Bioactivity Focus of α-Cyano-4-hydroxycinnamic acid (CHCA) Leads to Effective Multifunctional Aldose Reductase Inhibitors

Rubus urticifolius Compounds with Antioxidant Activity, and Inhibition Potential against Tyrosinase, Melanin, Hyaluronidase, Elastase, and Collagenase

In our study, using chromatographic techniques, we isolated three bioactive compounds, which were structurally elucidated as (E)-2-(3-(3,4-dimethoxyphenyl)acrylamido)-N-methylbenzamide (1), 4-Hydroxyquinoline-2-carboxylic acid (2), and (E)-2-Cyano-3-(4-hydroxyphenyl)acrylic acid (3), using spectroscopic methods. The anti-melanogenic, anti-inflammatory, antioxidant, and anti-aging properties were evaluated in vitro by measuring the activity of pharmacological targets including tyrosinase, melanin, NF-κB, hyaluronidase, elastase, collagenase, and Nrf2. Our results show that compound 1 is the most active with IC50 values of 14.19 μM (tyrosinase inhibition), 22.24 μM (melanin inhibition), 9.82-12.72 μM (NF-κB inhibition), 79.71 μM (hyaluronidase inhibition), 80.13 μM (elastase inhibition), 76.59 μM (collagenase inhibition), and 116-385 nM (Nrf2 activation) in the THP-1, HEK001, WS1, and HMCB cells. These findings underscore the promising profiles of the aqueous extract of R. urticifolius at safe cytotoxic concentrations. Additionally, we report, for the first time, the isolation and characterisation of these nitrogenous compounds in the R. urticifolius species. Finally, compound 1, isolated from R. urticifolius, is a promising candidate for the development of more effective and safer compounds for diseases related to skin pigmentation, protection against inflammation, and oxidative stress.

Length and rigidity of the spacer impact on aldose reductase inhibition of the 5F-like ARIs in a dual-occupied mode

The primary objective of this study was to investigate the structure-activity relationship of a new series of 5F-like Aldose Reductase Inhibitors (ARIs) using in silico docking method. In this perspective, 6 novel ARIs have been designed and synthesized. Evaluation of the inhibition of these compounds to ALR2 was carried on with epalrestat and 5F as the references. It was found that the spacer of 5F-like ARIs has a great influence on their inhibitory activity. Rigid spacer with length equal to 3 ∼ 4 carbon alkyl chain brings about better inhibitory activity. Among them, compound 4b was verified as the most active ARIs, where its IC₅₀ value was 16.8 ± 1.3 nM. Furthermore, in silico docking studies using AutoDock 4.2 as well as molecular simulation using GROMACS 2022.1 showed that 5F-like ARIs adopt a dual-occupation mode. The interaction energy (-25 to -74 kcal/mol), as well as MM-GBSA binding free energy (-37 to -65 kcal/mol) was positively correlated with their ALR2 inhibition constant (2000 to 16.8 nM). Docking interaction explained well the structure-activity relationship. A pharmacophore model has been set up for 5F-like ARIs thereafter. This model indicates that as an effective ARI, the entity should have four characteristics: an aromatic center, two hydrogen bond donors, and one hydrogen bond acceptor. By the way, all the 5F-like ARIs reported here are good to mild antioxidant with EC₅₀ value between 13.6 ± 1.2 and 71.1 ± 3.2 μM. All our data direct the further development of more optimal ARIs for the treatment of diabetic complication in the future.

Repurposing the aldose reductase inhibitor and diabetic neuropathy drug epalrestat for the congenital disorder of glycosylation PMM2-CDG

