and Kapoor (2001). The most widely used methods for measuring AC are those that involve the generation of radical species, where the presence of antioxidants determines the disappearance of radicals (Cao et al., 1993). It is important to use different assays, instead of relying on a single assay to assess and compare the antioxidant capacity. Thus, the second line of work was carried out to determine the antioxidant activity by FRAP and DPPH assays using nine different species of underutilized fruits. The FRAP value, scavenging activity and TPC of nine selected fruit species are presented in Table 3. The mean FRAP values of the studied fruits showed Maipighia punicirolia > Flacourtia rukam > Garcinia atroviridis > Psidium guajava = Carissa carandas = Ziziphus mauritiana > Pouteria campechiana > Syzygium malaccense. However, the means of FRAP values were significantly
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Table 3 Comparison of FRAP, scavenging activity and total phenolic content of underutilized fruits. Scientific name Maipighia punicirolia Flacourtia rukam Garcinia atroviridis Psidium guajava Carissa carandas Ziziphus mauritiana Pouteria campechiana Mangifera odorata Syzygium malaccense
Common name Ceri Rokam Manis Asam Gelugor Jambu Kerandang Bidara Kuning Telur Kuini Jambu Bol
FRAP value (mM) c
4.34 0.25 2.09 0.13d 0.67 0.08b 0.46 0.13ab 0.46 0.10ab 0.46 0.07ab 0.43 0.09ab 0.28 0.10a 0.22 0.03a
Scavenging activity (%) ecf
81.04 0.38 78.09 0.39bce 86.40 2.20f 74.62 1.19bec 43.57 1.53a 74.96 0.44bc 73.32 0.72b 45.68 11.09a 17.01 0.32d
Total phenolic content (mg GAE/100 g) 107.0 0.4a 40.0 0.2c 29.0 0.2d 31.1 0.1d 12.0 0.0f 41.0 0.3c 21.0 0.1b 8.0 0.0e 6.0 0.0e
Values are expressed as mean SD of triplicate measurement. Superscripts with different letters are significantly different at p < 0.05 within the same column.
different (p < 0.05) between M. punicirolia and other species, while the FRAP values of M. odorata, P. campechiana, Z. mauritiana, S. malaccense, P. guajava and C. carandas did not show any significant difference. For the DPPH assay, the radical scavenging activity of the studied fruits was in the order of G. atroviridis > M. punicirolia > F. rukam > Z. mauritiana > P. guajava > P. campechiana > M. odorata > C. carandas > S. malaccense. No significant difference was observed between vitamin C (as standard) and the studied fruits (M. punicirolia, F. rukam, P. guajava, Z. mauritiana and G. atroviridis). No significant difference was observed among P. campechiana, Z. mauritiana, P. guajava and F. rukam. M. punicirolia exhibited the highest TPC, followed by Z. mauritiana, F. rukam, P. guajava, G. atroviridis, P. campechiana, C. carandas, M. odorata and S. malaccense (Table 3). ANOVA indicated that the means of TPC were significantly different (p < 0.05) among the studied fruits. However, means of TPC of M. odorata and S. malaccense did not show any significant difference. No significant difference was found between P. guajava and G. atroviridis. In this study, the variation of AC and TPC of the studied fruits may be due to several reasons. The red colored fruits (M. punicirolia and F. rukam) contained high AC and TPC. Red, purple and blue color pigments present in the studied underutilized fruits could be anthocyanin compounds. Wang et al. (1997) showed that colored fruits such as grapes and cranberries contain high levels of anthocyanidins which have high antioxidant properties. GarciaAlonso et al. (2004) and Velioglu et al. (1998) reported that M. punicirolia had higher AC as compared to strawberry and raspberry. This might be due to anthocyanins present in this fruit, which have contributed to high AC (Kahkonen et al., 1999). Moreover, Guo et al. (1997) reported that high AC of fruits is most probably due to high polyphenol compounds such as phenolic acids and flavonoids. 4. Conclusions Malaysia has a great diversity of underutilized fruits that vary in appearance and organoleptic characteristics. There are great variations in the AC and TPC of the studied fruits. Garcinia prainiana, Phyllanthus emblica and Syzygium jambos have high potential to be sources of antioxidants. The correlation results indicated that along with phenolic compounds, other antioxidant components such as vitamins C and E and carotenoids could also contribute to the antioxidant capacity of underutilized fruits. There are many factors that could influence the antioxidant components and capacity such as varieties (cultivar/sub-species) and agronomic and environmental factors (climate, soils and light exposure). Acknowledgement The authors would like to acknowledge the Malaysian Agricultural Research and Development Institute (MARDI) for
