Abstract
The antioxidant efficiency of 70% aqueous methanolic extracts from the leaves of twelve selected Cotoneaster Medik. species was evaluated using four complementary in vitro tests based on SET- (single electron transfer) and HAT-type (hydrogen atom transfer) mechanisms (DPPH, FRAP, O2•− and H2O2 scavenging assays). The samples exhibited the dose-dependent responses in all assays with activity parameters of EC50 = 18.5–34.5 µg/mL for DPPH; 0.9–3.8 mmol Fe2+/g for FRAP; SC50 = 27.7–74.8 µg/mL for O2•−; and SC50 = 29.0–91.3 µg/mL for H2O2. Significant linear correlations (|r| = 0.76–0.97, p < 0.01) between activity parameters and total contents of phenolics (5.2%–15.4% GAE) and proanthocyanidins (2.1%–15.0% CYE), with weak or no effects for chlorogenic acid isomers (0.69%–2.93%) and total flavonoids (0.28%–1.40%) suggested that among the listed polyphenols, proanthocyanidins are the most important determinants of the tested activity. UHPLC-PDA-ESI-QTOF-MS analyses led to detection of 34 polyphenols, of which 10 B-type procyanidins, 5 caffeoylquinic acids and 14 flavonoids were identified. After cluster analysis of the data matrix, the leaves of Cotoneaster zabelii, C. splendens, C. bullatus, C. divaricatus, C. hjelmqvistii and C. lucidus were selected as the most promising sources of natural antioxidants, exhibiting the highest phenolic levels and antioxidant capacities, and therefore the greatest potential for pharmaceutical applications.
Highlights
The oxidative stress arising from an imbalance in the total antioxidant status of the human body is believed to be involved in pathogenesis of chronic diseases usually referred to as civilization diseases, including cardiovascular and neurodegenerative disorders, cancer, metabolic syndrome, diabetes and digestive diseases [1]
In order to more thoroughly assess the impact of phenolics on the antioxidant properties of the most valued samples grouped in the cluster CL-1, their average EC50 value (21.6 μg of the leaf dry weight/mL) for the DPPH test was recalculated to the phenolic effective concentration PEC50 with the use of the respective total phenolic content (TPC) levels
The current study demonstrates that the leaf samples of twelve Cotoneaster species cultivated in Poland possess significant and dose-dependent in vitro single electron transfer (SET)- and hydrogen atom transfer (HAT)-type antioxidant activities, which positively correlate with their total phenolic content (TPC)
Summary
The oxidative stress arising from an imbalance in the total antioxidant status of the human body is believed to be involved in pathogenesis of chronic diseases usually referred to as civilization diseases, including cardiovascular and neurodegenerative disorders, cancer, metabolic syndrome, diabetes and digestive diseases [1]. Besides of endogenous defense systems, dietary antioxidants, mainly plant polyphenols, play an important role in protecting the living cells against prooxidant factors, both metabolic and external (environmental) [2]. Molecules 2016, 21, 688 plant-based, potent antioxidants active in prevention of chronic diseases. A variety of plants have been studied for antioxidant activity and phenolic content, only few have been found to be sufficiently rich in low-molecular weight polyphenols characterized by high antioxidant potential and good bioavailability in internal applications [3,4]. Among plant families taxonomically featured by high content of low-molecular weight phenols, the Rosaceae family appears to be one of the most promising for future research. Apart from Aronia, Crataegus, Malus or Rubus species [5,6,7,8], widely known as functional or medicinal plants, the family comprises representatives being to date in traditional use only, and worth of investigation
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