In vitro hypoglycemic, antioxidant and antineurodegenerative activity of chokeberry (Aronia melanocarpa) leaves

Chokeberries (Aronia melanocarpa (Michx.) Elliot have recently become one of the most popular and widely used berry fruits, and there are numerous studies dealing with the investigation of their chemical composition and biological activities. Unlike berries, chokeberry leaves were far less investigated. Therefore, the aim of this study was to conduct a bioactivity-based analysis of chokeberry leaves collected after berries were harvested. Chemical analysis of hydroethanolic chokeberry extract and its ethyl acetate, n-butanol, and water fractions was performed. Antioxidant, hypoglycemic, and antineurodegenerative activities of the obtained samples were assessed by in vitro tests. The highest total phenolics content was found in n-butanol fraction (221.5 mg gallic acid equivalents/g dw). Fourteen compounds (six phenolic acids and eight flavonoids) were identified in the samples. Caffeoylquinic acid derivatives and quercetin glycosides were dominant phenolic compounds. The highest content of phenolic acids, as well as flavonoids, was recorded in n-butanol fraction (80.75 mg/g dw and 47.79 mg/g dw, respectively). This fraction was the most active in 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) assays. Also, the n-butanol fraction was the most effective inhibitor of acetylcholinesterase (AChE) and tyrosinase (TYR) enzymes. All samples showed a better inhibitory effect on α-glucosidase enzyme with inhibition concentrations IC50 = 4.21 - 9.22 μg/mL, than α-amylase enzymes (IC50 = 14.36 - 88.61 μg/mL). Pearson’s correlation between the content of individual phenolics and the results of biological tests was performed. Thus, hyperoside and isoquercitrin showed a significant correlation with DPPH and ABTS tests, caffeoylquinic acids with FRAP test, quercetin 3-O-vicianoside with β-carotene assay, hyperoside and isoquercitrin with α-amylase inhibition activity, and isorhamnetin 3-O-rutinoside with α-glucosidase inhibition assay. Considering the obtained results, chokeberry leaves represent a valuable natural source of phenolic compounds with promising potential for the development of new products with beneficial effects on human health