Inhibitory Effect of Roselle Aqueous Extracts-HPMC 6000 Gel on the Growth of Staphylococcus aureus ATCC 25923

INTRODUCTION: Roselle (Hibiscus sabdariffa L.) is one of medicinal plants commonly used as beverage herbal medicine. Complexity compounds in the aqueous extracts have provided good antibacterial activity by which growth of Gram negative and positive bacteria are inhibited. The aims of this research were to formulate HPMC 6000 gel containing the extract and investigate inhibitory activity of the extract and its gel formula against Staphylococcus aureus ATCC 25923.
METHODS: Thin-layer Chromatography on Silica-gel GF254 was used for analyzing flavonoids and Polyphenols using butanol-acetic acid-water (4: 1: 5) and chloroforms-ethyl acetate-formic acid (0.5: 9: 0.5) as eluent, respectively. The serial dilution of aqueous extracts powder in citrate buffer was made to obtain 0.50, 0.25, 0.10, 0.05 and 0.02 mg/mL solution. The Roselle aqueous extracts (3%) was formulated as a component of gel containing HPMC 6000 in various concentrations (2%, 3%, and 4%). A diffusion agar method on two layers of nutrient agar media was applied using Staphylococcus aureus ATCC 25923 and gentamicin 25 ppm as bacterial test and standard respectively. After incubating for 24 hours at 37°C, the inhibitory effect was denoted by clear zone around the hole and the inhibitory activity was measured as MIC.
RESULTS: The aqueous extract of Hibiscus sabdariffa L. contained flavonoid and polyphenol compound based on the TLC-chromatogram profile. It was found that the gel formula containing 3% of HPMC 6000 and the aqueous extract 3% gave a good physical characteristic and the lowest MIC (6.0 mg/ml), equivalent to 7.58 ppm of gentamicin standard at 12.0 mg/mL concentration.
DISCUSSION AND CONCLUSION: The HPMC 6000 at 3% (w/w) concentration in Roselle aqueous extracts gel preparation gave good physical characteristics. The gel preparation exhibited inhibitory activity against Staphylococcus aureus ATCC 25923 depicted by Minimum Inhibitory Concentration 6.0 mg/mL. The formula 2 is recommended and prospects for further investigated to be implemented as topical preparations.