PHYTOCHEMICAL CONSTITUENTS AND ANTIMICROBIAL PROPERTIES OF CRUDE LEAF EXTRACTS FROM Brucea antidysenterica J.F. MILL AND Tagetes minuta L. AGAINST SELECTED PATHOGENIC MICROORGANISMS

Abstract

Large proportions of the world’s population use traditional medicinal plants to treat various diseases. Brucea antidysenterica and Tagetes minuta are one of the most common medicinal plants used to treat infectious diseases in Ethiopia. This study was aimed to analyze major classes of secondary metabolites and evaluate the antimicrobial properties of crude leaf extracts from Brucea antidysenterica and Tagetes minuta against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus niger. Distilled water, ethanol and hexane were used for extraction. To determine total phenolic contents, total alkaloids and total terpenoids, standard procedures were used. Antimicrobial activities and minimum inhibitory concentration of the extracts were determined using disc diffusion and broth dilution method, respectively. Ciprofloxacin and distilled water were used as positive control and negative control, respectively. From the result, total terpenoids from hexane extract of Tagetes minuta was found 40.43±0.40 mg/g which is significantly different from the values of other extracts (P < 0.05). Likewise, total alkaloids of ethanol extract from Brucea antidysenterica was found 27.71±0.10 mg/g which was significantly different from values of other extracts. Except for 100mg/mL of Brucea antidysenterica, all the extracts showed antimicrobial activities. The zone of inhibition of ethanol extract from Brucea antidysenterica against Staphylococcus aureus was 11.33±0.58 mm with minimum inhibitory concentration of 12.50±0.17 mg/mL. Except for the 200 mg/mL of ethanol extract, Candida albicans was not inhibited by other extract types of Brucea antidysenterica. Similarly, ethanol extract from Tagetes minuta inhibited the growth of Staphylococcus aureus with a zone of inhibition of 16.33±0.58 mm and minimum inhibitory concentration of 8.33±3.61 mg/mL. Zone of inhibition of positive control against Staphylococcus aureus was 22.33±0.58 mm. In general, the plants studied produce secondary metabolites in different quantities and their extracts have the medicinal potential for treating bacterial and fungal infections