Antioxidant Capacity and Phenolic Contents of Three <i>Quercus</i> Species

Abstract

ABSTRACT. The antioxidant capability and phenolic contents of ethanol extracts (free phenolics) and ethyl acetate extracts (bound phenolics) of three Quercus species were estimated in this work. The antioxidant activities were examined by 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) free radical, reducing power and -carotene bleaching methods. HPLC was employed to detect major phenolic acids. The leaf extract of Q. salicina contained maximum total phenolics while the highest total flavonoid content was found in the leaf extract of Q. serrata. The antioxidant activities varied among three species. Bark extract of Q. salicina was the most potential and it was closed to levels of the standard antioxidative dibutyl hydroxytoluene (BHT). The bark extract of Q. serrata also showed promising antioxidant activities despite their eminence was negligibly lower than Q. salicina. Stronger antioxidant activities of free phenolics than those of the bound phenolics may be attributed to higher quantities of free phenolics in the barks of Quercus species, however total flavonoids may not contribute a critical role. By HPLC analysis, thirteen phenolic acids were detected in the leaf and bark extracts. Of them, Q. salicina showed maximum in number (ten compounds) and quantities of detected phenolic acids. Ellagic, chlorogenic and benzoic acids were dominant in Quercus species. Findings of this study revealed that leaves and barks of three Quercus species are rich source of antioxidants, and Q. salicina is the most promising and should be elaborated to exploit its pharmaceutical properties.

Morphological Observation and Correlation of Growth and Yield Characteristics with Grain Quality and Antioxidant Activities in Exotic Rice Varieties of Afghanistan

“…Shimamura et al [14] mentioned that oxidative degradation reduces the value of food and may have harmful effects on human health. Antioxidants inhibit oxidation of oxidizable substrates and are widely distributed in many food sources [32], thus they can support human health [13]. In this study, Jalalabad-14 showed high antioxidant activity compare to other varieties, meaning that the variety has high potential to act against oxidation reactions.…”

“…Food value declines with oxidative degradation and may have risky effects on human health [12]. Antioxidants, which play inhibitory roles against free radicle reactions [13], are the most important biochemical components of rice grain. Antioxidants are used as food additives to prevent oxidative rancidity and discoloration of foods [14].…”

Phenolic Compounds and Antioxidant Activity of Rice Straw Extract

“…Plant phenolic compounds are mainly found in the form of benzoic acid or cinnamic acid derivatives as well as glycosidic esters [31]. They possessed multiple biological activities such as antioxidant [32], antimicrobial [33], or antiinflammatory activity [34]. In this study, alkaline hydrolysis with Na 2 CO 3 at 90°C was used to release conjugated phenols.…”

Efficacy of N-Methyl-N-Nitrosourea Mutation on Physicochemical Properties, Phytochemicals, and Momilactones A and B in Rice

“…Additionally, bioactive compounds including antioxidants, phenolics, and momilactones play important roles in human health, pharmaceutical industries, and allelopathy [4,11,12]. Antioxidants effectively inhibit and neutralize free radical reactions by providing hydrogen or electron to the reaction chain [13]. Antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and others from synthetic sources are applied in food protection against oxidative damages [14]; however, concerns regarding the side effects of them have been increased among scientists and nutritionists.…”

“…Besides, they play key roles in several activities in plants, phenolics and flavonoids are vital constituents in the human diet [12,20]. Phenolics have positive effects on human health [13,21] and are considered as the most potent natural compounds of plants with antioxidant, antimicrobial, and anti-inflammatory activities [13,22]. Additionally, phenolic compounds play a crucial role in stabilizing lipids against peroxidation as well as preventing diabetes [23] and various types of oxidizing enzymes [24].…”