Two new neo-clerodane diterpenoids from Tinospora cordifolia stems

Phytochemical studies of the 70 % ethanol extract of Tinospora cordifolia stems led to the isolation of two new neo-clerodane diterpenoids, including tinocordifoliols C (1) and D (2). Their structures were determined by experimental 1D and 2D NMR, HR-ESI-MS, ECD, and statistical analyses, including DP4+ probability based on DFT calculations of NMR chemical shifts. According to the previous report for two neo-clerodane diterpenoids, tinocordifoliols A and B, the inhibitory activities of 1 and 2 against human arginases I and II were also evaluated. In contrast to the previously reported two neo-clerodane diterpenoids, 1 and 2 did not show inhibitory activities against human arginases I and II. These results provide insight into the structure-activity relationship of neo-clerodane diterpenoids.