The study was conducted to evaluate the antioxidant activity, toxicity test and antimicrobial property as natural food preservative of sappan heartwood (Caesalpinia sappan L.) water extract. The antioxidant and antimicrobial activities were evaluated using free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) in 96-well microdilution broth method. The extract concentration provided 50% inhibition (IC50) at 63.4µg/ml while vitamin C and Trolox acted at 9.1µg/ml and 11.6µg/ml, respectively. LD50 of the extract given orally was greater than 5g/kg in ICR mice and Wistar rats. The minimum inhibitory concentrations of sappan wood extract against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538, Salmonella typhimurium ATCC 13311 and Candida albicans ATCC 10231 were 250, 120, 500 and more than 16,000µg/ml, respectively. The MIC chloramphenicol and ketoconazol used as positive controls ranged from 0.97–62.5µg/ml for bacteria and 62.5µg/ml for yeast. The sappan wood extract at 2, 4, 8 times of the selected maximum bacteria MIC were added to the chilli paste which is Thai favorite food in order to determine the preservative property for 3 months. Total aerobic count in Thai chilli paste preserved with 2 MIC, 4 MIC and 8 MIC of sappan wood extract were reduced at 41.9%, 40.9% and 44.6%, respectively.
