Synergistic or additive antimicrobial activities of Indian spice and herbal extracts against pathogenic, probiotic and food-spoiler micro-organisms

Traditionally the people of India have a long-standing practice of using wide variety of herbal products in treatment of diseases or as preservatives in foods. Spices are indispensable components of Indian cuisines since ancient times. Spices are considered as rich source of bio-active antimicrobial compounds. The disc diffusion and MIC bioassays were performed with some selected Indian spices and herbs against some entero-pathogenic, probiotic or food-spoiler microbes. Widest inhibition zones (12-14 mm DIZ) were seen in cases of aqueous extracts of fenugreek, mustard and henna. Gram positive bacteria were more prone to these spices or herbal extracts than Gram negative bacteria and fungus. Klebsiella pneumonie and Aspergillus niger were the most resistant microbes while Staphylococcus aureus and E. coli were most susceptible strains. Combinations of the spices in several cases demonstrated synergistic or additive effect. No antagonistic effect was seen. Cumin and fenugreek or Black cumin and mustard combinations demonstrated higher synergistic antimicrobial effects.