Antioxidant and antimalarial properties of butein and homobutein based on their ability to chelate iron (II and III) cations: a DFT study in vacuo and in solution

Extracellular vesicles enhance the in vivo antitumor effects of millettia species-derived compounds in chronic myelogenous leukemia therapy

Several Millettia species are being investigated as medicinal ingredients due to their promising anti-cancer and anti-inflammatory properties. However, the application of Millettia species-derived compounds has been severely hindered by their poor aqueous solubility, rapid metabolism, and low bioavailability. Extracellular vesicles (EVs), which as membrane-bound phospholipid vesicle initiatively secreted through a variety of mammalian cells, are increasingly recognized as promising drug delivery vehicles. Therefore, EVs are with great potential to enhance both the stability and efficacy of the Millettia species-derived compounds in treatment. In this study, extracellular vesicles derived from chronic myelogenous leukemia cells are developed for delivering the extracts of Millettia speciosa Champ and Millettia pachyloba Drake-derived Homobutein. Notably, Homobutein-loaded EV (hEV) formed a stable and homogenous nanosized particle with high entrapment efficiency up to 55.7%. Moreover, EVs loaded with Homobutein were significantly more potent than free drugs in inhibiting K562 cell proliferation. The results demonstrated that intravenous injection of EV loaded with Homobutein effectively inhibits tumor growth in tumor-bearing mice compared to free Homobutein. Hence, this strategy can effectively enhance the efficacy of Millettia species-derived drugs in chronic myelogenous leukemia therapy.

Potent Antioxidant and Anti-Tyrosinase Activity of Butein and Homobutein Probed by Molecular Kinetic and Mechanistic Studies

Butein (BU) and homobutein (HB) are bioactive polyhydroxylated chalcones widespread in dietary plants, whose antioxidant properties require mechanistic definition. They were investigated by inhibited autoxidation kinetic studies of methyl linoleate in Triton™ X-100 micelles at pH 7.4, 37 °C. Butein had kinh = (3.0 ± 0.9) × 104 M-1s-1 showing a chain-breaking mechanism with higher antioxidant activity than reference α-tocopherol (kinh = (2.2 ± 0.6) × 104 M-1s-1), particularly concerning the stoichiometry or peroxyl radical trapping n = 3.7 ± 1.1 vs. 2.0 for tocopherol. Homobutein had kinh = (2.8 ± 0.9) × 103 M-1s-1, pairing the relative BDEOH measured by radical equilibration EPR as 78.4 ± 0.2 kcal/mol for BU and estimated as 82.6 kcal/mol for HB. The inhibition of mushroom tyrosinase (mTYR) by HB and BU was also investigated. BU gives a reversible uncompetitive inhibition of monophenolase reaction with KI' = 9.95 ± 2.69 µM and mixed-type diphenolase inhibition with KI = 3.30 ± 0.75 µM and KI' = 18.75 ± 5.15 µM, while HB was nearly competitive toward both mono- and diphenolase with respective KI of 2.76 ± 0.70 µM and 2.50 ± 1.56 µM. IC50 values (monophenolase/diphenolase at 1 mM substrate) were 10.88 ± 2.19 µM/15.20 ± 1.25 µM, 14.78 ± 1.05 µM/12.36 ± 2.00 µM, and 33.14 ± 5.03 µM/18.27 ± 3.42 µM, respectively, for BU, HB, and reference kojic acid. Molecular docking studies confirmed the mechanism. Results indicate very potent antioxidant activity for BU and potent anti-tyrosinase activity for both chalcones, which is discussed in relation to bioactivity toward protection from skin disorders and food oxidative spoilage.

DFT studies of camptothecins cytotoxicity IV — active and inactive forms of irinotecan

Structures of irinotecan (CPT-11) in neutral lactone, neutral carboxyl, and anionic carboxylate forms in singlet ground states and of their complexes with Cu(II) in doublet ground states are optimized using B3LYP/6-311G* treatment. Metal ion affinities (MIA), Cu charges and Laplacians of Cu-ligand bond critical points of possible CPT active sites are evaluated. The formation of Cu(II) complexes with the anionic carboxylate ligand leads to the release of CO2 that can cause a decrease in the concentration of the active lactone form due to equilibria between all forms of the drug. MIA values and electron density transfer to Cu increase in the sequence lactone < neutral carboxyl < anionic carboxylate. Both neutral forms of irinotecan exhibit lower MIA values than those of camptothecin, unlike the anionic carboxylate form.

