Physicochemical and microbiological characteristics of various stem bark extracts of Hopea beccariana Burck potential as natural preservatives of coconut sap

Abstract The bark of Hopea beccariana Burck is used to prevent damage to coconut sap. The purpose of this study was to determine the physicochemical and microbiological characteristics of various extracts of the bark of H. beccariana Burck as potential natural preservatives for coconut sap. The bark was extracted by maceration method for 24 h assisted by stirring using ethanol, methanol, n-hexane, and water at 60°C as solvent. The type of solvent used for extraction had a significant effect on the yield, total phenolic, total flavonoid, antioxidant activity, toxicity, and diameter of the inhibition zone against Lactobacillus plantarum. The highest yield was found in methanol extract at 22.34%, the highest total phenolic content was found in ethanol extract of 53.39 mg gallic acid equivalent/g extract, and the highest total flavonoid content was found in the aqueous extract at 60°C of 106.70 mg QE/g extract; all extracts have an IC50 value of 80.28–91.80 ppm (very strong antioxidant) and ascorbic acid of 5.78 ppm. Methanol extract is classified as very toxic with an LC50 of 38.21 ppm. The dominant compounds produced by gas chromatography–mass spectrometer were hexanedioic acid, bis(2-ethylhexyl) ester; ethyl oleate; 9-octadecenoic acid (Z)-, ethyl ester; and hexadecanoic acid, ethyl ester. The diameter of the inhibition zone for Saccharomyces cerevisiae was 13.50–14.72 mm, L. plantarum was 10.31–17.72 mm, and Leuconostoc mesenteroides was 13.25–18.06 mm. All extracts had minimum inhibitory concentration values of 2.5 mg/mL and minimum bactericidal concentration values of 2.5 mg/mL for n-hexane extract and 60°C water, while ethanol and methanol extracts had MBC values >50 mg/mL.