Abstract

Ursolic acid (UA) is regarded as one such compound that possesses many biological activities, such as anti-oxidation, anti-inflammatory, anticancer, and hepatoprotection, as well as the ability to induce apoptosis. Although it is present in the leaves and barks of many plants including apple peels, the traditional source to obtain large amount of this metabolite is Plumeria rubra. Its isolation is expensive and based on laborious extraction methods or obtained in low yield by synthetic methods. In this study, we determined the best extraction solvent of these compounds and verified the influence of season on the ursolic acid content. The High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD) was used to quantify ursolic acid in different months extracts. Analysis of variance (ANOVA) test followed by Turkey test were used in the statistical analysis. We demonstrated that ursolic acid was significantly more abundant in the months of May and July, and was in minor concentrations in the months of December, January, February and March. Differences in their composition during this consecutive seasons; summer (December, January, February and Mars), autumn to winter (May and July), were statistically significant. It is suggested that these differences were mainly due to the specific insects available in the three seasons. On the other hand, some authors related this to the pentacyclic triterpenes, just as ursolic acid, β-amyrine and lupeol are supposed to be toxic to insects due to their ability to inhibit acyl chain packing in the lipid bilayers of the insect’s membranes.

Key words: Plumeria rubra, ursolic acid, seasonal effect, high-performance liquid chromatography with diode-array detection (HPLC-DAD).