Reassessment of structures of flavonoids isolated from the fruits of Pongamia pinnata (L.) Pierre

Abstract

Pongamia pinnata (L.) Pierre, syn. Millettia pinnata (L.) Panigrahi; (family Fabaceae), is a native to tropical and temperate Asia. Its fruits, seeds and sprouts are used to treat abdominal tumours, bronchitis, fever, whooping cough, lumbago, piles, urinary discharges and diseases of the brain, eye, head and skin. A methanolic extract of the defatted fruits was subjected to silica gel column chromatography using petroleum ether, chloroform and methanol as eluants in order of increasing polarity to isolate the chemical constituents. The structures of the isolated phytoconstituents were elucidated on the basis of the spectral data analysis and chemical reactions. Four new flavonoids characterized as 5,6-furano-7,8-furano-4E¹-methoxyflavanol (pinnataflavonol, 1), cis-,cis-13-(3E¹-methoxy-4E¹-hydroxy- chalconyl-(13→13E¹)-3,4-dimethoxychalcone (pinnatabichalcone, 2), 5,7,2E¹,3E¹-tetrahydroxy-4E¹-methoxy-8-ethylflavonyl-(6→8a)-5a,7a,2E¹a,3E¹a,4E¹a-pentahydroxyflavone (pinnatabiflavone, 3) and cis,cis-13-(3E¹-methoxy-4E¹-hydroxychalconyl-(13→13E¹)-3-n-tetradecanyloxy-4-methoxychalcone (pinnatabichalconyl myristate, 6) together with the known compounds lanost-5-en-3I²-ol 3I²-D-glucopyranoside (4) and glyceryl 1-octadec-9E¹-enoate 2-tetradecanoate 3-phosphate (5) were isolated. All the phytoconstituents are reported from P. pinnata fruits for the first time.