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Effects of gamma irradiation on the yields of volatile extracts of Angelica gigas Nakai
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Radiation Physics and Chemistry 76 (2007) 1869–1874 www.elsevier.com/locate/radphyschem
Effects of gamma irradiation on the yields of volatile extracts of Angelica gigas Nakai Hye-Young Seoa, Jun-Hyoung Kima, Hyun-Pa Songb, Dong-Ho Kimb, Myung-Woo Byunb, Joog-Ho Kwonc, Kyong-Su Kima, a Department of Food and Nutrition, Chosun University, Gwangju 501-759, Republic of Korea Radiation Food Science and Biotechnology Team, Korea Atomic Energy Research Institute, Daejeon 305-353, South Korea c Department of Food Science & Technology, Kyungpook National University, Daegu 702-701, Republic of Korea
b
Received 27 December 2006; accepted 7 March 2007
Abstract The study was carried out to determine the effects of gamma irradiation on the volatile flavor components including essential oils, of Angelica gigas Nakai. The volatile organic compounds from non- and irradiated A. gigas Nakai at doses of 1, 3, 5, 10 and 20 kGy were extracted by a simultaneous steam distillation and extraction (SDE) method and identified by GC/MS analysis. A total of 116 compounds were identified and quantified from non- and irradiated A. gigas Nakai. The major volatile compounds were identified 2,4,6trimethyl heptane, a-pinene, camphene, a-limonene, b-eudesmol, a-murrolene and sphatulenol. Among these compounds, the amount of essential oils in non-irradiated sample were 77.13%, and the irradiated samples at doses of 1, 3, 5, 10 and 20 kGy were 84.98%, 83.70%, 83.94%, 82.84% and 82.58%, respectively. Oxygenated terpenes such as b-eudesmol, a-eudesmol, and verbenone were increased after irradiation but did not correlate with the irradiation dose. The yields of active substances such as essential oil were increased after irradiation; however, the yields of essential oils and the irradiation dose were not correlated. Thus, the profile of composition volatiles of A. gigas Nakai did not change with irradiation. r 2007 Elsevier Ltd. All rights reserved. Keywords: Angelica gigas Nakai; Gamma irradiation; Volatile components
1. Introduction Despite tremendous advances in modern medicine, plants continue to make important contributions to health care as witnessed by the increasing interest in alternative therapies (Rates, 2001). However, raw plant materials, normally carry a high bioburden due to their origins and as a result present potential hazards to consumers. During the harvesting, processing, storage and their distribution, medicinal herbs are also subject to deterioration from chemical and microbial processes. Thus, the use of a safe decontamination methodology would be an important step towards the consumer safety as well as therapeutic efficacy. The conventional method of decontamination has been fumigation with gaseous ethylene oxide, which is a process Corresponding author. Tel.: +82 62 230 7724; fax: +82 62 224 8880.
E-mail address: [email protected] (K.-S. Kim). 0969-806X/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2007.03.020
that is prohibited or increasingly restricted in many countries because of associated health hazards (Loaharanu, 1990; Dickman, 1991; Uiji, 1992). Consequently, safe alternative hygienic technologies are demanded. Various disinfectant technologies have been suggested and include electromagnetic radiation, photo-dynamic pulsing, ultrahigh pressure, and CO2 treatment. The highest expectations, however, are placed on the developments of irradiation as new food sanitation and processing method (Mertens and Knorr, 1992). The effect of gamma irradiation on the hygienic quality and extraction yields for numerous components of several medicinal herbs has been studied and reported that irradiation is effective method for microbiological decontamination of them, and the content of essential biologically active substances and pharmacological activity of medicinal herbs not change significantly with irradiation (Yook et al., 1998; Byun et al., 1999; Kim et al., 2000; Yu and Jo, 2000;
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Owczarczyk et al., 2000; Yu et al., 2004). But chromatographic analysis of some herbal extracts indicated that changes in total yield and constituents of volatile oil following irradiation were ranged from none to slight depending upon dose-based irradiation in variety of herbs (IAEA, 1992; Venskutonis et al., 1996; Chatterjee et al., 2000). It can be assumed, therefore, that the dose which can be applied and hence extent to the microbial kill may be limited by undesirable changes in volatile oil constituents, their yield and flavor quality. In this view, we assessed the stability of the active components of Angelica gigas Nakai, Danggui in Korean, after gamma irradiation. A. gigas Nakai of the Family Umbelliferae is a well-known source of oriental drugs used for the treatment of gynecological diseases (Ahn et al., 1996; Yook, 1990; Han et al., 1998). The major active components of A. gigas Nakai are the essential oil (a-pinene, limonene, b-eudesmol, and elemol) and coumarins (decursin and decursinol angelate) (Yun, 1995). A recent study on the safety of gamma-irradiated (10 kGy) danggui showed that the HPLC chromatograms of decursin and decursinol angelate in gamma-irradiated danggui were similar with those of non-irradiated sample (Yu and Jo, 2000). However, no reports are available about the effect of gamma irradiation on volatile compounds of danggui so far. The present study was undertaken to determine the possible changes in essential oils of A. gigas Nakai as a result of gamma irradiated. 2. Materials and methods 2.1. Materials A. gigas Nakai (Danggui) at the presterilization stage were purchased from a local retail shop. For gamma irradiation, lots (100 g) of the samples were vacuum packed and then irradiated with the following doses: 1, 3, 5, 10, and 20 kGy at 1271 1C using a cobalt 60 gamma-irradiator (Point source, AECL, IR-79, Nordion International Co. Ltd., Ottawa, Ont., Canada) at the Korea Atomic Energy Research Institute. The dose rate was 2.5 kGy/h with a dose rate error of 70.02 kGy. Absorbed doses were monitored with either a radical, or a ceric-cerous, dosimeter. The irradiated and non-irradiated control samples were stored at 18 1C until required for the experiments.
