Inhibitory effect of tannin extract from Acacia bark (Acacia mangium Willd.) against gastro-intestinal pathogenic bacteria

Abstract

Acacia (Acacia mangium Willd) is a fast growing tree species that widely found in Indonesia. Acacia bark contains a number of secondary metabolites such as tannin, saponin and flavonoid that may inhibit the growth of undesirable microbes incuding the pathogenic ones. The purpose of this research was to evaluate the antimicrobial activity of tannin extract obtained from Acacia bark against common pathogenic bacteria species present in the gastro-intestinal tract of livestock, i.e., Salmonella typhimurium and Eschericia coli as Gram negative bacteria. The disc diffusion method was employed for assessing the antimicrobial activity of Acacia tannin extract. Treatments consisted of negative control (NC), positive control by using chloramphenicol (PC), Acacia tannin extract at two concentrations, i.e., 1% (AT1) and 2% w/v (AT2), and commercial chestnut tannin at 1% (CT1) and 2% w/v (CT2). Data were analyzed by using analysis of variance and followed by a post-hoc test namely Duncan's multiple range test. Results showed that the inhibitory diameters formed on the activity assay of AT in the form powder, liquid and CT with concentration of 2% against Salmonella typhimurium bacteria were 17.3, 7 and 16 mm, respectively. Inhibitory diameters of AT powder, AT liquid and CT against Eschericia coli bacteria were 17.3, 0 and 17 mm, respectively. The AT powder resulted in a higher inhibition of both pathogenic bacteria species than that of liquid form (P<0.05), whereas its inhibitory effect was similar to commercial CT. In conclusion, 2% AT can be used to inhibit the growth of Salmonella typhimurium and Eschericia coli bacteria in which its magnitude of inhibition is comparable with commercial tannin extract from chestnut.