Prenylated Flavonoids from Pongamia pinnata

Pongamia pinnata (Leguminosae) is widely distributed along southeastern Asia to the west Pacific and north Australia. All parts of the plant have been used as crude drug for the treatment of tumors, piles, skin diseases, wounds, ulcers, etc. [1]. Extracts of the plant possess significant anti-diarrhoeal, anti-fungal, anti-plasmodial, anti-ulcerogenic, anti-inflammatory, analgesic activities [2 – 6]. Previous phytochemical examination of this plant indicated the presence of abounding prenylated flavonoids such as furanoflavones, franoflavonols, chromenoflavones, furanochalcones, and pyranochalcones [7 – 9]. During our ongoing research on this plant, a new prenylated chalcone, 2’-hydroxy-3, 4-methylenedioxy-5’-prenyl6”, 6”-dimethylpyrano-[3’, 4’ : 2”, 3”]chalcone (1) and a new prenylated flavone, 3’, 5’-dimethoxy-[2”, 3” : 8, 7]-furano flavone (2), have been isolated from the stem bark of this plant, along with five known compounds, 2’-hydroxy-6’-methoxy-6”, 6”dimethyl-chromeno-[4’, 3’ : 2”, 3”]-chalcone (3) [10], ovaliflavanone A (4) [11], 6,7,2,2-dimethylchromono8,γ ,γ-dimethylallylflavanone (5) [12] and isolonchocarpin (6) [13], millettocalyxin C (7) [14]. Their structural elucidations were based on the analyses of spectroscopic data.