Comparative physicochemical, phytochemical and acute toxicity studies of two Ocimum species in Western Uganda

Abstract

Ocimum gratissimum and Ocimum suave are species belonging to the Lamiaceae family; they have been domesticated and are widely grown in gardens in Western Uganda for its claimed beneficial effect in ethnomedical practice. This study was aimed at comparative evaluation of the physicochemical, phytochemical and acute toxicity potentials of their leaves. Dried leaves of O. gratissimum and O. suave were subjected to physicochemical analysis, crude extraction in methanol and sequential extraction in n-hexane, chloroform, ethylacetate and methanol. Phytochemical constituents of the crude extracts were determined by both qualitative and quantitative methods, while acute toxicity potentials were studied in female rats. Total caffeic acid derivatives contents, total flavonoid contents and reducing power assay were evaluated in the sequential extracts. The physicochemical parameters of leaves of O. gratissimum and O. suave showed similar profiles. The extraction yield, phytochemical constituents and acute toxicity effects of the crude extracts were not significantly different. Hexane, chloroform and ethylacetate extract of O. suave showed significant (p < 0.05) higher total flavonoid contents than corresponding extracts of O. gratissimum. Similarly, O. suave extracts showed a stronger positive correlation of phenolic content to antiradical power than the corresponding extracts of O. gratissimum.  Conclusively, the two species showed comparative physicochemical, phytochemical and acute toxicity profiles, and a positive correlation of phenolic contents to antiradical power. Key words: Lamiaceae, Uganda, phenolics, Ocimum gratissimum, Ocimum suave.