Carcinogenic Effects of Polycyclic Aromatic Hydrocarbons and Modulation by Coffee Compounds
Polycyclic aromatic hydrocarbons (PAHs) are cancer-causing agents, being a major concern for human health. Consequently, competent organizations established target compounds based on their occurrence and toxicity. The major source of PAHs exposition to human population is from food. Different PAHs are formed during the roasting of coffee beans, although their extractability from coffee powder to the brew is low, due to the low solubility in water. Coffee is considered by IARC as a possible human carcinogen, group 2B, due to association with bladder cancer, although the health-promoting properties of coffee gained relevance in the last years, especially due to modulating effects of caffeine, chlorogenic acid and the coffee diterpenes. These compounds can alter the bioactivation of PAHs, modulating activating enzymes (CYP1A1, CYP1A2, CYP1B1, EH, DD) and detoxifying enzymes (GST, UGT, NQO1). Heavy coffee consumption, depending on the type of coffee, may induce CYPs through the presence of PAHs, however, other coffee components exert protective effects mainly due to enhancement of detoxifying pathways. Caffeine acts competing with PAHs to the CYPs, since both are metabolized by them or also through the formation of complexes with PAHs, while the chemopreventive effects of coffee diterpenes against PAHs are mainly by the increase of GST and UGT. Chlorogenic acids also exert protective effects mostly due to enhanced GST and NQO1 activities, and also due to some inhibition of CYPs. Therefore, when considering the potential carcinogenicity of PAH in coffee drinking, the existence of coffee compounds with protective effect should be considered.