Relationship between biological activities and bioactive compounds in the fermented rice sap

Various rice (Oryza sativa L. var. indica), including white plain, purple plain, brown plain, white glutinous and purple glutinous rice, were fermented with Look Pang (a mixed culture of yeasts and molds). The sap samples were assayed for the bioactive compounds (unsaturated fatty acids, total phenolic compounds and total anthocyanin) and the biological activities (antioxidative, tyrosinase inhibition, cell proliferation and MMP-2 inhibition activities). The fermented purple plain sap samples at day 6th of the fermentation period showed high antioxidative, the highest tyrosinase inhibition and MMP-2 inhibition activities with low cytotoxicity to normal human skin fibroblast by SRB assay in comparing to other rice sap samples. This study has indicated the strong positive relationship between the bioactive compounds and the biological activities of the purple rice sap which can be further developed as functional foods and cosmetics.

Research highlights
► Sap from various Thai rice was prepared by the Thai wisdom process.
► The fermented purple plain rice sap exhibited the highest biological activities.
► The fermented purple plain rice sap contained high contents of bioactive compounds.
► Biological activities of rice sap had strong relationship with their bioactives.
► Potentials of the rice sap to be developed as functional foods have been indicated.