Antimicrobial activity of extract from Garcinia cowa leaf against Salmonella enterica Typhimurium ATCC 13311 on organic leafy lettuce

Abstract

Recently, there has been an increase in consumption of organic fresh fruits and vegetables around the world. Organic foods are produced without the use of any chemicals, and hence, natural plant compounds may be good alternative as natural antimicrobial treatment.  The objective of this study was to evaluate the antimicrobial effectiveness of aqueous extract from Garcinia cowa leaf on organic leafy lettuce inoculated with Salmonella enterica Typhimurium ATCC13311. The influence of exposure time was also investigated. Leaf samples were thoroughly washed in 1% NaOCl and placed in a biohood under UV light (254 nm) to reduce normal microflora. The leaf samples were inoculated with S. Typhimurium ATCC13311 (approx. 5 Log CFU/g) and dried. Inoculated leaves were immersed in solution containing 50 mg/ml extract of Garcinia cowa leaf. Samples were taken immediately (0 minutes) and also following at 5 and 15 minutes for enumeration of surviving Salmonella. The result showed that Garcinia cowa extract was effective against  S. Typhimurium ATCC13311. A decrease of approximately 2.5 Log CFU/g of Salmonella was observed after 5- minute exposure to the extract when compared with those of the distilled water control. The antibacterial activity  was also increased with exposure time. Moreover, Salmonella populations were  undetectable both in leaf samples and washed solution after 15-minute treatment with the extract. This study demonstrates the potential of Garcinia cowa extract to inhibit S. Typhimurium ATCC13311 on organic leafy lettuce, thus being alternative as natural antimicrobial washing solution.