Recent advances in the antioxidant activity and mechanisms of chalcone derivatives: a computational review

In this review, we have reported the antioxidant mechanisms and structure-antioxidant activity relationship of several chalcone derivatives, investigated in the recent past, based on the density functional theory (DFT) calculations, considering free radical scavenging and metal chelation ability. The antioxidant mechanisms include hydrogen atom transfer (HAT), sequential proton loss electron transfer (SPLET), single electron transfer followed by proton transfer (SET-PT), sequential proton loss hydrogen atom transfer (SPLHAT), sequential double proton loss electron transfer (SdPLET), sequential triple proton loss double electron transfer (StPLdET), sequential triple proton loss triple electron transfer (StPLtET), double HAT, double SPLET, double SET-PT, triple HAT, triple SET-PT, triple SPLET, proton-coupled electron transfer (PCET), single electron transfer (SET), radical adduct formation (RAF) and radical adduct formation followed by hydrogen atom abstraction (RAF-HAA). Furthermore, solvent effects have also been considered using different solvation models. The feasibility of scavenging different reactive oxygen and nitrogen species (ROS/RNS) has been discussed considering various factors such as the number and position of hydroxyl as well as methoxy groups present in the antioxidant molecule, stability of the species formed after scavenging reactive species, nature of substituent, steric effects, etc. This review opens new perspectives for designing new compounds with better antioxidant potential.

DFT studies of camptothecins cytotoxicity III: camptothecin, irinotecan and SN-38

Geometries of camptothecin, irinotecan, SN-38, and of their hypothetical Cu(II) complexes were optimized at the B3LYP/6-311G* level of theory. Their electron structure, evaluated in terms of Mulliken population analysis and Quantum Theory of Atoms-in-Molecule, was subsequently related to in vitro cytotoxicity. Electron density transfer from the relevant active sites to Cu decreases in the sequence irinotecan > SN-38 > camptothecin. The absolute values of their metal-ligand interaction energies exhibit the same trend. Discrepancy with the least relative in vitro cytotoxicity of irinotecan can be explained by differences in its pharmacokinetics.

X-ray Structure Determination, Antioxidant Voltammetry Studies of Butein and 2',4'-Dihydroxy-3,4-dimethoxychalcone. Computational Studies of 4 Structurally Related 2',4'-diOH Chalcones to Examine Their Antimalarial Activity by Binding to Falcipain-2

Malaria is a huge global health burden with resistance to currently available medicines resulting in the search for newer antimalarial compounds from traditional medicinal plants in malaria-endemic regions. Previous studies on two chalcones, homobutein and 5-prenylbutein, present in E. abyssinica, have shown moderate antiplasmodial activity. Here, we describe results from experimental and computational investigations of four structurally related chalcones, butein, 2′,4′-dihydroxy-3,4-dimethoxychalcone (DHDM), homobutein and 5-prenylbutein to elucidate possible molecular mechanisms by which these compounds clear malaria parasites. The crystal structures of butein and DHDM show that butein engages in more hydrogen bonding and consequently, more intermolecular interactions than DHDM. Rotating ring-disk electrode (RRDE) voltammetry results show that butein has a higher antioxidant activity towards the superoxide radical anion compared to DHDM. Computational docking experiments were conducted to examine the inhibitory potential of all four compounds on falcipain-2, a cysteine protease that is involved in the degradation of hemoglobin in plasmodium-infected red blood cells of the host. Overall, this work suggests butein as a better antimalarial compound due to its structural features which allow it to have greater intermolecular interactions, higher antioxidant activity and to create a covalent complex at the active site of falcipain-2.

Proportional coexistence of okanin chalcone glycoside and okanin flavanone glycoside in Bidens pilosa leaves and theoretical investigation on the antioxidant properties of their aglycones

