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      Alkylated Sesamol Derivatives as Potent Antioxidants

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          Abstract

          Sesamol is a phenolic derivative. Its antioxidant activity is low than that of Trolox and depends on benzodioxole moiety. Thus, a molecular modification strategy through alkylation, inspired by natural and synthetic antioxidants, was studied by molecular modeling at the DFT/B3LYP level of theory by comparing the 6-31+G(d,p) and 6-311++G(2d,2p) basis sets. All proposed derivatives were compared to classical related antioxidants such as Trolox, t-butylated hydroxytoluene (BHT) and t-butylated hydroxyanisole (BHA). According to our results, molecular orbitals, single electron or hydrogen-atom transfers, spin density distributions, and alkyl substitutions at the ortho positions related to phenol moiety were found to be more effective than any other positions. The trimethylated derivative was more potent than Trolox. t-Butylated derivatives were stronger than all other alkylated derivatives and may be new alternative forms of modified antioxidants from natural products with applications in the chemical, pharmaceutical, and food industries.

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          Oxidant and antioxidant balance in the airways and airway diseases.

          Although oxygen is a prerequisite to life, at concentrations beyond the physiological limits it may be hazardous to the cells. Since the lungs are directly exposed to very high amounts of oxygen, it is imperative for the organ to possess defences against possible oxidative challenge. The lungs are therefore endowed with an armamentarium of a battery of endogenous agents called antioxidants. The antioxidant species help the lungs ward off the deleterious consequences of a wide variety of oxidants/reactive oxygen species such as superoxide anion, hydroxyl radical, hypohalite radical, hydrogen peroxide and reactive nitrogen species such as nitric oxide, peroxynitrite, nitrite produced endogenously and sometimes accessed through exposure to the environment. The major non-enzymatic antioxidants of the lungs are glutathione, vitamins C and E, beta-carotene, uric acid and the enzymatic antioxidants are superoxide dismutases, catalase and peroxidases. These antioxidants are the first lines of defence against the oxidants and usually act at a gross level. Recent insights into cellular redox chemistry have revealed the presence of certain specialized proteins such as peroxiredoxins, thioredoxins, glutaredoxins, heme oxygenases and reductases, which are involved in cellular adaptation and protection against an oxidative assault. These molecules usually exert their action at a more subtle level of cellular signaling processes. Aberrations in oxidant: antioxidant balance can lead to a variety of airway diseases, such as asthma, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis which is the topic of discussion in this review.
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            Antioxidant Activity of Quercetin and Its Glucosides from Propolis: A Theoretical Study

            Among the multiple components of propolis, flavonoids contribute greatly to the antioxidant activities of propolis. Flavonoids mainly exist in the form of sugar-conjugated derivatives. Quercetin glycosides represent the predominant flavonoid fraction in propolis. In this work, density functional theory (DFT) calculations were applied to analyze the antioxidative properties of quercetin and its glucosides in the gas and in the liquid phase (ethanol, water). Three main antioxidant mechanisms, hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) were used to analyze the antioxidative capacity of the investigated compounds. Solvent effects dominantly affect SET-PT and SPLET. Thus, the thermodynamically preferred mechanism can be altered. HAT and SPLET are the thermodynamically dominant mechanisms in gas and solvent phases, respectively. Therefore, in the gas phase, the sequence of the antioxidative capacity is similar with the bond dissociation enthalpy values: quercetin > quercetin-5-O-glucoside > quercetin-7-O-glucoside > quercetin-3-O-glucoside > quercetin-3′-O-glucoside > quercetin-4′-O-glucoside. While, in the solvent phases, the sequence is similar with the proton affinity values: quercetin-4′-O-glucoside > quercetin-5-O-glucoside > quercetin > quercetin-3-O-glucoside > quercetin-7-O-glucoside > quercetin-3′-O-glucoside. OH groups in B-ring and C-ring contribute mainly to the antioxidative activities of quercetin and glucosides compared with A-ring.
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              Chemopreventive effect of resveratrol, sesamol, sesame oil and sunflower oil in the Epstein-Barr virus early antigen activation assay and the mouse skin two-stage carcinogenesis.

