采用超声波辅助-乙酸乙酯提取方法获得桐花树[Aegiceras corniculatum (Linn.) Blanco]叶片多酚提取物,研究了该提取物对酪氨酸酶活性的抑制作用及其动力学特征,并分析了该提取物对PPH·自由基的清除作用及其抗菌活性。结果显示:多酚提取物得率约为(122. 0±31. 4) mg·g g^-1  ,提取物中多酚含量约为(521. 8±17. 2) mg·g^-1 。该提取物对酪氨酸酶活性的抑制作用呈明显正相关的量效关系,IC50 为0. 650 g·L^-1 ,与阳性对照槲皮素对酪氨酸酶活性的抑制能力相近;该提取物通过降低酶活性实现对酪氨酸酶活性的抑制,且该抑制作用具有可逆性;随提取物质量浓度的提高酶促反应Km值增大、vm值减小,其动力学特征符合混合Ⅰ型抑制类型;对游离酶的抑制常数Ki为0. 833 g·L^-1,对酶-底物络合物的抑制常数Kis为1. 823 g·L^-1 ,表明该提取物与游离酶的亲和力大于其与酶-底物络合物的亲和力。随质量浓度提高,该提取物对DPPH·自由基的清除率逐渐增大并在0. 000 ~0. 600 g·L^-1 范围内呈明显量效关系,且IC₅₀ 为0. 304 g·L^-1 ,与0. 036 g·L^-1 槲皮素等效,显示该多酚提取物对自由基的清除能力较强。随质量浓度提高,该提取物对大肠杆菌(Escherichia coli)、金黄色葡萄球菌(Staphylococcus aureus)和枯草芽孢杆菌(Bacillus subtilis)的抑菌圈直径均逐渐增大,显示该提取物对3 种供试菌均有抑菌作用,最小抑菌浓度均为25 g·L^-1 。结果表明:通过深入的开发研究,桐花树叶片多酚提取物可作为兼具辅助防腐抑菌功能的新型酪氨酸酶抑制剂。

Polyphenol extracts from leaf of Aegiceras corniculatum (Linn.) Blanco were obtained by ultrasonic assisted-ethyl acetate extraction method, inhibition effect of the extracts on tyrosinase activityand its kinetic characteristics were researched, and its scavenging effect on DPPH· free radical and antibacterial activity were analyzed. The results show that yield of polyphenol extracts is about (122. 0±31. 4) mg·^g-1, in which polyphenol content in the extracts is about (521. 8±17. 2) mg·g^-1. The inhibition effect of the extracts on tyrosinase activity appears dose-effect relationship with obviously positive correlation, its IC50 is 0. 650 g·L^-1, which is close to inhibition capacity of quercetin, a positive control, to tyrosinase activity. The extracts achieve inhibiting tyrosinase activity by reducing its activity and its inhibition effect is reversible. With rising of mass concentration of the extracts, Km value of enzymatic reaction increases and vm value decreases, its kinetic characteristics is accord with the mixed Ⅰtype inhibition. The inhibition constant for free enzyme (Ki ) is 0. 833 g·L^-1 and that for enzyme-substrate complex (Kis) is 1. 823 g·L^-1, and it means that affinity of the extracts with free enzyme is higher than that with enzyme-substrate complex. With rising of mass concentration, scavenging rate of the extracts to DPPH· free radical increases gradually and appears obviously dose-effect relationship in range of 0. 000-0. 600 g·L^-1, and its IC50 is 0. 304 g·L^-1, which is equivalent to 0. 036 g·L^-1 quercetin, and it means that the polyphenol extracts has a stronger scavenging capability to free radical. With rising of mass concentration, antibacterial annulus diameters of the extracts to Escherichia coli, Staphylococcus aureus and Bacillus subtilis all increase gradually, which shows that the extracts have an antibacterial effect on the three tested bacteria, the minimum inhibitory concentration is 25 g·L^-1. It is suggested that by deep development and research, polyphenol extracts from leaf of A. corniculatum can be used as a new tyrosinase inhibitor with auxiliary antiputrefactive and bacteriostatic function.