Extraction and recovery of karanjin: A value addition to karanja (Pongamia pinnata) seed oil

Karanja (Pongamia pinnata) seed oil contains karanjin, a bioactive molecule with important biological attributes. The objective of this study was to develop a facile method for efficient recovery of karanjin. The seed oil was subjected to liquid–liquid extraction with methanol. The extract was further purified by chromatography on alumina followed by crystallization to afford karanjin, whose purity was ascertained by HPLC. The recovery of karanjin was ∼20% with >95% purity. The structure of the compound was elucidated by MS and NMR spectral analysis. Mass spectrum for the compound in ESI+ mode showed signals at 293 and 315 corresponding to (M+H+) and (M+Na+) adducts, respectively, confirming the molecular weight to be 292. 1H and 13C spectral data established the structure of the molecule to be a furano-flavonoid compound with the furan ring signals appearing at 7.78 (Hα)/145.4 (Cα) and 7.20 (Hβ)/103.9 (Cβ). 1H COSY, HMBC (H → C) and DEPT spectral data showed the annelation of furan and flavonoid rings to be at C7/C8 and C9/C10 positions, respectively, and a phenyl ring substitution at 2 (1′) position. Karanjin's recovery in pure form and high yield affords value addition to the seed oil for pharmaceutical applications.