Natural polyphenols in preclinical models of epilepsy.

Natural polyphenols are being tested both in preclinical and clinical settings for the treatment of different neurological disorders. The article describes the outcome of three polyphenols, resveratrol, epigallocatechin gallate, and quercetin, in preclinical animal models of epilepsy (both acute and chronic) and epileptogenesis. In theory, the antioxidant and neuroprotective properties of these natural polyphenols might be valuable in the management of acute seizures and the prevention of epileptogenesis. It is fascinating to observe that these polyphenols have a capacity to alter various signaling processes involved in the pathogenesis of epilepsy. The antiepileptic or antiseizure potential with these molecules delivers a mixed outcome. Some studies have demonstrated the usefulness of these molecules in preclinical models of epilepsy; however, contrary to the findings also exist. These molecules have poor bioavailability that may remain as the limiting factor in their clinical effects. The use of nanotechnology and other techniques have been tested to enhance bioavailability and brain penetration. There are no randomized double-blinded clinical studies establishing their antiepileptic effects in humans. It is concluded that more preclinical mechanism-based studies are needed to deliver a more certain picture regarding the use of natural polyphenols in the treatment of epilepsy.

Curcumin in epilepsy disorders.

Curcumin, a principal curcuminoid present in turmeric, has an antioxidant, anti-inflammatory and neuroprotective properties. Preclinical studies have indicated its beneficial effect for the treatment of epilepsy disorders. The molecule has an anti-seizure potential in preclinical studies, including chemical and electrical models of acute and chronic epilepsy. Curcumin also possesses an anti-epileptogenic activity as it reduces spontaneous recurrent seizures severity in a kainate model of temporal lobe epilepsy. The antioxidant and anti-inflammatory nature of curcumin might be responsible for its observed anti-seizure effects; nevertheless, the exact mechanism is not yet clear. The poor availability of curcumin to the brain limits its use in clinics. The application of nanoliposome and liposome technologies has been tested to enhance its brain availability and penetrability. Unfortunately, there are no randomized, double-blinded controlled clinical trials validating the use of curcumin in epilepsy. The present article analyzes different preclinical evidence illustrating the effect of curcumin in seizure models. The review encourages carrying out clinical trials in this important area of research. In conclusion, curcumin might be beneficial in patients with epilepsy disorders, if its bioavailability issues are resolved.

Natural polyphenols in the management of major depression.

INTRODUCTION: Natural polyphenols, the non-essential micronutrients, found in array of plant products, are known to affect various physiological and biochemical functions in the body. Studies have shown the protective effect of these polyphenols in different neurological and mental disorders. These polyphenols modulate monoaminergic neurotransmission in the brain and thus possess antidepressant-like activity at least in animal models of depression. AREAS COVERED: The present review discusses the use of these natural polyphenols in the treatment of major depression. The review article discusses the antidepressant potential of some important polyphenols such as amentoflavone, apigenin, chlorogenic acid, curcumin, ferulic acid, hesperidin, rutin, quercetin, naringenin, resveratrol, ellagic acid, nobiletin and proanthocyanidins. The mechanism of action of these polyphenols in the treatment of major depression is also discussed in detail. EXPERT OPINION: There is an exciting prospect in the discovery of natural polyphenols as therapeutic agents in the treatment of major depression.

Berberine: a plant alkaloid with therapeutic potential for central nervous system disorders.

Berberine, an isoquinoline alkaloid of the protoberberine type found in an array of plants, has been used in Indian and Chinese medicines as an antimicrobial, stomachic, bitter tonic and in the treatment of oriental sores. Although pharmacological investigations of berberine have been reported by many in the past, there is renewed interest in berberine because of its reported beneficial effect in various neurodegenerative and neuropsychiatric disorders. The alkaloid is reported to modulate neurotransmitters and their receptor systems in the brain. This review attempts to discuss the pharmacological basis of the use of berberine in various central nervous system and related disorders. Its protective effect in Alzheimer's, cerebral ischemia, mental depression, schizophrenia and anxiety are highlighted. However, more detailed clinical trials along with a safety assessment of berberine are warranted for positioning the alkaloid in the treatment of neurological disorders.

