Many stilbene glycosides can alleviate skin hyperpigmentation due to their inhibitory effect on tyrosinase. Mulberrosides in Morus alba L. are stilbene glycosides. In the present study, the inhibition of tyrosinase by five mulberrosides (S1–5), isolated from Morus alba L. was investigated and compared, and the inhibitory mechanism was explored. These five mulberrosides exhibited obvious inhibitory effects on tyrosinase only in a concentration-dependent manner, without time-dependence, indicating that they are reversible inhibitors of tyrosinase. S2, S1 and S5 inhibited tyrosinase activity with IC 50 values of 28.93, 75.94 and 151.72 μM, respectively, and were more active than kojic acid (IC 50 =169.13 μM). Kinetic studies revealed that S1, S2 and S4 were competitive inhibitors, while S3 and S5 were mixed inhibitors. Analysis of the fluorescent spectra showed that mulberrosides S1, S2 and S4 quenched the intrinsic fluorescence intensity of tyrosinase. A molecular docking study indicated that the interaction of tyrosinase with mulberrosides was reflected by compound scores as follows: S2>S5>S1>S3/S4>kojic acid, and hydroxy groups in the side chain of mulberrosides may play a crucial role in the binding of the enzyme. Our results suggest that mulberrosides in Morus alba L. could be further developed as whitening agents for enhanced performance against hyperpigmentation. Graphical
A simple method was developed for the determination of hydrophilic whitening agents (ascorbyl glucoside, magnesium ascorbyl phosphate, arbutin, hydroquinone, and kojic acid) in bleaching cosmetics by high performance liquid chromatography with electrochemical detection. The samples were prepared using microdialysis and were separated within ten minutes using isocratic elution. Linear calibration was achieved for concentrations between 0.10 and 10.00 micromolar. The limits of detection were from 0.6 to 2.0 nanomolar; the recoveries were between 91.43 and 108.04 percent, and the relative standard deviation was less than 6.88 percent. This method was used to determine whitening compounds in several cosmetics with on-line microdialysis and the zero net flux method. The procedure was fast, simple, selective, and suitable for routine analysis.
Jiaman Liu,Yanbiao Chen,Xinxin Zhang,Jie Zheng,Weiying Hu,Bo Teng
The application of hops could be extended to obtain higher commercial values. Tannins from hops were assessed for their tyrosinase inhibition ability, and the associated mechanisms were explored. Nuclear magnetic resonance (NMR) and high-performance liquid chromatography–electrospray ionization–tandem mass spectrometry (HPLC–ESI–MS/MS) revealed that the hop tannins were characterized as condensed tannins with (epi)catechin and (epi)gallocatechin as subunits and an average polymerization degree of 10.32. Tyrosinase inhibition assay indicated that hop tannins had an IC50= 76.52 ± 6.56 μM. Kinetic studies of the inhibition processes indicated the tannins provided inhibition through competitive–uncompetitive mixed reactions. In silico molecule docking showed that tannins were bound to the active site of tyrosinase via hydrogen and electrovalent bonds. Circular dichroism (CD) observed the structural variation in the tyrosinase after reacting with the tannins. Fluorescence quenching analysis and free radical scavenging assays indicated that the tannins had copper ion chelating and antioxidant activities, which may also contribute to inhibition. The intracellular inhibition assay revealed that the melanin was reduced by 34.50% in B16F10 cells. These results indicate that these tannins can be applied as whitening agents in the cosmetics industry.Keywords:hop tannins;polyphenols;condensed tannin;tyrosinase inhibitor;whitening agent
Sha Sha Li,Bo Yin,Hong Lin Zhai,Shao Hua Lu,Jia Ying Mi
Although UV-Vis spectroscopy has been applied in many fields, it still encounters some challenges in multi-component mixture analysis due to severe spectral overlapping and different interferences. In this paper, a Tchebichef curve moment (TM) approach has been developed and proposed for the quantitative analysis of five skin-whitening agents in several cosmetic products with different substrates based on conventional UV-Vis determination for the first time. First, the TMs were calculated from the raw UV-Vis spectra of mixed standard samples, and employed to establish linear quantitative models by stepwise regression. Then, the obtained models were applied to the analysis of real samples. The leave-one-out correlation coefficients (Rloo-cv) of the established models were more than 0.9948 within the linear ranges. The proposed approach was evaluated using intra- and inter-day precision (less than 5.98%) and recovery (ranging from 88.3 ± 2.8% to 109.2 ± 2.3%). The LODs and LOQs were less than 0.13 mg L−1 and 0.45 mg L−1, respectively. Compared with the classical methods, the proposed approach is not only more accurate, reliable and robust in the quality control analysis of cosmetic products, but also can extend effectively the application of conventional UV-Vis determination.
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