Bioactive compounds and antioxidant activity of organically grown tomato (Solanum lycopersicum L.) cultivars as affected by fertilization

Scientia Horticulturae 151 (2013) 90–96

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Bioactive compounds and antioxidant activity of organically grown tomato (Solanum lycopersicum L.) cultivars as affected by fertilization Anissa Riahi 1 , Chafik Hdider ∗,1 Laboratory of Horticulture, National Agricultural Research Institute of Tunisia, Tunis (Université de Carthage), Rue Hédi Karray 2049 Ariana, Tunisia

a r t i c l e

i n f o

Article history: Received 9 June 2012 Received in revised form 29 November 2012 Accepted 12 December 2012 Keywords: Organic production Tomato cultivar Fertilization Antioxidant activity Flavonoids Lycopene

a b s t r a c t In this study, the antioxidant properties of two tomato cultivars Firenze and Rio Grande grown organically in an open-field under different combinations of organic fertilizer sources were investigated, lycopene, total phenols and flavonoids contents, as well as lipophilic, hydrophilic and total antioxidant activities were determined. Significant differences were found between tomato cvs in lycopene and antioxidant activity. Firenze cv showed higher lycopene, lipophilic, hydrophilic and total antioxidant activities when compared to cv Rio Grande. On the other hand, even though antioxidant activity was affected by the different organic fertilizer treatments, tomato bioactive compounds were not affected whatever the cv. LAA ranged from 123.8 ␮M Trolox/100 g fresh weight (fw) in cv Rio Grande to 153.4 ␮M Trolox/100 g fw in cv Firenze and was significantly correlated to lycopene (r = 0.45; p < 0.05) content. HAA ranged from 81.5 ␮M Trolox/100 g fw in cv Rio Grande to 101.3 ␮M Trolox/100 g fw in cv Firenze and was not significantly correlated to total phenols and flavonoids contents. Although these data require confirmation over a longer period of time, this investigation emphasizes the satisfactory organic tomato antioxidant attributes. © 2012 Elsevier B.V. All rights reserved.

1. Introduction Organic tomato cultivation is a relatively recent introduction in Tunisia, but it has shown promise and can contribute to the promotion of agriculture. In fact, the demand for organically grown produce is increasing because of (a) the commercial opportunities offered by such products, (b) environmental concerns and (c) increasing consumer awareness of the relationship between foods and health. Tomatoes (Solanum lycopersicum L.) commonly used in the Tunisian diet, are a major source of antioxidants and contribute to the daily intake of a significant amount of these molecules. In fact, tomato fruit is a reservoir of diverse antioxidant molecules, such as carotenoids (especially lycopene), phenolics, flavonoids, vitamin C, vitamin E and tocopherols (Vinson et al., 1998; Karakaya et al., 2001; George et al., 2004; Mitchell et al., 2007). Lycopene, the red pigment of tomato, phenolics and flavonoids have received great interest during the last few years because of their antioxidant properties in relation to free radicals, suggesting protective roles in reducing risk of chronic diseases, such as cancer and cardiovascular disease (Rice-Evans et al., 1996; Rao and Agarwal, 2000).

∗ Corresponding author. Tel.: +216 71 230 024; fax: +216 71 230 667. E-mail address: hdider.chafi[email protected] (C. Hdider). 1 These authors contributed equally to the paper. 0304-4238/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scienta.2012.12.009

