Absence of alkaloids in Psychotria carthagenensis Jacq. (Rubiaceae)

Psychotria viridis and P. carthagenensis are often discussed in relation to the hallucinogenic beverage Ayahuasca, used for religious, medicinal and social purposes. The significance of including Psychotria species in this beverage has been understood on the basis of substantial amounts of tryptamine alkaloids detected on leaves of both P. viridis and P. carthagenensis. Nevertheless, there is a long lasting debate over the identification of which Psychotria species are actually traditionally employed. We here report that a P. carthagenensis leaf ethanol extract was found to be devoid of alkaloids. The extract significantly decreased mice body temperature (350 and 500 mg/kg). Toxicity assessment revealed that the extract induced sedation and slight ptoses (75% of animals treated with 1000 mg/kg). Lethality was not observed within 48 h. The data indicate that P. carthagenensis does have bioactive compound(s), possibly active at the central nervous system, but unlikely to be tryptamine alkaloids as in the case of P. viridis. Therefore, if P. carthagenensis is indeed used by ayahuasqueros, its chemical and pharmacological significance have yet to be elucidated.