Biswas Rajarshi, Chanda Joydeb, Kar Amit, Mukherjee Pulok K
School of Natural Product Studies, Department of Pharmaceutical Technology, Jadavpur University, Kolkata 700 032, India.
Food Chem. 2017 Oct 1;232:689-696. doi: 10.1016/j.foodchem.2017.04.008. Epub 2017 Apr 5.
The fruit of Dillenia indica L. is extensively used as a food additive. Betulinic acid (BA) is the most prominent secondary metabolite present in D. indica. This study screened the bioassay guided isolation of BA from D. indica and explored its tyrosinase inhibitory mechanism. Half maximal inhibitory concentration (IC) of BA were calculated as 13.93µM and 25.66µM for diphenolase and monophenolase. Enzyme kinetic analysis revealed that BA inhibited tyrosinase activity non-competitively. Further, conformational analysis of tyrosinase with BA was measured by fluorescence and circular dichroism spectroscopy. These results implied that diminish rigidity of enzyme might disturb the catalytic conformation of tyrosinase. Moreover, In-silico analysis confirmed probable binding polar and non-polar region on the active site of tyrosinase. Based on these findings, we suggest that BA from D. indica may be useful in preventing enzymatic browning reactions in food products.
五桠果的果实被广泛用作食品添加剂。桦木酸（BA）是五桠果中最主要的次生代谢产物。本研究筛选了从五桠果中生物测定导向分离BA的方法，并探讨了其酪氨酸酶抑制机制。BA对二酚酶和单酚酶的半数抑制浓度（IC）分别计算为13.93µM和25.66µM。酶动力学分析表明，BA对酪氨酸酶活性的抑制作用为非竞争性。此外，通过荧光和圆二色光谱法测定了BA与酪氨酸酶的构象分析。这些结果表明，酶刚性的降低可能会干扰酪氨酸酶的催化构象。此外，计算机模拟分析证实了酪氨酸酶活性位点上可能的结合极性和非极性区域。基于这些发现，我们认为五桠果中的BA可能有助于预防食品中的酶促褐变反应。
