Cerebroprotective effect of Eclipta alba against global model of cerebral ischemia induced oxidative stress in rats

Abstract

Oxidative stress is believed to contribute to neuronal damage induced by cerebral ischemia/reperfusion (I/R) injury. The present study was undertaken to evaluate the possible cerebroprotective and antioxidant effect of hydroalcoholic extract of Eclipta alba against global cerebral ischemia in the rat. Adult Wistar albino rats were treated with extract of Eclipta alba (250 and 500 mg/kg/day, p.o.) for 10 days. The global cerebral ischemia–reperfusion injury was induced by occluding bilateral common carotid arteries (BCCA) for 30 min, followed by 4 h reperfusion. Quercetin (20 mg/kg, i.p.) was used for the reference compound. After that, animals were sacrificed by decapitation, brain was removed, various biochemical estimations, cerebral edema, assessment of cerebral infarct size, and histopathological examinations were carried out. BCCA caused significant depletion in superoxide dismutase (SOD), glutathione peroxidase (GPx), reduced glutathione (GSH), catalase (CAT), glutahione-S-transferase (GST), glutathione ruductase (GR) and significant increase in malondialdehyde (MDA) in brain. Pretreatment with hydroalcoholic extract of Eclipta alba significantly reversed the levels of biochemical parameters and significantly reduced the edema and cerebral infarct size as compared to the ischemic control group. Eclipta alba at higher dose markedly reduced ischemia-induced neuronal loss of the brain. Reduction of cerebral edema, an early symptom of ischemia, is one of the most important remedies for reducing subsequent chronic neural damage in stroke. The results of the study show that Eclipta alba pretreatment ameliorates cerebral ischemia/reperfusion injury and enhances the antioxidant defense against BCCA occlusion induced I/R in rats; so it exhibits cerebroprotective property. HPLC fingerprint of hydroalcoholic extract of Eclipta alba was performed for conforming the coumestan present in the plant extract.

Introduction

Cerebrovascular disorders represent a major group of neurological diseases, which considerably impair the quality of life. Ischemia/reperfusion injury, stroke, vascular dementia and chronic cerebral hypoperfusion are among the most common cerebrovascular disorders, which are often accompanied by the degeneration of the nervous tissue, resulting in the loss of executive function and cognitive deficits. Free radical formation has been demonstrated during cerebral ischemia (Ste-Marie et al. 2000). Moreover, there is a burst of free radical generation at the onset of reperfusion after cerebral ischemia (Dirnagl et al. 1995). Brain is particularly susceptible to the damage due to oxidative stress because neurons are rich in polyunsaturated fatty acids and levels of endogenous antioxidant enzymes in neuronal tissue are low (Juurlink and Sweeney 1997). Therefore, oxidative stress may contribute to neuronal cell death due to ischemia and reperfusion. Several synthetic free radical scavengers have been evaluated in animal models of cerebral ischemia and reperfusion and have been shown to be protective (Itoh et al., 1990, Kuroda et al., 1999)

Eclipta alba (Linn.) Hassk [Synonym – Eclipta prostrata (Linn.)] (Family – Asteraceae) is commonly known as “Bhringarajah” (Sancrit), “Bhamgra” (Hindi), “Kadiggagaraga” (Kannada) which is one of the ten auspicious herbs that constitute the group dasapuspam. It is widely distributed throughout India (in paddy growing areas of India), China, Thailand, and Brazil. In many parts of India and in southwestern US it is grown commercially as a medicinal crop. The herb Eclipta alba contains mainly coumestans, i.e. wedelolactone and demethyl wedelolactone, polypeptides, polyacetylenes, thiophene-derivatives, steroids, triterpenes, flavonoids, (luteolin, luteolin-7-O-glucoside), alkaloid ecliptine and the ubiquitous stigmasterol (Sukh Dev, 2006, Wagner et al., 1986). It has been mentioned in ancient texts to be a nervine tonic (Uniyal et al. 1998) in addition to possessing hepatoprotective activity (Tabassum and Agarwal 2004). The aqueous and alcoholic extracts of the plant are proved to confer protection against the myotoxic effects of snake venom (Pithayanukul et al. 2004), lipid lowering activity and improved antioxidant property (Kim et al. 2008) hypotensive and immunosuppression (Christybapita et al. 2007) properties. Additionally, it is also reported to possess neuropharmacological activity (Thakur and Mengi 2005). Importantly wedelolactone suppresses LPS-induced caspase-11 expression by directly inhibiting the IKK Complex. Caspase-11 is a key regulator of proinflammatory cytokine IL-1b maturation and pathological apoptosis (Kobori et al. 2004). However, no investigative reports exist pertaining to its neuroprotective activity on cerebral ischemia and reperfusion injury; hence we undertaken to study the neuroprotective effect of hydroalcoholic extract of Eclipta alba against bilateral cerebral ischemia in rats.