Our interest has been centered on flavonol glycosides from Croton Menthodorus (Euphorbiaceae) and Aristeguietia discolor (Asteraceae). In this respect, the effect of flavonol glycosides from Croton Menthodorus (Euphorbiaceae) and Aristeguietia discolor (Asteraceae) was investigated on the naloxone-precipitated withdrawal contracture of the acute morphine-dependent guinea-pig ileum in vitro. Furthermore, the effect of these flavonol glycosides was also considered on DAGO (highly selective micro-agonist) and U50-488H (highly selective k-agonist) withdrawal to test whether the possible interaction of flavonol glycosides on opioid withdrawal involves micro- and/or k-opioid receptors. Flavonol glycosides from Croton Menthodorus (1 x 10(-5), 5 x 10(-5) and 1 x 10(-4) M) and from Aristeguietia discolor (1 x 10(-7)-1 x 10(-6)-1 x 10(-5) M) before or after the opioid agonists were able to both prevent and reverse the naloxone-induced contracture after exposure to micro (morphine and DAGO) or k (U50-488H) opiate agonists in a concentration-dependent fashion. Both acetylcholine response and electrical stimulation were reduced by flavonol glycosides treatment as well as the final opiate withdrawal was still reduced. The results of the present study indicate that flavonol glycosides were able to produce significant influence on the opiate withdrawal in vitro and these compounds were able to exert their effects both at micro and k opioid agonists.