The antioxidant capability in conventional tomato fruits is strongly affected by many cultural and abiotic factors. The influence of genotype (Ilahy et al., 2011a; Cano et al., 2003; Lenucci et al., 2006), agronomic technique (Dumas et al., 2003; Toor et al., 2006; Cano et al., 2003) and light and temperature (Pék et al., 2011; Rosales et al., 2006) on antioxidant properties has been studied. However, information on the bioactive compound contents and antioxidant activity of organic tomato as affected by cv and organic fertilization are scarce. Previously, Caris-Veyrat et al. (2004) and Aldrich et al. (2010) focused on the assessment of bioactive composition of some organic tomato and concluded that fruit antioxidant potential is affected by cvs. In addition, earlier, we found that the combination of compost with other organic fertilizer sources such compost extracts and biofertilizers can promote tomato yield and quality in organic system (Riahi et al., 2009a). However, in that study, antioxidant activity was not determined. The determination of antioxidant activity in the different fruit fractions allows a real evaluation of nutritional quality of food rather than the analysis of each single antioxidant compound (Pellegrini et al., 2007). In fact, due to the complexity of the composition of foods, their antioxidant power depends on the synergistic effects and redox interactions among the different nutrient and “non nutrient” molecules which together contribute to the supposed health benefits. In this study, the contents of some phytochemicals (lycopene, phenols and flavonoids) and the antioxidant activities (both lipophilic and hydrophilic) of two tomato cvs (Firenze and Rio

A. Riahi, C. Hdider / Scientia Horticulturae 151 (2013) 90–96 Table 1 Temperature (◦ C) and relative humidity (%) data recorded by the weather station of Mannouba research station, which was the closest to the experimental field where experiments were carried out. The reported values refer to 2008 and cover the entire tomato plant growing season (April–July). Extreme temperature (◦ C)

Months

Period of ten days

Relative humidity (%)

Minimum

Maximum

April

1 2 3

11.71 14.29 13.71

19.85 21.70 23.25

80.44 82.23 77.90

May

1 2 3

14.57 16.79 19.14

23.05 27.85 29.50

81.06 74.92 76.11

June

1 2 3

17.14 22.36 23.57

25.05 34.70 35.35

82.92 73.36 72.23

July

1 2 3

22.21 20.93 23.59

33.00 37.25 35.73

75.74 65.68 71.85

Grande) grown in field organic production system under different fertilizer treatments were studied. The correlation of lipophilic antioxidant activity (LAA) and hydrophilic antioxidant activity (HAA) with the different classes of antioxidants was also examined. 2. Materials and methods 2.1. Plant culture The field experiments were carried out in a field at Mannouba support research station (Northern Tunisia) during the 2008 growing season (April–July). The experiments were established in organic plot under meteorological data reported in Table 1. The plot had lain fallow in the previous rotation. Soil analysis of the plot gave the physicochemical characteristics shown in Table 2. The soil was a clay loam in texture with 282.5 g/kg clay, 175 g/kg loam and 315.2 g/kg sand and was rich in total (290.7 g/kg) and active (179.5 g/kg) calcareous material. The soil had adequate pH and electric conductivity for tomato and was rich in total nitrogen, phosphorus, potassium and magnesium but low in calcium and organic matter. Two tomato cvs commonly grown for the fresh market and processing in Tunisia were used, the open pollinated Rio Grande and the hybrid Firenze, all from Petoseed (Saticoy, CA, USA). Sowing was carried out in alveolar boxes at the end of February 2008. Transplanting took place on mid-April in double rows in an open field with spacing within rows and between double rows of approximately 40 cm and 150 cm respectively, matching a density of about 33,000 plants/ha. The experimental design Table 2 Physicochemical characteristics of soil, mixed compost and sheep manure used in the experiment. Characteristics

Soil

Mixed composta

Sheep manure

pH EC (ms/cm) OM (%) C (%) N (%) C/N ratio P (mg/kg) K (mg/kg) Ca (mg/kg) Mg (mg/kg)

7 0.13 1.90 1.10 0.16 6.88 45 869 68 728

8.37 1.24 49.20 28.52 1.47 19.40 6000 8900 13,200 5900

8.20 2.86 39.20 22.72 2.04 11.14 4400 10,200 13,500 5300

a

Mixed compost = 50% olive husk + 30% horse manure + 20% poultry manure.

