Investigation of antimicrobial activity of safflower (Carthamus tinctorius) and bitter melon (Momordica charantia L.) extracts against fish spoilage and food-borne pathogens

In the current study, the effect of safflower (Carthamus tinctorius) and bitter melon (Momordica charantia L.) extracts on growth of fish spoilage (Acinetobacter lwoffii, Pseudomonas oryzihabitans, Enterobacter cloacae, Shigella spp., Morganella psychrotolerans, Photobacterium phosphoreum) and food-borne pathogens (Staphylococcus aureus, Klebsiella pneumoniae, Enterococcus faecalis, Salmonella Paratyphi A), and their biogenic amine production in fish infusion (anchovy and mackerel) decarboxylase broth were investigated. The antimicrobial activity of safflower and bitter melon was determined by minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC). Enterococcus faecalis was the most susceptible bacteria against safflower extract with MIC value of 6.25 mg/ml, whilst bitter melon was the most effective against Enterobacter cloacae, Shigella spp. and Enterococcus faecalis (12.5 mg/ml). Significant differences were observed among groups in terms of ammonia and biogenic amine production (p<0.05). Acinetobacter lwoffii (254.05 mg/L) and Photobacterium phosphoreum (234.39 mg/L) was main bacteria produced the highest level of histamine in anchovy infusion decarboxylase broth. The highest tyramine production (2806.39 mg/L) in mackerel infusion decarboxylase broth was found for Enterococcus faecalis. The extracts generally reduced ammonia and biogenic amine production by bacteria in anchovy and mackerel broth, although the effect of the extracts on biogenic amine production varied depending on fish infusion broth, spesific bacteria and biogenic amine. Histamine production by Photobacterium phosphoreum was significantly inhibited in the presence of extracts (P<0.05). The study results showed that safflower and bitter melon extracts could be useful as antimicrobial in foods