Principais constituintes de flores de lúpulo: análise do potencial antioxidante e para o tratamento de gota, diabetes do tipo 2 e doença de Alzheimer

Abstract

Humulus lupulus Linnaeus (hop) is a plant species rich in phenolic compounds, used in the brewing process, which has a variety of secondary metabolites such as bitter acids, flavonoids, phenolic acids, essential oils, among other substances. Based on the above, this research aims to analyze the antioxidant potential of hops and verify its pharmacological properties to help the treatment of gout, type 2 diabetes and Alzheimer's disease, and the study of quantitation of the major compounds present in its flowers. Varieties of hop flowers planted in Brazil and commercial pellets were obtained and the extracts produced by soxhlet extraction (in hexane and methanol). The quantitation of bitter acids and xanthohumol was performed by high performance liquid chromatography (HPLC). Cultivars Herkules and Chinook-1 showed the highest contents of bitter acids and xanthohumol. The determination of the Total Phenolic Content showed significant results for the Saaz, Chinook-2, Chinook-1 and Herkules varieties. Corroborating with the results obtained from the analysis of the Total Phenolic Content, the Chinook-2 and Saaz varieties presented the best antioxidant activities in the DPPH• assay among the methanol extracts, and the Herkules and Chinook-1 varieties among the hexane extracts, confirming the high action of bitter acids, as observed for ICE-4 which showed activity close to the BHT standard. The ABTS•+ antioxidant assay demonstrated the high capacity of xanthohumol to inhibit this radical cation, higher to the positive control. The Herkules and Chinook-1 varieties showed the best antioxidant capacities, showing that the high content of bitter acids and xanthohumol reflect in greater effectiveness against oxidative stress. Extracts with a high concentration of xanthohumol demonstrated high capacity to capture hydroxyl radicals and inhibit the enzyme xanthine oxidase, significantly reducing the formation of uric acid. The results with the α-glucosidase enzyme revealed promising pharmacological action for all samples, being more effective than the commercial drug acarbose, with the standard xanthohumol presenting the best inhibitory action. The acetylcholinesterase enzyme inhibition assays showed that extracts rich in bitter acids were more effective, obtaining values close to the positive eserine standard.