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E.H.K. Ikram et al. / Journal of Food Composition and Analysis 22 (2009) 388–393 Kahkonen, M.P., Hopia, A.I., Vuorela, H.J., Rauha, J.P., Pihlaja, K., Kujala, T.S., Heinonen, M., 1999. Antioxidant capacity of plant extracts containing phenolic compounds. Journal of Agricultural and Food Chemistry 47, 3954–3962. Kaur, C., Kapoor, H.C., 2001. Review: antioxidants in fruits and vegetables—the millennium’s health. International Journal of Food Science and Technology 36, 703–725. Kaur, C., Kapoor, H.C., 2002. Anti-oxidant and total phenolic contents of some Asian vegetables. International Journal of Food Science and Technology 37, 153–161. Lai, L.S., Chou, S.T., Chao, W.W., 2001. Studies on the antioxidative activities of Hsian-tsao (Mesona procumbens Hemsl) leaf gum. Journal of Agricultural and Food Chemistry 49, 963–968. Leong, L.P., Shui, G., 2002. An investigation of antioxidant capacity of fruits in Singapore markets. Food Chemistry 76, 69–75. Mahatanatawee, K. Goodner, K., Baldwin, E., Manthey, J., Luzio, G., 2005. Total antioxidant activity of Florida’s tropical fruits. First report for Trust Food Project with Tropical Fruit Growers of South Florida. USDA-ARS Citrus and Subtropical Product Laboratory, Winter Haven, FL. Available at: http://www.tropicalfruitgrowers.com/FDPs/TFAntioxidant-report.pdf. Accessed 4/2/2009. Riboli, E., Norat, T., 2003. Epidemiologic evidence of the protective effect of fruit and vegetables on cancer risk. American Journal of Clinical Nutrition 78 (3), 559S– 569S. Rukayah, A., 1992. Buah-buahan Nadir Semenanjung Malaysia, Dewan Bahasa dan Pustaka, Kuala Lumpur, Malaysia.
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Contents lists available at ScienceDirect
Journal of Food Composition and Analysis journal homepage: www.elsevier.com/locate/jfca
Original Article
Antioxidant capacity and total phenolic content of Malaysian underutilized fruits Emmy Hainida Khairul Ikram a, Khoo Hock Eng a, Abbe Maleyki Mhd Jalil a, Amin Ismail a,*, Salma Idris b, Azrina Azlan a, Halimatul Saadiah Mohd Nazri a, Norzatol Akmar Mat Diton a, Ruzaidi Azli Mohd Mokhtar a a b
Department of Nutrition and Dietetics, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia Botany Division, Strategic Resource Research Center, Malaysian Agricultural Research and Development Institute (MARDI), 43400 Serdang, Selangor, Malaysia
A R T I C L E I N F O
A B S T R A C T
Article history: Received 1 November 2007 Received in revised form 16 February 2009 Accepted 2 April 2009
The purpose of this study was to evaluate the antioxidant capacity (AC) and total phenolic content (TPC) of selected Malaysian underutilized fruits. The 58 underutilized fruits of 32 different species from 21 genera were analyzed for AC and TPC. AC was measured using b-carotene bleaching, ferric reducing antioxidant potential (FRAP) and 2,2-diphenyl-1-picryl hydrazyl (DPPH) assays, and TPC was determined using the Folin–Ciocalteu reagent assay. Our findings showed that the fruits from genera of Pometia, Averrhoa, Syzygium, Sallacca, Phyllanthus, Garcinia, Sandoricum and Maipighia had higher AC compared to other studied genera. Among the underutilized fruits, Sandoricum and Phyllanthus fruits contained the highest TPC (>2000 mg/100 g edible portion). The correlation between AC and TPC varied. The study indicated that some of these underutilized fruits have the potential to be sources of antioxidant components. ß 2009 Elsevier Inc. All rights reserved.