2.3. Extraction of volatile compounds from A. gigas Nakai Fifty gram samples were taken each time and homogenized in a blender (MR 350CA, Braun, Spain) and mixed with 1 L distilled water. By maintaining the pH at 6.5, the resultant slurry was used for the quantitative analysis with 1 mL of n-butyl benzene added as an internal standard. The essential oils were extracted for 2 h with 200 mL redistilled n-pentane/diethyl ether (1:1, v/v) mixture using a simultaneous steam distillation and extraction (SDE, Likens & Nickerson type) apparatus as modified by Schultz et al. (Nikerson and Likens, 1966; Schultz et al., 1977) under the atmospheric pressure. The extract was dehydrated for 12 h over anhydrous sodium sulfate and concentrated to final volume approximately 1.5 mL using a Vigreux column. This sample was finally used for the GC/MS analyses. 2.4. Analysis and identification of volatile compounds by GC/MS Shimadzu GC/MS QP-5000 (Kyoto, Japan) in the electron impact (EI) mode was used for the quantitative analysis. The ionization voltage and temperature of injector and ion source were 70 eV, 250 and 230 1C, respectively. The mass spectrometer scanned from 41 to 350 m/z. A DB-WAX capillary column (60 m 0.25 mm i.d., 0.25 mm film thickness, J&W, USA) was used for the separation. The oven temperature was programmed as: 40 1C (isothermal for 3 min) which was ramped to 150 1C at 2 1C/min and then to 200 1C at 4 1C/min (isothermal for 20 min). Helium was used as the carrier gas at a flow rate of 1.0 mL/min with an injector volume of 1 mL using a 1:20 split ratio. Mass spectra were identified with the aid of our own mass spectral data and those contained within the WILEY 139, NIST 62 and NIST 12 libraries and mass spectral data books (Sadtler, 1986; Davies, 1990) as well as by the comparison of retention indices to reference data (Stehagen et al., 1974; Robert, 1995). The resultant slurry was used for the quantitative analysis with 1 mL of n-butyl benzene added as an internal standard: Component content ðmg=kg of DangguiÞ ¼
C 1000 g , A Bg
where A is the peak area% of each sample of internal standard, B is the amount of sample, and C is the peak area% of each component in sample.
2.2. Reagents 3. Results and discussion All the reagents used in the experiments were purchased from Sigma Co. (USA) and Fisher Scientific (USA). The organic solvents used for the extraction and chromatography were redistilled using a wire spiral packed double-distilling apparatus (Normschliff Geratebau, Wertheim, Germany) and Milli-Q water that was generated with a water purification system (Millipore Corporation, Bedford, USA).
3.1. Volatile compounds of non- and irradiated A. gigas Nakai The volatile compounds were extracted from the nonand irradiated A. gigas Nakai, plants using the SDE method and identified by GC/MS. The GC/MS chromatograms are shown in Fig. 1.
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Fig. 1. GC/MS chromatograms of volatile components in non- and irradiated Angelica gigas Nakai.
A total of 116 compounds were identified and quantified both from non- and irradiated samples and included 40 hydrocarbons, 35 alcohols, 15 esters, 12 aldehydes, 8 ketones, and 6 miscellaneous. The relative peak area% was different in each sample. The amount of volatile oils in non-irradiated A. gigas Nakai was obtained 0.313% yield, and in irradiated samples at dose of 1, 3, 5, 10, and 20 kGy were obtained at 0.314%, 0.313%, 0.310%, 0.312%, and 0.290%, respectively. The yields of volatile oils from nonand irradiated samples (up to 10 kGy) were not different. However, the yields from the irradiated sample at highest dose decreased slightly. a-Pinene was the dominant volatile compound in both non- and irradiated A. gigas Nakai samples, while the terpenoids (camphene, a-limonene, b-eudesmol, a-murrolene, and sphatulenol) were relatively more abundant than all other compounds. These results were similar to other studies on the volatile compounds of A. gigas Nakai and A. acutiloba Kitagawa (Cho et al., 2003). 2,4,6-Trimethyl heptane (13.39%) was especially abundant in the nonirradiated A. gigas Nakai. This compound is considered to originate from root and has no identifiable flavor characteristic. Marin et al. (2002) reported that 2,4,6trimethyl heptane is a pyrolysis products of cellulose, lignin, beech, and pine tree. 2,4,6-Trimethyl heptane content was decreased about 6% after irradiation, but their proportions were variable in a dose-dependent manner. The content of some compounds related to same chemical group were decreased at different doses of gamma irradiation by various proportions. The variations in content of the constituents upon gamma irradiation were observed in the present study could presumably be due to the radiation sensitivity of compounds with the dose employed. Such type of results has indeed been documented previously on the volatile compounds of irradiated herbs (IAEA, 1992; Variyar et al., 1998; Chatterjee et al., 2000; Gyawali et al., 2006). Minor components also identified were (E)-r-2-menthen1-ol, pinocarveol, verbenone, cuminol and a-eudesmol. These compounds have the flavor characteristics of wood, pine, turpentine, flower (Flavornet, 2005).
