Synthesis, in vitro, and in silico studies of fisetin and quercetin and their metal complexes as inhibitors of α-glucosidase and thrombin

Effect of polysaccharides on the inhibition and binding ability of hesperetin-copper(II) complex on α-glucosidase

The study aimed to investigate the inhibitory effect of hesperetin-copper (II) [Hsp-Cu(II)] on α-glucosidase in the presence of polysaccharides (xylan, β-glucan, low-, medium- and high-viscosity chitosan). The results showed that all the polysaccharides significantly reduced the inhibitory activity of α-glucosidase by Hsp-Cu(II), and the reduction effect of high-viscosity chitosan was the most significant. The polysaccharides significantly decreased the binding constant of Hsp-Cu(II)α-glucosidase, changed the binding sites of Hsp-Cu(II) to α-glucosidase and reduced the hydrogen bonds of Hsp-Cu(II) bound with α-glucosidase. Circular dichroism showed that the reduction of α-helix content in α-glucosidase caused by Hsp-Cu(II) was raised from 27.2 % to 29.5 %, 31.3 % and 32.7 % in the presence of xylan, β-glucan and high-viscosity chitosan, respectively, suggesting that the polysaccharides could restore the secondary structure of α-glucosidase. Fourier transforms infrared spectra showed that xylan and β-glucan formed hydrogen bonds with Hsp-Cu(II). The mechanism of the decreasing effect might be that the polysaccharides with the low viscosity compete with α-glucosidase to bind Hsp-Cu(II) through hydrogen bonds, restoring the catalytic center and active amino acid residues of Hsp-Cu(II) bound with α-glucosidase and the adsorption of high-viscosity chitosan decreases the binding affinity of Hsp-Cu(II) on α-glucosidase. The study may offer a reference for the development of Hsp-Cu(II)-based nutritional and healthy food for patients with hyperglycemia.

The Effects of Fisetin and Curcumin on Oxidative Damage Caused by Transition Metals in Neurodegenerative Diseases

Neurodegenerative diseases pose a significant health challenge for the elderly. The escalating presence of toxic metals and chemicals in the environment is a potential contributor to central nervous system dysfunction and the onset of neurodegenerative conditions. Transition metals play a crucial role in various pathophysiological mechanisms associated with prevalent neurodegenerative diseases such as Alzheimer's and Parkinson's. Given the ubiquitous exposure to metals from diverse sources in everyday life, the workplace, and the environment, most of the population faces regular contact with different forms of these metals. Disturbances in the levels and homeostasis of certain transition metals are closely linked to the manifestation of neurodegenerative disorders. Oxidative damage further exacerbates the progression of neurological consequences. Presently, there exists no curative therapy for individuals afflicted by neurodegenerative diseases, with treatment approaches primarily focusing on alleviating pathological symptoms. Within the realm of biologically active compounds derived from plants, flavonoids and curcuminoids stand out for their extensively documented antioxidant, antiplatelet, and neuroprotective properties. The utilization of these compounds holds the potential to formulate highly effective therapeutic strategies for managing neurodegenerative diseases. This review provides a comprehensive overview of the impact of abnormal metal levels, particularly copper, iron, and zinc, on the initiation and progression of neurodegenerative diseases. Additionally, it aims to elucidate the potential of fisetin and curcumin to inhibit or decelerate the neurodegenerative process.

Synthesis of quercetin-iron (Fe) complex and its in silico and in vitro confirmation towards antibacterial activity

Aim: In this study quercetin-iron complex (QFC) was synthesized, and the structural characterizations such as x-ray diffraction, field emission-scanning electron microscopy, energy-dispersive x-ray and Brunner-Emmitt-Teller adsorption-desorption isotherm analysis revealed the crystallinity state, surface morphology and nature of the adsorbing surface with surface area value. Methodology: Functional characterizations such as UV-visible spectrometric and Fourier transform infrared analysis collectively indicated the chemical changes that appeared after complex formation in terms of characteristic change in the spectrum and band position, respectively. Results: The in vitro antibacterial activity against Escherichia coli and Staphylococcus aureus has shown a dose-dependent decrease in colony count and achieved significant removal at 15 mg/ml concentration of QFC. Conclusion: The molecular docking study supports the therapeutic application of QFC.

Hesperetin-Cu(II) complex as potential α-amylase and α-glucosidase inhibitor: Inhibition mechanism and molecular docking

Inhibition of α-amylase and α-glucosidase activity is an effective way for controlling postprandial blood glucose-related diabetes. The study found that hesperetin-Cu(II) complex (Hsp-Cu(II)) exhibited a stronger inhibitory ability on α-amylase and α-glucosidase compared to hesperetin (Hsp), with smaller IC₅₀ values of Hsp-Cu(II) (60.3 ± 0.9 µM for α-amylase; 1.25 ± 0.03 µM for α-glucosidase) than Hsp (115.6 ± 1.1 µM for α-amylase; 55.2 ± 0.1 µM for α-glucosidase). Interestingly, Hsp-Cu(II) and acarbose exerted a synergistic effect on inhibition of α-glucosidase. The binding affinities of Hsp-Cu(II) to α-amylase and α-glucosidase were strong with the Ka values (binding constant) in the magnitude order of 10⁵, which was 9 times larger than Hsp. After interacting, Hsp-Cu(II) reduced α-helix contents of α-amylase and α-glucosidase, resulting in a looser conformation of these two enzymes. Molecular simulations manifested that Hsp-Cu(II) bound to the active center of enzymes driven by hydrogen bonds and interacted with the key catalytic amino acids (α-amylase: Gln63, Asp300 and His305; α-glucosidase: Tyr158, Asp215, Glu277 and Glu411), altering the conformation of enzymes, blocking the entrance of substrates, ultimately reducing the activities of α-glucosidase and α-amylase. This study has demonstrated that Hsp-Cu(II) may be a promising candidate of functional nutritional additive and medicine for the prevention of diabetes.

Metallophenolomics: A Novel Integrated Approach to Study Complexation of Plant Phenolics with Metal/Metalloid Ions

Plant adaptive strategies have been shaped during evolutionary development in the constant interaction with a plethora of environmental factors, including the presence of metals/metalloids in the environment. Among adaptive reactions against either the excess of trace elements or toxic doses of non-essential elements, their complexation with molecular endogenous ligands, including phenolics, has received increasing attention. Currently, the complexation of phenolics with metal(loid)s is a topic of intensive studies in different scientific fields. In spite of the numerous studies on their chelating capacity, the systemic analysis of phenolics as plant ligands has not been performed yet. Such a systematizing can be performed based on the modern approach of metallomics as an integral biometal science, which in turn has been differentiated into subgroups according to the nature of the bioligands. In this regard, the present review summarizes phenolics–metal(loid)s’ interactions using the metallomic approach. Experimental results on the chelating activity of representative compounds from different phenolic subgroups in vitro and in vivo are systematized. General properties of phenolic ligands and specific properties of anthocyanins are revealed. The novel concept of metallophenolomics is proposed, as a ligand-oriented subgroup of metallomics, which is an integrated approach to study phenolics–metal(loid)s’ complexations. The research subjects of metallophenolomics are outlined according to the methodology of metallomic studies, including mission-oriented biometal sciences (environmental sciences, food sciences and nutrition, medicine, cosmetology, coloration technologies, chemical sciences, material sciences, solar cell sciences). Metallophenolomics opens new prospects to unite multidisciplinary investigations of phenolic–metal(loid) interactions.