Phenolic Compounds from Pueraria lobata Protect PC12 Cells against Aβ-induced Toxicity

Bioassay-guided fractionation of the EtOAc-soluble extract of Pueraria lobata based on the inhibition of A beta-induced toxicity in PC12 cells resulted in the isolation of four known active compounds, genistein (8), biochanin A (9), sissotrin (10), and puerol B (11). Of these, genistein (8) and biochanin A (9) exhibited potent neuroprotective effects with ED50 values of 33.7 and 27.8 mu M, respectively. In addition, a new coumestan, 2-(alpha,alpha-dimethylallyl)coumestrol (1) was isolated and characterized, but proved to be inactive, as were additional seven known compounds. The structure of new compound 1 was determined using spectroscopic techniques.