Clitoria ternatea and the CNS

Abstract

The present investigation was aimed at determining the spectrum of activity of the methanolic extract of Clitoria ternatea (CT) on the CNS. The CT was studied for its effect on cognitive behavior, anxiety, depression, stress and convulsions induced by pentylenetetrazol (PTZ) and maximum electroshock (MES). To explain these effects, the effect of CT was also studied on behavior mediated by dopamine (DA), noradrenaline, serotonin and acetylcholine. The extract decreased time required to occupy the central platform (transfer latency, TL) in the elevated plus maze (EPM) and increased discrimination index in the object recognition test, indicating nootropic activity. The extract was more active in the object recognition test than in the EPM. The extract increased occupancy in the open arm of EPM by 160% and in the lit box of the light/dark exploration test by 157%, indicating its anxiolytic activity. It decreased the duration of immobility in tail suspension test (suggesting its antidepressant activity), reduced stress-induced ulcers and reduced the convulsing action of PTZ and MES. The extract exhibited tendency to reduce the intensity of behavior mediated via serotonin and acetylcholine. The effect on DA- and noradrenaline-mediated behavior was not significant. In conclusion, the extract was found to possess nootropic, anxiolytic, antidepressant, anticonvulsant and antistress activity. Further studies are necessary to isolate the active principle responsible for the activities and to understand its mode of action.

Introduction

Clitoria ternatea Linn (Family Fabaceae) is commonly known as “Butterfly pea.” The plant is a twining evergreen herb, which will grow up to 3 m (9 ft) high, climbing over any available prop. The stems are pubescent and spindly. The compound leaves are made of three to nine oval or elliptical leaflets. The flowers are 2–4 cm long and in various shades of blue with a yellow throat or pure white with a big standard petal. The fruits are pods, resembling thin peas. Native to the island of Ternate in the Molluca archipelago, this species is now widely grown as ornamental, fodder or medicinal plant. The roots and seeds have powerful laxative effects, the flowers are used to make collyrium and the leaves are used in Madagascar to relieve joint pain. The plant may start flowering 4 months after sowing. Roots, seeds and leaves of C. ternatea are commonly used in the Ayurvedic system of medicine. The roots are bitter, refrigerant, laxative, intellect promoting, diuretic, anthelmintic and tonic and are useful in dementia, hemicrania, burning sensation, leprosy, inflammation, leucoderma, bronchitis, asthma, pulmonary tuberculosis, ascites and fever. The leaves are useful in otalgia and hepatopathy, whereas seeds are cathartic (Anonymous, 1995). C. ternatea contains antifungal proteins and has been shown to be homologous to plant defensins (Osborn et al., 1995). Rai et al. (2001), using passive avoidance test and spatial learning T-maze, have shown that the aqueous root extract of C. ternatea enhances memory in rats. Taranalli and Cheeramkuczhi (2000) reported that the alcoholic extracts of aerial and root parts of C. ternatea at 300 and 500 mg/kg po doses in rats attenuated electroshock-induced amnesia. The extract at 300 mg/kg dose produced significant memory retention, and the root parts were found to be more effective. The authors suggested that C. ternatea extract increased rat brain acetylcholine content and acetylcholinesterase activity in a similar fashion to the standard cerebroprotective drug pyritinol. Because the other activities of C. ternatea have not been studied, we investigated the nootropic, anxiolytic, antistress and anticonvulsant activities using conventional animal models and also the effects on behavior mediated via dopamine (DA) (haloperidol-induced catalepsy), noradrenaline (clonidine-induced hypothermia), serotonin (lithium-induced head twitches) and acetylcholine (sodium nitrite-induced respiratory arrest).