Purpose: We evaluated the extract’s antimicrobial properties against spoilage bacteria (Alcaligenes faecali, Bacillus coagulans, and Pseudomonas putida) as well as its potential toxicity (using the Ames test) in order to provide additional information on functional properties and safety.
Methods: We tested freeze-dried samples of extracts of sappan heartwood extracted in hot water (5 hours reflux (HW)) and cold water (6 hours of shaking at room temperature (CW)). Antimicrobial tests were conducted using the disc diffusion method, while mutagenicity tests were accomplished using the Ames mutagenicity assay.
Results: Freeze-dried HW and CW extracts both exhibited antimicrobial activity against the tested bacterial strains; there were no significant differences (P > 0.5) between HW and CW samples in terms of their antimicrobial activity. B. coagulans was the most sensitive to the extracts, with an inhibition zone of about 18-19 mm at applications of 150 μg of dried extract per disc. At 1.5 mg per disc, the extracts effectively inhibited the growth of A. faecalis (25 mm) but not P. putida (9 mm). An Ames assay performed on Salmonella Typhimuriam TA 98 and TA 100 showed that neither HW extracts nor CW extracts exhibited mutagenicity at concentrations as high as 5 mg per plate.
Significance: These results demonstrate that sappanwood extract may have potential as a safe and natural food preservative.