Table 1 Relative content of functional groups in identified volatile components from control and irradiated Angelica gigas Nakai (unit; peak area%) Functional group No. Irradiation dose (kGy) 0 Hydrocarbons Aldehydes Ketones Esters Alcohols Miscellaneous Total
40 12 8 15 35 6
66.58 1.92 3.65 3.38 23.35 1.12
116 100
1 52.80 2.61 5.41 3.82 33.72 1.64 100
3 56.39 2.40 4.82 3.67 31.26 1.46 100
5 59.43 2.42 4.64 3.65 28.57 1.29 100
10 58.43 2.50 4.60 3.89 29.22 1.36 100
20 58.83 2.53 4.56 3.89 28.94 1.25 100
The relative areas obtained for each functional group in non-irradiated A. gigas Nakai were hydrocarbons (66.58%), alcohols (23.35%), esters (3.38%), aldehydes (1.92%), ketones (3.65%), and miscellaneous (1.12%) (Table 1). The content of hydrocarbons in irradiated samples at dose of 1, 3, 5, 10 and 20 kGy were 52.80%, 56.39%, 59.43%, 58.43% and 58.83%, respectively, below the 60% of the non-irradiated sample. The contents of alcohols in irradiated samples increased about 6% compared to control (about 23.35-31.14%), and were not significantly different with different irradiation dose. The contents of other functional groups in non- and irradiated samples were equivalent. 3.2. Comparison of essential oils in non- and irradiated A. gigas Nakai Essential oils of plants and their other products from secondary metabolism have had a great usage in folk medicines, food flavorings, fragrances, and the pharmaceutical industries (Satil et al., 2003; Kusmenoglu et al., 1995). Some of the biological activities of the essential oils have been known for long time (Digrak et al., 1999; Pattnaik et al., 1997; Dang et al., 2001; Grassmann et al., 2000). The percentage composition of the essential oils
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Table 2 Comparison of relative concentration by terpenoid groups in Angelica gigas Nakai (unit; peak area%) Functional group
No.
Irradiation dose (kGy) 0
1
3
5
10
20
Monoterpenes (C10)
Monoterpenes Oxygenated monoterpenes
25 9
44.14 15.75
38.30 20.26
41.05 18.93
44.68 18.26
42.66 18.11
42.46 17.66
Sesquiterpenes (C15)
Sesquiterpenes Oxygenated sesquiterpenes
30 12
4.03 13.21
5.34 21.08
4.56 19.16
4.24 16.76
4.41 17.66
4.75 17.71
Total
76
77.13
84.98
83.7
83.94
82.84
82.58
Table 3 Composition of major compounds identified in the essential oils from non- and irradiated Angelica gigas Nakai (unit; peak area%) RIa
888 1029 1067 1198 1269 1569 1661 1686 1714 1729 1854 2136 2189 2238 2250 a
Compound name
2,4,6-Trimethyl heptane a-Pinene Camphene a-Limonene r-Cymene (E)-r-2-Menthen-1-ol Pinocarveol Vervenol Verbenone a-Murrolene r-Cuminol Sphatulenol 2-Hydroxycyclopentadecanone a-Eudesmol b-Eudesmol
Irradiation dose (kGy) 0
1
3
5
10
20
13.39 30.89 4.10 4.29 1.07 1.17 1.22 2.15 1.44 1.52 1.07 1.85 1.56 1.90 5.01
6.61 24.61 4.27 4.86 1.15 1.72 1.48 3.19 1.77 2.30 1.39 2.36 2.84 2.88 8.22
7.97 26.33 4.44 4.87 1.19 1.46 1.40 3.05 1.77 1.87 1.33 1.95 2.33 2.72 8.02
7.74 28.94 5.11 5.53 1.19 1.56 1.37 2.91 1.81 1.67 1.27 1.50 2.07 2.35 7.17
8.38 27.40 4.88 5.44 1.24 1.31 1.42 2.69 1.77 1.83 1.20 1.81 2.08 2.35 7.25
8.59 27.12 4.94 5.43 1.28 1.23 1.33 2.22 1.73 1.90 1.25 1.80 2.06 2.36 7.25
Retention index.