Keywords: Underutilized fruit Inhibition of oxidation activity Antioxidant activity Scavenging activity Total phenolic content Food analysis Food composition
1. Introduction Epidemiological studies have shown that there is a positive association between intake of vegetables and fruits and reduced cardiovascular diseases (Hu, 2003) and certain cancers (Riboli and Norat, 2003). It is generally assumed that the main dietary constituents contributing to these protective effects are the antioxidant components (Agudo et al., 2007). Along with other antioxidant components, polyphenols (e.g. flavonoids) present in fruits and vegetables have been reported to be potential candidates in lowering cardiovascular diseases (Huxley and Neil, 2003; Joshipura et al., 2001). The protective effects could be due to their properties as free radical scavengers, hydrogen-donating compounds, singlet oxygen quenchers and/or metal ion chelators. Generally, Malaysians consume vegetables that are relatively abundant sources of antioxidant components with strong potential antioxidant activities (Amin and Lee, 2005; Amin et al., 2004, 2006). Similar to vegetables, tropical and subtropical fruits such as ciku, star fruits and guava have been reported to be rich in antioxidants (Leong and Shui, 2002). Besides the commonly consumed local fruits, some under-
* Corresponding author. Tel.: +60 3 8947 2435; fax: +60 3 8942 6769. E-mail address: [email protected] (A. Ismail). 0889-1575/$ – see front matter ß 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2009.04.001
utilized fruits are important in the Malaysian diet, especially in rural communities. Malaysia is one of the countries that has a rich diversity of underutilized fruits that grow wild in the region of Peninsular Malaysia, Sabah and Sarawak. Some of the underutilized fruits are rarely eaten, unknown and unfamiliar. Due to the broad spectrum of their flesh and skin color, these underutilized fruits may have potential benefits to human health. It is important to include these fruits in health promotion campaigns. In addition, some of these fruits have the potential to be used and processed as food products for local consumption. However, underutilized fruits have not received much attention as antioxidant sources compared to commercial fruits like guava, papaya and pineapple. This could be due to their lack of popularity among local communities, lack of information on nutritional compositions and physical qualities and the lack of promotional campaigns for these fruits. In Malaysia, many kinds of underutilized fruits are available, such as nam-nam (Cynometra sp.), bacang (Mangifera sp.), jambu bol (Psidium sp.), durian (Durio sp.), bidara (Ziziphus sp.), mertajam (Leppisanthes sp.), longan (Dimorcarpus sp.), lenggeng serawak (Pometia sp.), belimbing buloh (Averrhoa sp.), assam kelubi (Salacca sp.), buah melaka (Phyllanthus sp.), assam gelugor (Garcinia sp.), sentol (Sandoricum sp.), rambai Sarawak (Baccaurea sp.), remia (Bouea sp.), pulasan (Nephelium sp.) and others. These fruits are usually grown in orchards or fruit gardens around houses, and
