Application of 2% (v/v) of water extract of A. flava exhibited a positive respond against Salmonella typhii, Staphylococcus aureus, and Trichophyton rubrum. This extract also showed an ability to stabilize the acidity of fresh palm sap during the production process. From the toxicity test using BSLT method, water extract of A. flava was considered as a natural product with no toxicity. Therefore, water extract of A. flava can be utilized as a natural food additive, especially in the production of palm sugar.