From 300,000 plant species existing worlwide, only about 30% have been investigated scientifically. The development and introduction of highly selective and sensitive molecular-biologic bioassays into the screening of plant extracts and isolated biologically active compounds has influenced quality of medicinal plant research. These methods provide better knowledge and understanding of the mechanisms of the central nervous system (CNS) reaction on cellular and molecular level on herbal drug application. These assay also clear better mechanisms of interactions between herbal and synthetic drugs.
Plant substances may be valuable alternative for prevention and treatment of neurodegenerative diseases. Presently, over 60 plants with scientifically confirmed action on the CNS are known, however the ethnopharmacological study of Asia and the Pacific have identified further 47 plants affecting the CNS (mostly by different neurotransmission). Botanical medicines, such as St. John's wort, valerian, lemon balm, passionflower and ginkgo are most popular in phytotherapy and have become significant for depression, nervous, sleep disorders and others symptoms of dementia. Better explanation of the pharmacological action for biologically active compounds of plants may have important role in development of phytotherapy of CNS diseases.
Systematic review and analysis have shown different mechanisms of action for herbal medicines in the brain: influence of gene expression, signal transduction level and activity of drug transporters (blood brain barier), binding to receptor domains, inhibition of the neurotransmitters degradation and selective reuptace, improvement of microcirculation.
Investigations of Alzheimer's disease therapy are significant example of practical application of better understanding of molecular mechanisms of herbals action on the CNS. Several therapeutic strategies have been developed to treat neurodegenerative diseases including anti-inflammatory, anti-oxidant, anti-amyloid and anti-acetylcholinesterase approaches. The ethnobotanical studies have shown several plants with inhibitory effect on acetcholinesterase (i.e. Corydalis spp., Lavandula angustifolia, Petroselinum crispum, Ruta graveolens, Rosmarinus officinalis). Other authors have shown anti-amyloid activity for curcumin (Curcuma longa), huperzine A (Huperzia serrata), eugenol and b-asarone (Acorus gramineus), tenuigenin (Polygala tenuifolia), indirubins, Ginkgo biloba extract (Egb 761) and nicotine.
In conclusion, we know more about molecular mechanisms of action of herbal medicinal drugs and due to this knowledge we can optimize and rationalize phytotherapy.
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