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some grow wild in the rain-forest (Rukayah, 1992). These fruits are known by older folks to be associated with many nutritional and medicinal properties. There is a dearth of information on the antioxidant capacity (AC) and antioxidant components, including total phenolic content (TPC), of Malaysian underutilized fruits. Therefore, this work was initiated to determine AC and TPC of selected Malaysian underutilized fruits. In addition, the relationship between AC and TPC was determined. 2. Materials and methods 2.1. Preparation of sample and extract Two lines of research work consisting of 58 Malaysian underutilized fruits of 32 different species from 21 genera were conducted in this study. The first line of research work consisted of 51 underutilized fruits of 26 different species from 17 genera, while the second line of work consisted of 9 underutilized fruits of 9 different species from 8 genera. The fruits were sampled from different locations by the Strategic Resource Research Centre, Malaysian Agricultural Research and Development Institute, Malaysia. The fruits were grown wild and harvested at maturity at different time periods. Mature fruits for each sample were transported from the Centre directly to the analytical laboratory. The whole fruit was washed under running tap water to remove dirt and other foreign materials and wiped with tissue paper. The fruit was weighed for the whole and edible portions. The edible portion was then cut into small pieces and stored at 80 8C before lyophilization using a bench-top freeze dryer (Virtis, Gardiner, New York). The lyophilized fruits were ground into powder form, and kept at 20 8C prior to analysis. Methanolic extract was prepared by mixing 1 g of the lyophilized fruit powder with 80% methanol (v/v) at a ratio 1:4. The mixture was placed in a conical flask (wrapped with an aluminum foil) and agitated at 200 rpm, at 50 8C, with the aid of an orbital shaker (Heidolph Unimax 1010, Schwabach, Germany) for 2 h. The mixture was then filtered through a filter paper (Whatman No. 4) to obtain a clear solution. The extract was used for determination of AC and TPC. 2.2. b-Carotene bleaching method The inhibition activity of b-carotene oxidation by peroxide radicals of the fruit methanolic extract was determined according to a modified procedure, initially described by Velioglu et al. (1998). Briefly, 1.0 mL of b-carotene solution (0.2 mg/mL chloroform) was pipetted into a round-bottom flask containing 20 mL linoleic acid, 200 mL Tween 20 and 200 mL fruit extract. The mixture was then evaporated at 30 8C for 20 min using a rotary evaporator (Buchi Rotavor R-200, Switzerland) to remove chloroform. After evaporation, 50 mL of distilled water was immediately added to the mixture. The mixture was vigorous agitated for 5 min using an orbital shaker to form an emulsion. Aliquots (2.0 mL) of the emulsion were transferred into different test tubes. The mixture was then gently mixed and placed in a water bath at 50 8C for 2 h. Absorbance of the samples was recorded at 0 and 2 h at 470 nm using a Spectronic GenesysTM 5 spectrophotometer (Milton Roy Company, New York). All determinations were performed in triplicate. AC was calculated as percent of inhibition relative to control using the following equation from Al-Saikhan et al. (1995): Antioxidant capacity (%) = [(drcontrol–drsample)/drcontrol 100], where, drcontrol and drsample are the degradation bleaching rates of b-carotene in reactant mixed with fruit extracts at 0 and 2 h, respectively.
