THE CHEMICAL COSTITUENTS OF EGYPTIAN CITRUS SPECIES. AN EXAMINATION OF THE VOLATILE OIL AND LIGHT PETROLUM FRACTION OF ROUGH LEMON (CITRUS JAMBAHIRI LUSH.) LEAF

Abstract

A steam distilled oil obtained from rough lemon leaf (Citrus jambhiri Lush.) grown in Egypt was analyzed by gas liquid chromatography (GLC) and gas liquid chromatography –mass spectrometry (GLC- MS). A total of 139 chemical constituents were detected in the leaf oil. (E)-Caryophyllene was the major constituent in the oil with a peak area (%) of 14.47 followed by linalool (12.20 %), nerol (7.41%), limonene (7.06 %), γ-elemene (5.11%), (Z)-α-bisabolene (4.14%), δ-elemene (4.12%) and citronellal (3.37 %). Research was carried out to determine the aroma profile of Egyptian C. jambhiri leaf oil constituents as a contribution in the species taxonomy. In addition, the present study achieved a success of the isolation and characterization of four polymethoxyflavones (nobiletin, 5-Odemethylnobiletin, tangeretin, 5-hydroxy-3,6,7,8,3´,4´ hexamethoxyflavone), four sterols (a mixture of common sterols: stigmasterol and β-sitosterol, β- sitosterol-3-O-β - (6'-O-acetyl)-D - glucopyranoside, β-sitosterol-3-O-β-Dglucopyranoside), palmitic acid and long chain alcohol (1-octacosanol) from the light petroleum fraction obtained from the ethanol extract of the dried leaves. The chemical structure of the isolated compounds was established using MS (EI and FAB) and NMR (APT, H-COSY, HSQC and HMBC). The cytotoxic activity of 5-O-demethylnobiletin and 5-hydroxy-3,6,7,8,3´,4´- hexamethoxyflavone (5-HHxMF) was evaluated against human lung cancer (A549), human breast canc-er (MCF7) and human prostate cancer (PC3) cell lines. Both compounds showed significant growth inhibitory effects on the tested cell lines. 5-HHxMF exhibited more pronounced activity with IC50 40.4, 10.72 and 13.90 μM, respectively.