PHYTOCHEMICAL VARIABILITY AND ANTIMICROBIAL ACTIVITY OF EXTRACTS OF Citropsis articulata LEAVES FROM THREE TROPICAL FORESTS IN UGANDA

Abstract

Empirical evidence of the presence of bioactive compounds in plants is indispensable, given that medicinal plants play a pivotal role in the quest for new antimicrobials. In this study, leaves of Citropsis articulata from three forest reserves (Mabira, Budongo, and Kibale) in Uganda were extracted with distilled water and methanol using infusion and maceration methods, respectively. The total phenolic (TP), total flavonoid (TF), total alkaloid (TA) and total saponin (TS) contents of the extracts were evaluated using UV-Vis spectrophotometric based methods before the fingerprint of each extract was established using high-performance liquid chromatography. In vitro antimicrobial activities of the extracts were examined against standard strains of common pathogenic microbes, including Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and Candida albicans using agar well diffusion and microtitre plate-based assays. Results showed that the methanol extract had a significantly higher content of the secondary metabolites compared to the aqueous extract, with samples from Mabira showing the highest level of TP (68.92 mg GAE/g), samples from Budongo had the highest level of TF (11.28 mg QE/g) and TS (101.94 mg DE/g). In comparison, samples from Kibale showed the highest level of TA (66.29 mg AE/g). In the antimicrobial study, methanol extract showed significantly higher potency than the aqueous extract for all samples from the three locations. The plant extracts showed substantially high potency against Escherichia coli, with samples from Mabira exhibiting the maximum zone of inhibition (29.5±0.5 mm) at 50% w/v and lowest minimum inhibitory concentration (MIC) of 1.56% w/v. The extracts also demonstrated bactericidal (MBC) and fungicidal (MFC) potency against the test microorganisms in the order; Escherichia coli > Staphylococcus aureus > Pseudomonas aeruginosa > Candida albicans. This study demonstrated that Citropsis articulata leaves have potentially potent bioactive compounds that could be explored for future antimicrobial drug development.