Highly Oxygenated Flavonoids from the Leaves of Nicotiana plumbaginifolia (Solanaceae)

Nicotiana plumbaginifolia Viv. is an annual herb of the family Solanaceae, which grows abundantly in the weedy lands of Bangladesh . This plant possesses analgesic, antibacterial, anti-anxiety and hepatoprotective properties, and produces various phenolic compounds including flavonoids. The present study afforded determination of total phenolic and flavonoid contents, and for the first time, the isolation and characterization of highly oxygenated flavonoids, e.g., 3,3' ,5,6,7,8-hexamethoxy- 4',5'-methylenedioxyflavone (1), 3,3' ,4' ,5',5,6,7,8-octamethoxyflavone (2, exoticin), 6,7,4',5'-dimethylenedioxy-3,5,3'-trimethoxyflavone (3) and ( 3,3' ,4',5,5',8-hexamethoxy-6,7-methylenedioxyflavone (4) from the leaves of N. plumbaginifolia . All these flavonoids are rather rare natural products, and only found in a few genera, e.g.,Polygonum and Murraya. The structures of the isolated flavonoids were elucidated by comprehensive spectroscopic analyses, e.g., UV, 1H, 13C NMR, DEPT, HSQC, HMBC and MS.