probably provides the most important measure for the characterization of the respective plant (Paula and Manuel, 2001). The essential oil groups of the volatile compounds identified in A. gigas are shown in Table 2. Monoterpene hydrocarbons represent the larger fraction of the A. gigas Nakai root oil constituents (Table 2). The difference in odor of the Angelica root oils can be attributed to the compositional differences of the volatiles, especially in the relative amounts of various monoterpene hydrocarbons (Forsen, 1979). The high number of different monoterpene compounds is assumed to indicate a high quality of the oil aroma (Kerrola et al., 1994). Twenty-five kinds of monoterpene hydrocarbons including a-pinene, a-limonene, camphene, r-cymene, b-pinene, b-myrcene, and alloocimene were identified in all samples studied with the main component being a-pinene. The content of this group tended to decrease (41.83% from 44.14%) after gamma irradiation, a result caused by the reduction of a-pinene contents (Table 3). a-Limonene was the second most abundant component among the monoterpene hydrocarbons and its content tended to increase from 4.29% to 5.2370.33% after gamma irradiation.
The content of r-cymene also was increased after irradiation (1.07-1.2170.5%). The response of compounds for irradiation was found variable (Table 3). Sesquiterpene hydrocarbons represented 4.03% of all volatiles in A. gigas Nakai. The amount of sesquiterpene hydrocarbons in the irradiated samples exceeded 4.24%, and was greater than that determined in the non-irradiated sample. Nine kinds of sesquiterpenes were confirmed, with a-murrolene, g-elemene, and d-cadinene the primary components. These compounds had a tendency to increase following gamma irradiation. Oxygenated compounds of the terpene hydrocarbons confer special characteristics to the A. gigas Nakai root oil, such as particular odors and stability (Doneanu and Antiescu, 1998). The percentage of oxygenated terpenes in non- and irradiated samples at doses of 1, 3, 5, 10 and 20 kGy were 28.96, 41.34, 38.09, 35.02, 34.77 and 35.37%, respectively, and increased after irradiation (Table 2). Among these oxygenated terpenes, the amount of oxygenated sesquiterpenes was increased more than the oxygenated monoterpenes. These results agree with the study of Farag et al. (1995) that reported terpenes were
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converted to monoterpe-nesalcohols. b-Eudesmol, an oxygenated monoterpenes, was the major compound in this group, while verbenol, a-eudesmol, verbenone, and (E)-r2-menthen-1-ol were also detected. The a- and b-eudesmol were increased to 9.52% from 6.91%, with no major variation between the different irradiation doses. The remaining oxygenated terpene levels also did not vary significantly during irradiation. The yields of essential oils were increased 5–7% after irradiation, a result similar to that reported by Kim et al. (2000). Also, the profile of volatile components including the essential oils of A. gigas Nakai did not change significantly with irradiation and the content of volatiles did not differ from non- and irradiated samples. The results observed in this study agree with quantity of paeoniflorin in Paeoniae radix, i.e. no change with irradiation as cited by Yu et al. (2004). In addition, Owczarczyk et al. (2000) have reported that the content of biologically active substances, including the essential oils, flavonoids, glycosides, anthocyanins, and plants mucus did not change significantly after irradiation. 4. Conclusion In conclusion, the total yields of volatile compounds in A. gigas Nakai were not changed after irradiation, although the yields of essential oils were increased 5–7%. The major components of A. gigas Nakai were a-pinene, camphene, a-limonene, b-eudesmol, a-eudesmol, a-murrolene, and sphatulenol. Among the essential oils, oxygenated terpenes such as b-eudesmol, a-eudesmol, and verbenone were increased after irradiation, but their proportions were variable in a dose-dependent manner. The composition of volatiles in A. gigas Nakai was not significantly changed by irradiation. These results further support the notion that gamma irradiation process is chemically inert, and could be used the basis for the sterilization of medicinal herbs. Acknowledgements This study was supported by research funds from Chosun University, 2005. References Ahn, K.S., Sim, W.S., Kim, H.M., Han, S.B., Kim, I.H., 1996. Immunostimulating components from the root of Angelica gigas Nakai. Kor. J. Pharmacogn. 27, 254–261. Byun, M.W., Yook, H.S., Kim, K.S., Chung, C.K., 1999. Effects of gamma irradiation on physiological effectiveness of Korean medicinal herbs. Radiat. Phys. Chem. 54, 291–300. Chatterjee, S., Variyar, P.S., Gholap, A.S., Pudwal-Desai, S.R., Bongirwar, D.R., 2000. Effect of g-irradiation on the volatile oil constituents of turmeric (Curcuma longa). Food Res. Int. 33, 103–106. Cho, M.G., Bang, J.K., Chae, Y.A., 2003. Comparison of volatile compounds in plant parts of Angelica gigas Nakai and A. acutiloba Kitagawa. Korean J. Med. Crop Sci. 11, 352–357.
