Nigella sativaSeed Constituents and Anxiety Relief in Experimental Models

This study investigated anti-anxiety effects of Nigella sativa seed constituents (aqueous extract, fixed oil, volatile oil, and major constituents of the volatile oil) using male mice and the Y-maze and hole-board tests as models for exploration-induced anxiety and the water-lick test as a model for conflict-induced anxiety. The seed constituents were injected intraperitoneal into male mice and subjected to tests 1 h later. Except for the aqueous extract, all the tested constituents demonstrated an anti-anxiety effect in the Y-maze and hole-board tests. In the water-lick test, all constituents were ineffective in reducing anxiety except for the volatile oil. The failure to demonstrate anxiolytic effects in the water-lick conflict test may be due to this test model representing a more difficult task to the test animals as compared with the other test models. The anxiolytic activity of the volatile oil in the Y-maze and hole-board tests can be attributed to the contents thymoquinone, α-pinene, and p-cymene. The α-pinene and p-cymene appear to be excellent anti-anxiety agents in the hole-board test as these compounds did not retard spontaneous locomotor activity in treated animals. Exploration on the mechanism of action using the benzodiazepine antagonist flumazenil suggested that benzodiazepine receptor involvement might constitute almost 60 percent of activity of thymoquinone and α-pinene. Other seed constituents probably act through other receptors or different mechanisms.