EVALUATION OF THE ANTI-STRESS, ANTI-DEPRESSANT AND ANXIOLYTIC PROPERTIES OF PARQUETINA (Parquetina nigrescens Afzel.) AND FIG TREE (Ficus capensis Thunb.) LEAF EXTRACTS

Abstract

Depression and anxiety disorders are frequent psychiatric conditions identified as the most common stress-related mood disorders causing disability and premature death. The global socioeconomic burdens and suffering resulting from mood disorders are of tremendous impact and concern in society. Due to adverse effects of current antidepressant and anxiolytic drugs, a number of medicinal plants are being exploited as safer and more efficient alternatives. This research was therefore designed to evaluate the antidepressant and anxiolytic properties of leaf extracts of Parquetina nigrescens (PN) and Ficus capensis (FC), using two models: Pentylenetetrazol-induced anxiety and chronic Forced Swim Stress (FSS). Phytochemical evaluation, HPLC and GC-MS analyses, and in vitro antioxidant activity of hydro-ethanolic and aqueous leaf extracts of Parquetina nigrescens (PNET and PNAQ) and Ficus capensis (FCET and FCAQ) were evaluated by standard protocols. The sedative effect of the hydro-ethanolic extracts of the two plants in male Wistar rats was evaluated using the Diazepam sleeping time test. Anxiety was induced in male Wistar rats with a single dose of Pentylenetetrazol (20 mg/kg) intraperitoneally with or without post treatment with PNET or FCET (100, 150 and 250 mg/kg) or standard drugs, diazepam (1 mg/kg) or imipramine (30 mg/kg) for 14 consecutive days. The rats were subjected to behavioral test models of open field (OFT), elevated plus-maze (EPM) and forced swim (FST), on days 1 and 14, to evaluate the antidepressant and anxiolytic activity of the extracts. The antidepressant and anxiolytic effect of the extracts were also evaluated on chronic Forced Swim Stressed rats, which were subjected to 1 h swim stress daily for 7 days. Oxidative stress markers were determined in the hepatic and cerebral homogenates. Serotonin, cortisol and brain-derived neurotrophic factor levels were determined using Enzyme-Linked Immunosorbent assay kits. The dopamine level and acetylcholinesterase activity were also estimated. Hematological parameters, serum lipid profile, and liver function tests were determined. Phytochemical investigation revealed the presence of tannins, flavonoids, saponins, alkaloids, cardiac glycosides, anthraquinones, and terpenoids. HPLC analyses revealed the presence of phytochemicals (alkaloids, terpenoids and phenolic compounds) with mood modulatory properties. Isoquercitrin and chlorogenic acid, were higher in Parquetina nigrescens, while gallic acid, caffeic acid, rutin and quercetin, were higher in Ficus capensis. The extracts demonstrated high antioxidant capacity and radical scavenging ability in vitro. The extracts possess sleep-inducing properties. The duration of sleep was significantly (p<0.001) increased by the extracts. The extracts demonstrated antidepressant and anxiolytic potentials in the FST, OPM and EPM, and also ameliorated the anxiogenic and depressant behaviors induced by PTZ and Forced swim stress on the animals. The extracts demonstrated anti-inflammatory, antilipidemic, hepatoprotective, and anti-oxidative potentials in the two models used in this study. The extracts also demonstrated neurotransmitter modulatory ability by ameliorating the PTZ-induced and FSS-induced neurochemical dysfunction shown by alterations in the neurotransmitter levels, cortisol and BDNF levels, in both models. The acetylcholinesterase inhibitory activity and cortisol levels were significantly (p<0.05) reduced by the extracts compared with the induced and stressed groups. Likewise, the BDNF level was significantly (p<0.05) increased by the extracts compared with the induced and stressed groups. The results of this study indicates Parquetina nigrescens and Ficus capensis as good alternatives or drug adjuvants in the management of mood disorders, depression-like mental ailments and stress-related disorders, as well as management of aging and other degenerative diseases associated with the brain.