Fluorescence spectrometry based chromaticity mapping, characterization, and quantitative assessment of dental caries.

PURPOSE: Dental caries detection, especially the accurate detection of early caries, facilitates prompt interventions. It is reasonably common to use fluorescence imaging for classification and evaluation of caries, but lacks a quantitative, precise and easy-to-use characterization for practical applications. In this study a quantitative approach for caries stage detection by correlating caries spectral and chromatic features was examined. METHODS: A 405 nm LED light source was used as the excitation source. A hyperspectral imaging camera is employed to collect 336 spectral data of different caries stages. Four critical intervals for different stages of caries were extracted by fluorescence spectral features. The mapping relationship between caries spectral and chromatic features was established by Fast Formula Fitting (FFF) and Neural Network Fitting (NNF) methods. RESULTS: The 470-780 nm spectral power distribution was proved to be the best matching color waveband guiding the selection of filters in future instrument development. The correlation coefficients for the two fitting methods were 0.990 and 0.999, respectively. Both methods achieved caries stage prediction at the pixel level with high accuracy using color information. The visualization region in the chromaticity diagram was created. CONCLUSIONS: This quantitative method enables accurate prediction of caries on the entire tooth surface and facilitates the development of portable and low-cost caries detection instruments.

Synthesis and biological evaluation of unsymmetrical curcumin analogues as tyrosinase inhibitors.

Synthesis and biological evaluation of unsymmetrical curcumin analogues (UCAs) have been achieved. Tyrosinase inhibitory activities were found for most of the prepared synthetic UCAs. Among them, compounds containing 4-hydroxyl-substituted phenolic rings with C-2/C-4- or C-3/C-4-dihydroxyl-substituted diphenolic rings were more active (IC(50) = 1.74~16.74 µM) than 4-butylresorcinol and kojic acid, which suggested that the 4-hydroxyl groups in UCAs play a crucial role in tyrosinase inhibitory activities. The inhibition kinetics analyzed by Lineweaver-Burk plots revealed compounds 3c and 3i containing catecholic rings were mixed-competitive inhibitors, whereas compounds 3d and 3j containing resorcinolic rings were competitive inhibitors. The preliminary evaluation results of acute toxicity showed the representative 3d and 3j were non-toxic in mice dosed at 1,200 mg/kg. This research suggests that, with the advantage of being readily prepared small molecules, polyphenolic UCAs have the potential to develop into pharmacological inhibitors of tyrosinase.

Antioxidation and tyrosinase inhibition of polyphenolic curcumin analogs.

A series of polyphenolic curcumin analogs were synthesized and their inhibitory effects on mushroom tyrosinase and the inhibition of 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical formation were evaluated. The results indictated that the analogs possessing m-diphenols and o-diphenols exhibited more potent inhibitory activity on tyrosinase than reference compound rojic acid, and that the analogs with o-diphenols exhibited more potent inhibitory activity of DPPH free-radical formation than reference compound vitamin C. The inhibition kinetics, analyzed by Lineweaver-Burk plots, revealed that compounds B(2) and C(2) bearing o-diphenols were non-competitive inhibitors, while compounds B(11) and C(11) bearing m-diphenols were competitive inhibitors. In particular, representative compounds C(2) and B(11) showed no side effects at a dose of 2,000 mg/kg in a preliminary evaluation of acute toxicity in mice. These results suggest that such polyphenolic curcumin analogs might serve as lead compounds for further design of new potential tyrosinase inhibitors.

[Study on inhibitive effect of extracts from Scindapsus aureus on alpha-glucosidase and its antioxidant activity].

OBJECTIVE: To study the inhibitive effect of extracts from Scindapsus aureus on alpha-glucosidase and its antioxidant activity. METHODS: The 70% ethanol extracts was extracted by petroleum, ethyl acetate and n-butanol, and the inhibitory activity against alpha-glucosidases and antioxidative effects of each fraction were determined in vitro, and the inhibitory kinetics of ethyl acetate fraction was investigated. RESULTS: The inhibitory activity of ethly acetate fraction against alpha-glucosidase was higher as its IC50 was 43.63 microg/mL. The inhibition kinetics analyzed by Hnewaver-Burk plots showed that ethyl acetate fraction was a competitive type inhibitor, and the inhibition constants for free ennzyme (Ki) was determined to be 21.49 microg/mL. The antioxidative effects of ethly acetate and n-butanol fractions exhibited stronger than that of other fractions, the scavenging ability on DPPH at the concentration of 0.42 mg/mL were 88.5% and 93.6%. Ethly acetate fraction showed scavenging ability on autioxidantor, and the IC50 values was 0.27 mg/mL. CONCLUSION: Ethyld acetate fraction of extract from Scindapsus aureus has potential inhibitroy activity against alpha-glucosidase and antioxidant effects, and n-butanol fraction has great antioxidative effects.