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Background : The isoflavonoids, triterpene and polysaccharides were know as major components in Astragalus membranaceus Bunge. Especially, isoflavonoids are classified as ononin, calycosin-glucoside of glycon binding and formononetin, calycosin of aglycone binding. In this study, we performed fermentation by a lot of microorganisms which were derived foods.
Methods and Results : The A. membranaceus was extracted with 50% Ethanol and it was concentrated using rotary evaporator. In order to change in isoflavonoids, we fermented the A. membranaceus extracts with microorganisms which have β-glucosidase activity. we chose 20 microorganisms using esculin agar method and three strains with the highest activity of β -glucosidase were identified by pNP assay. The extracts of A. membranaceus were fermented during 3 days in sterilized distilled water, as 1 Brix and 3 Brix. The isoflavonoids of fermented extract, respectively days 0, 1, 2 and 3, were analyzed using High Pressure Liquid Chromatography (HPLC). In addition, the fermented A. membranaceus extracts was investigated about whitening effect using tyrosinase and radical scavenging activity by 1,1-diphenyl-2-picrylhydrazyl radical (DPPH). As a result of β-glucosidase activity by pNP assay, we selected two strains, Pediococcus pentosaceus (KACC 81017BP), Saccharomyces cerevisiae (KACC 83014BP). On the third day of fermentation of S. cerevisiae, isoflavone aglycone was the highest. The calycosin-glucoside and ononin in fermented A. membranaceus extract were reduced, calycosin and formononetin was increased compared to control. Also, we confirmed higher activity than control in tyrosinase inhibition rate on the third day of fermentation, as 78.38% and lower IC50 value of radical scavenging activity as 584.68 ㎍/㎖.
Conclusion : From the above results, we may suggest that A. membranaceus aboveground parts might have useful as a safe material for functional food and pharmaceutics.
