Iron(III), Chromium(III), and Copper(II) Complexes ofl-Norvaline and Ferulic Acid

Abstract

The complexation equilibria of L-norvaline (Nva) and ferulic acid (FA) were studied in aqueous solutions at room temperature (298 K) and in fixed ionic strength (0.15 mol 3 dm -3 NaNO 3 ) by means of potentiometry and spectrophotometry techniques. The ferric (Fe 3þ ), chromium (Cr 3þ ), and cupric (Cu 2þ ) complexing capacities of Nva and FA and their overall stability constants in aqueous solutions were obtained by the HYPERQUAD 2008 program from the potentiometric data. The concentration distributions of the various complex specia in solution were evaluated and discussed. The spectroscopic UV-visible measurements are carried out to give qualitative information about the confirmation of the complexes formed in these solutions. ' INTRODUCTIONIt is known that nonprotein amino acids, which are common in fodder plants, consumed animal feeds, and human foods, are a threat to human and animal health. 1 They possess a wide array of chemical structures and often contain functional groups not commonly present in natural products. 1,2 Some act as agonists or antagonists in the neurotransmission of higher animals. 1,2 Others influence the growth of fungi and bacteria. 1,2 Norvaline (C 5 H 11 NO 2 ) is an unusual nonproteinogenic branched-chain amino acid which has been of interest particularly in early enzymological research work. 3 Recently, it has been proved that L-norvaline (Nva) has antifungal activity as it inhibits arginase thus increasing arginine concentrations. 4 More specifically, Nva has been shown to inhibit homoserine dehydrogenase. 5 Moreover, some biological studies have indicated that Nva has antitubercular and antifungal actitvities. 6,7 Also, a lot of research has been focused on the role of antioxidant ferulic acid (FA) in several biological processes. 8 Taking into account the natural occurrence, biosynthesis, metabolism, and functions of nonprotein amino acids and phenolic acids, the study of their metal complexes gains much attention and is attracting more attention in equilibrium and biological chemistry. Hence, a study of metal-Nva-FA complexes may lead to better elucidation of the behavior of such compounds in biological systems and metal-Nva-FA interactions might be of therapeutic interest. A search in the literature shows that there has been quite a number of studies reported on the interaction between metal ions and Nva. 9-27 Most of these research works investigated the complexation equilibria of the copper(II), nickel(II), cobalt(II), manganese(II), uranyl(II), terbium(III), lanthanum(III), praseodymium(III), neodymium-(III), and trimethyltin(IV) metal ions with Nva using different electroanalytical techniques. However, there is no study conducted on the iron(III) or chromium(III) metal ion binary complexes of Nva, and any metal ion-norvaline mixed ligand complexes.Our recent publications describe the protonation equilibrium phenomena of essential amino acids, 28 hydroxamic acids, 29 phenolic compounds, 30 and nonprotein Nva, 31 L-canavanine 32 amino acids in aqueous and in aqueous-organic so...

Formation and Stability of Binary Complexes of Divalent Ecotoxic Ions (Ni, Cu, Zn, Cd, Pb) with Biodegradable Aminopolycarboxylate Chelants (dl-2-(2-Carboxymethyl)Nitrilotriacetic Acid, GLDA, and 3-Hydroxy-2,2′-Iminodisuccinic Acid, HIDS) in Aqueous Solutions

“…The stoichiometries and stability constants of binary metal-chelant complexes were determined from a composition model that was consistent with the titration data, made sense Information about the actual metal-chelant species present in aqueous systems at different equilibrium conditions, which are controlled by the pH of the solution, and have a detrimental effect on the bioavailability of the metals and their corresponding physiological and toxicological behavior [40]. Fig.…”

Coordinated Regulation of Species-Specific Hydroxycinnamic Acid Degradation and Siderophore Biosynthesis Pathways in Agrobacterium fabrum

“…An alternative reason is that ferulic acid needs to be coupled with iron to enter into cells, using a suitable transporter. Remarkably, strong coupling between ferulic acid and iron does occur (30), and ferulic acid is suspected to function as a siderophore (31).…”

Metal complexes of salicylhydroxamic acid and 1,10-phen-anthroline; equilibrium and antimicrobial activity studies

“…To determine the protonation and stability constants of SHAM, PHEN and their metal complexes, Hyperquad2008 was used to make nonlinear least square curve fitting based on experimental pH-potentiometric titration data as described in our previous work [17,[7][8][9][10][11][12][13][14]. Various models with possible compositions of complex species and estimation of its stability constants were proposed to the program.…”

“…These materials have been used as drugs and they are reported to possess a wide range of biological activities against bacteria, fungi and certain types of tumors. In a continuation of our research work oriented towards studying the acid-base and complexation equilibria of many biological oxygen and nitrogen donor drugs with different chelating property [7][8][9][10][11][12][13][14], the present work concerns the equilibrium studies and synthesis of some binary and mixed ligand complexes involving salicylhydroxamic acid, 1,10-phenanthroline.Most interest in the design of binary and ternary complexes as drugs has been centered on the area of antimicrobial and anticancer agents. Hereby, in this paper, we report the results of the equilibrium studies and synthesis of binary and ternary complexes of salicylhydroxamic acid (SHAM) and 1,10-phenanthroline (PHEN) (Scheme 1) as well as investigated their antibacterial and antifungal activities in order to orient future investigations towards the finding of new potent and safe antimicrobial drugs.…”