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was a split plot with four replicates of two main plots (cvs) and three sub-plots (organic fertilizer treatments). In addition to fertilization, the organic production methods included weed control with hand hoeing and plant pathogen control with some approved pesticides as described by Riahi et al. (2009a) and recommended by the Technical Center of Organic Agriculture, Chott Mariem, Tunisia. Drip irrigation ran for 1–2.5 h, at 1–2 day intervals, depending on potential evapo-transpiration, climate data and crop coefficient. The organic production methods were in accordance with national organic standards specifying the methods and practices and listing the substances allowed (such as natural fertilizers, pesticides, and so on) and prohibited (such as chemical fertilizers, synthetic pesticides and growth hormones). These organic Tunisian standards comply with European standards. Before tomato transplanting, the soil received different combinations of some organic fertilizer sources in crop cycle (depending on soil nutrient content, fertilizer sources characterizations and crop requirements). The organic fertilizer sources based on mixed compost combined with its water extract, sheep manure and an organic fertilizer (codahumus 20, Sustainable Agro Solutions, Lleida, Spain). The last was selected since it was commonly used by organic farmers in Tunisia. Codahumus 20 contained 11.2% (p/v) humic acid, 11.4% (p/v) fulvic acid and 3% (p/v) potassium oxide (K2 O). It had a density of 1.4 g/cm3 and contained 100 g/kg humic acids, 102 g/kg fulvic acids, 36 g/kg N, 26 g/kg P2 O5 and 45 g/kg K2 O. The three treatment combinations were as follows:

• T: (control) codahumus 20 (40 l/ha/cycle). • C: 40 t/ha of mixed compost (50% olive husk + 30% horse manure + 20% poultry manure) + mixed compost extract + codahumus 20. • CM: 20 t/ha sheep manure + 20 t/ha mixed compost + mixed compost extract + codahumus 20.

The mixed compost was mature (>six month) and prepared from horse manure, poultry manure and olive husk at the composting unit of the Technical Center of Organic Agriculture, Chott Mariem, Tunisia as follows: Mixed compost: 50% olive husk + 30% horse manure + 20% poultry manure. Horse manure came from extensive husbandry. The solid and dehydrated poultry manure originated from extensive husbandry on soil and was combined with the other ingredients such that the C/N ratio varied from 25 to 40 at the beginning of compost process. This is allowed by European regulation. Mixed compost was certified by ECOCERT (L’Isle Jourdain, France) before its use as soil amendment for organic crops. The most relevant characteristics of the mixed compost and sheep manure used in the experiment are shown in Table 2. The mixed compost contained 1.5% N and had low C/N ratio. Its salinity, estimated from electrical conductivity, was low. The mixed compost extract was prepared by combining mixed compost with water in an open container in a ratio of 1/5 (v/v). The mixture was stirred once and then allowed to ferment at ambient temperature for 1 week, as described by Weltzien (1992). The extract was filtered and applied immediately to the plants. Mixed compost was incorporated into the soil 1 month before planting. Codahumus 20 and mixed compost extract were applied on soil surface near the plant collar 1 month after planting and every 10 days thereafter for 2 months at rates of 40 L/ha per cycle and 0.5 L per plant respectively.

