Antioxidant effect of mono‐ and dihydroxyphenols in sunflower oil with different levels of naturally present tocopherols

Abstract

Antioxidant properties of mono- and dihydroxyphenolic acids and their alkyl esters were examined, with emphasis on the relationship between their molecular structure and antioxidant activity. Test media with different tocopherol level were used for determining the oxidative stability: original refined sunflower oil (total tocopherols 149.0 mg/kg), partially tocopherol-stripped sunflower oil (total tocopherols 8.7 mg/kg) and distilled fatty acid methyl esters (FAME) as a tocopherol-free medium. The chemical reaction of tocopherols with diazomethane tested for the purpose to eliminate their antioxidant activity failed due to the negligible degree of methylation of hydroxyl group in the tocopherol molecule. Caffeic acid and protocatechuic acid (3,4-dihydroxyphenolic acids) and their alkyl esters were found to be more active antioxidants than monohydroxyphenolic acid (p-hydroxybenzoic acid), 2,5-dihydroxyphenolic acid (gentisic acid), 3-methoxy-4-hydroxyphenolic acids (vanillic and ferulic acids) and their corresponding alkyl esters. Naturally present tocopherols in refined sunflower oil proved to have a synergistic effect on gentisic acid but not on its alkyl esters. In contrast, tocopherols showed an antagonistic effect on alkyl esters of caffeic acid, because their protection factors decreased with increasing level of tocopherols in the test medium. Moreover, the antioxidant activity of these alkyl esters decreased with increasing length of their alkyl chain in conformity with the polar paradox hypothesis.Practical applications:Tocopherols as naturally present antioxidants influence considerably the antioxidant activity of other antioxidants added to plant oils used as a test medium. Distilled fatty acid methyl esters prepared from refined sunflower oil may serve as an optimal tocopherol-free test medium. Some alkyl esters of phenolic acids were evaluated to be applicable as natural more lipophilic antioxidants in comparison with phenolic acids.

Polylactide films produced with bixin and acetyl tributyl citrate: Functional properties for active packaging

“…The product shelf life of lipid‐rich foods and bioactive compounds is highly dependent on their oxidative stability. Photo‐oxidation reactions are therefore a real concern to the food industry, leading to the degradation of vitamins and bioactive compounds, to the development of rancidity in fatty food products, and hence to the decrease in nutritional and organoleptic quality of food products 7,8 . Since the amount of energy carried by light beams is inversely proportional to their wavelength, UV light possess more energy than visible light, inducing a higher rate of photochemical oxidation processes 9,10 .…”

Degradation of selected nutrients in sunflower oils during long-term storage

“…Lipid oxidation is responsible for a gradual decrease in nutritional and sensory quality of lipidcontaining products (Hrádková et al 2013). In fact, lipid autoxidation and inadequate storage contribute significantly to the deterioration and reduction of the shelf-life of vegetable oils causing changes in colour, texture, odour and flavour, and loss of vitamins (Milanez & Pontes 2014).…”

Kazakh Ziziphora Species as Sources of Bioactive Substances

“…Similar activities were observed for caffeic acid ethylester (18). This compound showed antihypertensive, antioxidant and anti-inflammatory activities that can be connected with usage of Ziziphora against diseases of cardiovascular system [101][102][103][104][105][106][107][108][109][110][111][112]. Similarly, rosmarinic acid (19) possesses various activities, also connected with civilization diseases like cardiovascular system illnesses, chronic inflammations and cancer [113][114][115][116].…”

“…Caffeic acid (17) Z. clinopodioides [80] Anticancer potential reviewed [98] Protection of endothelial cells (review by Fuentes and Palomo [99]) General review on applications [100] O H O OH Ethyl ester of caffeic acid (18) Z. clinopodioides [4] Weak inhibitory activity on NO production stimulated by LPS and IFN-γ in RAW 264.7 cells [4] Antihypertensive [101,102] Anti-inflammatory [103][104][105] Antidiabetic [106] Inhibitory activity against amyloidogenesis [107] Antioxidative [108][109][110][111] Anticancer [112] O H…”