Oriental Foods and Herbs - American Chemical Society

Chapter 11

Antioxidants in Herbs of Okinawa Islands Nobuji Nakatani

Downloaded by UNIV OF GUELPH LIBRARY on July 26, 2012 | http://pubs.acs.org Publication Date: August 5, 2003 | doi: 10.1021/bk-2003-0859.ch011

Graduate School of Human Life Science, Osaka City University, Osaka, Japan

In the course of our searching for antioxidants from natural sources, we have focused on the plants which are traditionally used as food, tea and medicine in Okinawa, Japan. Several spices, such as Peucedanum japonicum Thunb (Botanbofu in Japanese), Musa balbisiana Colla (Ryukyubasho), Alpinia flabellata Ridley (Iriomotekumatakeran), Alpinia speciosa K. Schum (Getto), Smilax nervo-marginate Hayata (Sasabasankirai), Smilax china L var. kuru Sakaguchi ex Yamamoto (Okinawasarutoriibara)., Livistona chinensis R. Br var. subglobosa Becc (Biro), and Artemisia campestris L (Ryukyuyomgi). The present study describes the chemistry and antioxidant activity of these eight Okinawan herbs.

There are increasing much attention and interest in natural antioxidant, one of the most important nutraceuticals, not only for food preservation but for the prevention of numerous diseases such as atherosclerosis, diabetes and cancer, induced by oxidative stress (/). Our group has been engaging in isolation and structure elucidation of efficient antioxidants from natural resources, particularly from tropical spices and herbs (2-5). Recently we have focused on the subtropical plants, which grow in Yaeyama Islands, Okinawa, the southernmost part of Japan. Okinawa is well known as the island famous for world's highest longevity. The plants used in this study are Peucedanum japonicum Thunb 166

© 2003 American Chemical Society In Oriental Foods and Herbs; Ho, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2003.

167


(Botanbofu in Japanese), Musa balbisiana Colla (Ryukyubasho), Alpinia flabellata Ridley (Iriomotekumatakeran), Alpinia speciosa K. Schum (Getto), Smilax nervo-marginate Hayata (Sasabasankirai), Smilax china L var. kuru Sakaguchi ex Yamamoto (Okinawasarutoriibara)., Livistona chinensis R. Br var. subglobosa Becc (Biro), and Artemisia campestris L (Ryukyuyomgi). The leaves of these eight plants are traditionally used for vegetables and teas, and for flavoring rice cakes and meats by wrapping with. The present study describes antioxidant activity of the eight Okinawan herbs, their constituents and antioxidant evaluation measured by several methods.

Experimental Plant Materials

The leaves of eight herbs were collected on Iriomote Island, one of The Yaeyama Islands, Okinawa.

Extraction Procedure for Antioxidant Screening Dried and pulverized leaves were extracted with ten times volume (w/v) of acetone-water (8:2). After evaporation of acetone from the extract, ethyl acetate was added to the aqueous residue, then partitioned to give the ethyl acetatesolublefractionand the water-soluble fraction.

General Procedure for Isolation of Antioxidants from Okinawan Herbs Dried and pulverized leaves was successively extracted with hexane, dichloromethane, and 70% aqueous acetone at room temperature (Figure 1). Organic solvent of the 70% aqueous acetone extract was evaporated in vacuo. The residual aqueous solution was successively partitioned with ethyl acetate, nbutanol to give the ethyl acetate fraction, the n-butanol fraction and the watersoluble fraction. Each fraction was examined for antioxidant assay. The active fractions were purified with several kinds of chromatographic technique to isolate active constituents.

In Oriental Foods and Herbs; Ho, C., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2003.

168

Dried Herb I extracted with CH C1 2

CH C1 Extract 2

2

Residue

2

extracted with Acetone:H 0(7:3) 2

I extracted with C 0 ι (Supercritical Fluid Extraction : SFE)

•


2

SFE Extract

I

Residue

Extract I concentrated I partitioned between EtOAc and H 0 2

SFE Residue

I EtOAc-soluble Fraction

H 0 Layer 2

I

n-BuOH-soluble Fraction

partitioned between »-BuOH and H Q 2

H 0-soluble Fraction 2

Figure 1. Extraction andfractionation of Herbs.

