Flavonolignans and Biological Activity of Nannorrhops ritchiana Leaves

Objectives: This study aimed at isolating the polyphenolic compounds of 70% methanol extract ofNannorrhops ritchiana Griff. leaves and assaying the antioxidant and cytotoxic activities of the extract and main fractions. Methods: The methanol extract of the leaves of N. ritchiana was chromatographically fractionated using a bioactivity-guided approach. The isolated compounds were spectroscopically elucidated by UV, MS, 1H/13C NMR and 2D NMR spectroscopic techniques. The radical scavenging activity of the methanol extract and its fractions was evaluated using DPPH (2,2-Diphenyl-1-picrylhydrazyl) radical scavenging assay and their cytotoxic activity was assayed using SRB (3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyltetrazolium bromide) test against human hepatocellular liver carcinoma (HepG2), human alveolar adenocarcinoma (A549) and human prostate carcinoma (PC3) cell lines. Results: Eight compounds were isolated and identified for the first time from the leaves of N. ritchiana, comprising five flavonolignans;Indocalatin A (4) which is a rare compound that has been reported only once in nature, 9″-O-glucopyranosyl Salcolin A (5), 9″-O-glucopyranosyl Salcolin B (6) together with their aglycones, Salcolin A (7) and Salcolin B (8) along with three flavone glycosides; Tricin-7-O-rutinoside (1), Orientin (2) and Isoorientin (3). The methanol extract of N. ritchiana showed antioxidant activity with SC50 39.4 ± 1.06 μg/ml, while fraction IIshowed significant effect with SC50 of 6.1 ± 0.24 μg/ml in comparison with ascorbic acid (SC50 1.8 ± 0.35 μg/ml). The methanol extract and the fraction III showed a promising cytotoxic activity against selected cell lines especially the A549 with IC50 9.5 ± 1.98 μg/ml and HepG2 with IC50 8.15 ± 1.3 μg/ml, respectively. Conclusion: N. ritchiana leaf methanol extract is a new source of biologically active compounds, including flavonolignans.