Ji-Yuan Liang

Effect of esterification condensation on the Folin-Ciocalteu method for the quantitative measurement of total phenols

The Folin-Ciocalteu method is widely applied for the determination of the total phenolic contents in natural products. This method is significantly affected by the addition of sodium carbonate. The currently applied Folin-Ciocalteu methods may have been modified without any validation in the quantitative standards and the order of processes. In this study, serial experiments were performed to investigate the effect of phenolic calibrations based on the classic Folin-Ciocalteu method. Esterification condensations were observed in the assays with prior basification for gallic acid and catechin used as quantitative standards. The phenolic contents obtained in the samples differed depending on when basification occurred compared with the gallic acid calibration. The bias of the classic Folin-Ciocalteu method derived from cross-linkage of molecules was first defined in this study. The performance of the Folin-Ciocalteu method is optimised and validated again.

Blue light induced free radicals from riboflavin on E. coli DNA damage.

The micronutrients in many cellular processes, riboflavin (vitamin B(2)), FMN, and FAD are photo-sensitive to UV and visible light to generate reactive oxygen species (ROS). The riboflavin photochemical treatment with UV light has been applied for the inactivation of microorganisms to serve as an effective and safe technology. Ultra-violet or high-intensity radiation is, however, considered as a highly risky practice. This study was working on the application of visible LED lights to riboflavin photochemical reactions to development an effective antimicrobial treatment. The photosensitization of bacterial genome with riboflavin was investigated in vitro and in vivo by light quality and irradiation dosage. The riboflavin photochemical treatment with blue LED light was proved to be able to inactivate E. coli by damaging nucleic acids with ROS generated. Riboflavin is capable of intercalating between the bases of bacterial DNA or RNA and absorbs lights in the visible regions. LED light illumination could be a more accessible and safe practice for riboflavin photochemical treatments to achieve hygienic requirements in vitro.

Investigations of riboflavin photolysis via coloured light in the nitro blue tetrazolium assay for superoxide dismutase activity

Determination of the superoxide dismutase activity is an important issue in the fields of biochemistry and the medical sciences. In the riboflavin/nitro blue tetrazolium (B2/NBT) method, the light sources used for generating superoxide anion radicals from light-excited riboflavin are normally fluorescent lamps. However, the conditions of B2/NBT experiments vary. This study investigated the effect of the light source on the light-excitation of riboflavin. The effectiveness of the photolysis was controlled by the wavelength of the light source. The spectra of fluorescent lamps are composed of multiple colour lights, and the emission spectra of fluorescent lamps made by different manufacturers may vary. Blue light was determined to be the most efficient for the photochemical reaction of riboflavin in visible region. The quality of the blue light in fluorescent lamps is critical to the photo-decomposition of riboflavin. A blue light is better than a fluorescent lamp for the photo-decomposition of riboflavin. The performance of the B2/NBT method is thereby optimized.

Investigations of blue light-induced reactive oxygen species from flavin mononucleotide on inactivation of E. coli.

The micronutrients in many cellular processes, riboflavin, flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD) are photo-sensitive to UV and visible light for generating reactive oxygen species (ROS). Produced from phosphorylation of riboflavin, FMN is more water-soluble and rapidly transformed into free riboflavin after ingestion. This study investigated the application of visible blue light with FMN to development of an effective antimicrobial treatment. The photosensitization of bacterial viability with FMN was investigated by light quality, intensity, time, and irradiation dosage. The blue light-induced photochemical reaction with FMN could inactivate Escherichiacoli by the generated ROS in damaging nucleic acids, which was validated. This novel photodynamic technique could be a safe practice for photo-induced inactivation of environmental microorganism to achieve hygienic requirements in food processing.

Blue light induced free radicals from riboflavin in degradation of crystal violet by microbial viability evaluation

Crystal violet (CV) is applied in daily use mainly as a commercial dye and antimicrobial agent. Waste water containing CV may affect aquatic ecosystems. Riboflavin, also known as vitamin B2, is non-toxic and an essential vitamin required for the functions of the human body. Riboflavin is photosensitive to UV and visible light in terms of generating reactive oxygen species. This study investigated the potential application of blue light on riboflavin, so as to come up with an effective way of degrading CV during its treatment. Photosensitivity of CV leading to degradation in the presence of riboflavin was investigated by light intensity, exposure time, and irradiation dosage. The degradation of CV during riboflavin photolysis treatment was studied by a UV/vis spectrometry and chromatography. The effects of CV degradation on microbial viability are relevant when considering the influences on the ecosystem. This study proved that riboflavin photochemical treatment with blue light degrades CV dye by ROS formation. The riboflavin photolysis-treated CV solution appeared to be transparent during conformational transformations of the CV that was rearranged by free radical species generated from riboflavin photolysis. After riboflavin photolysis, colony-forming units (CFUs) were determined for each CV solution. CFU preservation was 85.2% for the CV dissolved riboflavin solution treated with blue light irradiation at 2.0mW/cm2 for 120min. Degradation of CV by riboflavin photochemical procedures can greatly reduce antimicrobial ability and serve as an environmental friendly waste water treatment method. Our results presented here concerning riboflavin photolysis in degradation of CV provide a novel technique, and a simple and safe practice for environmental decontamination processes.