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Radiation Physics and Chemistry 76 (2007) 1869–1874 www.elsevier.com/locate/radphyschem
Effects of gamma irradiation on the yields of volatile extracts of Angelica gigas Nakai Hye-Young Seoa, Jun-Hyoung Kima, Hyun-Pa Songb, Dong-Ho Kimb, Myung-Woo Byunb, Joog-Ho Kwonc, Kyong-Su Kima, a Department of Food and Nutrition, Chosun University, Gwangju 501-759, Republic of Korea Radiation Food Science and Biotechnology Team, Korea Atomic Energy Research Institute, Daejeon 305-353, South Korea c Department of Food Science & Technology, Kyungpook National University, Daegu 702-701, Republic of Korea
b
Received 27 December 2006; accepted 7 March 2007
Abstract The study was carried out to determine the effects of gamma irradiation on the volatile flavor components including essential oils, of Angelica gigas Nakai. The volatile organic compounds from non- and irradiated A. gigas Nakai at doses of 1, 3, 5, 10 and 20 kGy were extracted by a simultaneous steam distillation and extraction (SDE) method and identified by GC/MS analysis. A total of 116 compounds were identified and quantified from non- and irradiated A. gigas Nakai. The major volatile compounds were identified 2,4,6trimethyl heptane, a-pinene, camphene, a-limonene, b-eudesmol, a-murrolene and sphatulenol. Among these compounds, the amount of essential oils in non-irradiated sample were 77.13%, and the irradiated samples at doses of 1, 3, 5, 10 and 20 kGy were 84.98%, 83.70%, 83.94%, 82.84% and 82.58%, respectively. Oxygenated terpenes such as b-eudesmol, a-eudesmol, and verbenone were increased after irradiation but did not correlate with the irradiation dose. The yields of active substances such as essential oil were increased after irradiation; however, the yields of essential oils and the irradiation dose were not correlated. Thus, the profile of composition volatiles of A. gigas Nakai did not change with irradiation. r 2007 Elsevier Ltd. All rights reserved. Keywords: Angelica gigas Nakai; Gamma irradiation; Volatile components
1. Introduction Despite tremendous advances in modern medicine, plants continue to make important contributions to health care as witnessed by the increasing interest in alternative therapies (Rates, 2001). However, raw plant materials, normally carry a high bioburden due to their origins and as a result present potential hazards to consumers. During the harvesting, processing, storage and their distribution, medicinal herbs are also subject to deterioration from chemical and microbial processes. Thus, the use of a safe decontamination methodology would be an important step towards the consumer safety as well as therapeutic efficacy. The conventional method of decontamination has been fumigation with gaseous ethylene oxide, which is a process Corresponding author. Tel.: +82 62 230 7724; fax: +82 62 224 8880.
E-mail address: [email protected] (K.-S. Kim). 0969-806X/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2007.03.020
that is prohibited or increasingly restricted in many countries because of associated health hazards (Loaharanu, 1990; Dickman, 1991; Uiji, 1992). Consequently, safe alternative hygienic technologies are demanded. Various disinfectant technologies have been suggested and include electromagnetic radiation, photo-dynamic pulsing, ultrahigh pressure, and CO2 treatment. The highest expectations, however, are placed on the developments of irradiation as new food sanitation and processing method (Mertens and Knorr, 1992). The effect of gamma irradiation on the hygienic quality and extraction yields for numerous components of several medicinal herbs has been studied and reported that irradiation is effective method for microbiological decontamination of them, and the content of essential biologically active substances and pharmacological activity of medicinal herbs not change significantly with irradiation (Yook et al., 1998; Byun et al., 1999; Kim et al., 2000; Yu and Jo, 2000;
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Owczarczyk et al., 2000; Yu et al., 2004). But chromatographic analysis of some herbal extracts indicated that changes in total yield and constituents of volatile oil following irradiation were ranged from none to slight depending upon dose-based irradiation in variety of herbs (IAEA, 1992; Venskutonis et al., 1996; Chatterjee et al., 2000). It can be assumed, therefore, that the dose which can be applied and hence extent to the microbial kill may be limited by undesirable changes in volatile oil constituents, their yield and flavor quality. In this view, we assessed the stability of the active components of Angelica gigas Nakai, Danggui in Korean, after gamma irradiation. A. gigas Nakai of the Family Umbelliferae is a well-known source of oriental drugs used for the treatment of gynecological diseases (Ahn et al., 1996; Yook, 1990; Han et al., 1998). The major active components of A. gigas Nakai are the essential oil (a-pinene, limonene, b-eudesmol, and elemol) and coumarins (decursin and decursinol angelate) (Yun, 1995). A recent study on the safety of gamma-irradiated (10 kGy) danggui showed that the HPLC chromatograms of decursin and decursinol angelate in gamma-irradiated danggui were similar with those of non-irradiated sample (Yu and Jo, 2000). However, no reports are available about the effect of gamma irradiation on volatile compounds of danggui so far. The present study was undertaken to determine the possible changes in essential oils of A. gigas Nakai as a result of gamma irradiated. 2. Materials and methods 2.1. Materials A. gigas Nakai (Danggui) at the presterilization stage were purchased from a local retail shop. For gamma irradiation, lots (100 g) of the samples were vacuum packed and then irradiated with the following doses: 1, 3, 5, 10, and 20 kGy at 1271 1C using a cobalt 60 gamma-irradiator (Point source, AECL, IR-79, Nordion International Co. Ltd., Ottawa, Ont., Canada) at the Korea Atomic Energy Research Institute. The dose rate was 2.5 kGy/h with a dose rate error of 70.02 kGy. Absorbed doses were monitored with either a radical, or a ceric-cerous, dosimeter. The irradiated and non-irradiated control samples were stored at 18 1C until required for the experiments.
