Background: Coumarin derivatives as dihydrocoumarins have been reported to have multiple biological activities, such as antioxidant and anti-inflammatory properties. Apocynin (APO), which is a substituted-methoxy-catechol, is the most commonly used inhibitor of the multienzymatic complex NADPH-oxidase. Objective: To increase the potency of APO as an NADPH oxidase inhibitor and its antioxidant and anti-inflammatory activities, we synthesized a compound by combining the structural features of a dihydrocoumarin and APO. Method: The dihydrocoumarin-apocynin derivative (HCA) was synthesized and evaluated in antioxidant and cell-based bioassays and compared with APO. Results: We found that HCA (IC50 = 10 μM) acted as an inhibitor of NADPH oxidase (ex vivo assays) and was more potent than APO (EC50 > 10 µM). The inhibitory effect on NADPH oxidase was not related to simple radical scavenger activity. HCA was also a more effective radical scavenger than APO, as verified in the DPPH (EC50 = 50.3 versus EC50 > 100 µM), triene degradation (slope AUC/concentration 759 ± 100 versus 101 ± 15) and FRAP (slope 0.159 versus 0.015) assays. The tested compound demonstrated a similar activity as an inhibitor of the oxidative damage provoked by peroxyl radicals in erythrocyte membranes. Conclusion: HCA showed superior capacity as inhibitor of NADPH oxidase and antioxidant activity. These findings show that HCA could be an improved substitute for APO and deserves further in vivo anti-inflammatory studies.

Human serum albumin (HSA) is a target for reactive oxygen species (ROS), and alterations of its physiological functions caused by oxidation is a current issue. In this work, the amino-acid residues Trp-214 and Lys-199, which are located at site I of HSA, were experimentally and computationally oxidized, and the effect on the binding constant with phenylbutazone was measured. HSA was submitted to two mild oxidizing reagents, taurine monochloramine (Tau-NHCl) and taurine dibromamine (Tau-NBr₂). The oxidation of Trp-214 provoked spectroscopic alterations in the protein which were consistent with the formation of N′-formylkynurenine. It was found that the oxidation of HSA by Tau-NBr₂, but not by Tau-NHCl, provoked a significant increase in the association constant with phenylbutazone. The alterations of Trp-214 and Lys-199 were modeled and simulated by changing these residues using the putative oxidation products. Based on the Amber score function, the interaction energy was measured, and it showed that, while native HSA presented an interaction energy of −21.3 kJ/mol, HSA with Trp-214 altered to N′-formylkynurenine resulted in an energy of −28.4 kJ/mol, and HSA with Lys-199 altered to its carbonylated form resulted in an energy of −33.9 kJ/mol. In summary, these experimental and theoretical findings show that oxidative alterations of amino-acid residues at site I of HSA affect its binding efficacy.

Taurine bromamine (Tau-NHBr) is produced by the reaction between hypobromous acid (HOBr) and the amino acid taurine. There are increasing number of applications of Tau-NHBr as an anti-inflammatory and microbicidal drug for topical usage. Here, we performed a comprehensive study of the chemical reactivity of Tau-NHBr with endogenous and non-endogenous compounds. Tau-NHBr reactivity was compared with HOBr, hypochlorous acid (HOCl) and taurine chloramine (Tau-NHCl). The second-order rate constants (k2) for the reactions between Tau-NHBr and tryptophan (7.7 × 102 M−1s−1), melatonin (7.3 × 103 M−1s−1), serotonin (2.9 × 103 M−1s−1), dansylglycine (9.5 × 101 M−1s−1), tetramethylbenzidine (6.4 × 102 M−1s−1) and H2O2 (3.9 × M−1s−1) were obtained. Tau-NHBr demonstrated the following selectivity regarding its reactivity with free amino acids: tryptophan > cysteine ~ methionine > tyrosine. The reactivity of Tau-NHBr was strongly affected by the pH of the medium (for instance with dansylglycine: pH 5.0, 1.1 × 104 M−1s−1, pH 7.0, 9.5 × 10 M−1s−1 and pH 9.0, 1.7 × 10 M−1s−1), a property that is related to the formation of the dibromamine form at acidic pH (Tau-NBr2). The formation of singlet oxygen was observed in the reaction between Tau-NHBr and H2O2. Tau-NHBr was also able to react with linoleic acid, but with low efficiency compared with HOBr and HOCl. Compared with HOBr, Tau-NHBr was not able to react with nucleosides. In conclusion, the following reactivity sequence was established: HOBr > HOCl > Tau-NHBr > Tau-NHCl. These findings can be very helpful for researchers interested in biological applications of taurine haloamines.

In this study, the chemical composition, total phenolic content, and antioxidant activity (DPPH, ORAC and FRAP assays) of A. subrufescens and P. ostreatus , cultivated with handmade and commercials supplements, were compared. Additionally, the compounds ergosterol, saccharopine, and hexitol were identified in A. subrufescens by HPLC‐MS/MS. The antioxidant compound p ‐coumaric acid and dihexoses were found in both mushroom species. A. subrufescens presented higher total phenolic content (73.8±0.6 mg GAE 100 g^‐1) and antioxidant activity than P. ostreatus (16.6±0.5 mg GAE 100 g^‐1). The handmade supplement based on the waste of noble grains presented statistically similar phenolic content to the mushrooms cultivated with commercial ones Spawn Mate II SE (86.1±1.4 and 92.9±0.3 mg GAE 100 g^‐1, respectively). Therefore, the results support the use of handmade supplements base on agro‐wastes as a viable alternative to the use of high‐cost commercial ones.