| Summary: | 碩士 === 國立嘉義大學 === 食品科學系研究所 === 100 === The purpose of this study was to explore the value-added use of distilled Crossostephium chinense L. (C. chinense L.) leaf residues left after essential oil extraction. Fresh and distilled C. chinense L. leaves were extracted with water or 80% methanol, and the obtained extracts were then subjected to total phenolic contents measurement and bioactivities, including reducing power, antioxidant potency (AOP), antiglycation and xanthine oxidase (XO) inhibition, characterization. By comparing the total phenolic contents and bioactivity of extracts, 80% methanol is a more effective solvent than water, and distilled leaves were better than fresh ones in extraction. The fresh leaves were further investigated for thermal stability by steaming the samples for 0, 0.5, 1, 1.5 and 2 hours, followed by 80% methanol extraction and bioactivity evaluation. These results indicated that steamed leaf extract exhibited higher antioxidant activity compared with fresh leaf extract. Steaming for 0.5 hour increased the antioxidant activity to maximums level, whereas the activity declined at 0.5 hours. The antiglycation and XO inhibitory activities did not change significantly by steaming. The extracts from leaves steamed for different lengths of time had similar chromatogram profile as analyzed by HPLC. The heat tolerance of 80% methanol extract of fresh leaves was evaluated by heating in boiling water bath for different lengths of time. The total phenolic content, and XO inhibitory, antioxidant and antiglycation activities in the extract were not influenced by heating, while the linoleic acid peroxidation inhibitory effect increased as heated for 1.5 hours, and decreased as heating time extended to 2 hours. Accordingly, methanol extract of C. chinense L. leaves has high heat tolerance. To further identify the functional compounds, bioactive fractions of methanol extract were collected from semi-preparative HPLC and subjected to structural identification using LC/MS/MS. The major compound exhibited mass to charge ratio of m/z 354, which corresponded to 3-caffeoyl-D-guinic acid (chlorogenic acid). In conclusion, these results indicate that distilled C. chinense L. leaves contains thermal stable functional components exerting antioxidant, antiglycation and XO inhibition effects, and suggest the value-added use and nutraceutical potential of C. chinense L.
|
|---|
