Phytochemical and antimicrobial investigation of the leaves of five Egyptian mango cultivars and evaluation of their essential oils as preservatives materials

The sterols, hydrocarbons and fatty acids constituents of the leaves of five mango cultivars locally implanted in Egypt were identified. The effect of their essential oils (EOs) against food borne microorganisms was studied as preservative materials. The chemical constituents of the EOs isolated from mango leaves were identified by Gas Chromatography–Mass spectrometry (GC–MS) technique. Trans-caryophyllene, α–humulene and α–elemene were identified as terpene hydrocarbons, while 4-hydroxy-4-methyl-2-pentanone as oxygenated compounds were recorded in all tested cultivars with variable amounts. Results showed that Staphylococcus aureus and Escherichia coli were the most sensitive microorganisms tested for Alphonso EOs. On the other hand, Salmonella typhimrium was found to be less susceptible to the EOs of the studied cultivars. The EOs of different mango cultivars induced a steady decrease in the activity of amylase, protease and lipase at the minimum inhibitory concentration (MIC). The treatment of the tested bacteria with the EOs of mango cultivars caused a steady loss in enterotoxins even when applied at the sub-MIC. Bacteria-inoculated apple juice treated with minimum bactericidal concentration of Alphonso oil was free from the bacteria after 5 days of incubation at 25 °C. Eighteeen volatile compounds were found to reduce the activity of the amylase enzyme and the most active was cedrelanol (−7.6 kcal mol −1 ) followed by alpha-eudesmol (−7.3 kcal mol −1 ) and humulene oxide (−7 kcal mol −1 ). The binding mode of both of cedrelanol and alpha-eudesmol with amylase enzyme was illustrated.