Labdane diterpene andrographolide (1) is a major constituent of Andrographis paniculata and known to exhibit wide spectrum of biological activities. In this study, regioselective monoesters of (1) have been synthesized by using Amano lipase AK (Pseudomonas fluorescens) as a biocatalyst. Amano lipase AK was able to execute highly efficient esterification of hydroxyl group attached to C-14 carbon of (1) in presence of acyl donors. Among the various synthesized derivatives including two novel compounds such as andrographolide-14-propionate (3) and andrographolide-14-caproate (5) displayed antimicrobial activity against Staphylococcus aureus with low minimal inhibitory concentration (MIC) 4 µg/mL and 16 µg/mL respectively. Furthermore, they have shown low hemolysis activity at their respective MIC and increase in the permeability of the bacterial cell membrane as delineated by FITC uptake and SEM imaging studies.

拉丹烷二萜穿心莲内酯（1）是穿心莲的主要成分，已知具有广泛的生物活性。在这项研究中，通过使用Amano脂肪酶AK（荧光假单胞菌）作为生物催化剂合成了（1）的区域选择性单酯。在酰基供体的存在下，Amano脂肪酶AK能够对与（1）的C-14碳相连的羟基进行高效酯化。在各种合成的衍生物中，包括两种新化合物，如穿心莲内酯-14-丙酸酯（3）和穿心莲内酯-14-己酸酯（5）显示出对金黄色葡萄球菌的抗菌活性。最低抑菌浓度（MIC）较低，分别为4 µg / mL和16 µg / mL。此外，如FITC摄取和SEM成像研究所示，它们在各自的MIC处显示出较低的溶血活性，并且细菌细胞膜的通透性增加。