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The contribution of the fertilizer treatments in terms of macronutrient total concentrations was as follow: T (control): 1.4 kg N ha−1 , 1 kg P2 O5 ha−1 and 1.8 kg K2 O ha−1 ; C: 602.3 kg N ha−1 , 551.5 kg P2 O5 ha−1 and 467.7 kg K2 O ha−1 ; CM: 709.2 kg N ha−1 , 477.3 kg P2 O5 ha−1 and 435.4 kg K2 O ha−1 . The three fertilizer treatments differed in their macronutrient total concentration. The treatment T had the lowest N, P2 O5 and K2 O contents. C and CM fertilizer treatments had comparable N, P2 O5 and K2 O contents. 2.2. Initial physico-chemical analysis of soil, mixed compost and sheep manure Soil sampling was conducted just prior to compost amendment in February 2008. Five samples were collected from each production system plot and were taken from 0- 40 cm layer. The soil was sieved through a 2 mm mesh screen and air dried prior to analysis. Soil texture was determined by granulometry. Total calcareous material was determined using Bernard Calcimeter. Active calcareous material was determined by titration with 0.04 mol/L potassium permanganate. pH and electrical conductivity were measured in soil aqueous extract (1/5 w/v). Total N content was determined by the Kjeldahl method. Available P was determined according to the Olsen method. Exchangeable soil cations K+ , Ca2+ and Mg2+ were determined in ammonium acetate extract using a flame photometer. Soil organic matter was determined according to the Walkley and Black method. Mixed compost and sheep manure organic matter contents were determined after incineration at 600 ◦ C in a oven for 3 h. Compost and manure minerals were determined after mineralization and extraction in 1 mol/L nitric acid. 2.3. Fruit sampling Tomato fruits were hand harvested randomly from the rows and from the middle of each plant at the red-ripe stage. A sample of at least 2 kg of visually selected injury free red-ripe tomato fruits was harvested from each cv and fertilizer combination treatment, and delivered quickly to the laboratory. Tomato fruits were washed, cut into small pieces and ice-cold homogenized in a mixer (Braun, Kronberg, Germany). The obtained homogenates was immediately frozen at −20 ◦ C and used to determine the lycopene, total phenols and flavonoid contents, as well as the LAA and HAA within less than one week, in order to minimize the depletion of nutrients that inevitably occurs even during frozen homogenate storage (Phillips et al., 2010). 2.4. Analytical procedures 2.4.1. Determination of lycopene content Lycopene was extracted with hexane/ethanol/acetone (2/1/1 v/v/v) containing Butylated Hydroxy Toluene (BHT) and analyzed in a spectrophotometer (Cecil CE 2501, Cecil Instruments Ltd., Cambridge, England) at 503 nm as described by Fish et al. (2002). A molar extinction coefficient 17.2 × 104 was used for lycopene content determination and results were expressed in mg/kg fresh weight (fw). 2.4.2. Determination of total phenols Total phenols content was determined according to the Folin–Ciocalteu colorimetric method as modified in Eberhardt et al. (2000) and Singleton et al. (1999). Each sample (2 g) was extracted with 10 mL methanol for 24 h. 125 ␮L of this extract was diluted 1/5 (v/v) with distilled water in a test tube, 125 ␮L of Folin–Ciocalteu

reagent was added the mixture was allowed to stand for 3 min. Thereafter, 1.25 mL of 70 g/L sodium carbonate solution was added and the final volume was made up to 3 mL with distilled water. Each sample was allowed to stand for 90 min at room temperature before measurement at 760 nm against a blank in a spectrophotometer (Cecil CE 2501). The linear reading of standard curve was from 0 to 300 ␮g gallic acid/mL. Results were expressed in mg gallic acid equivalent (GAE)/g fw.

2.4.3. Determination of flavonoid content The flavonoid content was determined as described by Zhishen et al. (1999) on aliquots of the homogenous suspension (0.3 g). Fifty microliter aliquots of the methanolic extract were used for flavonoids determination. Samples were diluted with distilled water to a final volume of 0.5 mL, and 30 ␮L of 5% NaNO2 was added. After 5 min, 60 ␮L of 10% AlCl3 was added and finally 200 ␮L of 1 M NaOH was added after 6 min. The absorbance was read at 510 nm in a spectrophotometer (Cecil CE 2501) and flavonoid content was expressed as mg rutin equivalent (RE)/g fw.