Phosphomannomutase 2 deficiency, or PMM2-CDG, is the most common congenital disorder of glycosylation and affects over 1000 patients globally. There are no approved drugs that treat the symptoms or root cause of PMM2-CDG. To identify clinically actionable compounds that boost human PMM2 enzyme function, we performed a multispecies drug repurposing screen using a novel worm model of PMM2-CDG, followed by PMM2 enzyme functional studies in PMM2-CDG patient fibroblasts. Drug repurposing candidates from this study, and drug repurposing candidates from a previously published study using yeast models of PMM2-CDG, were tested for their effect on human PMM2 enzyme activity in PMM2-CDG fibroblasts. Of the 20 repurposing candidates discovered in the worm-based phenotypic screen, 12 were plant-based polyphenols. Insights from structure–activity relationships revealed epalrestat, the only antidiabetic aldose reductase inhibitor approved for use in humans, as a first-in-class PMM2 enzyme activator. Epalrestat increased PMM2 enzymatic activity in four PMM2-CDG patient fibroblast lines with genotypes R141H/F119L, R141H/E139K, R141H/N216I and R141H/F183S. PMM2 enzyme activity gains ranged from 30% to 400% over baseline, depending on genotype. Pharmacological inhibition of aldose reductase by epalrestat may shunt glucose from the polyol pathway to glucose-1,6-bisphosphate, which is an endogenous stabilizer and coactivator of PMM2 homodimerization. Epalrestat is a safe, oral and brain penetrant drug that was approved 27 years ago in Japan to treat diabetic neuropathy in geriatric populations. We demonstrate that epalrestat is the first small molecule activator of PMM2 enzyme activity with the potential to treat peripheral neuropathy and correct the underlying enzyme deficiency in a majority of pediatric and adult PMM2-CDG patients.

Editor's choice: Drug repurposing screens using worm and patient fibroblast models of PMM2-CDG led to the discovery of epalrestat, the first activator of PMM2 that targets the root cause of disease.

Yeast Models of Phosphomannomutase 2 Deficiency, a Congenital Disorder of Glycosylation

Phosphomannomutase 2 Deficiency (PMM2-CDG) is the most common monogenic congenital disorder of glycosylation (CDG) affecting at least 800 patients globally. PMM2 orthologs are present in model organisms, including the budding yeast Saccharomyces cerevisiae gene SEC53. Here we describe conserved genotype-phenotype relationships across yeast and human patients between five PMM2 loss-of-function missense mutations and their orthologous SEC53 mutations. These alleles range in severity from folding defective (hypomorph) to dimerization defective (severe hypomorph) to catalytic dead (null). We included the first and second most common missense mutations – R141H, F119L respectively– and the most common compound heterozygote genotype – PMM2^R141H/F119L – observed in PMM2-CDG patients. Each mutation described is expressed in haploid as well as homozygous and heterozygous diploid yeast cells at varying protein expression levels as either SEC53 protein variants or PMM2 protein variants. We developed a 384-well-plate, growth-based assay for use in a screen of the 2,560-compound Microsource Spectrum library of approved drugs, experimental drugs, tool compounds and natural products. We identified three compounds that suppress growth defects of SEC53 variants, F126L and V238M, based on the biochemical defect of the allele, protein abundance or ploidy. The rare PMM2 E139K protein variant is fully functional in yeast cells, suggesting that its pathogenicity in humans is due to the underlying DNA mutation that results in skipping of exon 5 and a nonfunctional truncated protein. Together, these results demonstrate that yeast models can be used to characterize known and novel PMM2 patient alleles in quantitative growth and enzymatic activity assays, and used as patient avatars for PMM2-CDG drug screens yielding compounds that could be rapidly cross-validated in zebrafish, rodent and human organoid models.

Conformational Differentiation of α-Cyanohydroxycinnamic Acid Isomers: A Raman Spectroscopic Study

Two α-cyanohydroxycinnamic acid positional isomers, α-cyano-4-hydroxycinnamic acid (CHCA4) and α-cyano-3-hydroxycinnamic acid (CHCA3), were characterized using Raman spectroscopy. We analyzed the implications of the collected Raman spectral shifts, and verified them through other spectroscopic techniques, to arrive at plausible three dimensional structures of CHCA3 and CHCA4. The positions of these groups were mapped by systematically analyzing the orientation and type of interactions functional groups make in each CHCA isomer. We determined whether or not the carboxylic moieties are forming dimeric links and ascertained the existence of ring-ring π-stacking interactions. We also assessed the nature of the hydrogen bonding between -CN and -OH groups. The results were then taken together to model plausible three dimensional structures for each compound. The data revealed a structure for CHCA4 that matches the published x-ray crystallographic structure. We then applied the same spectral analysis to CHCA3 to reveal its plausible three dimensional structure. The structural details revealed may account for the functional properties of the two α-cyanohydroxycinnamic acid positional isomers.