Seasonal Effects on Ingredients and Antioxidant Activities of Stem Extracts from Vitis thunbergii, Vitis flexuosa, and Vitis kelungensis in Taiwan

• Main Authors: Kai-Chung Cheng, 鄭凱中
• Other Authors: 吳志鴻
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/31874804846875255357

碩士 === 國立中興大學 === 森林學系所 === 96 === Vitis thunbergii, Vitis flexuosa, and Vitis kelungensis are three common wild-grapes in Taiwan. They have been used as a health protection crop to prevent some diseases, such as flu and hepatitis, etc. It is well-known that V. thunbergii and V. flexuosa stems contain various resveratrols. However, the potential bioactivities of those wild-grapes have not been studied to data. Thus, in this study, the antioxidant activities of methanolic extracts from V. thunbergii, V. kelungensis, and V. flexuosa stems in different seasons are evaluated by various in vitro antioxidant models, including DPPH radical scavenging assay, superoxide radical scavenging assay, ferrous ion chelating ability assay, reducing power assay, and total phenolic content assay. In addition, column chromatography (CC) and high performance liquid chromatography (HPLC) are employed to separate and purify maker ingredients of extracts from Vitis kelungensis, and identified by the analyses of mass spectroscopy and nuclear magnetic resonance spectroscopy (NMR), etc. Results revealed that, among all tested samples, V. kelungensis harvested in winter exhibited the strongest antioxidant activities in DPPH radical scavenging activity, superoxide radical scavenging activity, and ferrous ion chelating ability, as well as its antioxidant activities were similar to (+)-catechin, a well-known antioxidant. Furthermore, among all derived soluble fractions from the methanolic extracts of V. kelungensis stem, the BuOH fraction exhibited the strongest DPPH radical and superoxid radical scavenging activities with IC50 values of 2.9 μg/mL and 7.7 μg/mL, respectively. Additionally, the BuOH fraction also exhibited the highest reducing power (600.1 mg CE/g) and total phenolic content (330.6 mg GAE/g). Following by column chromatography and high performance liquid chromatography, 10 major constituents, including 3 phytosteroids (β-sitostenone, β-sitosterol and stigmasterol), 4 triterpenoids (lupeol, β-amyrin, betulinic acid and betulin), and 3 resveratrol derivatives ((-)-ε-viniferin, 2-(4-hydroxyphenyl)-2,3- dihydrobenzo[b]furan-3,4,6-triol and (+)-balanocarpol), were isolated and purified from the EtOAc fraction of V. kelungensis stem. Among them, 2-(4-hydroxyphenyl)- 2,3-dihydrobenzo[b]furan-3,4,6-triol was a new compound. On the other hand, the contents of (-)-ε-viniferin were ranged from 0.63 to 2.20 mg, 0.44 to 1.47 mg, and 0.66 to 1.54 mg per gram of aur-dried stems of V. thunbergii, V. flexuosa, and V. kelungensis , respectively. Accordinglly, in spring, V. thunbergii had the highest amount of (-)-ε-viniferin content, whereas, the lowest content of that was obtained in summer, while, the V. flexuosa stem, the highest (-)-ε-viniferin content was obtained in autumn, whereas the lowest content was found in winter. As for V. kelungensis stem, the higest (-)-ε-viniferin content was obtained in winter and spring, while the lowest content was found in autumn. Furthermore, a new compound, 2-(4-hydroxyphenyl)-2,3-dihydro- benzo[b]furan-3,4,6-triol, was only presented in V. thunbergii and V. kelungensis stems. Both species the highest amount of this new compound in spring with values of 1.96 mg/g and 0.89 mg/g, respectively. Similarly, (+)-balanocarpol was only presented in V. kelungensis and V. flexuosa stems. Among all seasons, these two species showed the highest amount of (+)-balanocarpol content in summer with value of 0.17 mg/g and 0.11 mg/g, respectively.