Inhibition of Pathogenic Bacteria Isolated from Some Nuts Seeds by Natural and Some Commercial Coumarins

Abstract

The antibacterial potential of a natural coumarin compound that was extracted from the root of Lotus lalambensis Schweinf and several commercial coumarin compounds (herniarin, xanthotoxin, umbelliferone and scopoletin) were investigated against five pathogenic bacteria (Staphylococcus epidermidis, Bacillus mycoides, Escherichia coli, Staphylococcus aureus and Bacillus cereus) that were isolated from different nut products. The natural coumarin showed the best antibacterial potential against the most sensitive bacteria (Staphylococcus aureus and Bacillus cereus) with a minimum inhibitory concentration of 62.5 μg ml-1. The antibacterial mechanism of different coumarin compounds was investigated by assessing the effect of coumarin on the membrane potential to quantify the alkaline phosphatase and lactate dehydrogenase activities of tested bacteria. The membrane potential of Staphylococcus aureus was higher in natural coumarin than in the control and commercial coumarin, followed by Bacillus cereus. The concentration of extracellular protein and the activity of lactate dehydrogenase and alkaline phosphtase were evaluated, and the bacteria that was treated with the natural coumarin had the highest antibacterial activity. The results showed the significant potential of coumarin in isolated DNA cleavage reactions. Our data also showed that the addition of natural coumarin and commercial coumarins resulted in a higher discharge of membrane potential in the supernatant. The conclusion revealed that the natural coumarin of Lotus lalambensis is potentially a significant source of useful molecules for the expansion of new antibacterial agents and the promising manipulation of natural coumarin to protect contaminated nuts and other foods against the pathogenic bacteria.