Ability of (-)-Mesquitol Isolated from Prosopis Juliflora Heartwood to Inhibit Fungal and Bacterial Growth in a Laboratory Test

Abstract

Studies were carried out to evaluate the ability of a novel flavonoid (-)-mesquitol isolated from Prosopis juliflora heartwood to inhibit fungal and bacterial growth. Pycnoporus sanquineus (PS) and Gloephyleum trabeum (GT) fungi were cultured in malt (30gm) and agar (40gm) inoculated with (none, 50, 100, 500 and 1000) ppm (-)-mesquitol in 9cm petri dishes and incubated in a sterile acclimatization chamber at 22°C and 70% RH. Fungal growth diameter was evaluated every 2 days for 14 days. Minimal Inhibitory concentration of (-)-mesquitol against bacterial strains: Escherichia coli, Salmonella anterica, Staphylococcus aureus, Listeria monocytogenes cultured in Trypcase Soja broth enriched with yeast extract and Escherichia faecalis cultured in Elliker broth was determined by two fold dilution of (-)-mesquitol in 96- well microtitre plates and incubated at 37°C. Bacterial growth was determined by measuring optical density of the suspension before and after 24 hrs incubation. Direct oxidation of (-)-mesquitol by laccase enzyme was carried out by measuring Ultra Violet (UV) absorbance at wavelength range (250nm- 650nm) every 2 minutes for 100minutes. (-)-mesquitol inhibited 70- 90% growth of Pycnoporus sanquineus (PS) and Gloephyleum trabeum (GT) fungi at 1000ppm respectively. Similarly it was able to inhibit over 22% of Escherichia faecalis bacteria at tested minimum concentration of 2.5mg/ml. In addition (-)-mesquitol induced laccase enzyme expression at UV absorbance range of 350 to 600nm similar to that of a known flavonoid (+)-catechin. These results suggest potential utilization of (-)-mesquitol and its derivatives in soap, cosmetic and shampoo industries.