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2.3. Total phenolic content (TPC) The content of reducing components (expressed as TPC) was estimated using the Folin–Ciocalteu assay according to a method developed by Velioglu et al. (1998), with slight modification. Briefly, 0.75 mL of 10-fold diluted Folin–Ciocalteu reagent and 100 mL of methanolic extract were placed in a test tube. The mixture was mixed and allowed to stand at room temperature for 5 min. Then, 0.75 mL of 6% (w/v) sodium carbonate solution was added. The mixture was homogenized and allowed to stand at room temperature for 90 min. TPC was determined using a Spectronic GenesisTM spectrophotometer at 725 nm. The standard calibration curve was plotted using gallic acid at the concentrations of 0.02–0.1 mg/mL. The TPC was expressed as gallic acid equivalent (GAE) mg/100 g edible portion. 2.4. Determination of ferric reducing antioxidant potential (FRAP) FRAP assay was performed according to the method of Benzie and Strain (1996). The FRAP reagent was prepared by mixing 16.7 mM FeCl36H2O and 8.3 mM 2,4,6-tripyridyl-s-triazine (TPTZ) with 250 mM acetate buffer, pH 3.6. A total of 75 mL fruit extract and 225 mL of distilled water was added to 2.25 mL of freshly prepared FRAP reagent in a test tube. The mixture was incubated at 37 8C throughout the reaction. The absorbance was read at initial and after 4 min at 593 nm using a UV–vis spectrophotometer during the monitoring period. The antioxidant potential of the fruit extract was determined based on a calibration curve plotted using FeSO47H2O at a concentration ranging between 400 and 2000 mM. 2.5. Determination of free radical scavenging activity (DPPH) The scavenging activity of the extract was determined based on 2,2-diphenyl-1-picryl hydrazyl free radical (DPPH) scavenging assay described by Lai et al. (2001). The fruit extract (200 mL) was mixed with 800 mL of 100 mM Tris–HCl buffer, pH 7.4. The mixture was then added to 1.0 mL of 500 mM DPPH (previously prepared in methanol). This was made up to the DPPH final concentration of 250 mM. The control was performed by mixing 200 mL of methanol with 1.0 mL DPPH. The mixture was then shaken vigorously and left to stand for 20 min at room temperature in a dark room. The absorbance was read using a UV–vis spectrophotometer at 517 nm with methanol as the blank. Triplicate measurements were carried out and their activity was calculated based on the percentage of scavenged DPPH as follows: Scavenging activity ð%Þ ¼ ½1 ðAbsorbance of sample at 517 nm=Absorbance of control at 517 nmÞ 100 2.6. Statistical analysis Data were expressed as mean standard deviation of triplicate measurements. Data were statistically analyzed using statistical software, SPSS version 14.0 for windows (SPSS Inc, Chicago, IL, USA). One-way analysis of variance (ANOVA) and Pearson correlation coefficients, were determined and the significant difference was set at p < 0.05. 3. Results and discussion In the first line of the study, a total of 51 samples in 17 genera underutilized fruit were analyzed for their AA and TPC using bcarotene bleaching and Folin–Ciocalteu reagent methods, respectively (Table 1). AC of the underutilized fruits ranged from 45% to
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Table 1 Total phenolic content and antioxidant capacity (based on b-carotene bleaching assay) of 52 underutilized fruits from 17 genera. Scientific name
Common name
Total phenolic content (mg GAE/100 g edible portion)
Antioxidant capacity (%)
Averrhoa bilimbi L. Baccaurea motteyana Baccaurea polyneura Bouea microphylla Cynometra cauliflora Dimorcarpus longan Durio kutejensis Durio zibenthinus
Belimbing Buloh Rambai Sarawak Jentik-Jentik Remia Nam-Nam Isau Durian Isu Kuning Durian Isu Oren
1261.63 31.41 1160.14 20.56 546.25 15.70 1064.68 19.40 1868.94 11.68 203.92 14.35 183.07 6.23 168.26 9.92
91.89 0.00 71.17 5.63 81.98 3.12 76.58 1.56 45.95 2.70 52.25 3.12 54.05 2.70 64.86 2.70
Durian Tutong
79.93 13.40 68.41 1.90 64.57 3.43
68.47 4.12 73.87 1.56 54.05 2.70
Durio sp.
