Antioxidant properties of hydroxycinnamic acids: a review of structure- activity relationships

Hydroxycinnamic acids (HCAs) are important phytochemicals possessing significant biological properties. Several investigators have studied in vitro antioxidant activity of HCAs in detail. In this review, we have gathered the studies focused on the structure-activity relationships (SARs) of these compounds that have used medicinal chemistry to generate more potent antioxidant molecules. Most of the reports indicated that the presence of an unsaturated bond on the side chain of HCAs is vital to their activity. The structural features that were reported to be of importance to the antioxidant activity were categorized as follows: modifications of the aromatic ring, which include alterations in the number and position of hydroxy groups and insertion of electron donating or withdrawing moieties as well as modifications of the carboxylic function that include esterification and amidation process. Furthermore, reports that have addressed the influence of physicochemical properties including redox potential, lipid solubility and dissociation constant on the antioxidant activity were also summarized. Finally, the pro-oxidant effect of HCAs in some test systems was addressed. Most of the investigations concluded that the presence of ortho-dihydroxy phenyl group (catechol moiety) is of significant importance to the antioxidant activity, while, the presence of three hydroxy groups does not necessarily improve the activity. Optimization of the structure of molecular leads is an important task of modern medicinal chemistry and its accomplishment relies on the careful assessment of SARs. SAR studies on HCAs can identify the most successful antioxidants that could be useful for management of oxidative stress-related diseases

Dabco containing acidic poly(ionic liquid): An efficient catalyst for the one-pot Preparation of 2,3-dihydroquinazoline-4(1H)-ones

1,4-Diazabicyclo[2.2.2]octane (DABCO) containing acidic poly(ionic liquid) (DAIL) has been prepared via condensation of 1,4-dichloro butane and DABCO, as an efficient acidic catalyst and has been applied in the one-pot preparation of 2,3-dihydroquinazolin-4(1H)-one derivatives. This catalyst has been characterized by FT-IR and TGA. According to the obtained results including time, yield and recyclability, DAIL could be considered as an efficient catalyst for organic transformations

Hypoglycemic activity of curcumin synthetic analogues in alloxan-induced diabetic rats.

The currently available therapies for type 2 diabetes have been unable to achieve normoglycemic status in the majority of patients. The reason may be attributed to the limitations of the drug itself or its side effects. In an effort to develop potent and safe oral antidiabetic agents, we evaluated the in vitro and in vivo hypoglycemic effects of 10 synthetic polyphenolic curcumin analogues on alloxan-induced male diabetic albino rats. In vitro studies showed 7-bis(3,4-dimethoxyphenyl)hepta-1,6-diene-3,5-dione (4) to be the most potential hypoglycemic agent followed by 1,5-bis(4-hydroxy-3-methoxyphenyl)penta-1,4-dien-3-one (10). Structure activity relationship (SAR) of the tested compounds was elucidated and the results were interpreted in terms of in vitro hypoglycemic activities. Furthermore, oral glucose tolerance test (OGTT) with compounds 4, 10 and reference hypoglycemic drug glipizide showed that compound 4 and glipizide had relatively similar effects on the reduction of blood glucose levels within 2 h. Thus, compound 4 might be regarded as a potential hypoglycemic agent being able to reduce glucose concentration both in vitro and in vivo

More than smell - COVID-19 is associated with severe impairment of smell, taste, and chemesthesis

Recent anecdotal and scientific reports have provided evidence of a link between COVID-19 and chemosensory impairments, such as anosmia. However, these reports have downplayed or failed to distinguish potential effects on taste, ignored chemesthesis, and generally lacked quantitative measurements. Here, we report the development, implementation, and initial results of a multilingual, international questionnaire to assess self-reported quantity and quality of perception in 3 distinct chemosensory modalities (smell, taste, and chemesthesis) before and during COVID-19. In the first 11 days after questionnaire launch, 4039 participants (2913 women, 1118 men, and 8 others, aged 19-79) reported a COVID-19 diagnosis either via laboratory tests or clinical assessment. Importantly, smell, taste, and chemesthetic function were each significantly reduced compared to their status before the disease. Difference scores (maximum possible change ±100) revealed a mean reduction of smell (-79.7 ± 28.7, mean ± standard deviation), taste (-69.0 ± 32.6), and chemesthetic (-37.3 ± 36.2) function during COVID-19. Qualitative changes in olfactory ability (parosmia and phantosmia) were relatively rare and correlated with smell loss. Importantly, perceived nasal obstruction did not account for smell loss. Furthermore, chemosensory impairments were similar between participants in the laboratory test and clinical assessment groups. These results show that COVID-19-associated chemosensory impairment is not limited to smell but also affects taste and chemesthesis. The multimodal impact of COVID-19 and the lack of perceived nasal obstruction suggest that severe acute respiratory syndrome coronavirus strain 2 (SARS-CoV-2) infection may disrupt sensory-neural mechanisms. © 2020 The Author(s) 2020. Published by Oxford University Press. All rights reserved