              Resveratrol, sesamol, sesame oil and sunflower oil are known natural dietary components with intrinsic cancer chemopreventive potentials. As a part of our study of dietary constituents as potential cancer chemopreventive agents, we have assessed the anti-cancer potentials of these products in the promotion stage of cancer development employing the in vitro Epstein-Barr virus early antigen activation assay induced by the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA). Further, we studied the activities of these compounds in the brine shrimp cytotoxicity assay as well as on the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging bioassay with a view to comparing some of the mechanisms of their anti-cancer activity. Finally, we compared the observed chemoprotective capabilities of the four products in the in vivo 7,12 dimethylbenz(a)anthracene initiated and TPA-promoted mouse skin two-stage carcinogenesis protocols. All the products tested showed a profound inhibitory effect on the Epstein-Barr virus early antigen induction using Raji cells. Comparatively, sesame oil was the most potent followed by sesamol and then resveratrol. Only sesamol and resveratrol showed a remarkable cytotoxic activity in the brine shrimp lethality assays as well as profound free radical scavenging activity in the DPPH bioassay. In both test systems, sesamol exhibited a more remarkable activity than resveratrol while sesame oil and sunflower oil did not exhibit any appreciable activity even at the highest concentrations tested (4000 microg ml(-1) ). In our in vivo assay at a 50-fold molar ratio to TPA, sesamol offered 50% reduction in mouse skin papillomas at 20 weeks after promotion with TPA. Under an identical molar ratio to TPA, resveratrol offered a 60% reduction in the papillomas in mouse at 20 weeks. Thus sesamol seems to be an almost equally potent chemopreventive agent. Sesame oil and sunflower oil offered 20 and 40% protection, respectively, in the mouse skin tumor model. The anti-oxidant capabilities of these compounds could not solely explain the observed anti-cancer characteristics. Resveratrol is present in grapes. Sesamol, a constituent of sesame oil and sunflower oil are regularly consumed dietary natural products. The observed chemopreventive effect of these products particularly warrants more attention since they already exist in the population with no known adverse effects.
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                Author and article information

                Contributors
                Role: Academic Editor
                Journal
                Molecules
                Molecules
                molecules
                Molecules
                MDPI
                1420-3049
                21 July 2020
                July 2020
                : 25
                : 14
                : 3300
                Affiliations
                [1 ]Núcleo de Estudos e Seleção de Moléculas Bioativas, Instituto de Ciências da Saúde, Universidade Federal do Pará, Belém 66075-110, Brazil; lanalicerodrigues30@ 123456gmail.com (L.R.F.); joy.farmc@ 123456gmail.com (J.K.L.V.); opps@ 123456ufpa.br (O.P.P.S.)
                [2 ]Programa de Pós-Graduação em Química Medicinal e Modelagem Molecular, Instituto de Ciências da Saúde, Universidade Federal do Pará, Belém 66075-110, Brazil; aherculanos@ 123456gmail.com (A.M.H.); oliveirakrm@ 123456gmail.com (K.R.H.M.O.); breno@ 123456unifap.br (C.B.R.S.)
                [3 ]Faculdade de Física, Instituto de Ciências Exatas e Naturais, Universidade Federal do Pará, Belém 66075-110, Brazil; antmchaves@ 123456yahoo.com.br
                [4 ]Department of Pharmaceutical Organic Chemistry, University of Granada, 18071 Granada, Spain; jmcampos@ 123456ugr.es
                [5 ]Laboratorio de Modelagem e Química Computacional—LMQC, Federal University of Amapá. Rod. Juscelino Kubitschek, Km 02, Macapá 68902-280, Brazil
                Author notes
                [* ]Correspondence: ivapalheta@ 123456gmail.com (I.C.P.); lqfmed@ 123456gmail.com (R.S.B.); Tel.: +55-91-3201-7202 (R.S.B.)
                Author information
                https://orcid.org/0000-0001-9509-7009
                https://orcid.org/0000-0002-9035-8123
                https://orcid.org/0000-0002-0271-335X
                Article
                molecules-25-03300
                10.3390/molecules25143300
                7397082
                32708143
                f5eb6d39-7611-42b1-bd7c-73c01fdff12d
                © 2020 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 07 June 2020
                : 15 July 2020
                Categories
                Article

                antioxidant capacity,sesamol,dft,electron transfer,hydrogen transfer

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