Advances on resource, biosynthesis pathway, bioavailability, and bioactivity of dihydrodaidzein

Abstract Compared with metabolic precursor daidzein, dihydrodaidzein exhibits higher activity and broader biological effects, and have gradually attracted the attention in recent years. This review provides a systematic overview of resources, physicochemical properties, in vivo metabolism and microbial transformation, bioavailability and bioactivity of dihydrodaidzein. Dihydrodaidzein is mainly derived from biosynthesis, and it can also be produced by chemical synthesis and enzyme catalyzation. Gut microorganisms play a key role in the in vivo metabolism of dihydrodaidzein, in which it can be generated from daidzein and further converted into the more active equol. There are several high productive strains of dihydrodaidzein identified, including Aeroto-Niu-O16, TM-40, Lactobacillus acidipiscis HAU-FR7 and Slackia isoflavoniconvertens DSM22006. Among others, these strains contain genes involved in isoflavone conversion, including the daidzein, dihydrodaidzein and tetrahydrodaidzein reductase ( dzr, ddr, tdr ) and dihydrodaidzein racemase ( ifcA ). Although dihydrodaidzein (0.14 g/L) exhibited better water solubility than of daidzein (0.085) and better absorbed, it also suffers low oral bioavailability. Therefore, emerging nanocarrier technologies can be explored to encapsulate dihydrodaidzein to enhance its cellular uptake, targeted delivery and functional efficacy. It has been found to have superior pharmacological activities in antioxidant, cardiovascular disease, prevention of osteoporosis and estrogen-like activity. A comprehensive summary of dihydrodaidzein will allow more researchers to target their research, thus promoting its use in food and nutraceuticals. Graphical abstract