Moduling isolation processes of Chlorella sorokiniana fractions of high inhibition activities on glycosidases

• Main Authors: Wu, Hsiaomei, 吳小梅
• Other Authors: Lai, Phoency
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/82626891793152563411

碩士 === 靜宜大學 === 食品營養學系 === 99 === Chlorella sp. is known to have many kinds of healthy functionality, partly relating to their potential inhibition activity against glycosidase enzymes. This study was to investigate the major chemical compositions, antioxidant activities (DPPH and ABTS free radicals), and inhibitory activities against glycosidase (alpha-glucoside, beta-glucoside and beta-glucuronidase) of various solvent extracts and fractions from Chlorella sorokiniana, in order to develop isolation processes for bioactive Chlorella fractions of high glucosidase inhibitory activities. Five solvents (n-hexane, ethyl acetate, acetone, ethanol and water) were applied in single solvent or mixture. The chemical composition results showed that 50% ethanol (50ES) and water soluble (WS) extracts of Chlorella sorokiniana contain a higher content in protein, total sugar and uronic acid (2560%, 2030% and 26%, respectively), in contrast to the other extracts. The monosaccharide composition in both 50ES and WS is mainly glucose (>50 mol %), followed by galactose, or ribose. Differently, the n-hexane (HS), ethyl acetate (EaS) and acetone (AS) extracts contained a higher content in total phenolics (51-53 mg/g) and chlorophylls. In the case of antioxidant activities, AS and mHS showed the highest DPPH-scavenging effects among the samples examined (80% and 85%, respectively, at 2 mg/mL extract). While, all 50% ethanol extracts (50ES, 95EI-50ES, 95EI-mHWI-50ES, mHWI-50ES, mHEaI-95EI-50ES, 25WI-50ES and 90WI-50ES) displayed good ABTS-radical scavenging effects (~90% at 2 mg/mL). For glycosidase inhibitory activities, the mWS exhibited a better alpha-glucosidase-inhibition rate than the other extracts (66.38 ± 0.66% at 10mg/mL). The 95EI-mWS and mHEaI-95EI-50EI-90WS extracts revealed the highest beta-glucosidase inhibition rate (91-92% at 10mg/mL). However, the beta-glucuronidase inhibition rate was the highest for 95EI-mHS extracts (89% at 10mg/mL). Enzymatic kinetics showed that the glycosidase inhibition mechanism of the fractions(mWS, 95EI-mWS and mHEaI-95EI-50EI-90WS) involved partially noncompetitive inhibition, and the fractions(95EI-mHS) involved mixed-type noncompetitive inhibition. In conclusion, the extract of high alpha-glucosidase inhibition activity could be better prepared from the WS fraction of mixed n-hexane-water extracts. Those of high beta-glucosidase inhibitory activity could be prepared from the water subfraction in n-hexane-water extracts on the 95% ethanol insoluble materials of Chlorella. And, that of high beta-glucuronidase inhibition activity was the best could be prepared from the n-hexane subfraction in n-hexane-water extracts on the 95% ethanol insoluble materials of Chlorella.