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With extreme temperatures, high levels of ultraviolet radiation and long dark periods, the Antarctic is the ideal place to search for new compounds with better pharmacological properties. The project "Lichens Depsides and Antarctic Depsidones: Antioxidant Study and Evaluation as Possible Inhibitors of Tau Protein Aggregation", funded by the Chilean Antarctic Institute (INACH), searched for compounds with pharmacological properties of the type antioxidant or may be useful in the treatment of Alzheimer's disease.
As a result of this study, a total of eight metabolites were isolated from Antarctic lichens Umbillicaria antarctica and Ramalina terebrata. From the badyzes carried out on these metabolites, parietin and tenuiorin could inhibit the aggregation of the Tau protein, key in the development of Alzheimer's disease. Of these, parietin was the one with the best results.
The variability and quantity of lichen-producing compounds (metabolites) would be determined primarily by environmental factors, demonstrating the importance of
Key Role
In some cases It has been proven that they play a key role in protecting against factors such as oxidative stress caused by high levels of UV radiation.
Deterrent effects against herbivores, protection against a broad spectrum of pathogens and influence on the development of other organisms have also been demonstrated.
Lichens have shown for the last time to be a good source of natural antioxidants, because of the strong presence and variety of polyphenolic molecules that are in their extracts. Polyphenols are compounds synthesized by plants in their fruits, leaves, stems and seeds, among others, whose main feature in their structure is that they have one or more hydroxyl groups (-OH). It is thought that the antioxidant properties of these molecules would be due to the presence of one or more of these groups, which would confer a high potential for inactivation of free radicals.
Alzheimer's disease is a neurodegenerative disease, more and more widespread in the world Clinically, it is characterized by the progressive loss of neurons, a fact that is manifested by memory loss, decreased capacity to perform routine tasks, disorientation, etc. Among the hypotheses that attempt to elucidate this disease, there is the accumulation inside and outside neurons of certain structures called "neurofibrillary tangles", the main components of which are hyperphosphorylated Tau protein.
Procedure
In normal operation, Tau protein is not a dangerous protein because it plays an important role in the field of stability and badembly of components of the skeleton of neurons (microtubules). In addition, we have seen that it participates in the union of these with other elements of the neural cytoskeleton.
The first part of this investigation consisted of collecting samples from the Ardley Peninsula and Fildes Bay. Thanks to the advice of the lichenologist Reinaldo Vargas, the correct taxonomic determination of the above mentioned species has been realized. Then the compounds of interest were purified, in order to elucidate their molecular structures by means of nuclear magnetic resonance studies and thus carry out the previously proposed tests.
At the end of this study, eight metabolites were isolated: gyrophobic acid, úsnico acid, lobaric acid, methyl atrauto, inositol, methyl orselinato, parietina and tenuiorina. The badysis performed on the U. antarctica extract by high resolution mbad spectroscopy allowed for the first time the identification of fifteen compounds for this species, four of which were reported for the first time . Similarly, R. terebrata extract also identified the presence of 22 metabolites
Antioxidant tests
The ability of the eight metabolites mentioned to neutralize or extinguish some free radicals generated biologically has has been evaluated by antioxidant tests. or synthetically.
The results showed that the compound that had the best performance was the gyrophobic acid. These results (obtained from the laboratory test of gyroporic acid with Tau synthetic protein) are quite logical, since the gyrophobe acid has more phenolic groups (4 OH). This fundamental fact could be the reason why the rest of the metabolites show a sharp decrease around their activities, with values approaching 80%.
From the screening performed on all compounds, only parietin and tenuiorin were able to inhibit the aggregation of Tau protein based on positive dose-response correlations. Of these, parietin had the best results at a concentration range of 3μg / ml (10μM) to 28μg / ml (100μM). At this latter concentration, the results show a 75% inhibition against aggregation of the protein.
Similarly, the total extracts of both species were evaluated. Concentration ranges from 100 μg / ml to 1000 μg / ml were used. The results obtained indicate that for R. terebrata at a concentration of 1000 μg / ml, the inhibitory activity against the Tau protein aggregation process was almost complete. While for the Antarctic of the United States, only 52.5% of the aggregation was inhibited.
For both species, it is possible to deduce, on the one hand, that antiplatelet activities are given by the group of metabolites.
research on the pharmacological properties of lichens has shown that many metabolites isolated from these organisms exhibit a wide variety of biological activities.
To date, there is still no pharmacological treatment capable of dealing with Alzheimer's disease. which is necessary to continue to explore other Antarctic lichen species in order to find new inhibitors of Tau protein aggregation.
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