Study On Selective Reduction Of Several Benzo [a] Pyrene Precursor Compounds In Tobacco

Benzo[a]pyrene belongs to polycyclic aromatic hydrocarbons, which was recognized to be carcinogenic by JARC and Candian government. Thus, to reduce benzo[a]pyrene in mainstream cigarette smoke has become one of the important research directions of the aspect of tobacco relieve harm and reduce tar.By the pyrolysis and thermogravimetric analysis of pure chemicals, and dose-effect relationship etc, combining the literature research and according to the method of chemical classification, the potential precursors of benzo[a]pyrene in tobacco were investigated in previous work.95%ethanol was chosed to extract tobacco and blend them with those had not been extract according to certain proportions (0%,10%,30%,50%and60%), meanwhile, the yields of7harmful components in mainstream cigarette smoke were analyzed. Firstly, the chemical compouds in extract and tobacco were analysed, and secondly, the physical and chemical properties of extracted tobacco has been researched by scanning electron microscope, thermogravimetric analyzer and dynamic moisture adsorption instrument.The results showed that:(1) Three kinds of chemical compounds, sterol, polyphenol, solanesol, were considered as the main precursors of benzo[a]pyrene in MSS.(2) Comparing with the normal tobacco, the contents of sitosterol and stigmasterol in extracted tobacco have selectively reduced by extraction of tobacco. The content of rutin reduces apparently and the content of solanesol reduces to a certain degree while the contents of other compounds do not change a lot. The content of nicotine which is extracted from95%ethanol has reached as high as75.42%. Meanwhile, there was a small amount of sterol in extract.(3) Surface morphology of tobacco extracted by ethanol has been studied using scanning electron microscope, compared with the normal tobacco, which’s structure was withered and rough. Meanwhile, the ethanol extracted tobacco was studied by dynamic moisture adsorption instrument, which showed that the water retention of tobacco that had been extracted was poorer.(4) Tobacco that had been extracted has the obvious difference with the normal tobacco in thermochemical property. The normal one has better combustibility. After the tobacco which has been blended according to certain proportions by thermal pyrolysis in gold surface reverberatory furnace, the emission of benzo[a]pyrene would first increase and then reduce with the increasing of the blending proportions.(5) The yields of seven harmful components (dry base) in the mainstream cigarette smoke reduced to a certain degree along with the increase of percentage, and especially the yields of CO, HCN, NH3and NNK. The above revealed harmful components in mainstream cigarette smoke could be reduced by ethanol extraction.In conclusion, by using95%ethanol extraction, the physical structure of the surface of tobacco was fully exposed and at the same time, the chemical compounds of tobacco was also changed, which leads to the change of tobacco both in its physical (surface structure and water retention capacity) and chemical quality (chemical compounds and thermochemical property). Therefore, the harmful compounds in MSS have reduced, so as to the effect of reducing harmful components.