不同水解方法对藜麦皂苷抑菌活性及酪氨酸酶抑制作用的影响

本实验以藜麦麸皮为材料，通过双相酸水解法、直接酸解法、酶解法三种方法去处理藜麦麸皮，并利用正丁醇萃取获得藜麦低级性皂苷。经过最低抑菌浓度（minimum inhibitory concentration，MIC）、最低杀菌浓度（minimum bactericidal concentration，MBC）及纸片法测定抑菌活性；并用酪氨酸酶抑制实验推测其抑制黑色素作用。最后用液相色谱质谱/质谱联用法（liquid chromatography electrospray ionisation tandem mass spectrometry，LC-MS/MS）和高效液相色谱法（high performance liquid chromatography，HPLC）来对抑菌和抑制酪氨酸酶活性效果最好的化合物进行定性定量分析。结果表明：经过双相酸水解转化的化合物活性最好，对金黄色葡萄球菌和沙氏肠炎杆菌的MIC=0.60 mg/mL，MBC=1.20 mg/mL，对表皮葡萄球菌的MIC=0.30 mg/mL，MBC=1.20 mg/mL；对铜绿假单胞菌有一定的抑制作用。0.5 mg/mL的转化物对酪氨酸酶的抑制率达到68.09%。根据LC-MS/MS及HPLC可知，经正丁醇萃取的水解后的化合物为皂苷。经过两相酸解后，部分皂苷发生了水解反应，造成了化合物极性的降低。利用双相酸水解法从藜麦麸皮中萃取藜麦皂苷元提高了化合物的活性，增强了皂苷的抑菌和酪氨酸酶抑制作用，并且提取率明显高于直接酸解法和酶解法。

Effects of Different Hydrolysis Methods on Antibacterial Activity and Tyrosinase Inhibition of Buckwheat Saponins

A large amount of saponins in quinoa bran was found to have biologically active. The activity of tyrosinase inhibition and bacteriostatic of less polar saponins in quinoa bran were investigated by different hydrolysis methods, such as biphasic acid hydrolysis method, direct acid hydrolysis and enzyme hydrolysis bran. Their active component was been speculated and conducted qualitatively and quantitatively. Bacteriostatic activity was determined by minimum bacteriostatic concentration (MIC), minimum bactericidal concentration (MBC) and paper disk method. The whitening effect of tyrosinase inhibition was evaluated. LC-MS/MS and HPLC were used to identify the active compounds qualitatively and quantitatively. The results showed that the compounds that hydrolyzed and converted by bipolar acid had the best activities with MIC of 0.60 mg/mL, MBC of 1.20 mg/mL for Staphylococcus aureus and Salmonella enteritidis, MIC of 0.30 mg/mL, MBC of 1.20 mg/mL for Staphylococcus epidermidis. It also had certain inhibitory effect on Pseudomonas aeruginosa. The inhibition rate of 0.5 mg/mL of the conversion compounds to tyrosinase reached 68.09%. According to LC-MS /MS and HPLC analysis, some saponins were hydrolyze after two-phase acid decomposition, resulting in the decrease of the polarity of the compounds. Extraction of saponins from quinoa bran by biphasic acid hydrolysis could improve the activity of compound and enhance the function of the inhibitory on bacteria and rosinase activity. The extraction rate was significantly higher than that of direct acid hydrolysis and single enzyme hydrolysis.