Ules26113220 Academic Editors: Jadwiga Handzlik and Katarzyna Kucwaj-Brysz Received: 7 Might 2021 Accepted: 26 Could 2021 Published: 27 MayAbstract: Heme and nonheme-type flavone synthase enzymes, FS I and FS II are accountable for the synthesis of flavones, which play an important function in different biological processes, and possess a wide array of biomedicinal properties like antitumor, antimalarial, and antioxidant activities. To acquire more insight into the mechanism of this curious enzyme reaction, nonheme structural and functional models were carried out by the use of mononuclear iron, [FeII (CDA-BPA)]2+ (six) [CDABPA = N,N,N’,N’-tetrakis-(2-pyridylmethyl)-cyclohexanediamine], [FeII (CDA-BQA)]2+ (five) [CDABQA = N,N,N’,N’-tetrakis-(2-quinolilmethyl)-cyclohexanediamine], [FeII (Bn-TPEN)(CH3 CN)]2+ (3) [Bn-TPEN = N-benzyl-N,N’,N’-tris(2-pyridylmethyl)-1,2-diaminoethane], [FeIV (O)(Bn-TPEN)]2+ (9), and manganese, [MnII (N4Py)(CH3 CN)]2+ (two) [N4Py = N,N-bis(2-pyridylmethyl)-1,2-di(2-pyridyl) ethylamine)], [MnII (Bn-TPEN)(CH3 CN)]2+ (four) complexes as catalysts, where the probable reactive intermediates, high-valent FeIV (O) and MnIV (O) are recognized and properly characterised. The results in the catalytic and stoichiometric reactions showed that the ligand framework plus the nature of the metal cofactor considerably influenced the reactivity with the catalyst and its intermediate. Comparing the reactions of [FeIV (O)(Bn-TPEN)]2+ (9) and [MnIV (O)(Bn-TPEN)]2+ (10) towards flavanone beneath exactly the same circumstances, a 3.5-fold distinction in reaction price was observed in favor of iron, and this worth is three orders of magnitude larger than was observed for the previously published [FeIV (O)(N2Py2Q)]2+ [N,N-bis(2-quinolylmethyl)-1,2-di(2-pyridyl)ethylamine] species. Keywords: flavone synthase; iron(IV)-oxo; manganese(IV)-oxo; oxidation; kinetic studies1. Introduction Flavones are low molecular weight phytochemicals that play a vital role in numerous biological processes and have a good influence on our overall health [1]. Due to their wide range of biological activities (malaria, anti-cancer, anti-diabetes, asthma, antiviral, antioxidant, anti-microbial, anti-ulcer, anti-inflammation, cardiovascular activity, neuroprotection, etc.) their syntheses have develop into critical goals of medicinal and bioorganic chemists [2]. Flavones may be synthesised by many methods such as Baker-Venkataraman-rearrangement from o-hydroxyacetophenone [1], and oxidation of flavanones employing different stoichiometric reagents which include DMSO/I2 [9], SeO2 [10], two,3dichloro-5,6-dicyano-1,4-benzoquinone [11], thallium salts [12] and manganese acetate [13]. The oxidation of flavanones by heme and nonheme iron-dependent TrkB Agonist custom synthesis enzymes is amongst the most significant methods for the duration of the biosynthesis of flavones. High-valent oxoiron(IV) intermediates as essential oxidants are well-established in each heme and nonheme enzymes, including cytochrome P450, bovine liver catalase (BLC) [14,15], flavone synthase II (FS II) [160], pterin-dependent phenylalanine hydroxylase [21], and -keto acid-dependent p38 MAPK Agonist Molecular Weight dioxygenases (taurine dioxygenase, TauD [224] and flavone synthase I, FS I) [258],Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Copyright: 2021 by the authors. Licensee MDPI, Basel, Switzerland. This short article is definitely an open access article distributed beneath the terms and situations with the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/l.