Metabólitos bioativos a partir de raízes de amoreira (Morus alba)

Abstract

Morus alba, popularly known as white mulberry, is a plant species native to Asia, but currently distributed worldwide. It is known for its pharmacological properties, being used in some countries for the treatment of various diseases. However, this use is based mainly on fruit and leaf preparations, with the potential of its roots being little used. The present work had as objective the study of ethanolic extracts of varieties of M. alba roots coming from Cuba, aiming the isolation of the main phytochemical constituents present in these matrices. From theethanolic extract of IZ 40 variety, four compounds were isolated using classical chromatographic (column chromatography) and instrumental (preparative HPLC) techniques. These were named BM 1, BM 2, BM 3 and BM 4. Characterization of the chemical structure of the isolated compounds was carried out from analyzes of uni and bidimensional nuclear magnetic resonance spectra, and mass spectrum. Compounds BM 1 and BM 2 were identified as the flavonoid morusin and the geranylated derivative of 2-arylbenzofuran, mulberrofuran B,respectively. The chromatographic profile of the isolated compounds and the ethanolic extracts of varieties IZ 13/6, IZ 40, IZ 56/4, IZ 64, Indonesia and Tigreada were obtained and, from these, quantification of compounds contents in the extracts was carried out. It was observedthat, with the exception of BM 2, the isolated compounds are the major constituents of the analyzed extracts. Considering the extract from which the compounds were isolated, the determined levels were 3.6% BM 2, 10.7% BM 3, 11.9% BM 1 and 13.5% BM 4. In order to verify the biological role of these chemical markers were performed bioassays to evaluate the antioxidant activity and neuroprotective capacity of them. The antioxidant activity was evaluated according to the methodologies of total antioxidant activity (phosphomolybdenum method), ferric reducing power (ferrocyanide method) and ABTS and DPPH radical sequestration capacity. For both assays, BM 2 presented the best results, especially from ABTS free radical capture, for which it presented an efficient concentration value at 50% (37.6 ± 1.7 g.mL-1) relatively close to the obtained for the standard ascorbic acid (17.6 ± 0.5 g.mL-1). The results obtained for the other compounds varied among the different protocols analyzed. Compound BM 1, despite presenting moderate antioxidant activity when analyzed independently, showed statistical correlation between its content in the extracts and theantioxidant activity presented by them, in most of the extracts. Regarding the neuroprotection assays, the inhibitory activity of enzyme acetylcholinesterase was evaluated for all ethanolic extracts and isolated compounds. In this assay, compound BM 1 (53.5 ± 0.1%) and extract ofIZ 40 variety (54.2 ± 0.1%) stood out as the strongest inhibitors. Subsequently, these two samples were submitted to the negative geotaxis test with Drosophila melanogaster flies, to verify the occurrence of protection against neurological lesions induced in individuals of thespecies by the toxin rotenone. There was a higher resistance to rotenone toxicity in the flies exposed first to the samples under analysis, in relation to those exposed to rotenone first. It was evidenced a neurodegenerative disease prevention character for these samples, making interesting the deepening of their studies.