DPPH radical scavenging and mixture effects of plant o‐diphenols and essential oil constituents

Abstract

A series of natural compounds were examined for potential synergistic and antagonistic antiradical activities. Four natural o‐diphenolic compounds, namely quercetin, rutin, (+)‐catechin, and rosmarinic acid as well as five common essential oil components: thymol, carvacrol, thymoquinone, p‐cymene, and γ‐terpinene were studied individually and in binary, ternary, and quaternary mixtures against DPPH•. The antiradical activities of the individual compounds were quantified according to the number of radicals scavenged per molecule of antioxidant and the EC50 parameter. Also, the different reaction patterns resulting to different stoichiometries are discussed. In binary and higher systems an additive effect was observed with any combination of the o‐diphenols. The monoterpenoid phenols carvacrol and thymol presented low DPPH radical scavenging activity and antagonistic interactions with the o‐diphenols, partially attributed to equilibrium phenomena. The rest essential oil components were inactive and did not interfere in the overall antiradical activity of any combination. Practical applications: Plant extracts can be used as antioxidants for lipid foods or combined with essential oils that provide antimicrobial protection. They contain a variety of active compounds, which might interact and affect the overall antioxidant activity. The present work examines the radical scavenging activity of the basic constituents of extracts, essential oils, and their mixtures. The results could have an impact on the production of natural antioxidants, since a cost effective industrial process involves the recovery of a multicomponent fraction rather than the isolation of single antioxidants. Also, they can be useful to estimate the antiradical activity of multicomponent herbal supplements. The antiradical activities of o‐diphenols commonly found in natural extracts (quercetin, rutin, (+)‐catechin, and rosmarinic acid) and essential oil components (thymol, carvacrol, thymoquinone, p‐cymene, and γ‐terpinene) were studied individually and in binary, ternary, and quaternary mixtures. An additive effect was observed with any combination of the o‐diphenols. Among the essential oil components, the monoterpenoid phenols carvacrol and thymol presented low DPPH radical scavenging activity and antagonistic interactions with the o‐diphenols partially attributed to equilibrium phenomena, while the rest were inactive and did not interfere in the overall antiradical activity of any combination.

Synthesis, Characterization, and the Antioxidant Activity of Carboxymethyl Chitosan Derivatives Containing Thiourea Salts

“…Due to the space barrier of the three benzene rings with resonance stabilization effect, the unpaired electrons on the middle nitrogen atoms cannot play their due electron pairing effect. It is purple when dissolved in anhydrous ethanol, and has the maximum absorption at the wavelength of 517 nm [24,32,33]. When DPPH can be combined or replaced with free radical scavenger to reduce the number of free radicals, the absorbance will be reduced, and the solution color will become lighter, so as to evaluate the ability of scavenging free radicals.…”

Six Common Herbs with Distinctive Bioactive, Antioxidant Components. A Review of Their Separation Techniques

“…Therefore, the number of radicals scavenged by each crocin molecule ( n ) corresponds to 2.4 (1:2.4) based on the formula n = 1/(2 × EC 50 ), where EC 50 is expressed as mol crocin /mol DPPH . A stoichiometric factor of such magnitude is close to the respective values of potent antiradical structures, such as the B-catecholic flavonoids [ 215 , 216 ]. Dar et al [ 217 ] determined even higher activity, comparing crocin with kaempferol ( n = 2, [ 216 ]) and ascorbic acid, that in terms of IC 50 (expressed as µmol/mL) the two latter present similar activity [ 217 ].…”

Recent Developments in Smart Food Packaging Focused on Biobased and Biodegradable Polymers

“…In this regard, synthetic antioxidants, such as butylated hydroxytoluene (BHT) or butylated hydroxyanisole (BHA), have been added to PLA (Jamshidian et al, 2012), gelatin (Sai-Ut et al, 2015), carrageenan (Wan Yahaya et al, 2019), gum cordia and carboxymethyl cellulose (Haq et al, 2015) films proving to effectively reduce lipid oxidation in several foods. However, the use of natural antioxidants like pure compounds (e.g., tocopherols, caffeic acid, chlorogenic acid, ferulic acid, rosmarinic acid, salvianolic acid, carnosic acid and ascorbic acid carvacrol, thymol, carnosol, quercetin, luteolin, apigenin, eriodictyol, catechin, rutin), plant and fruit extracts (e.g., rosemary, grape seed, green tea, oregano, murta, mint, marjoram, savory, and pomegranate peel), and essential oils or oleoresins from herbs and spices (e.g., cinnamon, lemongrass, clove, thyme, ginger, sage, oregano, pimento and bergamot) (Amorati et al, 2013;Sanches-Silva et al, 2014;Valdés et al, 2015;Ganiari et al, 2017;Tsimogiannis et al, 2017) is currently preferred. Likewise, it is important to mention the potential use of extracts obtained from plant by-products like barley husks, pomegranate peel, olive leaves, as sources of antioxidant agents (Pereira de Abreu et al, 2012;Barbosa-Pereira et al, 2013;Marcos et al, 2014;Qin et al, 2015;Yuan et al, 2015;de Moraes Crizel et al, 2016).…”