tannins and Neurodegenerative-Diseases

Globally, the burden of neurodegenerative disorders continues to rise, and their multifactorial etiology has been regarded as among the most challenging medical issues. Bioprospecting for seaweed-derived multimodal acting products has earned increasing attention in the fight against neurodegenerative conditions. Phlorotannins (phloroglucinol-based polyphenols exclusively produced by brown seaweeds) are amongst the most promising nature-sourced compounds in terms of functionality, and though research on their neuroprotective properties is still in its infancy, phlorotannins have been found to modulate intricate events within the neuronal network. This review comprehensively covers the available literature on the neuroprotective potential of both isolated phlorotannins and phlorotannin-rich extracts/fractions, highlighting the main key findings and pointing to some potential directions for neuro research ramp-up processes on these marine-derived products.

Topics: Animals; Biological Products; Humans; Neurodegenerative Diseases; Neuroprotective Agents; Phaeophyceae; Polyphenols; Seaweed; Tannins

Abnormal fibrillization of amyloidogenic peptides/proteins has been linked to various neurodegenerative diseases such as Alzheimer's and Parkinson's disease as well as with type-II diabetes mellitus. The kinetics of protein fibrillization is commonly studied by using a fluorescent dye Thioflavin T (ThT) that binds to protein fibrils and exerts increased fluorescence intensity in bound state. Recently, it has been demonstrated that several low-molecular weight compounds like Basic Blue 41, Basic Blue 12, Azure C, and Tannic acid interfere with the fluorescence of ThT bound to Alzheimers' amyloid-β fibrils and cause false positive results during the screening of fibrillization inhibitors. In the current study, we demonstrated that the same selected substances also decrease the fluorescence signal of ThT bound to insulin fibrils already at submicromolar or micromolar concentrations. Kinetic experiments show that unlike to true inhibitors, these compounds did neither decrease the fibrillization rate nor increase the lag-period. Absence of soluble insulin in the end of the experiment confirmed that these compounds do not disaggregate the insulin fibrils and, thus, are not fibrillization inhibitors at concentrations studied. Our results show that interference with ThT test is a general phenomenon and more attention has to be paid to interpretation of kinetic results of protein fibrillization obtained by using fluorescent dyes.

Topics: Amyloid; Amyloid beta-Peptides; Azure Stains; Benzothiazoles; Biological Assay; Diabetes Mellitus, Type 2; False Positive Reactions; Fluorescent Dyes; Humans; Insulin; Kinetics; Neurodegenerative Diseases; Protein Structure, Secondary; Spectrometry, Fluorescence; Tannins; Thiazoles

The root of Paeonia suffruticosa ANDREWS is an important Chinese crude drug used in many traditional prescriptions. 1,2,3,4,6-Penta-O-galloyl-beta-D-glucose (PGG), a major component of this crude drug, has been shown to possess potent anti-oxidant, anti-mutagenic and anti-proliferative effects. In the present study, we examined the effect of PGG on the expression of neuronal heme oxygenase-1 (HO-1), an inducible stress protein that degrades heme to the neuroactive molecule, carbon monoxide and the anti-oxidant, biliverdin. Exposure of Neuro 2A cells to PGG (10-50 microM) resulted in a concentration- and time-dependent induction of HO-1 mRNA, and protein expressions and heme oxygenase activity. Interestingly, pretreatment of the neuronal cells with PGG resulted in enhanced cellular resistance to hydrogen peroxide. This cytoprotective effect was reversed by zinc protoporphyrin IX, an inhibitor of heme oxygenase. This study showed that PGG could protect neuronal cells from oxidative stress via the induction of HO-1 gene expression.

Topics: Animals; Antioxidants; Brain Ischemia; Cell Death; Dose-Response Relationship, Drug; Drugs, Chinese Herbal; Gene Expression Regulation, Enzymologic; Heme Oxygenase (Decyclizing); Heme Oxygenase-1; Hydrogen Peroxide; Hydrolyzable Tannins; Neuroblastoma; Neurodegenerative Diseases; Neurons; Neuroprotective Agents; Oxidative Stress; Rats; RNA, Messenger; Tannins; Tumor Cells, Cultured