RESUMEN
Psychotria colorata (Will ex R&S) Muell.Arg. flowers are used by "caboclos" in the Amazon as the basis for a homemade analgesic. The study of P. colorata revealed the presence of several pyrrolidinoindoline alkaloids, some with opioid-like analgesic activity in vivo. Neurochemical studies of active alkaloids proved their capability of inhibiting [3H] naloxone binding, confirming the opioid nature of the analgesic activity. These data launched a broader screening of Psychotria species, including P. carthagenensis, P. brachyceras, P. leiocarpa, P. myriantha, P. suterella and P. brachypoda. The analysis of the analgesic activity of several Psychotria species, as well as of specific isolated compounds, allowed a tentative structure/activity relationship and opened a promising research avenue in the search for new analgesic drugs.