Condensed tannins from Ficus virens as tyrosinase inhibitors: structure, inhibitory activity and molecular mechanism

• Published in: PloS one 2014-03, Vol.9 (3), p.e91809
• Main Authors: Chen, Xiao-Xin, Shi, Yan, Chai, Wei-Ming, Feng, Hui-Ling, Zhuang, Jiang-Xing, Chen, Qing-Xi
• Format: Article
• Language: English
• Subjects: Bark; Biological products; Biology and Life Sciences; Catalysis; Chelates; Chelating Agents - chemistry; Chelating Agents - pharmacology; Chromatography; Computer and Information Sciences; Copper; Copper - chemistry; Desorption; Ecosystems; Education; Enzymatic activity; Enzyme activity; Enzymes; Ficus - chemistry; Ficus virens; Flavonoids; Fluorescence; Food; Free radicals; Fruits; High performance liquid chromatography; Hydroxyl groups; Inhibition; Inhibitors; Ionization; Ions; Lasers; Leaves; Life sciences; Liquid chromatography; Magnetic resonance; Mass spectrometry; Mass spectroscopy; Medicine and Health Sciences; Models, Molecular; Molecular Conformation; Molecular docking; Molecular modelling; Molecular Structure; Monophenol Monooxygenase - antagonists & inhibitors; Monophenol Monooxygenase - chemistry; NMR; Nuclear magnetic resonance; Nuclear Magnetic Resonance, Biomolecular; Oxidoreductases - antagonists & inhibitors; Physical Sciences; Phytochemicals; Plant Extracts - chemistry; Plant Extracts - pharmacology; Polymerization; Proanthocyanidins - chemistry; Proanthocyanidins - pharmacology; Procyanidins; Quenching; Quinones; Scientific imaging; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Spectroscopy; Substrate Specificity; Tannins; Tyrosinase; Wetlands
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0091809

Condensed tannins from Ficus virens leaves, fruit, and stem bark were isolated and their structures characterized by 13C nuclear magnetic resonance spectrometry, high performance liquid chromatography electrospray ionization mass spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The results showed that the leaves, fruit, and stem bark condensed tannins were complex mixtures of homo- and heteropolymers of B-type procyanidins and prodelphinidins with degrees of polymerization up to hexamer, dodecamer, and pentadecamer, respectively. Antityrosinase activities of the condensed tannins were studied. The results indicated that the condensed tannins were potent tyrosinase inhibitors. The concentrations for the leaves, fruit, and stem bark condensed tannins leading to 50% enzyme activity were determined to be 131.67, 99.89, and 106.22 μg/ml on monophenolase activity, and 128.42, 43.07, and 74.27 μg/ml on diphenolase activity. The inhibition mechanism, type, and constants of the condensed tannins on the diphenolase activity were further investigated. The results indicated that the condensed tannins were reversible and mixed type inhibitors. Fluorescence quenching, copper interacting, and molecular docking techniques were utilized to unravel the molecular mechanisms of the inhibition. The results showed that the hydroxyl group on the B ring of the condensed tannins could chelate the dicopper irons of the enzyme. Moreover, the condensed tannins could reduce the enzyme product o-quinones into colourless compounds. These results would contribute to the development and design of antityrosinase agents.