<i>In Vitro</i> Antibacterial Activity of Hydrogels Containing Tamarind Seed Husk Extracts against <i>Propionibacterium acnes</i>

Abstract

Propionibacterium acnes (P. acnes) is one of skin bacteria that induce acne comedone formation. Previous studies reported that P. acnes was susceptible to alcoholic seed husk extract of Tamarindus indica L. (T. indica), no studies have been reported about the susceptibility of water extract from tamarind seed husk to P. acnes. Therefore, the objectives of this investigation were to explore the antibacterial activity of water and ethanolic seed husk extracts from T. indica (wTSH and eTSH) against P. acnes and to compare antibacterial activity of hydrogels containing wTSH and eTSH extracts against P. acnes. wTSH and eTSH extracts were reddish brown powder, and oligomeric proanthocyanidin was identified by UV-Vis spectroscopy and high performance liquid chromatography as the main ingredient in the extracts. wTSH and eTSH extracts showed the average of total phenolic compounds of 408.3±0.01 and 385.5±0.02 mg GAE/g and exhibited very strong free radical scavenging ability by DPPH assay with IC50 value of 19.6±0.2 µg/ml and 18.8±0.2 µg/ml, respectively. In addition, wTSH and eTSH extracts showed good activity against P. acnes. The minimum inhibitory concentration (MIC) of wTSH and eTSH extracts was 500 and 250 µg/ml, and the minimum bactericidal concentration (MBC) of both extracts was 500 µg/ml. In conclusion, the hydrogels which composed of 0.1% wTSH or eTSH extracts, 2% HPMC, 15% glycerin and 1% paraben concentrate, exhibited weak acid with pH 5±2, good physical stability, i.e. good spreadability with pseudoplastic flow, and also exhibited noticeable anti P. acnes activity in fluorescent resazurin assay after storage in the accelerated conditions for 3 months.