Essential oil profiles of two Rubus varieties and the antimicrobial activities and lethality of their extracts

The essential oil composition of two varieties of the red raspberry, Rubus rosifolius (Red, R and Wine red, WR) was examined and the antimicrobial activity and brine shrimp lethality of their extracts determined. Plant samples were obtained and their essential oil profiles assessed using GC-MS analysis. Antimicrobial activity of the crude extracts of both plant varieties was assessed against drug-resistant and foodborne pathogens and the brine shrimp ethality assay was used to assess the potential lethality of the extracts. The quantity and identified essential oil components of the fruits varied between the varieties with the R variety having in greatest quantity the monoterpene, linalool, while that of the WR variety was found to be the sesquiterpene, α-cadinol. Analysis of the antimicrobial activity of the extracts against the growth of drug resistant pathogens showed the methanol extracts having greatest activity with zones of inhibition of 11 and 13 mm (for the R and WR varieties, respectively) against methicillin-resistant Staphylococcus aureus (MRSA). The methanol extracts also exhibited minimal activity against several food-borne pathogens including two strains of Escherichia coli, Listeriamono cytogenes and Enterobacter aerogenes. Brine shrimp lethality of the various extracts revealed that the essential oils of both plant varieties had the greatest activity with a LC50 value of 63 and 48 ppm for RHex and WRHex, respectively. The biological activities of the fruit extracts indicate that their utilization in the production of functional foods, nutraceuticals and pharmaceuticals should be further explored