New Insights into the Efficacy of Aspalathin and Other Related Phytochemicals in Type 2 Diabetes—A Review

In the pursuit of bioactive phytochemicals as a therapeutic strategy to manage metabolic risk factors for type 2 diabetes (T2D), aspalathin, C-glucosyl dihydrochalcone from rooibos (Aspalathus linearis), has received much attention, along with its C-glucosyl flavone derivatives and phlorizin, the apple O-glucosyl dihydrochalcone well-known for its antidiabetic properties. We provided context for dietary exposure by highlighting dietary sources, compound stability during processing, bioavailability and microbial biotransformation. The review covered the role of these compounds in attenuating insulin resistance and enhancing glucose metabolism, alleviating gut dysbiosis and associated oxidative stress and inflammation, and hyperuricemia associated with T2D, focusing largely on the literature of the past 5 years. A key focus of this review was on emerging targets in the management of T2D, as highlighted in the recent literature, including enhancing of the insulin receptor and insulin receptor substrate 1 signaling via protein tyrosine phosphatase inhibition, increasing glycolysis with suppression of gluconeogenesis by sirtuin modulation, and reducing renal glucose reabsorption via sodium-glucose co-transporter 2. We conclude that biotransformation in the gut is most likely responsible for enhancing therapeutic effects observed for the C-glycosyl parent compounds, including aspalathin, and that these compounds and their derivatives have the potential to regulate multiple factors associated with the development and progression of T2D.

Seleno-Functionalization of Quercetin Improves the Non-Covalent Inhibition of Mpro and Its Antiviral Activity in Cells against SARS-CoV-2

The development of new antiviral drugs against SARS-CoV-2 is a valuable long-term strategy to protect the global population from the COVID-19 pandemic complementary to the vaccination. Considering this, the viral main protease (Mpro) is among the most promising molecular targets in light of its importance during the viral replication cycle. The natural flavonoid quercetin 1 has been recently reported to be a potent Mpro inhibitor in vitro, and we explored the effect produced by the introduction of organoselenium functionalities in this scaffold. In particular, we report here a new synthetic method to prepare previously inaccessible C-8 seleno-quercetin derivatives. By screening a small library of flavonols and flavone derivatives, we observed that some compounds inhibit the protease activity in vitro. For the first time, we demonstrate that quercetin (1) and 8-(p-tolylselenyl)quercetin (2d) block SARS-CoV-2 replication in infected cells at non-toxic concentrations, with an IC50 of 192 μM and 8 μM, respectively. Based on docking experiments driven by experimental evidence, we propose a non-covalent mechanism for Mpro inhibition in which a hydrogen bond between the selenium atom and Gln189 residue in the catalytic pocket could explain the higher Mpro activity of 2d and, as a result, its better antiviral profile.

Synthesis, Characterization and Catalytic Activity of Metal Complexes of Flavone based Schiff Bases

A novel Schiff base ligand was achieved from the chemical transformation of flavone derivatives with o-phenylenediamine and its Co(II), Cu(II) and Ni(II) complexes were prepared and structurally elucidated by elemental analysis, magnetic and spectroscopic techniques. The spectroscopic and analytical data confirm square planar geometry of metal complexes and 1:1 metal to ligand stochiometry. The compounds were tested to ensure their ability to act as antimicrobial agents and catalyst in the aerial oxidation of benzaldehyde to benzoic acid. The result shows that the copper complex is excellent at its antimicrobial activity and also catalytic activity.

Microscopy and chemical analyses reveal flavone-based woolly fibres extrude from micron-sized holes in glandular trichomes of Dionysia tapetodes

