Bacteriostatic and Tyrosinase Inhibitory Activities of Different Polar Sites from Quinoa Bran

The bacteriostatic activity and inhibition of tyrosinase activity of different polar sites in quinoa bran was studied with the target of the inhibition zone size and inhibition rate of tyrosinase activity. Different polar sites in quinoa bran were obtained by ultrasonic extraction method with 75% ethanol. In order to screen out the four polar sites, extracting sequentially with petroleum ether, ethyl acetate, n-butanol three different solvents. Paper disk method was used to observe the in vitro inhibitory of different polar sites on four pathogenic bacterias. And the inhibitory effect of tyrosinase was valued according to the inhibition rate of tyrosinase activity. Using LC-MS/MS to infer its active ingredients and using high performance liquid chromatography quantitative analysis of relatively high active ingredients. The results showed that the n-butyl alcohol extracts showed it had high bacteriostatic activity on Gram-positive bacterias, and no significant effect on gram-negative bacterias. The minimum inhibition concentration (MIC) on Staphylococcus aureus and Staphylococcus epidermidis were 1.04, 0.52 mg/mL, respectively. And the minimum bactericidal concentration (MBC) were 2.08, 1.04 mg/mL, respectively. By comparing the antibacterial effect, it could be concluded that the polar sites of quinoa bran was superior to the some common traditional Chinese medicine. When the concentration of n-butyl alcohol fraction was 1 mg/mL, its inhibition rate of tyrosinase activity was 55.86%, and its inhibition ability was 58.96% with that of vitamin C. Through full scan by HPLC, the main substance of n-butyl alcohol fraction was deducted as quinoa saponin, and the purity was 62.6%. In summary, N-butyl alcohol fraction has obvious antibacterial activity and better inhibition of tyrosinase activity in the different polar sites of quinoa bran. And the main active substance is quinoa saponin.