Antimycobacterial, antiplasmodial studies and cytotoxicity of oleanolic acid and its derivative from Syzygium aromaticum Linn (Myrtaceae)

Malaria and tuberculosis are among the most common death causes and threats to human life globally. In a quest to find new antimalarial and anti-mycobacterial drugs, oleanolic acid (OA) was isolated from the flower buds of Syzygium aromaticum Linn (Myrtaceae). The derivative, 3-O-Acetyl-Oleanolic acid (OAA), was synthesized from the isolated product and the biological activities of the two compounds were compared. The antiplasmodial and antimycobacterial activity of oleanolic acid and its derivative were investigated against Plasmodium falciparum (Chloroquine Sensitive Strain) NF54 and Mycobacterium tuberculosis H37Rv. OAA exhibited IC50 of 4.3 µg/ml against P. falciparum, compared with an IC50 of 27.4 µg/ml for OA, while against M. tuberculosis OAA showed 0.1 µg/ml, compared with an IC50 of 0.042 µg/ml for OA. In the cytotoxicity studies, using the MTT assay, both compounds exhibited LC50 of > 300 µg/ml against both human embryonic kidney (HEK293) and hepatocellular carcinoma cell lines (HepG2), suggesting that the compounds are not cytotoxic at low to moderate concentrations against the tested cell lines. In conclusion, the derivative OAA improved the antiplasmodial activity but no improvement was shown for antimycobacterial activity, in comparison with the starting material OA. Thus, more derivatives could be designed, using OA as starting material, to obtain future antiplasmodial compounds.