| Summary: | 碩士 === 國立嘉義大學 === 食品科學系研究所 === 100 === Seeds of Oolong tea plant (Camellia sinensis) are reported to be rich in polyphenolic compounds and saponin. In this study, different ratio of water-based ethanol solutions (0, 30%, 60% and 95% v/v) were employed for extraction. The total polyphenolic compounds, total saponin contents, antioxidative capability, and inhibitory activity of key enzymes of controlling blood sugar (α-amylase and α-glucosidase) in vitro of each particular portion had been determined. The extraction with optimal expected health benefits was subjected to further investigation of in vitro glycation. The results reveal that 60% ethanol extracts possessed the highest contents of total polyphenolic compounds (25740 μg/g) and total saponins (307930 μg/g), thus could be considered as the better concentration of with high potency of total antioxidant capacity (IC50: 29.93 ppm) and DPPH free radical scavenging ability (IC50: 4.23 ppm); whereas, the best metal chelating activity (IC50: 355.46 ppm) was observed in the 95% ethanol extracts. Furthermore, 60% ethanol extracts showed mild inhibition on α-amylase activity (45.13%) and excellent inhibition on α-glucosidase activity (85.66%) in 500 ppm and 2.5 ppm total polyphenolic concentration, respectively. Therefore, the 60% extract was selected to undergo the stimulated glycation systems (BSA-Fructose, BSA-Glucose and BSA-MGO), this portion was able to effectively maintain the product of initial (ketoamine compounds) and that of intermediate (α-dicarbonyl compounds), so as to inhibit the production of advanced glycation end-products (AGEs). The fluorescence products representing the inhibition ratios were BSA-Fructose (28~81%), BSA-Glucose (38~54%), and BSA-MGO systems (17~73%) in different total polyphenolic concentrations (50~800 ppm) from 60% ethanol extract on day 7. By using the SDS-PAGE and gel intensity analysis, the 60% ethanol extracts could be able to retard the production of glycated protein according to the resulted evaluation using BSA-Glucose and BSA-MGO systems, but 60% ethanol extracts and aminoguanidine failed to inhibit crosslink of glycated protein on BSA-Fructose system.
60% ethanol extracts contains other components (carbohydrates and proteins), thus further extracts eluted by Amberlite XAD-7 adsorption resin column chromatography with different solvents (H2O/MeOH: 100/0, 70/30, 40/60, 20/80, and 0/100), and five fractions were collected after elution (F1~F5). Fractions of components and functional components were identified. The results of HPLC analysis indicated that F3 of isolated components were (-)-epicatechin and (+)-catechin. All fractions were possessed excellent total antioxidive capacity (75~97%) and DPPH free radical scavenging ability (72~83%) in 50 ppm total polyphenolic concentration, while metal chelating activity in 400 ppm of total polyphenolic concentration for F2 (83.50%) and F4 (61.11%) were better than other experimental fractions. Furthermore, F4 showed excellent inhibition on α-amylase activity (63.46%) and inhibition on α-glucosidase activity (100%) at 800 ppm and 2.5 ppm of total polyphenolic levels, respectively. In the study of in vitro the anti-glycation activity, the result showed a similar trend for the three different glycation systems (BSA-Fructose, BSA-Glucose, and BSA-MGO). The inhibitive strength of fluorescence products was F4 (67~82%)＞F3 (52~69%)＞F2 (32~61%) successively in 400 ppm total polyphenolic concentration from different fractions on day 7, and similar results between fluorescence products and glycated protein was observed using the SDS-PAGE and gel intensity analysis (Glucose or MGO), but only F4 possessed mild inhibition on production of glycated protein on BSA-Fructose. F4 fraction also possessed inhibition on saccaridase and anti-glycation activity. The further analysis regarding the functional components contained in the sample seeds is recommended. These results indicated that Oolong tea seeds possess excellent inhibitory effects on saccaridase and anti-glycation activities, therefore, could be adopted as diabetic functional for patients with diabetes mellitus. This potential of this approach can not only improve the economic climate of the tea farming industry, but provide new alternative food choice for diabetes mellitus.
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