Free Radical Scavenging Activity of Five Benzoic Acid Derivatives: A Theoretical M06-2X Study

The meta hybrid M06-2X functional combined with the 6-311++G(d,p) basis set are used to investigate the antioxidant activity of five benzoic acid derivatives naturally occurring in several plant food: gallic acid, para-hydroxybenzoic acid, protocatechuic acid, syringic acid and vanillic acid. To assess the antioxidant properties of these compounds, three mechanisms of free radicals scavenging are considered, namely the hydrogen atom transfer (HAT), stepwise electron transfer proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) models. The effect of polar environments on the antioxidant power of these compounds is mimicked in water and methanol using the IEF-PCM solvation method. Our findings suggest that HAT is the preferred mechanistic pathway in gas phase, while SPLET is favoured in polar mediums. Protocatechuic and gallic acids are the most active in gas and polar solutions respectively, whereas PHBA is the least active in all the environments considered. The O-H group in para position of the carboxylic group (O3-H for GA and O2-H for the rest) is confirmed to be the most reactive site in gas phase, while in solution it is either of the O1-H site (for PHBA, PCA, SA and VA) or O4-H groups (for GA). The “HOMO-rule” of free radical scavenging ability does not seem to account properly for the antioxidant properties of this set of chemicals.

Green process in benzoic acid derivatives synthesis/ Processo verde em síntese de derivados de ácido benzoico

Employing a methodology that meets various requirements of "Green Chemistry", the substances quinazolinyl benzoate (P1) and N-4-imidazolphenylbenzamide (P2) were synthesized through benzoylation reactions by the classical Schotten-Baumann method, in an aqueous environment and room temperature. The products were purified by recrystallization and characterized by melting point, thin layer chromatography (TLC) and infrared spectroscopy. Qualitative antioxidant activities with the diphenylpicrylhydrazyl radical (DPPH) and toxic potential against Artemia salina Leach larvae were also investigated. Only P2 indicated significant antioxidant activity. According to the medium lethal concentration values (LC50), used for P1 and P2, the toxic potential revealed, respectively, to be moderate for P1 and weak for P2. Despite the low yield obtained for the synthesis of P1, the characterizations indicate success in the preparations, within a synthetic strategy of low cost, efficient and ecologically sustainable.

Synthesis of ruthenium catalysts with chiral arene ligand derived from natural camphor

Ruthenium complex with chiral arene ligand [(camphor-arene)RuCl2]2 was synthesized by the reaction of RuCl3∙nH2O with the chiral diene, which was obtained from natural camphor in 3 steps. This complex catalyzed asymmetric hydrogenation of acetophenone (64-85% ee), but decomposed in the catalytic reactions involving C-H activation of 2-phenyl-pyridine or benzoic acid derivatives.

Synthesis, In Silico and In Vitro Evaluation of Antimicrobial and Toxicity Features of New 4-[(4-Chlorophenyl)sulfonyl]benzoic Acid Derivatives

The multi-step synthesis, physico-chemical characterization, and biological activity of novel valine-derived compounds, i.e., N-acyl-α-amino acids, 1,3-oxazol-5(4H)-ones, N-acyl-α-amino ketones, and 1,3-oxazoles derivatives, bearing a 4-[(4-chlorophenyl)sulfonyl]phenyl moiety are reported here. The structures of the newly synthesized compounds were confirmed by spectral (UV-Vis, FT-IR, MS, 1H- and 13C-NMR) data and elemental analysis results, and their purity was determined by RP-HPLC. The new compounds were assessed for their antimicrobial activity and toxicity to aquatic crustacean Daphnia magna. Also, in silico studies regarding their potential mechanism of action and toxicity were performed. The antimicrobial evaluation revealed that the 2-{4-[(4-chlorophenyl)sulfonyl]benzamido}-3-methylbutanoic acid and the corresponding 1,3-oxazol-5(4H)-one exhibited antimicrobial activity against Gram-positive bacterial strains and the new 1,3-oxazole containing a phenyl group at 5-position against the C. albicans strain.

Profiling of 2-Acetyl-1-Pyrroline and Other Volatile Compounds in Raw and Cooked Rice of Traditional and Improved Varieties of India

Herein, optimized headspace solid phase microextraction with gas chromatography–tandem mass spectrometry (HS-SPME-GC-MS/MS) was used to estimate the 2-acetyl-1-pyrroline (2-AP) in raw and cooked rice samples of ten different traditional and improved varieties. Furthermore, HS-SPME-GC-MS-based volatile profiling was subjected to untargeted analyses to identify major odorants in raw and cooked rice samples, and to understand chemical proximities among volatile profiles. Results showed that 2-AP content was remarkably increased in cooked rice compared to raw. Among the varieties studied, Pusa-1652 (Improved Kala Namak) and Kala Namak-2 were superior in the 2-AP content than Basmati varieties. Additionally, Govind Bhog, Kala Jeera and Jeera-32 had 2-AP content equivalent to or superior to Basmati rice varieties. Altogether, 18 and 22 volatiles were identified in the raw and cooked rice samples studied, respectively. Of these, ethyl butyrate, ethyl 3-methylbutanoate, 2-undecanone, ethyl benzoate, ethyl benzeneacetate, 2-methylnaphthalene, and 1-methylnaphthalene were characteristically detected in the cooked rice. The high amount of 2-ethyl-1-hexanol was uniquely found in raw rice samples, which can be a marker compound for freshly milled rice. Along with 2-AP, butanoic acid and benzoic acid derivatives, phenylethyl alcohol, ethyl 3-hydroxybutyrate, and indole may be responsible for the overall perceived characteristic Basmati-like aroma in cooked rice.

Antifungal Activity of Chemical Constituents from Piper pesaresanum C. DC. and Derivatives against Phytopathogen Fungi of Cocoa

In this study, the antifungal potential of chemical constituents from Piper pesaresanum and some synthesized derivatives was determined against three phytopathogenic fungi associated with the cocoa crop. The methodology included the phytochemical study on the aerial part of P. pesaresanum, the synthesis of some derivatives and the evaluation of the antifungal activity against the fungi Moniliophthora roreri, Fusarium solani and Phytophthora sp. The chemical study allowed the isolation of three benzoic acid derivatives (1–3), one dihydrochalcone (4) and a mixture of sterols (5–7). Seven derivatives (8–14) were synthesized from the main constituents, of which compounds 9, 10, 12 and 14 are reported for the first time. Benzoic acid derivatives showed strong antifungal activity against M. roreri, of which 11 (3.0 ± 0.8 µM) was the most active compound with an IC50 lower compared with positive control Mancozeb® (4.9 ± 0.4 µM). Dihydrochalcones and acid derivatives were active against F. solani and Phytophthora sp., of which 3 (32.5 ± 3.3 µM) and 4 (26.7 ± 5.3 µM) were the most active compounds, respectively. The preliminary structure–activity relationship allowed us to establish that prenylated chains and the carboxyl group are important in the antifungal activity of benzoic acid derivatives. Likewise, a positive influence of the carbonyl group on the antifungal activity for dihydrochalcones was deduced.