Potentials of curcumin as an antidepressant.

Major depression, a debilitating psychiatric disorder, is predicted to be the second most prevalent human illness by the year 2020. Various antidepressants, ranging from monoamine oxidase inhibitors to recently developed dual reuptake inhibitors, are prescribed for alleviating the symptoms of depression. Despite the availability of these blockbuster molecules, approximately 30% of depressed patients do not respond to the existing drug therapies and the remaining 70% fails to achieve complete remission. Moreover, antidepressants are associated with a plethora of side effects and drug-drug/drug-food interactions. In this context, novel approaches are being tried to find more efficacious and safer drugs for the treatment of major depression. Curcumin is one such molecule that has shown promising efficacy in various animal models of major depression. Although the mechanism of the antidepressant effect of curcumin is not fully understood, it is hypothesized to act through inhibiting the monoamine oxidase enzyme and modulating the release of serotonin and dopamine. Moreover, evidences have shown that curcumin enhances neurogenesis, notably in the frontal cortex and hippocampal regions of the brain. The use of curcumin in clinics for the treatment of major depression is limited due to its poor gastrointestinal absorption. The present review attempts to discuss the pharmacological profile along with molecular mechanisms of the antidepressant effect of curcumin in animal models of depression. A need for clinical trials in order to explore the antidepressant efficacy and safety profile of curcumin is emphasized.

Current investigational drugs for major depression.

BACKGROUND: The World Health Organization (WHO) report has predicted that major depression will become a key cause of illness-induced disability by the year 2020, second only to ischemic heart diseases. OBJECTIVES/METHODS: Although a large number of antidepressant drugs (from monoamine oxidase inhibitors and tricyclic antidepressants to dual reuptake inhibitors) are available for treatment of the disease, approximately 30% of patients failed to respond to this therapy. Therefore, the search for newer or novel drug targets for the treatment of major depression continues. Some of these targets include dopamine, triple reuptake inhibition, L-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) pathway, sigma-1 receptors, neurosteroids, melatonin, glutamate, 5HT6, 5HT7 serotonin receptor antagonists, beta-3 adrenoceptor antagonist, vasopressin V(Ib) receptor antagonists, NK2 tachykinin receptor antagonists, glucocorticoid receptor antagonists and corticotropin-releasing factor-1 receptor antagonists, as well as herbal antidepressant drugs. The present review attempts to discuss the status of some of these novel approaches and the drugs that are under investigation for the treatment of major depression. An attempt is also made to review the status of three indigenous plant-derived drugs, berberine, curcumin and rutin, as novel and safe future herbal antidepressants. RESULTS/CONCLUSION: There is an exciting future in the discovery of novel targets and target-specific agents for the management of major depression.

Curcumin potentiates the anti-inflammatory activity of cyclooxygenase inhibitors in the cotton pellet granuloma pouch model.

Curcumin is a yellow-colored plant polyphenol with a long history of medicinal use in ayurvedic, Chinese and Japanese medicine. Studies have reported the cyclooxygenase COX-2-inhibitory activity of this polyphenol; however, none of the studies have established its antiinflammatory activity in the rat cotton pellet granuloma pouch model, which mimics subchronic inflammation in humans. The present study was conducted to evaluate the effect of curcumin in the cotton pellet granuloma pouch model. Furthermore, the interaction of curcumin with standard anti-inflammatory drugs at subeffective doses was studied to evaluate its potential role as adjuvant therapy. Administration of curcumin (240 mg/kg i.p.), aspirin (160 mg/kg i.p.) or rofecoxib (5 mg/kg i.p.) for 6 days in the cotton pellet granuloma pouch test exhibited significant anti-inflammatory activity, as demonstrated by a decrease in both dry and wet weights of the cotton pellet as compared to the control animals. Lower doses of curcumin (120 mg/kg i.p.), aspirin (80 mg/kg i.p.) or rofecoxib (2.5 mg/kg i.p.) were ineffective. However, the combination of a subeffective dose of curcumin (120 mg/kg i.p.) with submaximal doses of aspirin (80 mg/kg i.p.) or rofecoxib (2.5 mg/kg i.p.) produced a synergistic effect. Furthermore, there was marked increase in tumor necrosis factor-alpha (TNF-alpha) levels (estimated by enzyme-linked immunosorbent assay, ELISA) in the serum of the animals implanted with cotton pellets presenting marked inflammatory events. Daily administration of curcumin, aspirin or rofecoxib decreased the levels of TNF-alpha, further demonstrating anti-inflammatory activity. Curcumin in combination with aspirin or rofecoxib caused a further decrease in serum TNF-alpha levels. In conclusion, the results of the present study demonstrate an anti-inflammatory effect for curcumin in the cotton pellet granuloma pouch test, possibly acting through COX enzyme inhibition, and further inhibiting the generation of inflammatory mediators such as TNF-alpha. These results point toward the usefulness of curcumin as adjuvant drug therapy along with standard anti-inflammatory drugs.

