Bioactive monoterpene phenol dimers from the fruits of Psoralea corylifolia L.

Abstract

Nine undescribed monoterpene phenol dimers, bisbakuchiols D-L (1–9), were isolated from the fruits of Psoralea corylifolia L. Their structures were elucidated based on extensive spectral analysis. The absolute configurations of 1–9 were specified by experimental and quantum chemical calculations of ECD spectra, and that of 1 was further established by X-ray diffraction analysis using Cu Kα radiation. Bisbakuchiols (1–4) were composed of two bakuchiols, one of which was cyclized via a C-7′/ C-12′ single bond to form a six-member ring, and connect to each other by C–4–O–C–13' bonds. Bisbakuchiols (7–9) had a pyran ring by linkage of C–8–O–C–12. In the enzyme assay, compounds 5 and 9 exhibited significant PTP1B inhibitory activities with IC50 values of 0.69 and 0.73 μM, and compounds 1 and 3 showed moderate PTP1B inhibitory activities. Furthermore, a molecular docking simulation of PTP1B and active compounds 5 and 9 showed that these active compounds possess low binding affinities ranging from −6.9 to −7.1 kcal/mol.