Incompatible effects of specific acids on the thermokinetics of 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane

Journal of Thermal Analysis and Calorimetry - 1,1-Bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (TMCH), an industrial initiator and cross-linking agent comprising two active peroxy bonds,...     

Influencing Factors on the Physicochemical Characteristics of Tea Polysaccharides

Tea polysaccharides (TPSs) are one of the main bioactive constituents of tea with various biological activities such as hypoglycemic effect, antioxidant, antitumor, and immunomodulatory. The bioactivities of TPSs are directly associated with their structures such as chemical composition, molecular weight, glycosidic linkages, and conformation among others. To study the relationship between the structures of TPSs and their bioactivities, it is essential to elucidate the structure of TPSs, particularly the fine structures. Due to the vast variation nature of monosaccharide units and their connections, the structure of TPSs is extremely complex, which is also affected by several major factors including tea species, processing technologies of tea and isolation methods of TPSs. As a result of the complexity, there are few studies on their fine structures and chain conformation. In the present review, we aim to provide a detailed summary of the multiple factors influencing the characteristics of TPS chemical structures such as variations of tea species, degree of fermentation, and preparation methods among others as well as their applications. The main aspects of understanding the structural difference of TPSs and influencing factors are to assist the study of the structure and bioactivity relationship and ultimately, to control the production of the targeted TPSs with the most desired biological activity.     

Validated reversed phase LC method for quantitative analysis of polymethoxyflavones in citrus peel extracts

Polymethoxyflavones (PMFs), which exist exclusively in the citrus genus, have biological activities including anti-inflammatory, anticarcinogenic, and antiatherogenic properties. A validated RPLC method was developed for quantitative analysis of six major PMFs, namely nobiletin, tangeretin, sinensetin, 5,6,7,4'-tetramethoxyflavone, 3,5,6,7,3',4'-hexamethoxyflavone, and 3,5,6,7,8,3',4'-heptamethoxyflavone. The polar embedded LC stationary phase was able to fully resolve the six analogues. The developed method was fully validated in terms of linearity, accuracy, precision, sensitivity, and system suitability. The LOD of the method was calculated as 0.15 microg/mL and the recovery rate was between 97.0 and 105.1%. This analytical method was successfully applied to quantify the individual PMFs in four commercially available citrus peel extracts (CPEs). Each extract shows significant difference in the PMF composition and concentration. This method may provide a simple, rapid, and reliable tool to help reveal the correlation between the bioactivity of the PMF extracts and the individual PMF content.     

Thermal hazard analysis of ALA nightclub fire debris

The fire that occurred at ALA nightclub was the deadliest nightclub fire in Taiwan. This study used the ALA nightclub fire as a case study and conducted a burning test based on the official fire investigation report. Fireworks that had been used during the performance were the cause of fire. Their heat release rate is approximately 180 kW, and the flame temperature is 300 °C. Soundproof foam collected from the fire debris was used to conduct a thermal analysis experiment under two different heating rates. In addition, related studies were referenced. It was found that when the sample was heated to between 45 and 55 °C, pyrolysis reaction started and the sample started to release harmful substances. The burning behavior of soundproof foam is considered ultrafast. When the heating temperature reaches between 225 and 370 °C, the sample releases 1,819.09–2,894.59 J g^?1 of heat. It is evident that it poses a serious degree of thermal hazard. Finally, it is recommended that the emergency egress time in entertainment establishments such as nightclubs should be kept between 60 and 90 s or less as a reference for fire safety strategies for nightclubs.     

Chemical studies of the antioxidant mechanism of theaflavins: radical reaction products of theaflavin 3,3′-digallate with hydrogen peroxide

The objective of the current study is to characterize the reaction products of theaflavin 3,3′-digallate, one of the major characteristic polyphenols of black tea, with hydroxyl radicals generated by hydrogen peroxide, with the aim of gaining insights into specific mechanisms of antioxidant reactions in physiological systems. Two major reaction products were isolated and identified using high-field 1D and 2D NMR spectral analysis. Both of them are A-ring fission products. The observation of these compounds indicates that the A ring rather than the benzotropolone moiety is the initial site for formation of reaction products in the hydrogen peroxide oxidant system.     

Comparison of supercritical fluid chromatography and liquid chromatography for the separation of urinary metabolites of nobiletin with chiral and non-chiral stationary phases

Nobiletin (NOB), a polymethoxylated flavone found in sweet orange (Citrus sinensis) peel, is currently recognized as a promising anti-inflammatory and anti-tumor agent. It is believed that, by undergoing metabolic biotransformation in vivo, nobiletin is demethylated by hepatic P450 enzymes, yielding multiple hydroxylated metabolites. However, it has not been possible to date to separate the two demethylated nobiletin metabolites, 3'-demethyl-NOB and 4'-demethyl-NOB (regio-isomers) on reversed-phase liquid chromatography (RPLC). Additionally, both display similar mass spectrometric fragmentation, resulting in difficulties to identify the dominant metabolite. A successful separation method was developed by utilizing supercritical fluid chromatography (SFC) with chiral stationary phase. The separation was also attempted with normal-phase liquid chromatography (NPLC) in both chiral and non-chiral modes. Chromatographic separation for the two nobiletin metabolites was superior by SFC than by LC, especially using chiral stationary phase. By comparing the SFC profile of the synthesized standards, the major nobiletin metabolite in mouse urine was identified as 4'-demethyl-NOB, with the concentration of 28.9 microg/mL.     

Flavour chemistry of methylglyoxal and glyoxal

Methylglyoxal (MGO) and glyoxal (GO), known as reactive carbonyl species, can be generated endogenously and exogenously (human body and food system). They are attracting increased attention because of their relationship with diabetes and flavour generation. In this review, their characteristics relating to flavour chemistry are discussed. MGO and GO can be detected in food systems by GC and HPLC after derivatization. MGO and GO formed in the Maillard reaction play important roles as precursors of aroma and colour compounds, especially in Strecker degradation, a major flavour generation reaction. When combined with amino acids they undergo Schiff base formation, decarboxylation and α-aminoketone condensation leading to heterocyclic aroma compounds such as pyrazines, pyrroles and pyridines. They attack amine groups in amino acids, peptides and proteins to form advanced glycation end products (AGEs) and cause carbonyl stress followed by oxidative stress and tissue damage. Therefore, many studies about scavengers of MGO and GO are seen. The influence of these scavengers on flavour generation is also discussed.     

Key Aspects of Amadori Rearrangement Products as Future Food Additives

Flavor is one of the most important factors in attracting consumers and maximizing food quality, and the Maillard reaction (MR) is highly-involved in flavor formation. However, Maillard reaction products have a big drawback in their relatively low stability in thermal treatment and storage. Amadori rearrangement products (ARPs), MR intermediates, can alternatively act as potential flavor additives for their better stability and fresh flavor formation ability. This review aims to elucidate key aspects of ARPs’ future application as flavorings. The development of current analytical technologies enables the precise characterization of ARPs, while advanced preparation methods such as synthesis, separation and drying processes can increase the yield of ARPs to up to 95%. The stability of ARPs is influenced by their chemical nature, pH value, temperature, water activity and food matrix. ARPs are associated with umami and kokumi taste enhancing effects, and the flavor formation is related to amino acids/peptides of the ARPs. Peptide-ARPs can generate peptide-specific flavors, such as: 1,6-dimethy-2(1H)-pyrazinone, 1,5-dimethy-2(1H)-pyrazinone, and 1,5,6-trimethy-2(1H)-pyrazinone. However, further research on systematic stability and toxicology are needed.