Archive for category Herbal Drugs'

Traditional Medicine for Memory Enhancement

Keywords • Acetylcholinesterase inhibitors • Alzheimer’s disease • Anti-inflammatory • Antioxidant • Estrogenic • Memory • Traditional medicine In traditional practices of medicine, numerous plants have been used to alleviate memory impairment both in healthy individuals and those with disease states which are now recognised as specific cognitive disorders such as Alzheimer’s disease. An ethnopharmacological approach has provided leads to identify plants and their compounds that may have potential to modulate cognitive abilities by different modes of action. A variety of therapeutic targets have been identified as relevant in the treatment of cognitive disorders, including modulation of the cholinergic system, which may be achieved by the inhibition of acetyl-cholinesterase, and neuroprotection against glutamate-induced overstimulation of N-methyl-D-aspartate (NMDA) receptors, by the use of NMDA receptor modulators. Other activities considered to be relevant in the alleviation of cognitive impairment include anti-inflammatory, antioxidant and estrogenic activities. Two of the currently licensed drugs used to treat cognitive symptoms in Alzheimer’s disease, galantamine and rivastigmine, Read more […]

Activities Relevant to the Treatment of Cognitive Disorders

Precursors of Acetylcholine Adequate availability of choline has been proposed to enable sufficient acetylcholine synthesis for neurotransmission. Precursors of acetylcholine (e.g. choline and lecithin) have been investigated for their effects on synthesis and release of acetylcholine, with a view to increasing acetylcholine release and cholinergic activity. Few clinical or animal studies have reported any significant beneficial effects on cognitive function with these compounds. Therapy failure may be due to impaired uptake mechanisms of choline causing the reduction in acetylcholine synthesis, and not due to insufficient choline supply. This is apparent as it has been reported that more choline occurs in the cerebrospinal fluid of Alzheimer’s disease patients than in patients without Alzheimer’s disease, and that choline levels increase with disease progression. Therapy with acetylcholine precursors may be limited by side-effects, including gastrointestinal disturbances such as nausea, vomiting and diarrhoea. Muscarinic Receptor Stimulation Direct cholinergic receptor stimulation has been explored as one therapeutic target to enhance cognitive function. Cholinergic agonists are reported to facilitate learning Read more […]

Anti-Inflammatory Activity

Some reports have indicated that the use of anti-inflammatory compounds may modify the progression of Alzheimer’s disease, since inflammatory processes have been linked with Alzheimer’s disease pathology. Some studies have indicated that non-steroidal anti-inflammatory drugs (NSAIDs), which inhibit cyclo-oxygenase activity, may reduce the risk of developing Alzheimer’s disease, and patients with rheumatoid arthritis, who often use NSAIDs, are suggested to have a lower incidence of Alzheimer’s disease. In addition to inhibition of cyclo-oxygenase, it has also been suggested that NSAIDs may act via other mechanisms such as anti-amyloidogenic effects. In view of the adverse effects commonly associated with cyclo-oxygenase inhibitors currently in clinical use, new anti-inflammatory compounds may be developed, including those which are naturally derived, which may have potential in modifying the progression of cognitive disorders such as Alzheimer’s disease with fewer adverse effects. There are numerous examples of plant extracts and their constituents which display anti-inflammatory effects. Consequently, there is some potential for novel anti-inflammatory agents to be identified from plant sources, although Read more […]

Antioxidant Activity

Antioxidants have been suggested to reduce the risk of developing dementia, although evidence to support this hypothesis is under review. Free-radical reactions, which are reported to initiate cell injury, have been implicated in the pathology of various diseases including ageing processes, atherosclerosis, ischemic heart disease and neurodegenerative diseases which involve cognitive impairment. Antioxidants have therefore been considered as a means to modify and minimise neuronal degeneration in cognitive disorders. A wide variety of plants have been associated with antioxidant effects. It is therefore not surprising that many different and structurally diverse phytochemicals have also shown antioxidant activity, including some cinnamic acids, coumarins, diterpenoids, flavonoids, monoterpenoids, phenylpropanoids and tannins. The antioxidant properties of Camellia sinensis Kuntze (Theaceae), commonly known as green tea, are well documented, and some studies suggest that Camellia sinensis extracts and some of the catechin components have protective mechanisms in neurodegenerative disorders. For example, (-)-epigallocatechin gallate had protective effects against beta-amyloid-induced neurotoxicity in vitro, an effect Read more […]

Estrogenic Activity

For a number of years, conclusions from epidemiological evidence indicated that estrogen-replacement therapy (estrogen-replacement therapy) had a preventative role against Alzheimer’s disease development, and estrogen treatment in women with Alzheimer’s disease enhanced cognitive function. The mechanisms by which estrogens may protect against Alzheimer’s disease are unclear but may be mediated via interaction with estrogen receptors in the CNS, or perhaps by effects on neurotransmitter systems, modulation of NGF, enhancement of cerebral blood flow or antioxidant effects or other unknown mechanisms. However, evidence from some more recent studies does not support an association between high estrogen levels and a reduced incidence of Alzheimer’s disease. Nevertheless, the estrogenic activities of some plant extracts have been explored as one possible explanation for their reputed memory-enhancing effects. Soya beans, the seeds of Glycine max Merr. (Leguminosae), form an important part of the traditional diet in China and other parts of the Far East and are frequently a staple of the diet of vegetarians and vegans. Soya contains isoflavones including genistein and daidzein, which have been characterised as phytoestrogens. Read more […]

