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

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 AM. Compound 2 could inhibit iNOS expression in LPS-induced RAW264.7 cells at a series of non-cytotoxic concentrations (<20 mu M). Furthermore, the bioassay results also suggested the primary SARs of 1-phenyl-2,3-dihydro-1H-indene based scaffold. (C) 2020 Elsevier Ltd. All rights reserved.