Anti-melanogenesis properties of condensed tannins from Vigna angularis seeds with potent antioxidant and DNA damage protection activities.

Condensed tannins contained in food are known to have many beneficial impacts on human health. In this study, we attempt to evaluate the structural features, antityrosinase effects, anti-melanogenesis properties, antioxidant activity and DNA damage protection activity of condensed tannins purified from the seeds of Vigna angularis (Willd.) Ohwi et Ohashi. MALDI-TOF MS, ESI-Full-MS, and HPLC-ESI-MS demonstrated that condensed tannins are composed of procyanidins, prodelphinidins and their gallates, among which procyanidins are the dominant components. As reversible and mixed-type inhibitors of tyrosinase, condensed tannins from V. angularis strongly inhibited the monophenolase and odiphenolase activities with IC50 values of 130.0 ± 0.5 and 35.1 ± 2.0 µg mL-1, respectively. What's more, condensed tannins had a good inhibitory effect on cell proliferation, cellular tyrosinase activity, and melanogenesis of B16 mouse melanoma cells. Based on fluorescence quenching analyses, these compounds were determined to be effective quenchers of the enzyme and its substrates. According to molecular docking, the strong interaction between condensed tannins and tyrosinase was mainly driven by hydrogen bonding and hydrophobic force. In addition, condensed tannins showed a powerful antioxidant capacity and DNA damage protection activity. Therefore, condensed tannins from V. angularis have feasible applications in food, medicine, and the cosmetics industry.

Avocado Proanthocyanidins as a Source of Tyrosinase Inhibitors: Structure Characterization, Inhibitory Activity, and Mechanism.

Proanthocyanidins were purified from avocado (Persea americana) fruit, and their structures were analyzed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and high-performance liquid chromatography-electrospray ionization-QTRAP mass spectrometry (HPLC-ESI-QTRAP MS) techniques. The results obtained from mass spectrometry (MS) analysis demonstrated that the proanthocyanidins were homo- and heteropolymers of procyanidins, prodelphinidins, propelargonidins, and procyanidin gallate. From the enzyme analysis, the results showed that they could inhibit the monophenolase and diphenolase activities of tyrosinase. The inhibition mechanism of the proanthocyanidins on the enzyme was further studied, and the results indicated that they were reversible and competitive inhibitors. Finally, the results acquired from molecular docking, fluorescence quenching, and copper ion interacting tests revealed that adjacent hydroxyl groups on the B ring of proanthocyanidins could chelate the dicopper catalytic center of the enzyme. In addtion, proanthocyanidins were proven to be an efficient quencher of substrates. This study would lay a scientific foundation for their use in agriculture, food, and nutrition industries.