Abstract:
Different varieties of chemical preservatives are used as antimicrobial to prevent the growth of bacterial food spoilage. However, health and economic concerns have led to an intensive search for natural plant extracts that can safely be used as substitutes for synthetic antimicrobials and preservatives to partially or completely inhibit the growth of bacteria.
The aim of this current work was to evaluate the antimicrobial activity of Trigonella foenum graecum L. seeds solvent extracts against Escherichia coli, Staphylococcus aureus, Salmonella typhi and Bacillus cereus by agar well diffusion method. The crude phytochemicals from fenugreek seed were extracted using a mixture of three solvents (methanol, ethanol, and acetone). The experimental design was based on Box-Behnken design (BBD) that was used to obtain process variables and their levels. The experimental factors were a mixture of solvent type (acetone, ethanol and methanol) concentrations (75%, 85.5% and 96%) on extract yield, total phenols (TP), total flavonoids (TF) and total tannins (TT). The antimicrobial effects of the fenugreek crude seed extracts were determined by the zone of inhibition, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against each food borne bacteria. The maximum zones of inhibition (mm) were 8.9 (at 75% acetone, 96% ethanol and 96% methanol), 6.9 (at 75% acetone, 85.5% ethanol and 96% methanol), 23 (at 85.5% acetone, ethanol and methanol) and 6.8 (96% acetone, 85.5% ethanol and 96% methanol) found against E.coli, S.aureus, S. typhi and B. cereus respectively. The minimal inhibitory concentration (MIC) ranged (mg/ml) between 2 to 8 and the minimal bactericidal concentration (MBC) ranged (mg/ml) between 8 to 32. The maximum crude seed extract yield obtained was 14.6±0.62% at 85.5% acetone, ethanol and methanol, and the total phenol at 96% acetone, 75% ethanol and 85.5% methanol, total flavonoid at 85.5% acetone, 96% ethanol and methanol and tannin contents at 85% acetone, ethanol and methanol were 14.77mg(GAE)/g, 5.31mg(QAE)/g and 2.43mg (TAE)/g respectively. This study reveals that the fenugreek seed can be potential rich source of antimicrobial against food borne pathogens and further work should be done on the practical application of the fenugreek seed extracts on different food stuffs.