ABSTRACT
BACKGROUND: Various factors may trigger Alzheimer's disease and the cholinergic hypothesis, which is one of the most widely accepted, argues damage to the brain nuclei, may reduce the production of the choline acetyltransferase enzyme, and cause a decline in the synthesis of acetylcholine (ACh). Studies have thus focused on discovering molecules that are capable of inhibiting the action of cholinesterase enzymes that degrade ACh, thereby preventing the evolution of the disease. OBJECTIVE: The aim of the present study is to assess the anticholinesterase properties of extracts of medicinal plants in a semi-arid region of Northeast of Brazil. MATERIALS AND METHODS: The species were selected by way of an ethnobotanical study and were collected if there were some indications that they are related to the nervous system. The plant samples were extracted using hexane, ethyl acetate, and methanol. Anticholinesterase activity in vitro was assessed by way of bioautography in thin layer chromatography and microassays in 96-well plates. RESULTS: Twenty-three species of plant were collected, and 75 extracts were analyzed. The bioautography revealed that 26.7% of the samples showed inhibitory activity against the acetylcholinesterase (AChE) enzyme. After the test for false positives, 8% of the samples were found to inhibit AChE. Thirty samples were analyzed by microassay (500 µg/mL), on which 86.7% showed moderate to powerful anticholinesterase activity. CONCLUSION: Of the extracts tested, Citrus limonum, Ricinus communis, and Senna occidentalis stand out as was the most promising in terms of anticholinesterase activity and may serve as a guide for the discovery and development of new substances for the treatment of AD. SUMMARY: The bioautography revealed that 26.7% of the samples showed inhibitory activity against the acetylcholinesterase enzymeSamples were analyzed by microassay (500 µg/mL), upon which 86.7% showed moderate to powerful anticholinesterase activityCitrus limonum, Ricinus communis, and Senna occidentalis stand out as being the most promising in terms of anticholinesterase activityC. limonum, R. communis, and S. occidentalis may serve as a guide for the discovery and development of new substances for the treatment of Alzheimer's disease. Abbreviations used: AChE: Acetilcolinesterase.
ABSTRACT
CONTEXT: Different habitat conditions can be responsible for the production of secondary metabolites and for the antioxidant properties of plant products. OBJECTIVE: Thus, the aim of this study was to evaluate whether the antioxidant activity and tannin concentrations in the stem bark of Spondias tuberosa Arruda (Anacardiaceae) varied with collection site. MATERIAL AND METHODS: The bark was collected from 25 individual trees, distributed in five different landscape units, as follows: agroforestry gardens, areas of pastures, maize cultivation areas, mountain areas and mountain bases, with the former 3 being considered as anthropogenic habitats, and the latter 2 considered as habitats with native coverage. The study was conducted in the rural area of the city of Altinho, Pernambuco State (Northeast Brazil). The DPPH (1,1-diphenyl-2-picrylhydrazyl) method was used to measure the antioxidant activity and tannin concentrations were evaluated by using the radial diffusion method. RESULTS: The results demonstrated that there were no significant differences among the tannin concentrations of the individuals from the native (6.27% ± 1.75) or anthropogenic areas (4.63% ± 2.55), (H = 2.24; p > 0.05). In contrast, there were significant differences (H = 5.1723; p < 0.05) among the CE50 means of the antioxidant activities of the individuals from the native (32.10 µg/ml ± 5.27) and anthropogenic areas (27.07 µg/ml ± 2.29). However, correlations between the tannin concentrations and antioxidant activity of the extracts were not observed in the native (r = 0.39; p > 0.05) or in the anthropogenic areas (r = 0.38; p > 0.05). DISCUSSION AND CONCLUSION: Because the variation of the antioxidant capacity of S. tuberosa bark was not accompanied by a variation in the tannin concentration, this property may be related to the presence of other metabolite(s).