Plants as a Source of Useful Therapeutic Agents in Cognitive Diseases

Numerous plants are reputed in traditional practices of medicine to alleviate the cognitive decline that can be associated with general ageing, but they may also be relevant in the treatment of specific cognitive disorders such as Alzheimer’s disease and other dementias. Thus, plants reputed to have ‘anti-ageing’ or ‘memory-enhancing’ effects could also be considered for their potential efficacy in disorders now recognised to be associated with cognitive dysfunction, including those conditions in which dementia occurs. A mixture of plants is commonly prescribed in some practices of traditional medicine including Ayurveda and traditional Chinese medicine (TCM). The plant constituents may not only act synergistically with other constituents from the same plant, but they may also enhance the activity of compounds from other plants in a particular remedy or herbal formula. For example, the interaction of a compound at a target receptor may affect the activity of another compound at that receptor, possibly due to allosteric effects, which can occur at some types of receptor. An ethnopharmacological approach can assist with the search for plants and, eventually, potential new drugs that could be relevant for the treatment Read more […]

Plants Used in Traditional Ayurvedic Medicine

Ayurvedic medicine is the oldest medical system in the world with written records in Sanskrit dating back at least 5000 years. It originates from the Indian subcontinent and has also influenced the traditional medical system in Thailand. The practice of Ayurvedic medicine is now widely used throughout the world as a complementary medicine. Areca catechu L. Arecoline is the major alkaloid of those present in betel or areca nuts, the fruit of the palm tree Areca catechu L. (Arecaceae), which is extensively chewed to induce salivation and euphoria throughout the Indian subcontinent and other parts of southeast Asia. It is estimated that 500 million people regularly chew betel nut (often referred to as ‘pan’ or ‘paan’ in India) in a form which is usually shredded, mixed with lime and wrapped in a leaf from the Piper betel Blanco (Piperaceae) plant, although chewing of betel nuts has been positively correlated with an incidence of oral cancer. As a direct result of the cholinergic activity induced by this plant, excessive salivation occurs, which is associated with a muscarinic effect, and CNS stimulatory and euphoric effects develop, which is considered to be associated with a nicotinic receptor stimulant effect. Arecoline Read more […]

Bacopa monniera

Bacopa monniera Wettst. (Scrophulariaceae), known by the common name ‘brahmi’, has been used in Ayurvedic medicine for almost 3000 years as a nerve tonic and to improve intellect and memory. Various investigations have attempted to substantiate and identify a scientific basis for the reputed effects. A number of in vivo studies have shown Bacopa monniera extracts to improve cognitive function. The mode of action to explain these effects has yet to be fully elucidated. Some studies suggest that the antioxidant effects of Bacopa monniera may protect the CNS from oxidative damage. Extracts of Bacopa monniera have been reported to induce a dose-related increase in superoxide dismutase, catalase and glutathione peroxidase activities in the rat frontal cortex, striatum and hippocampus, to dose-dependently inhibit nitric oxide (nitric oxide)-related toxicity (DNA damage) in cultured rat astrocytes and to inhibit aluminium-induced neurotoxicity in the rat brain. The antioxidant effects of Bacopa monniera have also been suggested to alter amyloid plaque formation. In addition to antioxidant effects, Bacopa monniera has also shown anti-inflammatory activity in vivo. It is reported to modulate the cholinergic system and has an Read more […]

Centetta asiatica

An ancient Ayurvedic remedy, Centella asiatica (L.) Urb. (Apiaceae), also known by the synonym Hydrocotyle asiatica L., is reputed to restore youth, memory and longevity. In Sanskrit, and commonly as an herbal product, it is known as ‘gotu kola‘. An Ayurvedic formulation composed of four herbs including Centella asiatica, is used to retard age and prevent dementia, and the herb combined with milk is given to improve memory. In TCM Centella asiatica has been used for various disorders, such as traumatic diseases, and for combating physical and mental exhaustion. The essential oil from Centella asiatica leaf contains monoterpenoids, including bornyl acetate, α-pinene, β-pinene and γ-terpinene, all of which are reported to inhibit acetylcholinesterase. However, monoterpenoid acetylcholinesterase inhibitors are weak compared to the anti-cholinesterase alkaloid, physostigmine. In view of the relatively weak anti-cholinesterase activity of monoterpenoids reported to date, it is unlikely that they would be therapeutically effective in cognitive disorders. The pharmacological basis to explain the reputed antiamnesic effects of Centella asiatica has been explored in a number of studies. An alcoholic extract of Centella Read more […]

Curcuma longa

Regarded as a ‘Rasayana’ herb in Ayurveda to counteract ageing processes, Curcuma longa L. (Zingiberaceae) has also been used for culinary purposes and in the textile industry. Much research has focused on curcumin, a curcuminoid from C. longa rhizomes, and it has been shown to modulate a variety of molecular targets. In particular, studies have shown that some curcuminoids are associated with antioxidant and anti-inflammatory activities, but in general, studies with particular attention to cognitive disorders and any clinical relevance are lacking. In addition, further evaluation of potentially active compounds from Curcuma longa, other than the curcuminoids, may contribute to the understanding of the traditional uses of this herb. The antioxidant activity of curcumin is well documented, and it is suggested to be the underlying mechanism to explain a number of beneficial effects on cognition. Curcumin was shown to be neuroprotective in vitro and protected against ethanol-induced brain injury in vivo following oral administration, an effect that was related to a reduction in lipid peroxide levels and enhancement of glutathione in rat brain. A neuroprotective action of curcumin was also observed in an animal model of Read more […]