Hepatoprotective and cytotoxic activities of Delonix regia flower extracts

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Fractionation of the ethanolic extract of the flowers of Delonix regia led to the isolation of three sterols, namely, stigmasterol (1.54 %), β-sitosterol and its 3-O-glucoside (6.93 %), a triterpene, namely, ursolic acid (3.61 %) and four flavonoids: quercetin (2.92 %), quercitrin (0.59 %), isoquercitrin (3.87 %) and rutin (5.12 %) in addition to the amino acid L- azeditine-2-carboxylic acid. The structures of the isolated compounds were established on the basis of physicochemical properties and spectral analysis (IR, UV, EI/MS, 1H-NMR and 13C-NMR). The concentration of the isolated compounds was determined by HPLC technique. The ethanolic extract and its non-polar and flavonoid rich fraction as well as the isolated compounds evidenced cytotoxic activities against human liver cancer cell line (HEPG2) which were potent for ursolic acid (IC50 0.55 μg/ml) and L-azeditine-2-carboxylic acid (IC50 2.51 μg/ml). Meanwhile, rutin and isoquercitrin were inactive. Moreover, the ethanolic extract and its two fractions were tested for hepatoprotective activity against CCl4 induced hepatic cell damage in rats at two dose levels (50 and 100 mg/kg), and the flavonoid rich fraction showed statistically significant hepatoprotection at 100 mg/kg. The presence of the aforementioned flavonoids with their efficient free radical scavenging properties may explain this liver protection ability. This could suggest the use of the ethanolic extract of the flowers of D. regia as a chemopreventive agent against the two main causes of liver damage; liver toxicity by chlorinated agents and liver cancer.

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