Eco-Friendly Synthesis of an Oxovanadium(IV)-bis(abietate) Complex with Antimicrobial Action

Abstract

The search for less expensive and viable products is always one of the challenges for research development. Commonly, the synthesis of coordination compounds involves expensive ligands, through expensive and low-yield routes, in addition to generating toxic and unusable residues. In this work, the organic ligand used is derived from the resin of a reforestation tree, Pinus elliottii var. elliottii. The synthesis method used Pinus resin and an aqueous solution of vanadium(III) chloride at a temperature of 80 °C. The procedure does not involve organic solvents and does not generate toxic residues, thus imparting the complex formation reaction a green chemistry character. The synthesis resulted in an unprecedented oxovanadium(IV)-bis(abietate) complex, which was characterized by mass spectrometry (MS), chemical analysis (CHN), vibrational (FTIR) and electronic spectra (VISIBLE), X-ray diffraction (XRD), and thermal analysis (TG/DTA). Colorimetric studies were performed according to the CIELAB color space. The structural formula found, consisted of a complex containing two abietate ligands, [VO(C20H29O2)2]. The VO(IV)-bis(abietate) complex was applied against microorganisms and showed promising results in antibacterial and antifungal activity. The best result of inhibitory action was against the strains of Gram-positive bacteria S. aureus and L. monocytogenes, with minimum inhibitory concentration (MIC) values of 62.5 and 125 μmol L−1, respectively. For Gram-negative strains the results were 500 μmol L−1 for E. coli; and 1000 μmol L−1 for Salmonella enterica Typhimurium. Antifungal activity was performed against Candida albicans, where the MIC was 15.62 μmol L−1, and for C. tropicalis it was 62.5 μmol L−1. According to the MFC analysis, the complex presented, in addition to the fungistatic action, a fungicidal action, as there was no growth of fungi on the plates tested. The results found for the tests demonstrate that the VO(IV)-bis(abietate) complex has great potential as an antimicrobial and mainly antifungal agent. In this way, the pigmented ink with antimicrobial activity could be used in environments with a potential risk of contamination, preventing the spread of microorganisms harmful to health.

Green Synthesis of Na abietate Obtained from the Salification of Pinus elliottii Resin with Promising Antimicrobial Action

“…The recrystallized salt was characterized and applied as an antimicrobial agent against fungi and bacteria. The salt has been used as a precursor ligand in the preparation of coordination compounds with transition metals [ 9 , 10 ]. The resulting compounds have different colors depending on the metal used, as well as antimicrobial properties when used as pigments in commercial white paint.…”

“…No matching files were found in the Inorganic Crystal Structure Database (ICSD), International Centre for Diffraction Data (ICDD), and Crystallography Open Database (COD). The initial analysis of the X-ray diffraction profile showed that Na abietate has a structure characteristic of a non-crystalline molecular substance [ 9 , 10 ], with broad diffraction peaks and low intensity. The degree of crystallinity was found to be around 52%, with a crystallite size of 21.9 Å.…”

“…Additionally, the compound was also tested against the Candida albicans (ATCC 10231) fungus. The methodology used was that of the Clinical and Laboratory Standards Institute (CLSI) [ 25 , 26 ], adapted from the work of [ 10 ].…”

“…The culture medium used for the bacteria was Mueller–Hinton (MH) broth, and that for the fungus was Sabourand dextrose broth. A Na-abietate solution (2 mmol L −1 ) was added to well “A” and diluted up to well “H” as described in [ 10 ]. Then, the microorganism inoculum was added.…”

“…Abietic acid (C19H29COOH) is a diterpenoid that belongs to the terpene class and is found mainly in pine trees. Some works have already reported its antibacterial and antifungal efficacy; thus, abietic acid and its derivatives have an important potential as an alternative for new drugs, to be applied against antimicrobial resistance [ 5 , 6 , 7 , 8 , 9 , 10 ].…”