In-vitro antibacterial potential of bran extracts of selected Philippine rice (Oryza sativa) cultivars
2018
Morales, A.V. | Zapater, J.E.I. | Cacerez, J.C.A. | Manaois, R.V.
This study determined the in-vitro antibacterial activity of bran Philippine rice varieties with varying pericarp colors. Rice samples were first screened for free, bound and total phenolic content. Six samples, namely one white (non-pigmented), two red, and three black/purple varieties were then selected and evaluated for in vitro antibacterial property. Crude bran extracts were tested against six common Foodborne pathogens, namely Salmonella enteric, Escherichia coli, Listeria monocytogenes, Clostridium perfringens, Enterococcus faecalis, and Staphylococcus aureus using agar well diffusion, bacterial growth curve, and minimum inhibitory concentration (MIC) assays. Results showed that pigmented rice generally had higher free, bound and total phenolic content than non-pigmented varieties. Agar well diffusion assay revealed that except for the extract of Black Rice 3, all selected pigmented rice brans at 100, 500 or 700 mg/mL concentrations displayed inhibitory property against S. aureus and C. perfringens only. Ethanolic extracts of the bran samples exhibited higher zones of inhibition than methanolic extracts, with the highest values observed in Black Rice 2. Growth curve assay test showed that viable cells of S. aureus decreased by 4 to 6 log using 5 to 100mg/mL ethanol extracts of pigmented rice starting at 5 hr incubation. Black Rice 2 was the most effective in preventing the growth of S. aureus and 2.5-3.125 mg/ml for C. perfringens, indicating mild antibacterial activities against the two Foodborne pathogens. In conclusion, pigmented rice bran can therefore be natural antimicrobial agents for potential use in food and/or pharmaceutical industries or other applications.
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