Photo-catalytic polymerization of catechin molecules in alkaline aqueous

Polyphenols are associated with a wide range of physiological properties. Catechin is a flavan-3-ol with five phenolic hydroxyl groups. After blue light illumination, the transparent solution of catechin became yellowish. The effects of visible light illumination (400-800nm) were investigated on molecular structures and antioxidant capacities of catechin. Under the neutral or alkaline aqueous with the illumination of blue light, the photolysis and polymerization of catechin were observed in this study. A chromogenic catechin dimer was separated and identified as a proanthocyanidin by the chromatographic technique and mass spectrometry. For quantitative evaluation, the signal intensities of the catechin and the photochemical product show a negative correlation in the liquid chromatograms. The oligomer of flavan-3-ols (catechin dimer) is suggested as a dimeric B type proanthocyanidin, which has the molecular formula C30H26O12 and 578.14g/mol in exact mass. The mass spectrum of catechin dimer had characteristic ion signals in m/z 577, 560, 439Da. However, the total phenolic contents and scavenging O2- activity of catechin treated by blue light illumination are not changed significantly at the neutral or alkaline aqueous. Our results of photocatalytic oligomers of catechin provide a novel way to explain the sensory changes of green tea and a biochemical mechanism under the irradiation environments.

Effects of Blue-Light-Induced Free Radical Formation from Catechin Hydrate on the Inactivation of Acinetobacter baumannii, Including a Carbapenem-Resistant Strain.

Catechin is a flavan-3-ol, a derivative of flavans, with four phenolic hydroxyl groups, which exhibits a wide range of physiological properties. Chromatographic analyses were employed to examine the effects of blue light irradiation on the changes of catechin hydrate in an alkaline condition. In particular, the detection of a superoxide anion radical (O2•−), a reactive oxygen species (ROS), and the inactivation of Acinetobacter baumannii (A. baumannii)—including a carbapenem-resistant A. baumannii (CRAB)—was investigated during the photoreaction of catechin hydrate. Following basification with blue light irradiation, the transparent solution of catechin hydrate turned yellowish, and a chromogenic catechin dimer was separated and identified as a proanthocyanidin. Adding ascorbic acid during the photolytic treatment of catechin hydrate decreased the dimer formation, suggesting that ascorbic acid can suppress the photosensitive oxidation of catechin. When catechin hydrate was irradiated by blue light in an alkaline solution, O2•− was produced via photosensitized oxidation, enhancing the inactivation of A. baumannii and CRAB. The present findings on the photon-induced oxidation of catechin hydrate provides a safe practice for the inactivation of environmental microorganisms.

Effects of 462 nm Light-Emitting Diode on the Inactivation of Escherichia coli and a Multidrug-Resistant by Tetracycline Photoreaction

The adaptability of bacterial resistance to antibiotics contributes to its high efficiency during evolution. Tetracycline (TC) is a broad-spectrum antimicrobial agent. Chromatographic analyses and mass spectrometry were used to study the effects of the light illumination of a 462 nm light-emitting diode (LED) on the conformational changes of TC in a phosphate buffer solution (PBS, pH 7.8). Especially, the inactivation of superoxide anion radicals (O2•−) and Escherichia coli (E. coli), including that of a multidrug-resistant E. coli (MDR E. coli), were investigated during the photolysis of TC. A photolysis product of TC (PPT) was generated in an alkaline solution after the illumination of a blue light. The mass spectra of PPT had characteristic ion signals in m/z 459, 445, and 249.1 Da. The PPT has the molecular formula of C22H22N2O9, and the exact mass is 458.44 g/mol. The inactivation of MDR E. coli is not significant with TC treatment. The drug-resistant ability of MDR E. coli has a less significant effect on PPT, and the changed conformation of TC retained the inactivation ability of MDR E. coli upon blue light photoreaction. With TC, illuminated by a blue light in a pH 7.8 PBS, O2•− was generated from TC photolysis, which enhanced the inactivation of E. coli and MDR E. coli. A 96.6% inactivation rate of MDR E. coli was reached with TC under 2.0 mW/cm2 blue light illumination at 25 ± 3 °C for 120 min, and the effects of the TC-treated photoreaction on MDR E. coli viability repressed the growth of MDR E. coli by 4 to 5 logs. The present study of the blue light photoreaction of TC offers a new approach to the inactivation of MDR E. coli.