Durian Hutan
292.79 14.35 113.95 2.5 123.27 3.29
60.36 8.69 47.75 4.13 –
Garcinia atroviridis Garcinia parvifolia Garcinia prainiana
Assam Gelugor Kundung Sarawak Cerapu
68.41 0.95 95.84 3.43 1668.15 11.68
72.97 2.70 79.28 7.80 91.90 0.00
Leppisanthes rubiginosa
Mertajam
1110.21 38.99 1308.26 79.94
54.05 2.70 50.45 5.63
Phyllanthus emblica Pometia sp. Salacca conferta Syzygium jambos Psidium guajava Ziziphus mauritania Mangifera foetida
Buah Melaka Lengeng Sarawak Assam Kelubi Jambu Mawar Jambu Susu Bidara Bacang Gelok Bacang
Mangifera odorata
Kuini
Mangifera pajang
Bambangan Bambangan Masam Manis Mata Kucing Pulasan Hijau Pulasan Hitam Pulasan Kuning Sentol Tempatan Sentol Bangkok
2664.97 115.40 894.61 81.19 1455.29 62.14 555.57 28.33 1394.94 81.04 1321.98 4.14 763.49 11.52 491.94 8.55 815.61 24.26 579.71 5.29 763.50 11.52 849.63 27.06 663.10 8.55 487.00 8.23 523.21 16.21 388.80 9.93 245.06 15.87 372.89 4.14 2664.97 115.40 291.69 13.20 268.65 2.51 229.70 12.46 906.13 28.99 433.78 10.96 549.54 14.25 221.47 10.71 339.97 20.58 275.79 7.60 240.67 18.50 433.78 12.46 144.67 1.65 3185.05 59.00 1022.99 92.70
81.98 5.63 97.30 0.00 84.68 8.69 90.09 3.12 63.96 7.80 57.66 8.26 90.99 1.56 79.28 3.12 97.30 0.00 83.78 0.00 31.53 4.13 68.47 4.12 75.68 2.70 72.07 1.56 74.78 4.13 69.37 1.56 71.17 3.12 93.69 1.56 81.08 2.70 72.07 4.13 66.67 3.12 79.27 3.12 73.87 1.56 62.16 2.70 81.08 0.00 68.47 1.56 48.65 2.70 56.76 0.00 72.07 4.13 74.77 1.56 76.58 4.13 74.77 3.12 85.59 1.56
Nephelium malaiense Nephelium ramboutan-ake
Sandoricum macropodum
97%. Cynometra cauliflora contained the lowest AC compared to other studied fruits. The AC (>70%) of the studied genera was in the order of Pometia > Averrhoa > Syzygium > Salacca > Phyllanthus > Garcinia > Sandoricum > Baccaurea > Bouea > Nephelium (Fig. 1). High AC was observed in the studied fruits that had sour (e.g. Baccaurea, Garcinia, Mangifera and Pometia) and bitter tastes (e.g. Phyllanthus and Averrhoa). In the b-carotene bleaching assay, oxidation of linoleic acid releases linoleic acid peroxide as free radicals that oxidize b-carotene resulting in discoloration, thus decreasing the absorbance value (Talcott et al., 2000). A linear relationship was found between the ability of the sample extract to inhibit oxidation and antioxidant capacity. In this study, it was observed that the same
genera of fruits from different locations exhibited a variation in antioxidant capacity. These findings agree with those of Salunkhe and Desai (1988). Among 17 genera of the studied fruits, Sandoricum and Phyllanthus contained the highest TPC (>2000 mg/100 g edible portion), while other 7 genera contained a moderately high amount of TPC (Bouea < Leppisanthes < Averrhoa < Ziziphus < Psidium < Salacca < Cynometra), ranging from 1000 to 2000 mg GAE/100 g edible portion. Mangifera, Syzygium, Garcinia, Baccaurea and Pometia fruits contained 509, 556, 611, 853, and 894 mg GAE/ 100 g of TPC, respectively. The lowest values of TPC were found for Durio, Dimorcarpus and Nephelium fruits (<500 mg/100 g) (Table 1).
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391
Fig. 1. Total phenolic content and antioxidant capacity of 17 genera of underutilized fruits. Values are expressed as mean SD of triplicate measurements.