2.4.4. Lipophilic and hydrophilic antioxidant activity assay The measurement of LAA and HAA was performed using the trolox equivalent antioxidant capacity (TEAC) assay. The antioxidant activity was measured using the ABTS decoloration method (Pellegrini et al., 2007). The TEAC assay is standardly used for antioxidant activity assessment of fruit and vegetables, its numerous advantages consist in reproducibility, simplicity, and a good estimate of the antioxidant activity of pure compounds and complex matrices (Thaipong et al., 2006; Pellegrini et al., 2007). Lipophilic and hydrophilic antioxidants were extracted from 0.3 g homogenous suspension (three replicates) with 50% methanol or 50% acetone respectively at 4 ◦ C under constant shaking (300 rpm) for 12 h. Samples were centrifuged at 10,000 × g for 7 min and the different supernatants were recovered and used for antioxidant activity measurements. The antioxidant activities were measured at 734 nm in a spectrophotometer (Cecil CE 2501). Two different calibration curves were constructed using freshly prepared trolox solutions for LAA and HAA determinations. Values were expressed as ␮M Trolox/100 g fw. 2.5. Statistical analysis Effect of fertilizer treatments on bioactive properties and antioxidant activities of tomato cvs were assessed by analysis of variance (ANOVA). When a significant difference was detected, means were compared using the least significant difference (LSD) test (p < 0.05). All statistical analysis was performed using SAS Version 6.1 software (SAS Institute, Cary, NC, USA). Correlations were done using Pearson’s correlation coefficient (r).

3. Results 3.1. Lycopene content Lycopene contents (Fig. 1) were significantly different between studied tomato cvs grown under the different fertilizer treatments (p < 0.01). Lycopene ranged from 78.4 mg/kg fw in Rio Grande to 117.8 mg/kg fw in cv Firenze. The results also showed an interaction between cvs and fertilizer treatments (p < 0.05). Consequently, Firenze cv showed significantly higher lycopene content than cv Rio Grande just in T and C treatments. Lycopene contents recorded for the experiment were not significantly different between studied organic fertilizer treatments (p > 0.05).

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Fig. 1. Lycopene content in two tomato cvs grown under fertilizer treatments T: codahumus 20; C: 40 t/ha of mixed compost (50% olive husk + 30% horse manure + 20% poultry manure) + mixed compost extract + codahumus 20; and CM: 20 t/ha sheep manure + 20 t/ha mixed compost + mixed compost extract + codahumus 20. Values represent mean ± S.E. of four replicates.

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Fig. 4. Lipophilic antioxidant activity in two tomato cvs grown under fertilizer treatments T: codahumus 20; C: 40 t/ha of mixed compost (50% olive husk + 30% horse manure + 20% poultry manure) + mixed compost extract + codahumus 20; and CM: 20 t/ha sheep manure + 20 t/ha mixed compost + mixed compost extract + codahumus 20. Values represent mean ± S.E. of four replicates.

GAE/g fw and from 0.109 mg RE/g fw to 0.113 mg RE/g fw, respectively. 3.3. Lipophilic and hydrophilic antioxidant activity

Fig. 2. Total phenol content in two tomato cvs grown under fertilizer treatments T: codahumus 20; C: 40 t/ha of mixed compost (50% olive husk + 30% horse manure + 20% poultry manure) + mixed compost extract + codahumus 20; and CM: 20 t/ha sheep manure + 20 t/ha mixed compost + mixed compost extract + codahumus 20. Values represent mean ± S.E. of four replicates.

3.2. Total phenol and flavonoid content Total phenol and flavonoid contents of the tomato cvs Firenze and Rio Grande grown under the different fertilizer treatments are shown in Figs. 2 and 3, respectively. Total phenol and flavonoid contents recorded for the experiment were not significantly different between tomato cvs (p > 0.05) and treatments (p > 0.05). Total phenol and flavonoid ranged from 0.154 mg GAE/g fw to 0.162 mg

Fig. 3. Flavonoid content in two tomato cvs grown under fertilizer treatments T: codahumus 20; C: 40 t/ha of mixed compost (50% olive husk + 30% horse manure + 20% poultry manure) + mixed compost extract + codahumus 20; and CM: 20 t/ha sheep manure + 20 t/ha mixed compost + mixed compost extract + codahumus 20. Values represent mean ± S.E. of four replicates.

