Antimicrobial And Antioxidant Activities Of Orthosiphon Stamineus Benth. With Emphasis On Rosmarinic Acid Content
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Date
2011-06
Authors
Ho, Chun Hoong
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Publisher
Universiti Sains Malaysia
Abstract
Orthosiphon stamineus Benth. is a commonly planted herbal plant and is easily available in Malaysia. This herb is used in traditional medicine to treat a wide range of diseases. In this research, five types of O. stamineus extracts obtained through different ratios of analytical grade methanol (0, 25, 50, 75 and 100 %) and distilled water were tested against nine strains of food-borne bacteria in vitro using disc diffusion assay. From this assay, V. parahaemolyticus was found to be the most susceptible bacteria. V. parahaemolyticus was then subjected to further tests of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). From MIC test, V. parahaemolyticus was most susceptible to 50 % and 75 % of methanolic extracts. The fractionation of 50 % methanolic extract yielded six fractions, with fraction 5 possesses highest antibacterial activity against V. parahaemolyticus. These 50 % and 75 % methanolic extracts as well as fraction 5 gave the lowest MIC values of 1.56 mg/mL. Of all the crude extracts, fractions and the control samples, only fraction 5, chloramphenicol and lactic acid gave MBC values. Total phenolic assay analysis for crude extracts showed that 50 % methanolic extract possesses highest phenolic content. HPLC analysis of the crude extracts and fractions showed that fraction 5, followed by 50 % methanolic extracts contains the highest rosmarinic acid concentration. The 50 % methanolic extract was found to possess the highest free radical scavenging activity in DPPH free-radical scavenging assay, which also contains high concentrations of rosmarinic acid among the crude extracts, suggests that the presence of rosmarinic acid contributes tremendously to
the extracts’ free radical scavenging activity. The inhibitory effect of the 50 % methanolic crude extracts was then further evaluated on shrimp samples, taking into account of the total aerobic bacteria and V. parahaemolyticus counts.
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Keywords
Antimicrobial and antioxidant activities of orthosiphon stamineus benth , With emphasis on rosmarinic acid content