Extraction And Enzymatic Acylation Of Bamboo Leaves Flavonoids

Firstly, the ultrasonic-assisted surfactant extraction of total flavonoids from bamboo leaves was studied by the one way experiment and response surface methodology. The extraction yield of total flavonoids was investigated with respect to ultrasound power, surfactant type, surfactant critical micelle (CMC) concentration and solvent/solid ratio. The results showed that the optimal conditions for the extraction of total flavonoids at40kHz ultrasonic power and ambient temperature were ultrasound power of420W, SDS as the extraction surface with a concentration of25.20×10-3mol/L, extraction time of20min, and a solvent/solid ratio of23:1(mL/g, SDS solution to bamboo leaves). Under these conditions, the yield of total flavonoids could reach2.30%.Furthermore, this study enzymatically acrylates two kinds of flavonoids from bamboo-leaf extracts, isoorientin and isovitexin, with different fatty acids as acyl donors using Candida antarctica lipase B (CALB). The conversion yield ranged from35to80%for fatty acids with different chain lengths. Higher isoorientin and isovitexin conversion yields (>75%) were obtained using lauric acid in tert-amyl-alcohol as the reaction medium.1H,13C nuclear magnetic resonance spectroscopy, and electrospray ionization mass spectrometry analysis showed that, in the presence of CALB, acylation occurred at the isoorientin and isovitexin primary hydroxyl group of glucose moiety and only monoesters were detected.Ultimately, the lipophilicity and anti-radical activity of the acylated derivatives of isoorientin and isovitexin. By determining the1-octanol/water partition coefficients and DPPH-,-OH radical scavenging activity, it was found that introducing a long chain acyl group into isoorientin and isovitexin improved their lipophilicity but reduced their antiradical activity.