2.3. Extraction of volatile compounds from A. gigas Nakai Fifty gram samples were taken each time and homogenized in a blender (MR 350CA, Braun, Spain) and mixed with 1 L distilled water. By maintaining the pH at 6.5, the resultant slurry was used for the quantitative analysis with 1 mL of n-butyl benzene added as an internal standard. The essential oils were extracted for 2 h with 200 mL redistilled n-pentane/diethyl ether (1:1, v/v) mixture using a simultaneous steam distillation and extraction (SDE, Likens & Nickerson type) apparatus as modified by Schultz et al. (Nikerson and Likens, 1966; Schultz et al., 1977) under the atmospheric pressure. The extract was dehydrated for 12 h over anhydrous sodium sulfate and concentrated to final volume approximately 1.5 mL using a Vigreux column. This sample was finally used for the GC/MS analyses. 2.4. Analysis and identification of volatile compounds by GC/MS Shimadzu GC/MS QP-5000 (Kyoto, Japan) in the electron impact (EI) mode was used for the quantitative analysis. The ionization voltage and temperature of injector and ion source were 70 eV, 250 and 230 1C, respectively. The mass spectrometer scanned from 41 to 350 m/z. A DB-WAX capillary column (60 m 0.25 mm i.d., 0.25 mm film thickness, J&W, USA) was used for the separation. The oven temperature was programmed as: 40 1C (isothermal for 3 min) which was ramped to 150 1C at 2 1C/min and then to 200 1C at 4 1C/min (isothermal for 20 min). Helium was used as the carrier gas at a flow rate of 1.0 mL/min with an injector volume of 1 mL using a 1:20 split ratio. Mass spectra were identified with the aid of our own mass spectral data and those contained within the WILEY 139, NIST 62 and NIST 12 libraries and mass spectral data books (Sadtler, 1986; Davies, 1990) as well as by the comparison of retention indices to reference data (Stehagen et al., 1974; Robert, 1995). The resultant slurry was used for the quantitative analysis with 1 mL of n-butyl benzene added as an internal standard: Component content ðmg=kg of DangguiÞ ¼
C 1000 g , A Bg
where A is the peak area% of each sample of internal standard, B is the amount of sample, and C is the peak area% of each component in sample.
2.2. Reagents 3. Results and discussion All the reagents used in the experiments were purchased from Sigma Co. (USA) and Fisher Scientific (USA). The organic solvents used for the extraction and chromatography were redistilled using a wire spiral packed double-distilling apparatus (Normschliff Geratebau, Wertheim, Germany) and Milli-Q water that was generated with a water purification system (Millipore Corporation, Bedford, USA).
3.1. Volatile compounds of non- and irradiated A. gigas Nakai The volatile compounds were extracted from the nonand irradiated A. gigas Nakai, plants using the SDE method and identified by GC/MS. The GC/MS chromatograms are shown in Fig. 1.
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Fig. 1. GC/MS chromatograms of volatile components in non- and irradiated Angelica gigas Nakai.
A total of 116 compounds were identified and quantified both from non- and irradiated samples and included 40 hydrocarbons, 35 alcohols, 15 esters, 12 aldehydes, 8 ketones, and 6 miscellaneous. The relative peak area% was different in each sample. The amount of volatile oils in non-irradiated A. gigas Nakai was obtained 0.313% yield, and in irradiated samples at dose of 1, 3, 5, 10, and 20 kGy were obtained at 0.314%, 0.313%, 0.310%, 0.312%, and 0.290%, respectively. The yields of volatile oils from nonand irradiated samples (up to 10 kGy) were not different. However, the yields from the irradiated sample at highest dose decreased slightly. a-Pinene was the dominant volatile compound in both non- and irradiated A. gigas Nakai samples, while the terpenoids (camphene, a-limonene, b-eudesmol, a-murrolene, and sphatulenol) were relatively more abundant than all other compounds. These results were similar to other studies on the volatile compounds of A. gigas Nakai and A. acutiloba Kitagawa (Cho et al., 2003). 2,4,6-Trimethyl heptane (13.39%) was especially abundant in the nonirradiated A. gigas Nakai. This compound is considered to originate from root and has no identifiable flavor characteristic. Marin et al. (2002) reported that 2,4,6trimethyl heptane is a pyrolysis products of cellulose, lignin, beech, and pine tree. 2,4,6-Trimethyl heptane content was decreased about 6% after irradiation, but their proportions were variable in a dose-dependent manner. The content of some compounds related to same chemical group were decreased at different doses of gamma irradiation by various proportions. The variations in content of the constituents upon gamma irradiation were observed in the present study could presumably be due to the radiation sensitivity of compounds with the dose employed. Such type of results has indeed been documented previously on the volatile compounds of irradiated herbs (IAEA, 1992; Variyar et al., 1998; Chatterjee et al., 2000; Gyawali et al., 2006). Minor components also identified were (E)-r-2-menthen1-ol, pinocarveol, verbenone, cuminol and a-eudesmol. These compounds have the flavor characteristics of wood, pine, turpentine, flower (Flavornet, 2005).