Mango (Mangifera indica) was previously reported to have a TPC in the range of 47 mg GAE/100 g (Brunswick Labs, 2002) to 209 mg GAE/100 g edible portion (Sonia et al., 2007). However, our findings showed a higher value of TPC in Mangifera foetida, Mangifera odorata and Mangifera pajang (221–2665 mg GAE/ 100 g). Mahatanatawee et al. (2005) reported lower values of TPC (159–232 mg GAE/100 g) for different species of Syzygium fruit compared to our findings. The presence of lypophilic compounds in the fruits may contribute to variation in TPC. Deepa et al. (2006) and George et al. (2005) reported that the Folin–Ciocalteu reagent method may overestimate TPC, because reducing agents, such as ascorbic acid, may interfere with the results. However, different phenolic compounds have different responses in the Folin– Ciocalteu method (Heinonen et al., 1998; Kahkonen et al., 1999). Underutilized fruits that contained high TPC may not have high AC, as shown in Fig. 1. Leppisanthes fruit had 46% of AC and 1869 mg GAE/100 g of TPC, while Pometia fruit had 97% of AC with moderate amount of TPC (895 mg GAE/100 g). Similar results were obtained for Garcinia, Nephelium and Syzygium fruits. Our findings are in agreement with Mahatanatawee et al. (2005). Moreover,
Table 2 Relationship between antioxidant capacity and total phenolic content. Genera
Correlation coefficient (r)
Bouea Garcinia Pometia Cynometra Averrhoa Nephelium Mangifera Leppisanthes Durio. Dimorcarpus Syzygium Psidium Phyllanthus Baccaurea Salacca Sandoricum Ziziphus
0.955 0.852** 0.410 0.352 0.333 0.062 0.072 0.148 0.382* 0.596 0.620 0.733 0.823 0.839* 0.887 0.923** 0.997*
Data were statistically analyzed using Pearson correlation coefficient test. * Indicates a significant difference at the level of p < 0.05. ** Indicates a significant difference at the level of p < 0.01.
Amarowicz et al. (1993) also reported that flaxseed with the lowest TPC had exhibited the highest AC. Pearson correlations coefficient showed that among 17 studied fruit genera, 5 genera showed positive correlations, while the other 12 genera showed negative correlations between AC and TPC (Table 2). There was a high and significant correlation (p < 0.01) between AC and TPC (r = 0.93). Sandoricum fruit exhibited the highest positive correlation (r = 0.852); Ziziphus fruit showed the highest negative correlation (r = 0.997). Previous studies suggested that there was a strong correlation between AC and TPC (Deighton et al., 2000; Soong and Barlow, 2004; Dykes et al., 2005). Similar studies on AC using b-carotene bleaching coupled with oxidation of linoleic acids and Folin assay had found a positive correlation between AC and TPC (Tsushida et al., 1994; Kaur and Kapoor, 2002). However, there are findings indicating that AC and TPC do not correlate with each other (Sun and Ho, 2004; Amin and Lee, 2005; Amin et al., 2006). The molecular antioxidant response of phenolic compounds in methyl linoleate varies remarkably depending on their chemical structure (Statue-Gracia et al., 1997). Thus, the AC of an extract cannot be predicted on the basis of its phenolic content, but also requires proper characterization of individual phenolic compounds. However, there are several reasons to explain the ambiguous relationship between AC and TPC found in published studies. The variations may be due to a high content of reducing agents such as ascorbic acid, minerals and carotenoids in the fruits (George et al., 2005; Deepa et al., 2006), high protein content or genetic, agronomic and environmental influences (Jagdish et al., 2007). There are several methodological limitations for antioxidant determinations, which were reported by Kaur and Kapoor (2001). The most widely used methods for measuring AC are those that involve the generation of radical species, where the presence of antioxidants determines the disappearance of radicals (Cao et al., 1993). It is important to use different assays, instead of relying on a single assay to assess and compare the antioxidant capacity. Thus, the second line of work was carried out to determine the antioxidant activity by FRAP and DPPH assays using nine different species of underutilized fruits. The FRAP value, scavenging activity and TPC of nine selected fruit species are presented in Table 3. The mean FRAP values of the studied fruits showed Maipighia punicirolia > Flacourtia rukam > Garcinia atroviridis > Psidium guajava = Carissa carandas = Ziziphus mauritiana > Pouteria campechiana > Syzygium malaccense. However, the means of FRAP values were significantly
