molecules Article Exploring the 20-Hydroxy-Chalcone Framework for the Development of Dual Antioxidant and Soybean Lipoxygenase Inhibitory Agents Ioanna Kostopoulou 1, Andromachi Tzani 1, Nestor-Ioannis Polyzos 1, Maria-Anna Karadendrou 1, Eftichia Kritsi 2,3, Eleni Pontiki 4, Thalia Liargkova 4, Dimitra Hadjipavlou-Litina 4 , Panagiotis Zoumpoulakis 2,3 and Anastasia Detsi 1,* 1 Laboratory of Organic Chemistry, Department of Chemical Sciences, School of Chemical Engineering, National Technical University of Athens, Heroon Polytechniou 9, Zografou Campus, 15780 Athens, Greece; [email protected] (I.K.); [email protected] (A.T.); [email protected] (N.-I.P.); [email protected] (M.-A.K.) 2 Institute of Chemical Biology, National Hellenic Research Foundation, 48, Vas. Constantinou Avenue, 11635 Athens, Greece; [email protected] (E.K.); [email protected] (P.Z.) 3 Department of Food Science and Technology, University of West Attica, Ag. Spyridonos, 12243 Egaleo, Greece 4 Laboratory of Pharmaceutical Chemistry, School of Pharmacy, Faculty of Health Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; [email protected] (E.P.); [email protected] (T.L.); [email protected] (D.H.-L.) * Correspondence: [email protected]; Tel.: +30-210-7724126 0 Citation: Kostopoulou, I.; Tzani, A.; Abstract: 2 -hydroxy-chalcones are naturally occurring compounds with a wide array of bioactiv- Polyzos, N.-I.; Karadendrou, M.-A.; ity. In an effort to delineate the structural features that favor antioxidant and lipoxygenase (LOX) Kritsi, E.; Pontiki, E.; Liargkova, T.; inhibitory activity, the design, synthesis, and bioactivity profile of a series of 20-hydroxy-chalcones Hadjipavlou-Litina, D.; bearing diverse substituents on rings A and B, are presented. Among all the synthesized derivatives, Zoumpoulakis, P.; Detsi, A. Exploring chalcone 4b, bearing two hydroxyl substituents on ring B, was found to possess the best combined the 20-Hydroxy-Chalcone Framework activity (82.4% DPPH radical scavenging ability, 82.3% inhibition of lipid peroxidation, and satisfac- for the Development of Dual tory LOX inhibition value (IC50 = 70 µM). Chalcone 3c, possessing a methoxymethylene substituent Antioxidant and Soybean on ring A, and three methoxy groups on ring B, exhibited the most promising LOX inhibitory activity Lipoxygenase Inhibitory Agents. µ Molecules 2021, 26, 2777. https:// (IC50 = 45 M). A combination of in silico techniques were utilized in an effort to explore the crucial doi.org/10.3390/molecules26092777 binding characteristics of the most active compound 3c and its analogue 3b, to LOX. A common H-bond interaction pattern, orienting the hydroxyl and carbonyl groups of the aromatic ring A Academic Editor: Luisella Verotta towards Asp768 and Asn128, respectively, was observed. Regarding the analogue 3c, the bulky (-OMOM) group does not seem to participate in a direct binding, but it induces an orientation capable Received: 24 January 2021 to form H-bonds between the methoxy groups of the aromatic ring B with Trp130 and Gly247. Accepted: 30 April 2021 Published: 8 May 2021 Keywords: chalcones; aurones; butein; sulfuretin; antioxidant activity; lipoxygenase inhibition; molecular docking Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction Chalcones (1,3-diaryl-2-propen-1-ones) (Figure1) constitute a large and important group of bioactive compounds belonging to the flavonoid family. They possess an impor- tant role in medicinal chemistry since they are privileged scaffolds used as lead compounds Copyright: © 2021 by the authors. for the discovery of new drugs. Thus, the isolation from natural sources (plants, flowers, Licensee MDPI, Basel, Switzerland. fruits, vegetables etc.), as well as the organic synthesis of chalcones have been intensified This article is an open access article during the last decades due to their wide spectrum of bioactivity. The presence of a α,β- distributed under the terms and unsaturated carbonyl system in chalcone derivatives enable them to exhibit a wide range conditions of the Creative Commons of biological activities such as antioxidant, anti-inflammatory, [1], anticancer [2], antibacte- Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ rial [3], antimalarial [4], tyrosinase inhibitory activity [5], anti-HIV [6], anti-leishmanial [7], 4.0/). while they are also potential neuroprotective agents [8,9]. The chalcone derivatives which Molecules 2021, 26, 2777. https://doi.org/10.3390/molecules26092777 https://www.mdpi.com/journal/molecules Molecules 2021, 26, x FOR PEER REVIEW 2 of 24 Molecules 2021, 26, 2777 2 of 24 [2], antibacterial [3], antimalarial [4], tyrosinase inhibitory activity [5], anti-HIV [6], anti- leishmanial [7], while