New isoflavones and bioactive constituents from the fruits of Psoralea corylifolia

Psoralea corylifolia (Chinese name Buguzhi), dry fruits of leguminous plant P. corylifolia L., is one of the most popular traditional Chinese medicines. This crude drug has used for the treatment of pollakiuria, enuresis, osteoporosis, depression, and various kidney problems. It is reported to contain coumarins, flavonoids, alkaloids, essential oil, and terpenoids. Many of these compounds were found to exhibit anti-allergic, antioxidant, antitumor, insecticidal, and antimicrobial activities. Investigation on n-hexane- and EtOAc-soluble fractions of the fruits of P. corylifolia has led to the isolation of two new isoflavones, 7-O-methylcorylifol A (1) and 7-O-isoprenylcorylifol A (2), together with eight known compounds, including angelicin (3), psoralen (4), bavachalcone (5), bakuchiol (6), 12,13-dihydro-12,13-epoxybakuchiol (7), p-hydroxybenzaldehyde (8), b-sitosterol (9), and stigmasterol (10). The structure of new compounds 1 and 2 was determined through spectroscopic and MS analyses. Among the isolated compounds, psoralen (4) exhibited inhibition (IC₅₀ value = 1.10±0.60µg/mL) of superoxide anion generation by human neutrophils in response to formyl-L-methionyl-L-leucyl-L-phenylalanine/cytochalasin B (fMLP/CB).

Figure 1: Structures of new compounds 1 and 2

Acknowledgement: This research was supported by grants from the National Science Council of the Republic of China (No. NSC 95–2320-B-127–001-MY3 and NSC 98–2320-B-127–001-MY3), awarded to J.-J. C.

References: 1. Huang T C, Ohashi H (1993) 'Leguminosae' in 'Flora of Taiwan', 2nd ed., Editorial Committee of the Flora of Taiwan, Taipei, Taiwan, Vol. 3, pp. 160–396.