Effect of Withania somnifera Dunal root extract against pentylenetetrazol seizure threshold in mice: possible involvement of GABAergic system.

Withania somnifera (ashwagandha) is a widely used herb in the Ayurvedic system of medicine. The objective of the present study was to elucidate the effect of W. somnifera root extract (Ws) alone or in combination with exogenous gamma-amino butyric acid (GABA), a GABA receptor agonist or with diazepam, a GABA receptor modulator against pentylenetetrazol (PTZ, iv) seizure threshold in mice. Minimal dose of PTZ (iv, mg/kg) needed to induce different phases (myoclonic jerks, generalized clonus and tonic extension) of convulsions were recorded as an index of seizure threshold. Ws (100 or 200 mg/kg, po) increased the PTZ seizure threshold for the onset of tonic extension phase whereas a lower dose (50 mg/kg, po) did not show any effect on the seizure threshold. Co-administration of a sub-effective dose of Ws (50 mg/kg, po) with a sub-protective dose of either GABA (25 mg/kg, ip) or diazepam (0.5 mg/kg, ip) increased the seizure threshold. The results suggested that the anticonvulsant effect of W. somnifera against PTZ seizure threshold paradigm involved the GABAAergic modulation.

Withania somnifera: an Indian ginseng.

Withania somnifera, popularly known as Ashwagandha is widely considered as the Indian ginseng. In Ayurveda, it is classified as a rasayana (rejuvenation) and expected to promote physical and mental health, rejuvenate the body in debilitated conditions and increase longevity. Having wide range of activity, it is used to treat almost all disorders that affect the human health. The present review discusses the pharmacological basis of the use of W. somnifera in various central nervous system (CNS) disorders, particularly its indication in epilepsy, stress and neurodegenerative diseases such as Parkinson's and Alzheimer's disorders, tardive dyskinesia, cerebral ischemia, and even in the management of drug addiction.

Effect of withdrawal of diazepam or morphine treatment on gastric motility (charcoal meal test) in mice: possible role of different central and peripheral receptors.

Increased gastrointestinal motility in mice as one of the withdrawal symptoms of commonly abused drugs like diazepam or morphine and its possible mechanism of action was studied. Male Laka mice (20-25 g) were made addict to either diazepam (20 mg/kg, ip for 7 days) or morphine (10 mg/kg, sc for 9 days). Withdrawal symptoms were noted 24 hr after the last injection of diazepam or morphine. The animals were injected with Ro 15-1788 (flumazenil) (1 mg/kg, ip) or naloxone (2 mg/kg, ip) in the respective group to precipitate the withdrawal symptoms. Gastrointestinal motility was assessed by charcoal-meal test. Animals developed tolerance to acute sedative effect of diazepam, and similarly to the acute nociceptive action of morphine. On abrupt cessation of these drugs after chronic treatment the animals showed hyperlocomotion and hyperreactivity in diazepam withdrawal group and hyperalgesia on hot plate in morphine withdrawal groups, respectively. Increase in gastrointestinal motility was observed in all the drug withdrawal groups. Treatment with respective antagonists, Ro 15-1788 (flumazenil) and naloxone precipitated the withdrawal symptoms. The results suggest the involvement of both central and peripheral receptors of benzodiazepines and opioid (mu) receptors in the withdrawal symptoms of the benzodiazepines and morphine, respectively.