LAA and HAA values in Firenze and Rio Grande tomato cvs grown under the different fertilizer treatments are shown in Figs. 4 and 5, respectively. LAA were significantly different between studied tomato cvs (p < 0.001). LAA ranged from 123.8 ␮M Trolox/100 g fw in cv Rio Grande to 153.4 ␮M Trolox/100 g fw in cv Firenze. When fertilizers data were combined, Firenze cv showed significantly higher LAA than cv Rio Grande (p < 0.05). LAA values obtained during this study varied significantly between the studied organic fertilizer treatments (p < 0.001) and ranged from 134.4 ␮M Trolox/100 g fw to 141.7 ␮M Trolox/100 g fw. When cvs data were combined, T and CM treatments showed the highest LAA (p < 0.05). Regarding HAA, values were significantly different between studied tomato cvs (p < 0.001). HAA ranged from 81.5 ␮M

Fig. 5. Hydrophilic antioxidant activity in two tomato cvs grown under fertilizer treatments T: codahumus 20; C: 40 t/ha of mixed compost (50% olive husk + 30% horse manure + 20% poultry manure) + mixed compost extract + codahumus 20; and CM: 20 t/ha sheep manure + 20 t/ha mixed compost + mixed compost extract + codahumus 20. Values represent mean ± S.E. of four replicates.

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Trolox/100 g fw in cv Rio Grande to 101.3 ␮M Trolox/100 g fw in cv Firenze. When fertilizer data were combined, Firenze cv had significantly higher HAA than cv Rio Grande (p < 0.05). HAA recorded for the experiment varied significantly between the organic fertilizer treatments (p < 0.001). HAA ranged from 89.1 to 93.6 ␮M Trolox/100 g fw. When cvs data were combined, T and CM treatments showed the highest HAA (p < 0.05). In this study, total antioxidant activity (LAA + HAA) ranged from 205.3 ␮M Trolox/100 g fw in cv Rio Grande in C fertilizer treatment to 254.7 ␮M Trolox/100 g fw in cv Firenze in CM treatment. In general, LAA accounted for 60% of the total antioxidant activity in the red ripe stage of fruit maturity.

Table 3 Pearson correlation coefficients (r) and related significance between antioxidant content and antioxidant activities; n (sample size) = 24; ns = no significant correlation.

4. Discussion

concentration and C and CM were comparable, higher LAA values were obtained during this study in T and CM treatments. This is probably due to the presence of other lipophilic compounds apart from lycopene produced by plants which are likely related to the dynamic biological properties of the soil ecosystem. In this context, Flores et al. (2009) showed that treatments with organic or mineral fertilizers did not affect the pepper antioxidant activity. The lipophilic antioxidant activity accounted for 60% of the total antioxidant activity. Similar proportions (51–58%) were previously found by Ilahy et al. (2009) in different tomato cvs grown conventionally in open field. Moreover, Takeoka et al. (2001) and George et al. (2004) reported higher antioxidant activity in the tomato hexane fraction containing lycopene than the methalonic fraction. The ratio between lipophilic and hydrophilic antioxidant activity in tomato depends on fruit maturity. However, it depends also on other factors as season of culture. Ilic´ et al. (2009) reported that in tomatoes this ratio (lipophilic and hydrophilic) changed from approximately from 1:1.5 in mature green fruit to 1:1 in light red fruit. In our experiment, this ratio was 1:0.7 in the red ripe stage of fruit maturity. A similar ratio was previously found by Takeoka et al. (2001), George et al. (2004) and Ilahy et al. (2009) in open field tomato Considering the data from all tomato cvs and combined fertilizer treatments, significant correlation between LAA values and lycopene content (r = 0.45; p < 0.05) was obtained (Table 3). These results showed that LAA of organic tomato is particularly attributed to the presence of lycopene, in agreement with this well recognised fact in conventional tomato (Raffo et al., 2002; Cano et al., 2003; Toor et al., 2005; Ilahy et al., 2011b). For total phenol content, values are comparable with those reported by Riahi et al. (2009a) (0.15–0.17 mg GAE/g fw). However, they are lower than those obtained by Aldrich et al. (2010) ranging from 0.6 to 0.9 mg GAE/g fw for organically grown tomatoes. In this experiment, the obtained values are close to the range reported by George et al. (2004) (0.07–0.22 mg GAE/g fw) and Brat et al. (2006) (0.14 mg GAE/g fw) for conventional tomato. In tomato fruits, flavonoids represent the major component of the total phenol content (Toor et al., 2005). In this study, the flavonoid values are close to the range found in tomato cvs grown in conventional systems by Ilahy et al. (2009) (0.106–0.512 mg RE/g fw). Total phenol and flavonoid contents in Firenze cv are similar to those found in cv Rio Grande, which confirms the findings of Riahi et al. (2009a) in organic system. However, our result disagrees with those found by other authors who reported that variety affects total phenols in organic tomatoes (Aldrich et al., 2010). Total phenol and flavonoid contents were not significantly different between the studied organic fertilizer treatments. This is in agreement with the results previously found by Zhao et al. (2007) for organic lettuce and Toor et al. (2006) for conventional tomatoes. The role of organic nutrient sources in production of plant total phenols and flavonoids is now unclear, but our results support the current evidence which suggests that factors other than nutrition may be primarily involved (Rosen and Allan, 2007; Riahi et al., 2009b),

