Study On Preparation And Functions Of Hypoglycemic Components From Corn Silk

This article taked corn silk as raw material. Microwave-assisted extraction was adoptedto simultaneous extract totals aponins and total flavonoids from corn silk. Based on singlefactor test and orthogonal test, the optimum extraction technology was determined andcompared with the ultrasonic extraction and reflux extraction.Four extracts were obtained byusing different polar solvents such as petroleum ether, N-butyl alcohol, ethyl acetate andwater. According to their reducing power and scavenging activities for DPPH· radicals,hydroxyl radicals (·OH) and superoxide anion radicals (O2﹣·), antioxidant activities of differentpolar fractions were compared. The hypoglycemic effect of crude extraction, N-butyl alcoholfraction and ethyl acetate fraction from corn silk were studied. The effective hypoglycemicpart was selected and the main functional components in the two fractions were analyzed.Conclusions were as follows:The main factors that influenced the extraction rate of total flavonoids and saponins fromcorn silk were microwave power, followed by the microwave time and solid-liquid ratio. Theoptimum extraction condition was as follows1:40solid-liquid ratio (m:v),420W microwavepower,6min extraction time and60%ethanol as solvent. Under this condition, extractionrates of total saponins and total flavonoids both reached1.51%. Compared with the ultrasonicextraction and reflux extraction, microwave-assisted extraction was more rapid andconvenient, and the extraction rate was higher than the two methods nearly5%and40%.The crude extract and different polarity fractions of flavonoid extracts from corn silkwere showed antioxidant activities, and existed observably dose-effect relationships. N-butylalcohol fraction had the best reducing power and scavenging effects for DPPH· radicals andhydroxyl radicals, while ethyl acetate fraction had the best scavenging effects for superoxideanion radicals. At the total flavonoids concentration of25μg/mL, the extracts all showed strong scavenging effects of DPPH·,·OH and O﹣2·, which were99.35%,75.84%,94.27%,respectively.The hypoglycemic experiments showed that: After the mice were orally administeredwith N-butanol fraction and ethyl acetate fraction. The symptoms of " a little more than threedisease " with diabetic mice were obviously improved, the fasting blood glucose were bothreduced significantly (P<0.05) and the glucose tolerance of diabetic mice were both improvedsignificantly (P<0.01). In general, the effect of N-butyl alcohol fraction is better than that ofethyl acetate fraction.Through the functional compounds analysis, several main functional compounds inN-butanol fraction were all higher than that of ethyl acetate fraction. The content of totalsaponins of24.21%was highest, the content of total flavonoids followed by nearly22%. Andthe flavones glycoside A(2"-O-α-L-rhamnosyl-6-C-3"-deoxyglucose-3’-methoxy-luteolin)was an important flavonoids compounds, which were about1/3of the total flavonoids.Therefore, we speculated saponins and flavonoids may be the main functional compound withantioxidant activity and hypoglycemic effect.