Isolation and purification of condensed tannins from flamboyant tree and their antioxidant and antityrosinase activities.

Flamboyant tree, a kind of medicinal plant, was studied as a source of condensed tannins. The antioxidant activities of the condensed tannins from the leaf, fruit, and stem bark of flamboyant tree were screened by ABTS radical and hydroxyl radical scavenging activity methods. The results indicated that these compounds possessed potent antioxidant activity. Their structures were then characterized by high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS) after thiolytic degradation. The results showed that the leaf condensed tannins were composed of afzelechin/epiafzelechin, catechin/epicatechin, and gallocatechin/epigallocatechin, while the fruit and stem bark condensed tannins had afzelechin/epiafzelechin and catechin/epicatechin. In addition, the condensed tannins were evaluated for their antityrosinase ability. They were found to have significant antityrosinase activity. The IC50 values were 35 ± 2.0 and 40 ± 0.5 μg/ml for the condensed tannins of fruit and stem bark, respectively. Further, fluorescence quenching and copper interacting techniques were utilized to unravel the molecular mechanisms of the inhibition. The results showed that the hydroxyl group of the condensed tannins could chelate the dicopper center of the enzyme and interact with tryptophan residues. Our studies revealed that condensed tannins might be suitable for use in food, agriculture, cosmetic, nutraceutical, and pharmaceutical applications.