Evaluation of Anti-Escherichia coli K88 from Diarrhea Piglets and Phytochemicals of Galangal Rhizome Extracts

Abstract

This study investigated the antimicrobial effect of galangal rhizome extracts against Escherichia coli K88 from diarrhea pigs. Galangal rhizome was extracted with 4 solvents: Water, ethanol, methanol and ethyl acetate. The extracts determination against E. coli K88 by disc diffusion method, minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Results showed that inhibition diameters of galangal extract with ethyl acetate against E. coli K88 was significantly higher than that of galangal extracted with water, ethanol and methanol. However, the inhibition was significantly lower than that of streptomycin drug. The MIC and MBC values ​​of ethyl acetate extracts against E. coli K88 were 0.39 and 0.78 mg/mL, respectively. Standard bacteria, pathogenic S. aureus ATCC6538, also used for testing antibacterial effect of galangal extract revealed the ethanol and methanol and ethyl-acetate extracts antibacterial effect against S. aureus. The phytochemicals tests performed on the extracts of galangal rhizome confirms the presence phenolic compounds exhibited antimicrobial activity. This study demonstrated antibacterial efficacy of galangal extracted with ethyl acetate to further develop as a substitute for antibiotics. HIGHLIGHTS The galangal rhizome extracted with ethyl acetate exhibited a strong antimicrobial effect against E. coli K88, which known to cause diarrhea in piglets The observed antibacterial effect of ethyl acetate extract of galangal was attributed to the high presence of specific compounds, namely phenol, 4-(2-propenyl), acetate, as well as 3 sesquiterpenoids compounds that were exclusively found in ethyl acetate extract These sesquiterpenoids include 3-(1,5-dimethyl-4-hexenyl)-6-methylene-1-cyclohexene; and 1,5-dimethyl-8-(methylethylidene)-1,5-cyclodecadiene and (-)-5-oxatricyclo[8.2.0.0(4,6)] dodecane, 12-trimethyl-9-methylene; and 3-phenyl-1,4(e)-dodecadiene GRAPHICAL ABSTRACT