Coffee methylxanthines and human health effects

Coffee plants contain two different kinds of alkaloid secondary metabolites delivered from nucleotides. One type is purine alkaloids, such as caffeine (1,3,7-N-trimethylxanthine) and theobromine (3,7-N-dimethylxanthine); the other is the pyridine alkaloid, trigonelline (1-N-methylnicotinic acid). Caffeine is the most common purine alkaloid found in coffee seeds (mainly in endosperms). The beans of most cultivars of Arabica coffee (Coffea arabica) contain up to 1.0% caffeine, while Robusta coffee beans (Coffea canephora) contain about 2.0% caffeine. It is known to be rapidly and nearly completely (up to 90%) absorbed by the stomach with peak plasma concentrations occurring within 20–40 minutes. Worldwide coffee consumption promotes interest in coffee in terms of health as well as the incidence of diseases. Due to its rich composition of active compounds, coffee is suggested to improve some physiological effects. However, studies showed that the balance between caffeine and active components (e.g., polyphenols) determines the occurrence of the course of the diseases. There is a problem if caffeine alone and coffee (beverage containing caffeine) should be considered as agents showing the same effect in the human body. Moreover, the effect of dose of consumed coffee was considered.