Condensed Tannins from Ficus virens as Tyrosinase Inhibitors: Structure, Inhibitory Activity and Molecular Mechanism

Abstract

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.

The Bioactive Compounds and Antioxidant Activity of Food Products of Rhizophora stylosa Fruit (Coffee and Tea Mangrove)

“…The C2 gave resonance at 75 ppm for cis form, but the resonance for trans form was not detected. It indicates that terminal units were all in cis form [21]. The C3 signals of both cis and trans isomers occurred at 71 ppm and at 36 ppm showed the extension units of C4 atoms.…”

“…As shown in Figure 3, 13 C-NMR spectrum of the precipitate reveals a typical polymer of condensed tannins, containing procyanidin (dominant) and prodelphinidin (minor) units [18,19]. The signal assignment was compared based on previous study [18][19][20][21]. The peaks at 150 and 160 ppm (C5, C7, C8a), 143.8 ppm (C3 , C4 ), 114.2 to 118 ppm (C2 , C5 and C6 ), and 94 to 100 ppm (C8 and C6) showed the presence of procyanidin units (PC).…”

“…Then, the peaks at 131 ppm (C4 , C1 ) and 104 to 108 ppm (C2 , C6 ) showed the presence of prodelphinidin units (PD). In addition, the ratio of 2,3-cis to 2,3-trans isomers could be determined through the distinct differences in their respective C2 chemical shifts from the region peaks area between 70 and 90 ppm [18,21]. The C2 gave resonance at 75 ppm for cis form, but the resonance for trans form was not detected.…”

Anti-tyrosinase kinetics and antibacterial process of caffeic acid N-nonyl ester in Chinese Olive (Canarium album) postharvest

“…It was usually used to study the interaction between conformation of protein molecules and small molecules [29]. Cary Eclipse fluorescence spectrophotometer was used to record the fluorescence intensities with an excitation wavelength of 280 nm and emission slit widths of 5 nm [30]. C-7 and C-9 did not have any fluorescence phenomenon at this excitation wavelength.…”

“…According to recent studies [30], the structure of the tyrosinase was used as the initial model for docking simulations after removal of the caddie protein, the exogenous ions, and water molecules (PDB ID: 2y9w). The 3D structures of the ligands and C-9 were prepared with Chembiodraw Ultra 14.0.…”