Abstract:
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, 1
H-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.