Antimalarial Biflavonoids from the Roots of Ochna serrulata (Hochst.) Walp

Aims: To isolate and evaluate the biological activities of the compounds present in the roots of Ochna serrulata.

Study Design: Laboratory isolation of compounds by using various chromatographic methods, and cytotoxicity and antimalarial evaluations of the isolated compounds.

Place and Duration of Study: School of Chemistry and Physics, College of Agriculture, Engineering and Science, University of KwaZulu-Natal (UKZN), from September 2009 to June 2012.

Methodology: Methanol extract of the pulverised roots of O. serrulata were subjected to different chromatographic techniques. Structures were established by using 1D and 2D NMR techniques and MS. The compounds were subjected to cytotoxicity tests to evaluate their growth inhibitory effects on renal (TK 10), melanoma (UACC62) and breast (MCF7) cancer cell lines using a sulforhodamine B (SRB) assay. Antimalarial evaluations were done against chloroquine-resistant strains of Plasmodium falciparum (FCR-3).

Results: Three new biflavonoids; 4,4′,7-tri-O-methylisocampylospermone A (1), 4‴-de-O-methylafzelone A (2) and serrulone A (3) along with irisolone 4′-methyl ether (4), 3',4'-dimethoxy-6,7-methylenedioxyisoflavone (5), iriskumaonin 3′-methyl ether (6), lophirone L (7), a mixture of biflavanone 1 and campylospermone A, syringaresinol (8), and 16α,17-dihydroxy-ent-kauran-19-oic acid (9). Compound 1 showed antimalarial activity with IC50 11.46 µM, followed by compound 3 (26.52 µM) and lastly compound 2 (38.43 µM). In the same test, 4 demonstrated antimalarial activity at IC50 40.72 µM, 8 (42.66 µM), 6 (93.69 µM), 9 (106.48 µM) and the rest did not show any significant activity. Upon cytotoxicity evaluation against three different cancer cell lines, the compounds displayed no significant activity.

Conclusion: The genus is comprised of biflavonoids of varying nature, some of which expressed interesting biological activities with no/low toxicity.