Antiulcer activity
Ocimum sanctum may be considered as a drug of natural origin which possesses both anti-inflammatory and antiulcer activity [32]. The fixed oil present in it was reported to have antiulcer activity against aspirin, indomethacin, alcohol, histamine, reserpine, serotonin and stress-induced ulceration in rats [33]. It also exhibited gastric secretion inhibiting activity in pylorus ligated rats. The lipooxygenase inhibitory, antihistaminic and antisecretory action may contribute to its antiulcer property [34]. It has been reported that leukotriene antagonist and 5-lipoxygenase inhibitors are capable of inhibiting alcohol and NSAIDs-induced gastric ulceration in rats [35]. Therefore the protection afforded by the fixed oil of O. sanctum against alcohol and NSAIDs-induced gastric ulceration could also be due to inhibition of 5-lipoxycenase pathway or to leukotriene's antagonistic activity [36]. Histamine-induced gastric ulceration is known to be mediated by enhanced gastric acid secretion as well as by vasospastic action of histamine [37]. Hence, it may be suggested that O. sanctum fixed oil has suppressed the histamine-induced vasospastic effect and gastric secretion. Reserpine-induced gastric ulceration has been attributed to the degranulation of the gastric mast cells and consequent liberation of histamine which is believed to be cholinergically mediated [38]. The antiulcer effect of O. sanctum fixed oil could be due to its histamine antagonistic and anticholinergic effects. Serotonin-induced ulceration is believed to arise from a disturbance of gastric mucosal microcirculation and the oil appears to improve such a disturbance. Since the development of ulcers by serotonin and reserpine usually takes about 18 hours, it may also be inferred that the oil has a sustained effect [39]. Stress-induced ulcers are probably mediated by histamine release with enhancement in acid secretion and a reduction in mucous production. The stress-induced ulcers can be prevented partially or entirely by vagotomy; vagal over-activity has been suggested to be the principal factor in stress-induced ulceration [40]. Accordingly, the protective action of O. sanctum fixed oil against stress-induced ulceration could be due to its histamine antagonistic, anticholinergic and antisecretory effects. Further studies are however required to evaluate the exact mechanism of action or it could have multiple mode of action