Table 1 Relative content of functional groups in identified volatile components from control and irradiated Angelica gigas Nakai (unit; peak area%) Functional group No. Irradiation dose (kGy) 0 Hydrocarbons Aldehydes Ketones Esters Alcohols Miscellaneous Total
40 12 8 15 35 6
66.58 1.92 3.65 3.38 23.35 1.12
116 100
1 52.80 2.61 5.41 3.82 33.72 1.64 100
3 56.39 2.40 4.82 3.67 31.26 1.46 100
5 59.43 2.42 4.64 3.65 28.57 1.29 100
10 58.43 2.50 4.60 3.89 29.22 1.36 100
20 58.83 2.53 4.56 3.89 28.94 1.25 100
The relative areas obtained for each functional group in non-irradiated A. gigas Nakai were hydrocarbons (66.58%), alcohols (23.35%), esters (3.38%), aldehydes (1.92%), ketones (3.65%), and miscellaneous (1.12%) (Table 1). The content of hydrocarbons in irradiated samples at dose of 1, 3, 5, 10 and 20 kGy were 52.80%, 56.39%, 59.43%, 58.43% and 58.83%, respectively, below the 60% of the non-irradiated sample. The contents of alcohols in irradiated samples increased about 6% compared to control (about 23.35-31.14%), and were not significantly different with different irradiation dose. The contents of other functional groups in non- and irradiated samples were equivalent. 3.2. Comparison of essential oils in non- and irradiated A. gigas Nakai Essential oils of plants and their other products from secondary metabolism have had a great usage in folk medicines, food flavorings, fragrances, and the pharmaceutical industries (Satil et al., 2003; Kusmenoglu et al., 1995). Some of the biological activities of the essential oils have been known for long time (Digrak et al., 1999; Pattnaik et al., 1997; Dang et al., 2001; Grassmann et al., 2000). The percentage composition of the essential oils
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Table 2 Comparison of relative concentration by terpenoid groups in Angelica gigas Nakai (unit; peak area%) Functional group
No.
Irradiation dose (kGy) 0
1
3
5
10
20
Monoterpenes (C10)
Monoterpenes Oxygenated monoterpenes
25 9
44.14 15.75
38.30 20.26
41.05 18.93
44.68 18.26
42.66 18.11
42.46 17.66
Sesquiterpenes (C15)
Sesquiterpenes Oxygenated sesquiterpenes
30 12
4.03 13.21
5.34 21.08
4.56 19.16
4.24 16.76
4.41 17.66
4.75 17.71
Total
76
77.13
84.98
83.7
83.94
82.84
82.58
Table 3 Composition of major compounds identified in the essential oils from non- and irradiated Angelica gigas Nakai (unit; peak area%) RIa
888 1029 1067 1198 1269 1569 1661 1686 1714 1729 1854 2136 2189 2238 2250 a
Compound name
2,4,6-Trimethyl heptane a-Pinene Camphene a-Limonene r-Cymene (E)-r-2-Menthen-1-ol Pinocarveol Vervenol Verbenone a-Murrolene r-Cuminol Sphatulenol 2-Hydroxycyclopentadecanone a-Eudesmol b-Eudesmol
Irradiation dose (kGy) 0
1
3
5
10
20
13.39 30.89 4.10 4.29 1.07 1.17 1.22 2.15 1.44 1.52 1.07 1.85 1.56 1.90 5.01
6.61 24.61 4.27 4.86 1.15 1.72 1.48 3.19 1.77 2.30 1.39 2.36 2.84 2.88 8.22
7.97 26.33 4.44 4.87 1.19 1.46 1.40 3.05 1.77 1.87 1.33 1.95 2.33 2.72 8.02
7.74 28.94 5.11 5.53 1.19 1.56 1.37 2.91 1.81 1.67 1.27 1.50 2.07 2.35 7.17
8.38 27.40 4.88 5.44 1.24 1.31 1.42 2.69 1.77 1.83 1.20 1.81 2.08 2.35 7.25
8.59 27.12 4.94 5.43 1.28 1.23 1.33 2.22 1.73 1.90 1.25 1.80 2.06 2.36 7.25
Retention index.