Effect of organic co-solvents in the evaluation of the hydroxyl radical scavenging activity by the 2-deoxyribose degradation assay: The paradigmatic case of α-lipoic acid

The 2-deoxyribose degradation assay (2-DR assay) is an in vitro method broadly used for evaluating the scavenging activity against the hydroxyl radical (HO). One of the major drawbacks of the assay, however, is that only water soluble compounds can be tested for their radical-scavenging activity. Lipoic acid (LA) is an excellent scavenger of HO but it exhibits a low solubility in the aqueous milieu of the 2-DR assay and a high tendency to polymerize under a variety of conditions. We used LA as a paradigmatic substrate to evaluate the effect of several organic co-solvents in increasing its solubility. Most of these solvents, however, demonstrated to be potent scavengers of HO making their use in the 2-DR assay improper. On the other hand, acetonitrile showed a remarkably low reactivity toward HO (rate constant ~8.7×106M-1s-1) which allowed us to use it as a co-solvent in the preparation of stock solutions of LA ~5mM. We therefore evaluated the radical-scavenging activity of LA by the 2-DR assay in a relatively large range of concentrations, 1-200μM. We found that the rate constant for LA+HO is diffusion-controlled (~1×1010M-1s-1 in water at 25°C) and uninfluenced by the presence of small quantities of acetonitrile. Therefore, the use of acetonitrile in the 2-DR assay does not interfere with the test and may increase the solubility of the radical scavengers

Inhibition of Alzheimer's BACE-1 by 2,6-dialkyl-4-chromon-3-yl-1,4-dihydropyridine-3,5-dicarboxylates

Alzheimer’s disease is the most common cause of dementia in the elderly, and no disease-modifying therapy is yet available for this devastating pathology. Deposition of different physicochemical forms of amyloid-β peptides is a critical phase in the pathogenesis of Alzheimer’s disease. β-Site amyloid precursor protein cleaving enzyme 1 (BACE-1) is a major enzyme responsible for amyloid-β production; therefore, inhibition of this enzyme represents a promising approach for the discovery of amyloid-β-lowering agents. In this study, a series of novel 2,6-dialkyl-4-chromon-3-yl-1,4-dihydropyridine-3,5-dicarboxylates (14–23) were synthesized and assessed as BACE-1 inhibitors using the Förster resonance energy transfer-based enzyme assay. Synthesized dihydropyridines exhibited weak-to-relatively-good BACE-1 inhibitory activities. Enzyme inhibitory activities ranged from 6.84 ± 6.62 (23) to 51.32 ± 1.04 (14) percent enzyme inhibitions at the concentration of 10 μM. The structure–activity relationship study showed that the presence of 4-[7-(ethanoyloxy)-4-oxo-4H-chromen-3-yl] moiety at C4 position of dihydropyridine ring (14, 16 and 18) confers higher activity compared with other substitutions at this position. Docking simulation predicted a key H-bond interaction between Asp32 residue and dihydropyridine NH group. Moreover, all docked dihydropyridines made good hydrophobic contacts with S1 and S2 subpockets of BACE-1. A good correlation between estimated binding affinities (pKi) and experimental BACE-1 inhibitory activities at 10 μM was obtained (R 2 = 0.639). The findings of this study suggested that 2,6-dialkyl-4-chromon-3-yl-1,4-dihydropyridine-3,5-dicarboxylates could be promising scaffolds for the discovery of novel BACE-1 inhibitors for management of Alzheimer’s disease