Many secondary metabolites affect the central nervous system in insects and animals. Secondary metabolites that have central nervous system effects and that have been studied in humans include alkaloids, terpenes, and phenolic compounds.
Humans have used alkaloid-containing plants medicinally for thousands of years. Medicinal and social alkaloids include atropine, ephedrine, cocaine, morphine, nicotine, and caffeine.
Caffeine is the most widely consumed psychoactive substance in the world. It is an antagonist of the inhibitory adenosine A1 and A2 receptors, which is responsible for the stimulation, and also causes constriction of blood vessels in the brain. Caffeine also increases activity in dopamine neuronal systems. At low doses, caffeine increases alertness and improves performance on tests of attention. At high doses, caffeine can cause anxiety, insomnia, rapid heart beat, and agitation.
Nicotine is found in tobacco (Nicotiana tabacum). Nicotine binds to acetylcholine receptors and increases the release of acetylcholine, serotonin, and other neurotransmitters. It increases dopamine activity, which is associated with its addictive effect. Clinical trials in smokers and non-smokers show that nicotine improves performance on tests of memory and attention.
|Ginkgo biloba / Maurice Godefridi|
Ginkgo (Ginkgo biloba) leaves contain a number of terpenes, including bilobalide and ginkgolides A, B, C, and J. Effects of ginkgo leaf extracts in the central nervous system include modulation of several neurotransmitter systems, enhanced blood flow in the brain, and scavenging of free radicals. Ginkgo is one of the most popular herbal products, and it is used to improve cognitive performance. More than 30 clinical trials have tested the effects of ginkgo on cognitive function in people with dementia or age-related cognitive impairment. One meta-analysis concluded that the evidence for cognitive improvement with ginkgo supplementation is inconsistent, while another meta-analysis concluded that ginkgo improves attention, executive function, and long-term memory.
Lemon balm (Melissa officinalis) contains a variety of monoterpenoids and sesquiterpenes. Effects of lemon balm on the central nervous system include binding to specific cholinergic receptors, increased activity of the neurotransmitter gamma-aminobutyric acid (GABA), and antioxidant activity. Limited clinical trials have shown that lemon balm has anti-anxiety effects, improves agitation and quality of life in people with severe dementia, but has inconsistent effects on memory.
Asian ginseng (Panax ginseng) roots contain 40 or more triterpene saponins known as ginsenosides. Ginseng root extracts have neuroprotective effects, modulate the neuroendocrine system and the synthesis of nitric oxide, which relaxes blood vessels and influences many cellular activities. Clinical trials have shown that ginseng improves accuracy on memory tests and improves the speed of performing attention tasks. The impact of ginseng on mood has been inconsistent in clinical trials to date.
Sage (Salvia officinalis) contains a range of monoterpenes. Effects on the central nervous system include anti-inflammatory activity and decreased breakdown of the acetylcholine neurotransmitter. Clinical trials have demonstrated improved memory, attention, and alertness in healthy people after single doses of sage extract and improved cognitive function in people with Alzheimer's disease after 16 weeks of an alcoholic tincture of sage.
Valerian (Valeriana officinalis) root contains a variety of terpenes, including the valepotriates and valerenic acid. Valerian compounds modulate serotonin receptor subtypes, GABA, and adenosine receptors and have anxiolytic activity. Some clinical trials suggest that valerian improves sleep quality; others were not conclusive.
|Hypericum perforatum / Maurice Godefridi|
Curcumin is a polyphenol from turmeric (Curcuma longa). Curcumin prevented cognitive deficits and improved learning and memory in mouse models of Alzheimer's disease. Curcumin also reversed amnesia in rats. Many small pilot studies have been conducted in humans, but there are few controlled clinical trials to support a benefit of curcumin in brain function.
Epigallocatechin-3-gallate (EGCG) and related polyphenols are present in tea (Camellia sinensis). In vitro and animal studies suggest that EGCG may have protective effects in Alzheimer's disease and Parkinson's disease. EGCG improved cognitive performance and increased antioxidant capacity in rats. In epidemiological studies, greater consumption of green tea is associated with reduced risk of cognitive impairment and neurodegenerative disorders.
