Formation of Dihydroxybenzenes in Cigarette Smoke. Part 2. Contribution from Quinic Acid and Myo-Inositol

Formation of dihydroxybenzenes in cigarette smoke is a subject of considerable interest because some dihydroxybenzenes are co-carcinogens, (e.g., catechol and certain alkylcatechols), and others such as hydroquinone can form metabolites that have toxic or carcinogenic properties. This present study describes the contribution of tobacco quinic acid (or (1S,3R,4S,5R)-1,3,4,5-tetrahydroxycyclohexanecarboxylic acid) and myo-inositol (or (1R,2R,3S,4S,5R,6S)-cyclohexane-1,2,3,4,5,6-hexol) to the formation of dihydroxybenzenes in cigarette smoke. The study is a continuation of a previous one showing the contribution of chlorogenic acid and rutin as precursors for these compounds (6). The yields of dihydroxybenzenes formed by pyrolysis of quinic acid and myo-inositol are relatively high and both quinic acid and myo-inositol can be present in some tobacco types at levels as high as 1% by weight. The level of these compounds makes them potentially important contributors to the formation of dihydroxybenzenes in cigarette smoke. Similar to the previous study on other dihydroxybenzene precursors from tobacco, this present study was done in three parts: 1) pyrolytic evaluation of the amount of dihydroxybenzenes in smoke generated from isolated quinic acid and myoinositol; 2) analysis of smoke from cigarettes made from a variety of tobaccos (14 single grades) and two blended cigarettes, followed by correlations of dihydroxybenzene yields from these cigarettes with the level of quinic acid and myo-inositol in the tobaccos; 3) addition of quinic acid or myo-inositol to several tobaccos followed by the smoking of the spiked cigarettes and measurement of the dihydroxybenzenes yield increase. The study performed on a variety of single-grade tobacco cigarettes and for two blended-tobacco cigarettes (one being the 2R4F Kentucky reference) shows that the contribution of quinic acid and of inositol to the formation of catechol and hydroquinone in smoke depends on the blend, as previously shown for chlorogenic acid and rutin. The study results suggest that quinic acid and myo-inositol may be major contributors to the formation of dihydroxybenzenes in cigarette smoke. Although the calculations do not provide precise numbers for the contribution of quinic acid and inositol to the formation of dihydroxybenzenes, these results suggest that the contribution could be as high as 50 to 60% of the level of dihydroxybenzenes.