Chromatographic analyses and in vitro screening of the antimicrobial activity of tannins extract of fenugreek seeds grown in the Taghit region (Southwest of Algeria)

Abstract

Fenugreek (Trigonella foenum-graecum L.) is an annual herbaceous plant belonging to the Fabaceae family. The seeds of the fenugreek plant are known to have important medicinal, therapeutic and nutritional properties. The objective of this study was to characterize and evaluate the antimicrobial activity of Trigonella foenum-graecum L. seeds’ tannins extract grown in Taghit town (Bechar-Algeria). After degreasing the plant material, the tannins were extracted by maceration using ethyl acetate, dichloromethane, and acetone and analyzed by two analytical techniques: Thin-Layer Chromatography (TLC) and High-Pressure Liquid Chromatography (HPLC). The antimicrobial effect was evaluated by the agar diffusion method, against 26 microbial strains, with the determination of the minimal inhibitory concentration by the broth macrodilution technique. The TLC and HPLC results of the tannins extract of fenugreek seeds showed the presence of tannic acid, phloroglucinol, resorcinol, and catechol where tannic acid was the major constituent of this extract. From a concentration of 30 mg/mL, the antimicrobial effect results showed a proportional relationship between the concentration of the extract and the antimicrobial activity. A low to medium antimicrobial effect against the tested species was found due to the increased multidrug resistance of the tested strains. The uropathogenic strains, namely S. aureus, Klebsiella sp, Candida albicans, and E. coli (7), as well as S. aureus American Type Culture Collection (ATCC) 25923 and B. cereus ATCC 14579 – which were more susceptible compared to the other tested bacteria – with an activity index varying from 0.33 to 1.09 compared to gentamicin. This consolidates the place of fenugreek seeds within traditional herbal medicine. This species has great potential as a herbal antibacterial agent.