probably provides the most important measure for the characterization of the respective plant (Paula and Manuel, 2001). The essential oil groups of the volatile compounds identified in A. gigas are shown in Table 2. Monoterpene hydrocarbons represent the larger fraction of the A. gigas Nakai root oil constituents (Table 2). The difference in odor of the Angelica root oils can be attributed to the compositional differences of the volatiles, especially in the relative amounts of various monoterpene hydrocarbons (Forsen, 1979). The high number of different monoterpene compounds is assumed to indicate a high quality of the oil aroma (Kerrola et al., 1994). Twenty-five kinds of monoterpene hydrocarbons including a-pinene, a-limonene, camphene, r-cymene, b-pinene, b-myrcene, and alloocimene were identified in all samples studied with the main component being a-pinene. The content of this group tended to decrease (41.83% from 44.14%) after gamma irradiation, a result caused by the reduction of a-pinene contents (Table 3). a-Limonene was the second most abundant component among the monoterpene hydrocarbons and its content tended to increase from 4.29% to 5.2370.33% after gamma irradiation.
The content of r-cymene also was increased after irradiation (1.07-1.2170.5%). The response of compounds for irradiation was found variable (Table 3). Sesquiterpene hydrocarbons represented 4.03% of all volatiles in A. gigas Nakai. The amount of sesquiterpene hydrocarbons in the irradiated samples exceeded 4.24%, and was greater than that determined in the non-irradiated sample. Nine kinds of sesquiterpenes were confirmed, with a-murrolene, g-elemene, and d-cadinene the primary components. These compounds had a tendency to increase following gamma irradiation. Oxygenated compounds of the terpene hydrocarbons confer special characteristics to the A. gigas Nakai root oil, such as particular odors and stability (Doneanu and Antiescu, 1998). The percentage of oxygenated terpenes in non- and irradiated samples at doses of 1, 3, 5, 10 and 20 kGy were 28.96, 41.34, 38.09, 35.02, 34.77 and 35.37%, respectively, and increased after irradiation (Table 2). Among these oxygenated terpenes, the amount of oxygenated sesquiterpenes was increased more than the oxygenated monoterpenes. These results agree with the study of Farag et al. (1995) that reported terpenes were
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converted to monoterpe-nesalcohols. b-Eudesmol, an oxygenated monoterpenes, was the major compound in this group, while verbenol, a-eudesmol, verbenone, and (E)-r2-menthen-1-ol were also detected. The a- and b-eudesmol were increased to 9.52% from 6.91%, with no major variation between the different irradiation doses. The remaining oxygenated terpene levels also did not vary significantly during irradiation. The yields of essential oils were increased 5–7% after irradiation, a result similar to that reported by Kim et al. (2000). Also, the profile of volatile components including the essential oils of A. gigas Nakai did not change significantly with irradiation and the content of volatiles did not differ from non- and irradiated samples. The results observed in this study agree with quantity of paeoniflorin in Paeoniae radix, i.e. no change with irradiation as cited by Yu et al. (2004). In addition, Owczarczyk et al. (2000) have reported that the content of biologically active substances, including the essential oils, flavonoids, glycosides, anthocyanins, and plants mucus did not change significantly after irradiation. 4. Conclusion In conclusion, the total yields of volatile compounds in A. gigas Nakai were not changed after irradiation, although the yields of essential oils were increased 5–7%. The major components of A. gigas Nakai were a-pinene, camphene, a-limonene, b-eudesmol, a-eudesmol, a-murrolene, and sphatulenol. Among the essential oils, oxygenated terpenes such as b-eudesmol, a-eudesmol, and verbenone were increased after irradiation, but their proportions were variable in a dose-dependent manner. The composition of volatiles in A. gigas Nakai was not significantly changed by irradiation. These results further support the notion that gamma irradiation process is chemically inert, and could be used the basis for the sterilization of medicinal herbs. Acknowledgements This study was supported by research funds from Chosun University, 2005. References Ahn, K.S., Sim, W.S., Kim, H.M., Han, S.B., Kim, I.H., 1996. Immunostimulating components from the root of Angelica gigas Nakai. Kor. J. Pharmacogn. 27, 254–261. Byun, M.W., Yook, H.S., Kim, K.S., Chung, C.K., 1999. Effects of gamma irradiation on physiological effectiveness of Korean medicinal herbs. Radiat. Phys. Chem. 54, 291–300. Chatterjee, S., Variyar, P.S., Gholap, A.S., Pudwal-Desai, S.R., Bongirwar, D.R., 2000. Effect of g-irradiation on the volatile oil constituents of turmeric (Curcuma longa). Food Res. Int. 33, 103–106. Cho, M.G., Bang, J.K., Chae, Y.A., 2003. Comparison of volatile compounds in plant parts of Angelica gigas Nakai and A. acutiloba Kitagawa. Korean J. Med. Crop Sci. 11, 352–357.
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