Comparison of volatile and semivolatile compounds from commercial cigarette by supercritical fluid extraction and simultaneous distillation extraction

Supercritical carbon dioxide fluid extraction (SFE) was studied as a rapid method for extraction of volatile and semivolatile compounds of Chinese commercial cigarettes. The method was compared with simultaneous distillation and extraction (SDE). Temperature and pressure for the SFE were optimized. The extracts obtained by the two methods showed different characters in composition and represented differently the flavor characteristics of tobacco; compared to SDE, SFE can extract compounds within a shorter time and avoid the thermal degradation and solvent contamination of samples. The extracts by the two extraction methods are complementary for investigating the flavor characteristic of tobacco products.

Stable expression of human cytochrome P450 2D6*10 in HepG2 cells

AIM:Over 90% of drugs are metabolized by the cytochrome P-450 (CYP) family of liver isoenzymes.The most important enzymes are CYPIA2, 3A4,2C9/19,2D6 and 2E1.Although CYP2D6 accounts for<2% of the total CYP liver enzyme content,it mediates metabolism in almost 25% of drugs.In order to study its enzymatic activity for drug metabolism, its cDNA was cloned and a HepG2 cell line stably expressing CYP2D6 was established.METHODS:Human CYP2D6 cDNA was amplified with reverse transcription-polymerase chain reaction (RT-PCR) from total RNA extracted from human liver tissue and cloned into pGEM-T vector,cDNA segment was identified by DNA sequencing and subcloned into a mammalian expression vector pREP9.A cell line was established by transfecting the recombinant plasmid of pREP9-CYP2D6 to hepatoma HepG2 cells.Expression of mRNA was validated by RT-PCR.Enzyme activity of catalyzing dextromethorphan Odemethylation in postmitochondrial supernant (S9) fraction of the cells was determined by high performance liquid chromatography (HPLC).RESULTS:The cloned cDNA had 4 base differences, e.g.100 C→T, 336 T→C,408 C→G and 1 457 G→C,which resulted in P34S,and S486T amino acid substitutions, and two samesense mutations were 112F and 136V compared with that reported by Kimura et al (GenBank accession number: M33388).P34S and S486T amino acid substitutions were the characteristics of CYP2D6*10 allele.The relative activity of S9 fraction of HepG2-CYP2D6*10 metabolized detromethorphan O-demethylation was found to be 2.31±0.19nmol·min^-1·mg^-1 S9 protein (n=3),but was undetectable in parental HepG2 cells.CONCLUSION:cDNA of human CYP2D6*IOcan be successfully doned.A cell line,HepG2-CYP2D6*10,expressing CYP2D6*10 mRNA and having metabolic activity,has been established.

Effect of La_2O_3/γAl_2O_3 Catalyst on the Activation of CH_4 and CO_2 to C_02 Hydrocarbons under Non-equilibrium Plasma

In the reaction of methane and carbon dioxide to C2 hydrocarbons under non-equilibrium plasma, methane conversion was decreased, but selectivity of C2 hydrocarbons was increased when using La2O3/?Al2O3 as catalyst. So the yield of C2 hydrocarbons was higher than using plasma alone. The synergism of La2O3/?Al2O3 and plasma gave methane conversion of 24.9% and C2 yield of 18.1%. The distribution of C2 hydrocarbons changed when Pd- La2O3/?Al2O3 was used as catalyst, the major C2 product was ethylene.