Diarylheptanoids from aerial bulbils of Dioscorea batatas

Dioscorea batatas Decne. (Dioscoreaceae) grows as a perennial herb, and is widely distributed or cultivated in Korea, Japan and China. The rhizomes and bulbils of D. batatas have been used as tonics, and crude drug for the treatment of diabetes and diarrhea in the traditional Chinese medicine. Also, its rhizome is a well-known edible plant. Previous studies on D. batatas have afforded mainly steroids, steroid glycosides and phenanthrene derivatives. In our continuing studies to find bioactive compound from natural products, we have found that the MeOH extract of D. batatas bulbil has anti-inflammatory activity. The MeOH extract was fractionated by using Diaion HP-20 column with consecutive elution (H₂O˜MeOH, and acetone). A new and five known diarylheptanoids were isolated from the subfractions by means of chromatographic separation. The known compounds were identified as meso-hannokinol, hexahydrocurcuminol, 5-hydroxyplatyphyllone, (3R,5S)-3,5-dihydroxy-1-(4′-hydroxyphenyl)-7-(3″-methoxy-4″-hydroxyphenyl)heptane, (3R,5S)-3,5-dihydroxy -1-(4′-hydroxyphenyl)-7-(3″,4″-hydroxyphenyl) heptane, respectively by comparison of their spectral data with literature values. The structure of a new diarylheptanoid was determined as (1S, 3R, 5S)-1,3,5-trihydroxy-1,7-bis(4′-hydroxyphenyl)heptane from its spectral data and chemical evidence. Inhibitory effects of the isolated compounds on nitric oxide, TNF-α and IL-6 production were evaluated in lipopolysaccharide-activated RAW 264.7 cells.