Results and Discussion Antioxidant Screening of Okinawan Herbs The antioxidant activities of the ethyl acetate-soluble and the water-soluble fractions were measured by the ferric thiocyanate method (6). The activity of both soluble fractions of eight species decreased in the order BHT> P. japonicum > S. nervo-marginate > L. chinensis > Art. campestris > S. china > M. balbisiana > Alp. speciosa > Alp. flabellata > α-tocopherol. Similar results were obtained when the antioxidant of these specimens were measured by the TBA method. The antioxidant activity of bothfractionsof all herbs was stronger than that of α-tocopherol (natural antioxidant) at the same concentration of 0.02%. The activity of the ethyl acetate-soluble and the water-soluble fractions of Art. campestris was comparable to that of butylated hydroxy toluene (BHT, synthetic antioxidant).


169 DPPH Radical Scavenging Activity of Okinawan Herbs The DPPH radical scavenging activity (6) of each fraction was evaluated by direct ESR measurements. The relative peaks height of the DPPH radical to the standard signal intensity of the manganese oxide appears dose-dependent. The concentration at which the scavenging activity of the tested fractions showed 50% of control (IC value) was determined for the ethyl acetate-soluble, the water-soluble fractions, α-tocopherol, and L-ascorbic acid. The activity of the ethyl acetate-soluble fraction of each species decreased in the order α-tocopherol > L-ascorbic acid > Alp.flabellata> S. china > Art. campestris > P. japonicum > M. balbisiana > Alp. speciosa > L chinensis based on the statistical analysis. S. nervo-marginate did not show any significant differences against five species (P. japonicum, M. balbisiana, Alp. flabellata, S. china, and Art. campestris). The activity of the water-solublefractionsdecreased in the order α-tocopherol > L-ascorbic acid > P. japonicum > Alp.flabellata> S. china > M. balbisiana > Art. campestris, > Alp. speciosa > L. chinensis > S. nervo- marginate. In addition, the radical scavenging activity of the water-soluble fractions also showed a stronger activity than those of the ethyl acetate-soluble fractions.


50

Evaluation of the Scavenging Activity on Superoxide Anion Radical (0 ~) 2

Superoxide anion radical ( 0 ) was generated by hypoxanthine (HPX) / xanthine oxidase (XOD) (6). The 0 " scavenging activity of the water-soluble fractions was measured by the ESR spin-trapping technique. The activity decreased in the order L-ascorbic acid > P. japonicum, > S. china, > Alp. flabellate, > S. nervo-marginate > Art. campestris > M. balbisiana > L. chinensis. The activity of Alp. speciosa was stronger than that of L. chinensis. There was no significant difference between the activity of Alp. speciosa and that of M balbisiana or Art. campestris. 2

2

Evaluation of the Inhibitory Activity Against Xanthine Oxidase (XOD) (17) As for the evaluation of the scavenging activity against 0 * in the HPX/XOD system, it should be taken in consideration that each testedfractionmight inhibit XOD itself which generates 0 " (6). All thefractionsdid not show any significant inhibitory activity against XOD except for S. china, which inhibited 30% of the enzyme activity. This finding indicates that all plants except for 5. china directly scavenged 0 \ In conclusion based on the total results on screening tests, it is clear that the antioxidant and the radical scavenging activities of the water-solublefractionof 2

2

2


170 P. japonicum showed the highest activity among all fractions of tested herbs. Further study on the isolation and structure determination of antioxidants were done on Peucedanum japonicum, Artemisia campestris and Alpinia speciosa.


Compounds Isolated from n-Butanol Soluble Fraction of Peucedanum japonicum P. japonicum belongs to Umbelliferae. The leaves and roots of this plant have been used as a wholesome vegetable and a folk medicine for the treatment of cough, diuretic, tonic, and nerve sedative in the Yaeyama Islands and southeast Asian countries. It is reported that some coumarins isolated from this plant were found to possess pharmacological activities (7-9). The n-butanol fraction of P. japonicum was purified by silica gel column chromatography to afford several phenolic compounds. Based on NMR and MS spectroscopic analyses, the structure of isolated compounds were determined as quercetin 3-0glucoside (1, isoquercitrin), quercetin 3-0-rhamnosyl-(l,6)-glucoside (2, rutin), 3-O-caffeoylquinic acid (3), 4-

Oriental Foods and Herbs - American Chemical Society

Recommend Documents