Antimicrobial activities of Longan (Euphoria longan L.) skin and seeds
The methanolic extracts from seeds and skin of Longan (Euphoria longan L.) were tested for antimicrobial activity with five strains of pathogenic bacteria including Staphylococcus aureus, Bacillus cereus, Psuedomonas aeruginosa, Enterococcus faecalis, Escherichia coli and one strain of pathogenic yeast, Candida albicans. The antimicrobial activities of each extract were screened by agar diffusion before conducting with broth macrodilution methods for determining minimal inhibitory concentration (MIC) . The phenolic content of skin and seed extracts was evaluated by analytical high performance liquid chromatography (HPLC) . The results show that the methanolic extract of Longan skin (10mg/ml) inhibited growth of S. aureus, P. aeruginosa and C. albicans were 15, 11 and 9mm of inhibition zone and MIC values were 4.42, 8.84 and 1.11mg/ml, respectively. The inhibition zones of Longan seed extract (10mg/ml) were 17, 12 and 11mm and MIC values were 3.19, 1.59 and 1.59mg/ml for S. aureus, P. aeruginosa, and C. albicans, respectively. The phenolic content of skin and seed extracts were 13.38 and 88.51g/kg of dry weight. It was concluded that the antimicrobial activity was not related to content of phenolic compounds. However, it may be due to types of phenolic compounds presented in the extracts and solubility of extracts [3, 4].
Acknowledgements: 1, Faculty of Science and Faculty of Medical Technology, Rangsit University, Phaholyothin Road, Lakhok, Pathumthani 12000, Thailand. 2, Associate Professor Omboon Luanratana, head of Department of Pharmacognosy, Faculty of Pharmacy, Mahidol University, Sri-Ayuthaya Road, Rajathevi, Bangkok 10400, Thailand.
References: 1. NCCLS. (1998) Performance standards for Antimicrobial Susceptibility testing: Fifth Informational Supplement M100-S8 18 (1). National Committee for Clinical Laboratory Standards.
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3. Cowan, MM. (1999) Clin Microbiol Rev 12: 564–582.
4. Cushnie, TPT. et. al. (2003) Microbiol Res. 158: 281–289.