Study On Antifungal Activity Of Tobacco Extracts

In this study, with NC82, CF87, FC8, V2, B22, Jing YH, Ge X3 as material, with hexane, ethanol, 95% ethanol, 80% ethanol, methanol, acetone, ethyl acetate, petroleum ether(30-60 ℃), dichloromethane as extraction solvent, to explore the antifungal and antibacterial activity, main active substance and potential mechanism of tobacco extracts, agar plate test and cup method was conducted to evaluate the inhibitory effect of different tobacco extracts. The antifungal-components of tobacco extracts were measured by HPLC and GC-MS. The ultra-microstructure of V.mali under the effect of tobacco leaf secretion was revealed using scanning electron microscope(SEM) and transmission electron microscope(TEM). The main results were as follows:(1) Tobacco extracts had no inhibitory effect on gram-negative bacteria—E.coli and Pseudomonas aeruginosa, had slight inhibitory effect on gram-positive bacteria —Staphylococcus aureus and Bacillus subtilis.(2) Tobacco extracts had inhibitory effect to the mycelium of V. mali and other 10 kinds of plant pathogens, especially the inhibitory effect of Ascomycetes subphylum pyrenomycetes—Colletot tichumgloeosporioides, V.mali and deuteromycotina hyphomycetes—Fusarium oxysporum Schl, Cotton-wilt Fusarium, Fusarium oxysporum wilt is better, the inhibitory rate was more than 50%. For example the inhibitory rate of 0.5 g/m L CF87 fresh tobacco leaves’ hexane extract to V. mali was 94%, EC50 was 0.185 g/m L; to Colletot tichumgloeosporioides was 58%, EC50 was 0.422 g/m L.(3) The antifungal activity of tobacco extract is related to the solvent’s polarity. The antifungal activity of weak polar solvents’ extract(dichloromethane, ethyl acetate, petroleum ether, hexane) was superior to that of the strong polar solvent’s extract.Considering the price, the experimental operation and the impact on health, hexane is suitable as extraction solvent of tobacco extract.(4) Drawn from the comparison of antifungal activity of different varieties of tobacco extract, the extract of tobacco varieties CF87 was significantly higher than that of the rest tobacco varieties. This shows that antifungal activity of tobacco extract is related to tobacco varieties.(5) Different organs of tobacco extracts had different antifungal activities. The inhibitory effect of tobacco flower’s extract was significantly better than that of tobacco leaves’ extract. The inhibitory effect of different tobacco organs’ extracts on V. mali is the best, the inhibitory rate of 0.5 g/m L tobacco flowers’ extract to V. mali was 95%.(6) Before and after curing tobacco leaves’ extract has different antifungal activity. The inhibitory effect of fresh tobacco extract on three kinds of tested fungi is significantly better than the cuered tobacco extract. Tobacco curing is the processing of baking, redrying etc. to fresh tobaccoleaves, many active components in tobacco leaves will be damaged and affect the inhibitory activity.(7) By verifying the antifungal activity of pure substance and mixed substance of chlorogenic acid, solanesol, rutin and nicotine, analysising the correlation of the content of main antifungal secondary metabolites of tobacco extract and its antifungal activity, it showed that cembranoids may be the main antifungal substance. There had no obvious correlation between the polyphenols, flavonoids, sterols, terpenoids and tobacco’s antifungal activity. According to the active components and their relative antifungal effect of different extracts, together with preliminary confirmation of the leaf secretion, it was speculated that cembranoids was the main antifungal substance, which might act on the hyphal cell wall.