Structural elucidation, bio-inspired synthesis, and biological activities of cyclic diarylpropanes from Horsfieldia kingii

Abstract Bioactivity-guided phytochemical investigation on 70% aqueous acetone extracts of the twigs and leaves of Horsfieldia kingii led to the isolation of two novel cyclic diarylpropanes (1 and 2) bearing a 2,3-dihydro-1H-indene core, one new diarylpropane (3), six known diarylpropanes (4–9), one flavanol (10), and seven lignans (11–17). Their structures were determined by extensive spectroscopic analysis, electronic circular dichroism calculations, and X-ray diffraction crystallography. Moreover, a biomimetic synthesis of 1 and 2 were accomplished in four steps. The in vitro nitric oxide production inhibition tests of these compounds revealed that compounds (±)-2, (+)-2, (−)-2, and 10 were potential with IC50 values lower than 10 μM. Compound 2 could inhibit iNOS expression in LPS-induced RAW264.7 cells at a series of non-cytotoxic concentrations (