ANTIMICROBIAL POTENCY AND PHYTOCHEMICAL CONTENTS OF THREE COMMON NIGERIA MEDICINAL PLANTS' LEAF EXTRACTS

Abstract

Morinda lucida, Tithonia diversifolia and Carica papaya are three medicinal plants commonly used for curing several diseases in traditional medicine. However, comparative scientific information as regards their antibacterial, antifungal, and phytochemical properties remains limited. Fresh leaves of Morinda lucida, Tithonia diversifolia, and Carica papaya were harvested and extracted by soaking pulverized samples of the plants in 250 mL of water and ethanol. The phytochemical constituents were determined by subjecting the decoction to qualitative and quantitative tests using standard methods. The antimicrobial and antifungal activities were determined by solidified Mueller-Hinton agar plate and solidified Potato Dextrose agar plate respectively. Alkaloids, flavonoids, saponins, tannins, and terpenoids were shown to be the primary metabolites in the ethanolic extract of the three plant species. Cardiac glycosides are only present in T. diversifolia. Aqueous and ethanolic leaf extracts of the three species had significant, but varying antibacterial activity and no antifungal properties. Ethanolic extracts of Morinda lucida were the most active against Escherichia coli with a 30 mm zone of inhibition and very active against Klebsiella pneumonia and Enterobacter aerogenes with 28 mm and 24 mm zone of inhibition, respectively. The aqueous extracts of T. diversifolia were more active against Staphylococcus aureus, Serratia marscences, and Enterobacter aerogenes than ethanolic extract. The ethanolic decoction of C. papaya was active against Enterococci. This study showed that depending on the decoction solvent and the microbes under investigation, the leaf extracts of the three plant species have a tolerable but variable level of activity.