Vitor A. Kerber

Analgesic Properties of Umbellatine from Psychotria umbellata

Interesting analgesic activity has been previously identified in alkaloids isolated from the genus Psychotria (Rubiaceae). We here report the analgesic activity of umbellatine, a new glycoside indole monoterpene alkaloid isolated from Psychotria umbellata. Umbellatine produced a dose-dependent (100-300 mg/kg) analgesic effect, partially reversed by naloxone, in the tail-flick and hot-plate models. These results suggest an analgesic effect at least in part associated with the activation of opioid receptors. In the formalin- and capsaicininduced pain models, umbellatine (100-300 mg/kg) elicited significant and dose-related antinociception. Umbellatine acts synergistically when co-administered with the NMDA antagonist MK-801. These results indicate the involvement of NMDA receptors in the umbellatine mechanism of action. Such a combined mode of action can be of relevance for developing analgesics useful in neurophatic pain.

Brachycerine, a novel monoterpene indole alkaloid from Psychotria brachyceras

Brachycerine (1), an unusual alkaloid from the leaves of Psychotria brachyceras, was characterized through spectroscopic data interpretation and its stereochemistry established by NOE difference techniques. Brachycerine (1) was found to be restricted to shoots in rooted cuttings of P. brachyceras (0.018 +/- 0.004% dry weight), and accumulation was unaffected by root induction treatment with auxin.

Psychollatine, a Glucosidic Monoterpene Indole Alkaloid from Psychotria umbellata

A monoterpene indole alkaloid, psychollatine ( 1), was isolated from Psychotria umbellata leaves. Its structure was characterized by interpretation of spectroscopic data and by comparison of its NMR data with those of croceaine A ( 2) from Palicourea crocea. The configuration of psychollatine ( 1) was established by NOE difference and circular dichroism (CD) techniques, while its conformation was evaluated through molecular modeling studies and NMR coupling constants.

Indole monoterpene alkaloids from leaves of Psychotria suterella Müll. Arg. (Rubiaceae)

1. Subject and sourcePsychotriasuterellaMuull. Arg. (Rubiaceae) is a shrub or small tree ofup to 2m in.height, that is found in coastal tropical forests of Southern Brazil, ranging from RiodeJaneirotoRioGrandedoSul(DillemburgandPorto,1985).PlantswerecollectedintheruralareaofthecityofTreesForquilhas,RS,Brazil,inthesummerof1999and#identified by botanist Marcos Sobral (Faculty ofPharmacy, Universidade Federaldo Rio Grande do Sul-UFRGS). A voucher specimen (ICN 98870) has beendeposited in the UFRGS herbarium.2. Previous workPsychotria (Rubiaceae) is a complex genus, with estimates of1000–1650 species(Nepokroeff et al., 1999). Segregation ofspecies into new genera has been proposedbased on molecular and morphological analyses (Nepokroeff et al., 1999; Taylor,