St. John's wort (SJW; Hypericum perforatum) extract contains a variety of phenolic compounds that have an impact on brain function, including phenolic acids, flavonoids, hyperforin, and hypericin. SJW extracts have been reported to inhibit reuptake of serotonin, dopamine, and GABA, but this finding is highly doubtful. Other reports include increased neurotransmitter sensitivity and altered receptor binding. Clinical trials have established that SJW is an effective treatment in people with mild to moderate depression.
Resveratrol is found in the skin of red grapes (Vitis vinifera) and in some other edible plants. Resveratrol preserved behavior and cognitive performance in older rats with brain injuries. In healthy humans, single doses of resveratrol increased blood flow and oxygen uptake in the frontal cortex of the brain, suggesting it may have benefits in Alzheimer's disease and other neurological disorders.
Soy (Glycine max) extract contains isoflavones such as genistein, daidzein, and glycetin that have very weak estrogen-like effects. Several clinical trials have shown that soy isoflavones modestly improve neurocognitive function and mood in postmenopausal women, but other clinical trials showed no improvement. Compared to a diet with no soy isoflavones, a diet rich in soy isoflavones was associated with improved short-term and long-term memory in men and women.
The authors conclude that the literature describing the effectiveness of herbal extracts for improving brain function is "somewhat equivocal." Research on caffeine and nicotine has been hampered by the addictive nature and serious adverse effects attributed to these alkaloids. Research is progressing among plants containing terpenes, particularly ginkgo and valerian. However, the methodological quality of some of the clinical trials has been poor, and results have been inconsistent. Interest in the potential cognitive benefits of curcumin, EGCG, resveratrol, and soy isoflavones is relatively recent, and human clinical trials are still in the early stages.
The authors describe challenges in developing plant-based products to prevent or reverse age-related cognitive decline. Challenges include identifying the active components, understanding the synergism among the active components, defining the environmental stressors and growing conditions under which plants produce increased amounts of secondary metabolites, and standardizing plant products to provide beneficial amounts of active compounds.
Algemeen advies voor het geheugen. Een gedeelte van het fytoschema uit cursus fytotherapie
Concentratie verbeteren door meditatie, biofeedback, geheugentraining....
-vitamine B en E : tarwekiemolie
-onverzadigde vetzuren: vette vis (sardines), noten
-lecithine: noten, plantaardige olie, eidooiers, bonen
-Vicia faba - Tuinboon: bevat féverolen, een vorm van L-dopa (Parkinson?)
Algemeen: hersencirculatie verbeteren, anti-oxydantwerking, neurotransmitters beïnvloeden (acetyl-choline, dopamine), algemeen toniserend.
Ginkgo biloba (basiskruid) eventueel combineren met
+ Vinca minor - Kleine maagdepalm: hersendoorbloeding, zuurstofvoorziening
+ Rosmarinus officinalis - Rozemarijn (etherische olie): ook uitwendig
+ Thymus vulgaris - Echte tijm
+ Melissa officinalis - Citroenmelisse: na een verlies, bij verdriet
+ Panax ginseng - Koreaanse ginseng: bij vermoeidheid, asthenie
+ Zeewieren: bij trage schilklier (ouderen), op stofwisseling en reminaliserend
Nutritherapie / Orthomoleculair
fosfatidyl-choline (PC), de basiscomponent in lecithine, heeft invloed op neurotransmitter acetyl-choline, die zorgt voor prikkeloverdracht in de hersenen, kan concentratie en geheugen verbeteren ook bij Alzheimer
fosfatidyl-serine (PS): belangrijkste fosfolipide in de hersenen acetyl-l-carnitine: aminozuur, kan de activiteit van neurotransmitters verbeteren, kan cellulaire energie (ATP) verhogen DHA (docosahexaeenzuur): omega-3-vetzuur in grijze hersenmassa, van belang voor ontwikkeling hersenmateriaal, komt voor in moedermelk
DHEA (dehydro epiandrosteron): hormonale stof (in bijnieren) met invloed op geheugen, voorstadium van steroidstoffen
Literatuur Phytotherapie in der Geriatrie. Ztschr. Phytoth. 18 (1991) Crook - Effects of PS in age-associated memory impariment. Neurology 1991 Soderberg - Fatty acid compositon of brain phospholipids in ageing ans Alzheimer's disease. Lipids 1991.