Antidepressant effect of methanol extract of smokeless tobacco and identification of its bioactive components

Abstract

Purpose: To investigate the antidepressant effect of methanol extract of smokeless tobacco and identify its bioactive compounds. Methods: Adult Wistar rats were randomly assigned to five groups of five rats each: normal control group, standard (reference) control group as well as 100, 200 and 500 mg/kg extract group. The extract, standard drug (imipramine) and normal saline were administered via the intraperitoneal (i.p.) route. The rats were subjected to forced swim test (FST) and tail suspension test (TST) to assess the antidepressant effect of methanol extract of smokeless tobacco. Gas chromatography–mass spectrometry (GC-MS) was used to identify the bioactive compounds of the extract. Results: The oral LD50 of the extract was > 2000 mg/kg. Significant decrease in immobility time was observed after single administration of imipramine (p < 0.05). The extract significantly and dosedependently decreased the immobility time, but increased climbing and swimming times, when compared with normal control group (p < 0.05). The immobility time of stressed rats regardless of sex was significantly and dose-dependently lowered, relative to normal control group (p < 0.05). Four major compounds were identified in the extract: nicotine (45.88 %); 1,5-dimethyl-2-pyrrolidinone (23.00 %), nhexadecanoic acid (11.31 %) and vitamin A aldehyde (9.38 %). Conclusion: These results demonstrate that the methanol extract of smokeless tobacco possesses antidepressant and mood-elevating effects in rats. However, its use should be discouraged since it contains a number of hazardous and carcinogenic components such as N-nitroso compounds and benzo(a)pyrene which are categorized as Class-I carcinogens.