Background Dionysia tapetodes, a small cushion-forming mountainous evergreen in the Primulaceae, possesses a vast surface-covering of long silky fibres forming the characteristic “woolly” farina. This contrasts with some related Primula which instead form a fine powder. Farina is formed by specialized cellular factories, a type of glandular trichome, but the precise composition of the fibres and how it exits the cell is poorly understood. Here, using a combination of cell biology (electron and light microscopy) and analytical chemical techniques, we present the principal chemical components of the wool and its mechanism of exit from the glandular trichome. Results We show the woolly farina consists of micron-diameter fibres formed from a mixture of flavone and substituted flavone derivatives. This contrasts with the powdery farina, consisting almost entirely of flavone. The woolly farina in D. tapetodes is extruded through specific sites at the surface of the trichome’s glandular head cell, characterised by a small complete gap in the plasma membrane, cell wall and cuticle and forming a tight seal between the fibre and hole. The data is consistent with formation and thread elongation occurring from within the cell. Conclusions Our results suggest the composition of the D. tapetodes farina dictates its formation as wool rather than powder, consistent with a model of thread integrity relying on intermolecular H-bonding. Glandular trichomes produce multiple wool fibres by concentrating and maintaining their extrusion at specific sites at the cell cortex of the head cell. As the wool is extensive across the plant, there may be associated selection pressures attributed to living at high altitudes.

Antioxidant and Cardioprotective Evaluation of Some N-(3-Chloro-2-oxo-4- arylazetidin-1-yl)-2-[(4-oxo-2-aryl-4H-chromen-7-yl)oxy]acetamide Derivatives

A series of N-(3-chloro-2-oxo-4-arylazetidin-1-yl)-2-[(4-oxo-2-aryl-4H-chromen-7-yl)oxy]acetamide derivatives [SLP VI 1(a-d)-2(a-d)] were synthesized from 7-hydroxy flavone derivatives through the intermediate Schiff bases. The synthesized compounds were investigated for in vitro antioxidant property by DPPH radical scavenging assay. The title compounds with good antioxidant potency were further evaluated for possible cardioprotective effect by doxorubicin induced cardiotoxicity. All biochemical changes were normalized after oral administration of the test compounds at the dose of 50 μg/kg. The results showed the significant (p < 0.05) increase in antioxidant enzymes catalase and superoxide dismutase in heart tissue homogenates. These observations enable us to conclude that the synthesized derivatives SLP VI 1b, VI 1c, VI 2b and VI 2d have cardioprotective activity against doxorubicin induced cardiotoxicity. Further, an attempt has been made to perform in silico studies on the synthesized compounds to predict the interaction between test ligands and prospective cardiovascular protein targets using molecular docking tools. The title compounds have good binding affinity with MAPkinase P38 and PKCβ cardiovascular targets.

Effect of Flavone Derivatives on Vincristine and Oxaliplatin Induced Peripheral Neuropathy in Mice

Introduction: Therapy with anticancer drugs like paclitaxel, platinum complexes and vincristine result in severe peripheral neuropathy. Very few treatment options are available to overcome this debilitating side effect. Flavone and its monohydroxy derivatives have been proved to possess anti-nociceptive and anti-inflammatory effects in animal models. Aim: To investigate flavone, 5-hydroxy flavone, 6-hydroxy flavone and 7-hydroxy flavone for their effect on neuropathy induced by vincristine and oxaliplatin in mice. Materials and Methods: In this experimental animal study, neuropathy was induced in mice by multiple doses of vincristine or a single dose of oxaliplatin. The manifestations of mechanical allodynia, cold allodynia and thermal hyperalgesia were measured by von Frey’s hair aesthesiometer, acetone spray test and hot water tail immersion test. The data was subjected to ANOVA followed by Dunnett’s test for multiple comparison and paired t-test at appropriate places. Results: Flavone and monohydroxy flavones significantly reduced the paw withdrawal response scores due to mechanical allodynia and cold allodynia resulting from vincristine or oxaliplatin administration (p<0.05). The tail withdrawal latency due to thermal hyperalgesia was also significantly increased by different flavone derivatives (p<0.05). However, 7-hydroxy flavone was ineffective in oxaliplatin-induced mechanical allodynia and vincristine induced thermal hyperalgesia. Analysis of the results indicated that the manifestations of neuropathy induced by vincristine or oxaliplatin were amenable to treatment with flavone derivatives in the following order; cold allodynia>thermal hyperalgesia>mechanical allodynia. Opioid mediated antinociceptive effect, interaction with cation channels and anti-inflammatory effect of the investigated flavones may be suggested as possible mechanisms for their beneficial effects in neuropathy due to chemotherapeutic agents. Conclusion: Various neuropathic manifestations induced by vincristine and oxaliplatin were effectively attenuated by flavone and monohydroxy flavones.

