Plants and their chemical compounds affecting β-amyloid and secretase activity as potential sources of neuroprotective herbal medicinal products. Part 1.
Plant preparations, especially fractions of biologically active compounds may play an important role in improving the life quality of patients with diagnosed dementia as well as delaying the progress of neurodegenerative diseases through various mechanisms of pharmacological action. Recent years have brought a number of reports on the issue, nevertheless, it seems that there is still a lack of detailed, synthetical analysis.So far, main biological markers of Alzheimer’s disease pathogenesis which is currently the most common form of dementia, are the β-amyloid plaques deposits, neurofibrillary degeneration processes and atrophy of cholinergic neurons in the brain regions crucial for memory processes maintenance. At present, acetylcholinesterase inhibitors are the main drugs for the treatment of Alzheimer’s disease. In our previous review article, we pointed out the interesting mechanisms of action such as inhibition of acetyl-, butyrylcholinesterases and the antioxidant activity of bio-compounds of selected medicinal plants from Lamiaceae family (including rosmarinic acid). The aim of this paper is to systematize the knowledge about the influence of plant extracts and isolated natural compounds (e.g. cryptotanshinone, epigallocatechin gallate) on the pathway of β-amyloid formation and deposition in pharmacological models, especially by interacting with the brain enzyme, α- and β-, γ-secretase or on their genes expression. This is a long-established trend of research in search of new neuroprotective drugs from natural sources which raises new therapeutic hopes. Salvia miltiorrhiza and Camellia sinensis, medicinal plants from Asia, have interesting therapeutic potential in neurodegenerative disorders. In addition to them, there are known at least 10 Asian plants extensively researched in this area (e.g. Aralia cordata, Magnolia officinalis, Perilla frutescens, Polygala tenuifolia, Punica granatum, Sophora flavescens). However, due to the fact that many aspects of their phytochemical, neurochemical and pharmacological activities are not well known, further studies should be performed in this field.