The natural source, physicochemical properties, biological activities and metabolism of astilbin.

Astilbin is a dihydroflavanol found in many plants and processed foods. Astilbin possesses multiple health-beneficial bioactivities and has received great attention. Hence, the natural source, physicochemical properties, biological activities and metabolism of astilbin are summarized in the present article. Wall. and Roxb. are the main resource for astilbin purification because of high content. Because of chemical instability, astilbin amount in foods is dependent on the processing and storage conditions. The degradation of astilbin includes isomerization and decomposition. The interconversion of astilbin and its isomers occurs through a chalcone intermediates, which significantly affects the taste of wine during storage. Many factors such as temperature, pH, metal ions and food additives could affect the chemical stability of astilbin. Astilbin exhibits very novel selective immunosuppressive activity, which is not found in other compounds. The rhamnose moiety of astilbin is essential for this bioactivity. After digestion, astilbin was mainly absorbed and transported in circulatory blood in its intact form, and only one metabolite, 3'-O-methylastilbin, was found. Although having many bioactivities, astilbin faces the challenge of poor bioavailability. Some promising strategies were developed for improving its bioavailability, particularly through fabrication the zein nanoparticles.