Tetramethylpyrazine potentiates arsenic trioxide activity against HL-60 cell lines

The objective of this study was to evaluate the effects of tetramethylpyrazine (TMP) in combination with arsenic trioxide (As2O3) on the proliferation and differentiation of HL-60 cells. The HL-60 cells were treated with 300 µg/mL TMP, 0.5 µM As2O3, and 300 µg/mL TMP combined with 0.5 µM As2O3, respectively. The proliferative inhibition rates were determined with MTT. Differentiation was detected by the nitroblue tetrazolium (NBT) reduction test, Wright’s staining and the distribution of CD11b and CD14. Flow cytometry was used to analyze cell cycle distribution. RT-PCR and Western blot assays were employed to detect the expressions of c-myc, p27, CDK2, and cyclin E1. Combination treatment had synergistic effects on the proliferative inhibition rates. The rates were increased gradually after the combination treatment, much higher than those treated with the corresponding concentration of As2O3 alone. The cells exhibited characteristics of mature granulocytes and a higher NBT-reducing ability, being a 2.6-fold increase in the rate of NBT-positive ratio of HL-60 cells within the As2O3 treatment versus almost a 13-fold increase in the TMP + As2O3 group. Cells treated with both TMP and As2O3 expressed far more CD11b antigens, almost 2-fold compared with the control group. Small doses of TMP potentiate As2O3-induced differentiation of HL-60 cells, possibly by regulating the expression and activity of G0/G1 phase-arresting molecules. Combination treatment of TMP with As2O3 has significant synergistic effects on the proliferative inhibition of HL-60 cells.

Assessment Of Robustness On Analysis Using Headspace Solid-phase Microextraction And Comprehensive Two-dimensional Gas Chromatography Through Experimental Designs.

Plackett-Burman experimental design was applied for the robustness assessment of GC×GC-qMS (Comprehensive Two-Dimensional Gas Chromatography with Fast Quadrupolar Mass Spectrometric Detection) in quantitative and qualitative analysis of volatiles compounds from chocolate samples isolated by headspace solid-phase microextraction (HS-SPME). The influence of small changes around the nominal level of six factors deemed as important on peak areas (carrier gas flow rate, modulation period, temperature of ionic source, MS photomultiplier power, injector temperature and interface temperature) and of four factors considered as potentially influential on spectral quality (minimum and maximum limits of the scanned mass ranges, ions source temperature and photomultiplier power). The analytes selected for the study were 2,3,5-trimethylpyrazine, 2-octanone, octanal, 2-pentyl-furan, 2,3,5,6-tetramethylpyrazine, and 2-nonanone e nonanal. The factors pointed out as important on the robustness of the system were photomultiplier power for quantitative analysis and lower limit of mass scanning range for qualitative analysis.

Antimicrobial activity of pyrazine and quinoxaline N,N’-dioxide heterocyclic compounds

The nitrogen heterocyclic organic compounds 1,4 dioxide pyrazine and quinoxaline derivatives have been widely studied due to their potential use as synthetic drugs. The thermochemical study of three N,N´-dioxides: 2,3,5-trimethylpyrazine-1,4-dioxide, tetramethylpyrazine-1,4-dioxide and 6-chloro-2,3-dimethilquinoxaline 1,4-dioxide has been recently developed in order to establish relationships among the energetical, structural and reactivity properties [4,5]. Several studies have reported their pharmacological activity, particularly as antimicrobial agents [1,2,3]. It has also been established a relation between energetical and structural properties and biological activity, once these compounds present N – oxide bonds, increasing their oxidative capacity. The present work reports the study of antimicrobial activity for those compounds against the bacteria Geobacillus stearothermophylus, Staphylococcus aureus, Streptococcus agalactiae, Escherichia coli and also against the yeasts Saccharomyces cerevisiae PYCC 4072, Candida albicans PYCC3436T, Candida tropicalis PYCC, Issatchenka Orientalis PYCC. The determination of the minimal inhibitory concentration (MIC), points to an antimicrobial activity and the preliminary results indicate that these compounds may be potential candidates as antimicrobial drugs with clinical, agriculture or food industries applications.

Effect of citric acid and glycine addition on acrylamide and flavor in a potato model system

Acrylamide levels in cooked/processed food can be reduced by treatment with citric acid or glycine. In a potato model system cooked at 180 degrees C for 10-60 min, these treatments affected the volatile profiles. Strecker aldehydes and alkylpyrazines, key flavor compounds of cooked potato, were monitored. Citric acid limited the generation of volatiles, particularly the alkylpyrazines. Glycine increased the total volatile yield by promoting the formation of certain alkylpyrazines, namely, 2,3-dimethylpyrazine, trimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, tetramethylpyrazine, and 2,5-diethyl-3- methylpyrazine. However, the formation of other pyrazines and Strecker aldehydes was suppressed. It was proposed that the opposing effects of these treatments on total volatile yield may be used to best advantage by employing a combined treatment at lower concentrations, especially as both treatments were found to have an additive effect in reducing acrylamide. This would minimize the impact on flavor but still achieve the desired reduction in acrylamide levels.