Avaliação neurofarmacológica das atividades tipo ansiolítica e/ou antidepressiva da fração diclorometano, ácido oleanólico e (E)-metilisoeugenol das folhas de pimenta pseudocaryophyllus (Gomes) L. R. Landrum (Myrtaceae) quimiotipo (E)-metilisoeugenol

Abstract

Depression and anxiety are widely acclaimed as psychiatric disorders of global concern. These disorders are among the leading causes of disability worldwide. Unsatisfactory responses of patients to the available pharmacotherapy make the search for new drugs a necessity. Medicinal plants remain important source of new drugs and new chemical entities. The ethnopharmacological knowledge and previous data have revealed calming and anxiolytic like effects of the organic leaf extract of Pimenta pseudocaryophyllus (Gomes) L.R. Landrum. The present study sought to investigate antidepressive like effect of dichloromethane fraction (DF) of the ethanolic leaf extract of Pimenta pseudocaryophyllus as well as anxiolytic and antidepressive like effects of oleanolic acid (OA), (E) methyl isoeugenol (MIE) and possible mechanisms of action that are involved. Animal models like barbiturate-induced sleep, light dark box test (LDB), elevated plusmaze (EPM), open field (OF), wire hanging test, pentylenetetrazol-induced convulsion test, forced swimming test (FST), tail suspension test (TST) were conducted to evaluate behavioural alterations that were elicited by the administrations of vehicle, DF, OA, MIE or reference drugs. Bioassays (ex vivo and in vitro) of monoamine oxidase (MAO) and quantification of hippocampal level of brain derived neurotrophic factor (BDNF) were conducted in an attempt to elucidate possible mechanisms of action. Oral administration of DF 125, 250 or 500 mg/kg (potentiated the hypnotic effect of sodium pentobarbital). In the TST and FST, DF 125 or 250 mg/kg induced antidepressant-like response. The data obtained in the OF suggest sedative effect of DF at 500 mg/kg. Pretreatment (i.p) with pchlorophenylalanine methyl ester (PCPA) 100 mg/kg (serotonin depletor) or 𝛼-methyl-ptyrosine (AMPT) 100 mg/kg (catecholamine depletor) blocked anti-immobility effect of DF viii in the FST. The enzymatic activity of MAO remained unaltered by DF. Oral administration of OA (5-20 mg/kg) increased the duration of barbiturate - induced sleep and demonstrated anxiolytic like effect in both LDB and EPM. In the FST and TST, OA 5-20 mg/kg elicited antidepressant like effect without altering locomotion activity of the animals. The antidepressant like effect of OA was attenuated by NAN-190 (non-selective antagonist of 5-HT1A), AMPT, PCPA, WAY and PRAZ. Chronic administration of OA increased hippocampal level of BDNF. Oral administration of MIE 250 or 500 mg/kg potentiated hypnotic effect of sodium pentobarbital without protecting mice against PTZ - induced convulsion. The parameters evaluated in the LDB, EPM and OF demonstrated anxiolytic like property of MIE. This effect was blocked by WAY (selective antagonist of 5-HT1A) pretreatment. MIE 125 or 250 mg/kg showed antidepressant like effect in the FST. Locomotion activity of the animal in the OF remained unaltered by MIE administration at 125 or 250 mg/kg. Pretreatment of mice with PCPA attenuated antidepressant like property of MIE. In conclusion, our findings demonstrated anxiolytic and/or antidepressant like effects of dichloromethane fraction, oleanolic acid and (E) methyl isoeugenol, thereby suggesting the involvement of monoaminergic pathway.