In this study, the organic tomato cvs showed normal to high lycopene contents, comparable to those grown in previous years in conventional field tomato (Hdider et al., 2007) ranging from 44.7 to 87.6 mg/kg fw. The reported values are close to the range previously published for field grown organic tomatoes by PerkinsVeazie (2007) (49.5–106.5 mg/kg fw) and Riahi et al. (2009a) (76.9–119.4 mg/kg fw). However, they are higher than those found by Caris-Veyrat et al. (2004) for organic tomatoes grown in a plastic tunnel ranging from 36 to 42 mg/kg fw. Field-grown tomatoes generally present higher levels of lycopene (Lenucci et al., 2006). These results confirm that organic tomato can achieve satisfactory lycopene content as suggested by Perkins-Veazie (2007). The results also showed that Firenze cv had generally higher lycopene content than the cv Rio Grande and confirm that genotype significantly affects lycopene content in organic tomato as reported by Perkins-Veazie (2007) and Riahi et al. (2009b). Lycopene content was not significantly different between organic fertilizer treatments. These results are in line with those of Toor et al. (2006) showing that treatments with chicken manure or Grass-clover mulch did not significantly affect tomato lycopene content. However, that study was conducted under greenhouse conditions and was not within an organic production system. Differences in the content of lycopene are much higher depending on the maturity stage and year of production rather than differences between fertilization. Ilahy et al. (2011a) reported that lycopene content changes significantly during maturation and accumulates mainly in the deep red stage. Moreover, Garcia and Barrett (2006) reported that temperature greater than 32.2 ◦ C during the growing season result in smaller lycopene concentrations in tomatoes and concluded that growing season or year and growing location are highly significant factors affecting the lycopene concentration in tomatoes. Several authors have studied LAA and HAA in conventional tomato (George et al., 2004; Lenucci et al., 2006; Ilahy et al., 2009). However, little information is known concerning these antioxidant activities and their correlation with phytochemical compounds in organic tomato. LAA values obtaining in this study are comparable with those previously reported by Ilahy et al. (2009) (137.3 ␮M Trolox/100 g fw) for field-grown conventionally tomato cv. However, they are higher than those found by Cano et al. (2003) and Raffo et al. (2006) ranging between 26 and 88 ␮M Trolox/100 g fw for different cvs grown under greenhouse conditions. Field-grown tomatoes generally present higher levels of LAA than those grown under greenhouse. This can be due to the high levels of antioxidants present in the lipophilic fraction. The differences in LAA between cvs are in agreement with those found by Lenucci et al. (2006) and Ilahy et al. (2009) and are mainly due to genotypic factors. As expected, due to its higher amount of detected lycopene, Firenze cv showed a higher LAA than cv Rio Grande. Despite the fact that the T fertilizer treatment had the lowest macronutrient total

