A novel 15-spiro diterpenoid dimer from Andrographis paniculata with inhibitory potential against human carboxylesterase 2.

The phytochemical investigation of Andrographis paniculata resulted in the isolation of a novel 15-spiro diterpenoid dimer bisandrographolide G (1). Its structure was determined by 1D and 2D NMR, HRESIMS, electronic circular dichroism (ECD), and TD DFT calculations of ECD spectra. It showed potent inhibitory activity against human carboxylesterase 2 (CES 2) with an IC50 value of 4.61 ± 0.23 µM, and it was defined as a mixed-competitive type inhibitor with a Ki value of 8.88 µM based on the inhibition kinetics result. This finding gave us a hit to develop new generation of human CES 2 inhibitors.