they are also potential neuroprotective agents [8,9]. The chalcone possessderivatives hydroxyl which and possess methoxy hydroxyl substitution and methoxy on aromatic substitution rings A on and aromatic B have demonstratedrings A and B potentialhave demonstrated anti-leishmanial potential and anti anti-trypanosomal-leishmanial and activities anti-trypanosomal by acting on aactivities number by of molec-acting ularon a targets.number Moreover,of molecular free targets. hydroxyl Moreover, groups arefree essential hydroxyl to groups increase are their essential activity to (suchincrease as antioxidanttheir activity and (such antimicrobial) as antioxidant while and methoxy antimicrobial) groups while decrease methoxy it. Regarding groups decrease antitumor it. activity,Regarding it isantitumor possibly positivelyactivity, it is affected possibly in positively the presence affected of methoxy in the presence substitutions of methoxy on the aromaticsubstitutions ring on [10 the]. aromatic ring [10]. Figure 1. General structure and numbering scheme of the chalcone andand auroneaurone framework.framework. Another flavonoidflavonoid subclass,subclass, auronesaurones ((Z)-2-benzylidenebenzofuran-3-(2H)-ones)((Z)-2-benzylidenebenzofuran-3-(2H)-ones) ((FigureFigure1 1)) are oxidative oxidative cyclization cyclization products products of of chalcones chalcones that that rarely rarely appear appear in nature in nature and andare less are lessstudied studied than than chalcones. chalcones. So Sofar far aurones aurones have have been been exploited exploited via via isolation from floweringflowering plantsplants[ 11[11,12,12]],, invasive invasive weeds weeds [13 [13]], mosses, mosses [14 [],14] and, and marine marine brown brown algae algae [15], [15] via, organicvia organic synthesis synthesis [16,17 [16] and,17] biosynthesisand biosynthesis from chalconefrom chalcone precursors precurso by thers keyby the enzyme key en- au- reusidinzyme aureusidin synthase synthas [18]. Sulfuretine [18]. Sulfuretin [19] and aureusidin[19] and aureusidin [20] consist [20] representative consist representative naturally occurringnaturally occu aurones,rring bearing aurones, different bearing hydroxylation different hydroxylation patterns, while patterns, some while methoxy-aurones some meth- alsooxy- occuraurones in naturealso occur [21,22 in]. nature Aurones [21 constitute,22]. Aurones promising constitute bioactive promising compounds bioactive exhibiting com- amongpounds others,exhibiting antioxidant among others, [17], antifungal antioxidant [23 [17]], anticancer, antifungal [ 24[23]],, antimicrobial anticancer [24] [25, antimi-], anti- leishmanialcrobial [25], [anti16],- antimalarialleishmanial [16] [26],, antimalarial anti-inflammatory [26], anti activity-inflammatory [27], and activity consist potential[27], and effectiveconsist potential agents for effective the treatment agents offor Alzheimer’s the treatment disease of Alzheimer’s [28]. Consequently, disease [28] during. Conse- the lastquently, decades, during there the is last an increasedecades, in there publications is an increase concerning in publications their isolation, concerning synthesis, their andiso- bioactivitylation, synthesis evaluation., and bioactivity evaluation. In this work, work, among among the the sy synthesizednthesized compounds compounds the the synthesis synthesis of two of two naturally naturally oc- occurring chalcones and aurones, such as butein (4a) and sulfuretin (7a), is also presented. curring chalcones0 0 and aurones, such as butein (4a) and sulfuretin (7a), is also presented. Butein (2’,4,4’,3,4-tetrahydroxy-chalcone),3,4-tetrahydroxy-chalcone) occurs in many unrelatedunrelated generagenera includingincluding Butea Dahlia, Coreopsis, and Searsia and has been isolated in good yields [[29]29].. Chemically, butein has been been synthesized synthesized through through various various organic organic synthetic synthetic methods methods including including micro- mi- crowave irradiation in the presence of PdCl2(PPh3)2, ammonium formate in THF [30], aldol wave irradiation in the presence of PdCl2(PPh3)2, ammonium formate in THF [30], aldol condensation catalyzed by the novel acid catalyst thionyl chloride (SOCl2)/ethyl alcohol condensation catalyzed by the novel acid catalyst thionyl chloride (SOCl2)/ethyl alcohol (EtOH) [31], Claisen–Schmidt condensation between protected 2,4-dihydroxyacetophenone (EtOH) [31], Claisen–Schmidt condensation between protected 2,4-dihydroxyacetophe- and 3,4-dihydroxybenzaldehyde in the presence of basic catalyst, and subsequent removal none and 3,4-dihydroxybenzaldehyde in the presence of basic catalyst, and subsequent of the protecting