Synthesis, Molecular Docking and Biological Evaluation of Novel Flavone Derivatives as Potential Anticancer Agents Targeting Akt

Background: Flavonoids are naturally occurring compounds with versatile healthpromoting effects against various diseases. Objective: This aim of this paper is to synthesize and evaluate the biological activity of novel flavone derivatives against cancer. Methods: A new series of 2-hydroxy-α,β-unsaturated ketones 2a-h, was synthesized via the reaction of N-substituted-indole-3-carboxaldehyde 1a-h with 2-hydroxy acetophenone in the presence of piperidine. The oxidative cyclization of 2a-h using hydrogen peroxide/KOH and/or dimethyl sulfoxide/I2 produced the corresponding 2-(N-substituted-1H-indol-3-yl)-3-hydroxy-4H-chromen- 4-ones 3a-h and 2-(N-substituted-1H-indol-3-yl)-4H-chromen-4-ones 4a-h, respectively. Antiproliferative activities for synthesized series were investigated against HCT-116 colon and MCF- 7 breast cancer cell lines. Molecular downstream effects were evaluated using RT-PCR. Moreover, molecular docking was carried out to pinpoint the binding mode of the most active compounds into the active site of Akt enzyme (PDB ID: 3QKK). Results: All compounds exhibited an anti-proliferative activity range of 52-97% and 67.2-99% against HCT-116 and MCF-7, respectively. Compounds 3b, 3h, 3g and 4h had a minimal inhibitory effect on normal BJ1 cells indicating their safety profile. Compounds 3b and 4h, in particular, exhibited the most potent antiproliferative activity against HCT116 and MCF7, meanwhile compounds 3g, 3h and 4g showed potent to moderate activity. Compound 3b had IC50 of 78.3 μM and 53.9 μM against HCT-116 and MCF-7 respectively with comparable IC50 for doxorubicin of 65.1 μM and 45.02 μM. Compound 3b exhibited significant down-regulation for Akt and significant up-regulation of CAS9 and CDKN1genes in all tested cell lines. Conclusion: The synthesized flavone derivatives and particularly compound 3b exhibited promising anticancer activity through Akt inhibition.

Screening of small molecules using the inhibition of oligomer formation in α-synuclein aggregation as a selection parameter

The aggregation of α-synuclein is a central event in Parkinsons’s disease and related synucleinopathies. Since pharmacologically targeting this process, however, has not yet resulted in approved disease-modifying treatments, there is an unmet need of developing novel methods of drug discovery. In this context, the use of chemical kinetics has recently enabled accurate quantifications of the microscopic steps leading to the proliferation of protein misfolded oligomers. As these species are highly neurotoxic, effective therapeutic strategies may be aimed at reducing their numbers. Here, we exploit this quantitative approach to develop a screening strategy that uses the reactive flux toward α-synuclein oligomers as a selection parameter. Using this approach, we evaluate the efficacy of a library of flavone derivatives, identifying apigenin as a compound that simultaneously delays and reduces the formation of α-synuclein oligomers. These results demonstrate a compound selection strategy based on the inhibition of the formation of α-synuclein oligomers, which may be key in identifying small molecules in drug discovery pipelines for diseases associated with α-synuclein aggregation.

Formation of flavone-based wooly fibres by glandular trichomes of Dionysia tapetodes

Dionysia tapetodes, a small cushion-forming mountainous evergreen in the Primulaceae, possesses a vast surface-covering of long silky fibres forming the characteristic “wooly” farina. This contrasts with some related Primula which instead possess a powdery farina. Using a combination of cell biology and analytical chemical techniques, we provide a detailed insight of wooly farina formation by glandular trichomes that produce a mixture of flavone and substituted flavone derivatives, including hydroxyflavones. Conversely, our analysis show that the powdery form consist almost entirely of flavone. The wooly farina in D. tapetodes is extruded through specific sites at the surface of the glandular head cell, characterised by a small complete gap in the plasma membrane, cell wall and cuticle. The data is consistent with formation and thread elongation occurring from within the cell. The putative mechanism of wool thread formation and its stability is discussed.