苦荞茎叶提取物对“红宝石”马铃薯多酚氧化酶抑制效果研究

Inhibition Effect of Stem and Leaf Extracts of Tartary Buckwheat on Potato (Solanum tuberosum Ruby) Polyphenol Oxidase

褐变一直困扰着马铃薯的加工开发利用,而多酚氧化酶是马铃薯酶促褐变的关键酶。为筛选安全无毒、处理简单的多酚氧化酶抑制剂,本研究以苦荞茎叶磷酸盐缓冲液提取物、乙醇提取物和水提取物为褐变抑制剂,研究其对红宝石马铃薯多酚氧化酶的抑制效果。结果显示,3种提取物对马铃薯多酚氧化酶均具有显著地抑制效果,使该酶活力下降50%所需的浓度(IC50)分别为0.21、0.28、0.41 mg/m L。磷酸盐提取物的作用效果最强,乙醇提取物的作用效果次之,水提取物的作用效果最弱,3种苦荞茎叶提取物对酶的抑制作用均为非竞争性可逆抑制,其抑制常数(KI=KIS)分别为0.21、0.33、0.56 mg/m L。对3种提取物中总黄酮、蛋白质含量进行定量测定,结果表明,磷酸盐提取物中不仅含有较高含量的黄酮类物质,同时蛋白质含量也较高,推测这可能是磷酸盐缓冲液提取物抑制效果最好的原因。研究结果可为探寻马铃薯多酚氧化酶新的天然抑制剂和马铃薯深加工过程中褐变的控制提供新的思路和参考依据。

Browning has been plagued potato processing for a long time, and polyphenol oxidase（PPO） is one of the key enzymes in the process of browning in potatoes. In present study, three kinds of extracts（phosphate buffer, 50 %ethanol, distilled water） from tartary buckwheat stems and leaves were investigated on the inhibition on potato（Solanum tuberosum Ruby） PPO. The results showed that all the extracts had significant inhibitory effect on potato PPO. The inhibitors concentrations leading to 50%（IC50） of the enzyme activity lost were 0.21 mg/m L, 0.28 mg/m L,0.41 mg/m L, respectively. The phosphate extract had the strongest inhibitory effect, followed by ethanol extract. Kinetic analyses showed that the inhibition mechanism of all three extracts was non competitive inhibition, and the inhibition constants（KI=KIS） were 0.21 mg/m L, 0.33 mg/m L, 0.56 mg/m L, respectively. Meanwhile, the content of total flavones and proteins in the three extracts were determined, the results showed that higher content of total flavones and proteins were obtained from phosphate buffer extracts, which could be reasons for the better inhibitory effect.The results would provide new idea and reference for the exploration of natural inhibitor of potato PPO, and browning prevention in the potato processing.