Evaluation of Antimicrobial Activity in Extracts of Different Parts of Three Tagetes Species

Abstract

Indiscriminate use of antibiotics often results in the development of resistant microbial strains. The unprecedented increase in cases of antimicrobial drug resistance, the discovery of newer agents, particularly from natural plant metabolites, are required for the control of such prevalent and recurring infectious diseases worldwide. This study aimed to evaluate antibacterial and antifungal activities of extracts from different parts of Tagetes patula, Tagetes erecta, and Tagetes minuta, which are important medicinal plants. Five grams of airdried flower, leaf, and bud (only for T. patula and T. erecta) samples were extracted three times with methanol: water (4:1) at room temperature in the dark for 24 h. The methanol: water extracts were combined, filtered, and concentrated to dryness using a rotary evaporator at 40 degrees C. The extracts were screened for their in vitro antimicrobial activities against nine indicator strains [three Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, and Enterococcus faecalis), three Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa) and three fungi (Candida albicans, Aspergillus niger, and Phytophthora erythroseptica)] by Agar well diffusion assay. Broth microdilution method was used to determine minimum inhibition concentrations (MIC) of the extracts that showed antimicrobial activity against Gram-positive bacteria and P. erythroseptica. The T. patula leaf extracts led to the highest antibacterial activity against B. subtilis ATCC 6633 with an inhibition zone of 17 mm and a MIC value of 256 mu g/ml. The bud and flower extracts of T. patula were potent against the same strain at an intermediary level. Also, the T. erecta bud extracts inhibited the growth of E. faecalis ATCC 29212 at a moderate level. In this study, only the T. patula flower extracts showed antifungal activity against P. erythroseptica strain with a MIC value of 426.7 mu g/ml. Our findings make an excellent contribution to revealing the antimicrobial activity of T. erecta, T. patula and T. minuta by comparing the methanol-extracted leaf, bud, and flower parts at a single experimental setup.