Microglia, the immune regulatory and inflammatory cells of the central nervous system (CNS), can be activated in response to a variety of neurodegenerative and neuroinflammatory conditions. Activation of microglia results in the production of proinflammatory materials such as tumor necrosis factor-a (TNF-a), interleukin-1 and 6, reactive oxygen species (ROS), and nitric oxide (NO) in response to injury. [1][2][3][4] Large amounts of NO produced by inducible nitric oxide synthase (iNOS) can rapidly react with superoxide anion radical (· O 2 Ϫ ) to produce peroxynitrite anion (ONOO Ϫ ). 5,6) These reactive nitrogen species might be involved in the pathogenesis of various neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease and ischemia. 7) As a neuromodulator in CNS, NO participates in brain development, pain perception, memory, neuronal plasticity and behavior.8) The excessive amounts of NO has been observed in damaged tissues associated with type I diabetes, arthritis, or nephritis, 9) suggesting that deregulation of iNOS expression is linked to many diseases. The expression and activity of iNOS are increased in chronic diseases, such as inflammation or cancer.10) Generally the iNOS along with the release of NO by microglia contributes to progress neurodegeneration and aggravate diseases. Therefore, the inhibitors of NO production may have beneficial therapeutic effects in the treatment of diverse diseases.In order to find new iNOS inhibitors from medicinal plants, we have screened inhibitory activity of NO production in lipopolysaccharide (LPS)-activated BV-2 mouse microglial cells. The methanol extract of Psoralea corylifolia L. (Fabaceae) showed remarkable inhibitory effects on NO production. The seeds of P. corylifolia have been used traditionally for the treatment of stomachic, deobstruent, anthelmintic, diuretic, vitiligo and certain skin diseases. 11,12) Several reports revealed that its seeds contain antimutagenic coumarins, antioxidants, antibacterial and antiplatelet flavonoids. [13][14][15][16] This article describes the identification of two prenylflavonoids from Psoralea corylifolia and their inhibitory activity of NO production in LPS-activated microglial cells.
MATERIALS AND METHODS
Plant MaterialsThe dried seeds of Psoralea corylifolia were purchased from the Kyungdong oriental drug market in Seoul, Korea and authenticated by Prof. T. H. Kim at the College of Pharmacy, Sookmyung Women's University. A voucher specimen (No. SPH 04005) was deposited in the herbarium of the Sookmyung Women's University. The plant materials (540 g) were extracted three times with MeOH and the combined extracts (130 g) were successively partitioned with n-hexane, EtOAc and BuOH.The EtOAc soluble fraction (53 g) was subjected to silica gel column chromatography eluting with an n-hexane-EtOAc gradient system (50 : 1-1 : 5) to afford active fractions A 1 (0.8 g) and A 2 (3.6 g). Repeated silica gel column chromatography of fraction A 1 with a gradient elution of n-hexaneEtOAc (30 : 1-1 : 1) to give ...