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Table 3 Comparison of FRAP, scavenging activity and total phenolic content of underutilized fruits. Scientific name Maipighia punicirolia Flacourtia rukam Garcinia atroviridis Psidium guajava Carissa carandas Ziziphus mauritiana Pouteria campechiana Mangifera odorata Syzygium malaccense
Common name Ceri Rokam Manis Asam Gelugor Jambu Kerandang Bidara Kuning Telur Kuini Jambu Bol
FRAP value (mM) c
4.34 0.25 2.09 0.13d 0.67 0.08b 0.46 0.13ab 0.46 0.10ab 0.46 0.07ab 0.43 0.09ab 0.28 0.10a 0.22 0.03a
Scavenging activity (%) ecf
81.04 0.38 78.09 0.39bce 86.40 2.20f 74.62 1.19bec 43.57 1.53a 74.96 0.44bc 73.32 0.72b 45.68 11.09a 17.01 0.32d
Total phenolic content (mg GAE/100 g) 107.0 0.4a 40.0 0.2c 29.0 0.2d 31.1 0.1d 12.0 0.0f 41.0 0.3c 21.0 0.1b 8.0 0.0e 6.0 0.0e
Values are expressed as mean SD of triplicate measurement. Superscripts with different letters are significantly different at p < 0.05 within the same column.
different (p < 0.05) between M. punicirolia and other species, while the FRAP values of M. odorata, P. campechiana, Z. mauritiana, S. malaccense, P. guajava and C. carandas did not show any significant difference. For the DPPH assay, the radical scavenging activity of the studied fruits was in the order of G. atroviridis > M. punicirolia > F. rukam > Z. mauritiana > P. guajava > P. campechiana > M. odorata > C. carandas > S. malaccense. No significant difference was observed between vitamin C (as standard) and the studied fruits (M. punicirolia, F. rukam, P. guajava, Z. mauritiana and G. atroviridis). No significant difference was observed among P. campechiana, Z. mauritiana, P. guajava and F. rukam. M. punicirolia exhibited the highest TPC, followed by Z. mauritiana, F. rukam, P. guajava, G. atroviridis, P. campechiana, C. carandas, M. odorata and S. malaccense (Table 3). ANOVA indicated that the means of TPC were significantly different (p < 0.05) among the studied fruits. However, means of TPC of M. odorata and S. malaccense did not show any significant difference. No significant difference was found between P. guajava and G. atroviridis. In this study, the variation of AC and TPC of the studied fruits may be due to several reasons. The red colored fruits (M. punicirolia and F. rukam) contained high AC and TPC. Red, purple and blue color pigments present in the studied underutilized fruits could be anthocyanin compounds. Wang et al. (1997) showed that colored fruits such as grapes and cranberries contain high levels of anthocyanidins which have high antioxidant properties. GarciaAlonso et al. (2004) and Velioglu et al. (1998) reported that M. punicirolia had higher AC as compared to strawberry and raspberry. This might be due to anthocyanins present in this fruit, which have contributed to high AC (Kahkonen et al., 1999). Moreover, Guo et al. (1997) reported that high AC of fruits is most probably due to high polyphenol compounds such as phenolic acids and flavonoids. 4. Conclusions Malaysia has a great diversity of underutilized fruits that vary in appearance and organoleptic characteristics. There are great variations in the AC and TPC of the studied fruits. Garcinia prainiana, Phyllanthus emblica and Syzygium jambos have high potential to be sources of antioxidants. The correlation results indicated that along with phenolic compounds, other antioxidant components such as vitamins C and E and carotenoids could also contribute to the antioxidant capacity of underutilized fruits. There are many factors that could influence the antioxidant components and capacity such as varieties (cultivar/sub-species) and agronomic and environmental factors (climate, soils and light exposure). Acknowledgement The authors would like to acknowledge the Malaysian Agricultural Research and Development Institute (MARDI) for
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