The aim of this study was to identify bioactive secondary metabolites from Ochna rhizomatosa with potential inhibitory effects against HIV and Plasmodium falciparum. A phytochemical study of O. rhizomatosa root barks resulted in the identification of three new biflavonoids (1–3), along with four known ones (4–7). Compound 7 (Gerontoisoflavone A) was a single flavonoid present in the rootbark of the plant and was used as a reference. Compound 1 (IC₅₀ = 0.047 µM) was the only one with a noteworthy inhibitory effect against HIV-1 integrase in vitro. Chicoric acid (IC₅₀ = 0.006 µM), a pure competitive inhibitor of HIV-1 integrase, was used as control. Compound 2 exhibited the highest antiplasmodial activity (IC₅₀ = 4.60 µM) against the chloroquine-sensitive strain of Plasmodium falciparum NF54. Computational molecular docking revealed that compounds 1 and 2 had the highest binding score (−121.8 and −131.88 Kcal/mol, respectively) in comparison to chicoric acid and Dolutegravir (−116 and −100 Kcal/mol, respectively), towards integrase receptor (PDB:3LPT). As far as Plasmodium-6 cysteine s48/45 domain inhibition is concerned, compounds 1 and 2 showed the highest binding scores in comparison to chloroquine, urging the analysis of these compounds in vivo for disease treatment. These results confirm the potential inhibitory effect of compounds 1 and 2 for HIV and malaria treatment. Therefore, our future investigation to find inhibitors of these receptors in vivo could be an effective strategy for developing new drugs.

In a continuation of our study on constituents of P. guineense now focusing on the search for saponins, phytochemical investigation of the n-BuOH fraction of P. guineense stem bark led to the isolation of three previously undescribed triterpenoid saponins, named guineenosides A─C (1─3). Their structures were established on the basis of extensive analysis of 1D and 2D NMR (¹H, ¹³C NMR, DEPT, COSY, TOCSY, NOESY, HSQC, HSQC-TOCSY and HMBC) and HRESIMS experiments, and by chemical evidence as 3-O-{α-l-rhamnopyranosyl-(1 → 3)-β-d-xylopyranosyl-(1 → 2)-α-l-arabinopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 3)-[α-l-arabinofuranosyl-(1 → 4)]-α-l-rhamnopyranosyl-(1 → 3)-β-d-fucopyranosyl} polygalacic acid 28-O-α-l-rhamnopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 3)-β-d-xylopyranosyl ester (1), 3-O-{α-l-rhamnopyranosyl-(1 → 3)-β-d-xylopyranosyl-(1 → 2)-α-l-arabinopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 3)-[α-l-arabinofuranosyl-(1 → 4)]-α-l-rhamnopyranosyl-(1 → 3)-β-d-fucopyranosyl} polygalacic acid 28-O-β-d-glucopyranosyl-(1 → 3)-α-l-rhamnopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 3)-β-d-xylopyranosyl ester (2), and 3-O-{α-l-rhamnopyranosyl-(1 → 2)-β-d-xylopyranosyl-(1 → 3)-β-d-fucopyranosyl} polygalacic acid 28-O-[α-l-rhamnopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 3)-β-d-xylopyranosyl ester (3). This is the first report of triterpenoid saponins from P. guineense.