Compounds

TEAC assay r

p

Lycopene

LAA 0.45 HAA

<0.05

Total phenolics Flavonoids

0.13 0.17

ns ns

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including environmental stresses, such as pathogen pressures in organic system (Young et al., 2005). Regarding HAA, the obtained values are slightly lower than those obtained by Ilahy et al. (2009) in conventional tomato cv (129.1 ␮M Trolox/100 g fw). The higher HAA values came from Firenze cv, confirms the influence of genotype on hydrophilic antioxidant activity as reported by George et al. (2004) for conventionally grown tomatoes. Higher HAA values were recorded during this study in T and CM treatments. As for LAA, this is probably due to the presence of other hydrophilic compounds apart from phenols and flavonoids produced by plants which are likely related to soil ecosystem properties. Flores et al. (2009) also found no difference in hydrophilic antioxidant activity between organic and mineral fertilized pepper. Considering our data, no significant correlations between HAA values and total phenol (r = 0.13; p > 0.05) or flavonoid contents (r = 0.17; p > 0.05) were found (Table 3). Recently, similar result was reported for tomato by Ilahy et al. (2011b) in conventional system. This may be due to the fact that hydrophilic extract contains other compounds that influence the organic tomato antioxidant activity. Kahkonen et al. (1999) reported that the antioxidant capacity might not always correlate with the amount of phenols. HAA can also depend on synergistic effect among all hydrophilic antioxidants and their interactions with other constituents of the fraction (Jiménez et al., 2002; Lenucci et al., 2006). The total antioxidant activity values found in this study are higher than those found by Aldrich et al. (2010) ranging from 122.2 to 196.7 ␮M Trolox/100 g fw for organically grown tomato cvs. These differences in total antioxidant activity are mainly due to genotypic or/and environmental agricultural factors. However, the values are comparable to those reported by Ilahy et al. (2009) (266.4 ␮M Trolox/100 g fw) for conventionally grown tomato who also found that lipophilic antioxidant activity represented 51–58% of the total antioxidant activity in the evaluated tomato cultivars. 5. Conclusion Although the limited biological variability (just one year sampling) is taken into account in this study, it gives a general but defined idea of the trends of antioxidant capability in two tomato cvs grown organically under different fertilizer combinations. In all fertilizer treatments, Firenze cv had a higher level of lycopene in comparison to the cv Rio Grande. This also correlated with its high LAA. The results also showed that T and CM fertilizer treatments can promote organic tomato antioxidant activity. This experiment will be repeated in future years to confirm these results and to investigate if there is a gradual improvement in organic tomato quality as organic matter accrues and builds soil fertility. Acknowledgement The authors wish to thank the Institution for Agricultural Research and Higher Education and Ministry of Higher Education and Scientific Research for their financial support. References Aldrich, H., Salandanan, K., Kendall, P., Bunning, M., Stonaker, F., Külen, O., Stushnoff, C., 2010. Cultivar choice provides options for local organic and conventional production of more nutritious tomatoes. J. Sci. Food Agric. 90 (15), 2548–2555. Brat, P., Georgé, S., Bellamy, A., Du Chaffaut, L., Scalbert, A., Mennen, L., Arnault, N., Amiot, M.J., 2006. Daily polyphenol intake in France from fruit and vegetables. J. Nutr. 136, 2368–2373. Cano, A., Acosta, M., Arnao, M.B., 2003. Hydrophylic and lipophylic antioxidant activity changes during on-vine ripening of tomatoes (Lycopersicon esculentum Mill.). Postharvest Biol. Technol. 28 (1), 59–65. Caris-Veyrat, C., Amiot, M.J., Tyssandier, V., Grasselly, D., Buret, M., Mikolajczak, M., Guilland, J.C., laude, G.J., Bouteloup-Demange, C., Borel, P., 2004. Influence of organic versus conventional agriculture practice on the antioxidant

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