New Isoflavones from the Fuits of Psoralea corylifolia and their Anti-inflammatory Activity

Psoralea corylifolia L. (Leguminosae) is an annual herb distributed in India, Malay peninsula, Indonesia, China, and Taiwan [1]. Dry fruit of P. corylifolia Linn is one of the most popular Traditional Chinese Medicine (TCM) and officially listed in Chinese Pharmacopoeia [2]. This crude drug has been used for the treatment of spermatorrhea, nephritis, asthma, pollakiuria, and various inflammatory diseases. Various flavonoids, isoflavones, meroterpenes, coumestans, and their derivatives were isolated from this plant in previous studies. Many of these compounds exhibit anti-inflammatory, phytoestrogen, anti-nitric oxide synthase (iNOS), anti-platelet aggregation, antibacterial, and anti-Helicobacter pylori activities. Three new isoflavone derivatives, 7-O-methylcorylifol A (1), 7-O-isoprenylcorylifol A (2), and 7-O-isoprenylneobavaisoflavone (3), have been isolated from the fruits of P. corylifolia, together with 9 known compounds (4-12). The structures of these new compounds were determined through spectroscopic and MS analyses. Among the isolated compounds, 7-O-methylcorylifol A (1) and psoralen (5) exhibited potent inhibition (IC₅₀ values ≤10.89µM) of superoxide anion generation by human neutrophils in response to N-formyl-L-methionyl-L-leucyl-L-phenylalanine/cytochalasin B (fMLP/CB). 7-O-Isoprenylcorylifol A (2), 7-O-isoprenylneobavaisoflavone (3), and 12,13-dihydro-12,13-epoxybakuchiol (7) inhibited fMLP/CB-induced elastase release with IC₅₀ values ≤14.30µM. In addition, compounds 2, bakuchiol (6), 7, and psoralidin (10) showed potent inhibition with IC₅₀ values ≤36.65µM, against lipopolysaccharide (LPS)-induced nitric oxide (NO) generation.

[1] Huang TC, Ohashi H. 1993. Leguminosae. In: Flora of Taiwan, 2nd edition. Editorial Committee of the Flora of Taiwan: Taipei, Taiwan; 1993; 3: 160 – 396.

[2] Pharmacopoeia of the People's Republic of China. Chemical Industry Publications: Beijing; 2005; 1: 129 – 130.