Bidens pilosa plant has been shown to produce okanin flavanone glycoside and its chalcone derivative. In most other plants, due to chalcone isomerase enzyme, the flavanone tends to exist in higher proportions than their chalcone precursors. Herein we have utilized liquid chromatography-mass spectrometry approach and shown that within the leaves of Bidens pilosa plant the two okanin glycosides exist in unusual equal proportional distribution, which indicates that Bidens pilosa plant is an alternative rich source of these highly sought-after antioxidant molecules. The aglycone okanin chalcone (ONC) and okanin flavanone (ONF) have experimentally been shown to exhibit antioxidant activity. However, experimental findings have not conclusively determined which of the two compounds is a more potent antiradical than the other. Herein, the density functional theory (DFT) method is utilized to establish, from structural and thermodynamic energetic considerations, the preferred antioxidant molecule between the two aglycone okanins. A theoretical study on the antioxidant properties of ONC and ONF has been performed by considering their radical scavenging and metal cation (Mⁿ⁺, where M = Cu(II) or Fe (III)) chelation ability. The study has been performed using B3LYP/6-31 + G(d,p) method. In the case of the metal chelation mechanism, the LANL2DZ pseudo-potential was selected to describe the selected Mⁿ⁺ cations. The results of the study suggest that ONC is a better radical scavenger than ONF because of the extended electron delocalization on its neutral radical, which is due to the presence of conjugation within the ONC neutral radical after hydrogen atom abstraction. In the metal chelation mechanism, it is noted that the binding energies depend on the media, the nature of the ligand and the cation and the cation coordination site on the ligand. The charge and the spin density on Mⁿ⁺ decrease on coordination to the ligand. The ability of the ligands to reduce Mⁿ⁺ cations, coupled with the strong Mⁿ⁺ binding properties, has significant implication on the antioxidant ability of both okanins. However, since ONC⋅⋅⋅M⁺ⁿ interaction results in higher binding energy than ONF⋅⋅⋅M⁺ⁿ interaction, the implication is that ONC is a preferred free metal ion chelator than ONF.

Experimental and quantum-chemical study of differential absorbance spectra of environmentally relevant species: A study of quercetin deprotonation and its interactions with copper (II) ions

This study compared the experimental and theoretically calculated differential absorbance spectra (DAS) of quercetin, which is a typical model compound of natural organic matter (NOM) that is found in biochemical and environmental systems. Absorbance spectra of quercetin, which has five exchangeable protons, were generated at each state of deprotonation and its binding with Cu(II) ions. The spectra showed that the emergence of characteristic peaks in the experimental DAS was associated with the deprotonation of quercetin and its binding with Cu(II). Calculations of the theoretical DAS were conducted based on the time-dependent density functional theory (TD-DFT) methods and yielded results that were consistent with the experimental DAS data because the features in the absorbance spectra were primarily associated with the electron transitions from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) in the molecule. The appearance of the characteristic peaks in the DAS reflects the changes of the structure and electron distribution of the organic molecules that are induced by water treatment or environmental processes.

The Anti-inflammatory Effects of Dietary Anthocyanins against Ulcerative Colitis

Ulcerative colitis (UC), which is a major form of inflammatory bowel disease (IBD), is a chronic relapsing disorder of the gastrointestinal tract affecting millions of people worldwide. Alternative natural therapies, including dietary changes, are being investigated to manage or treat UC since current treatment options have serious negative side effects. There is growing evidence from animal studies and human clinical trials that diets rich in anthocyanins, which are pigments in fruits and vegetables, protect against inflammation and increased gut permeability as well as improve colon health through their ability to alter bacterial metabolism and the microbial milieu within the intestines. In this review, the structure and bioactivity of anthocyanins, the role of inflammation and gut bacterial dysbiosis in UC pathogenesis, and their regulation by the dietary anthocyanins are discussed, which suggests the feasibility of dietary strategies for UC mitigation.

Extract of Rhus verniciflua stokes protects against renal ischemia-reperfusion injury by enhancing Nrf2-mediated induction of antioxidant enzymes

Ischemia-reperfusion injury (IRI) may cause acute kidney disease (AKD) by mediating the oxidative stress-induced apoptosis of parenchymal cells. The extract of Rhus verniciflua Stokes (RVS) is used as a traditional herbal medicine as it exhibits anti-oxidant, anti-apoptotic and anti-inflammatory properties. Therefore, the current study investigated the therapeutic effect and the underlying mechanism of RVS on IRI-induced AKD in vivo and in vitro. The current study assessed the effects of RVS on a mouse model of renal IRI and in hypoxic human renal tubular epithelial HK-2 cells. The results demonstrated that the IRI-induced elevation of blood urea nitrogen, serum creatinine and lactate dehydrogenase was significantly attenuated by the intraoral administration of RVS (20 mg/kg/day) for 14 days prior to surgery. It was demonstrated that IRI surgery induced histological damage and cellular apoptosis in renal parenchyma, which were attenuated by pretreatment with RVS. Furthermore, in HK-2 cells incubated with 300 µM CoCl₂ to induce chemical hypoxia, it was demonstrated that RVS treatment significantly inhibited cell death and the production of reactive oxygen species (ROS). Furthermore, RVS treatment upregulated the levels of endogenous antioxidant enzymes, including heme oxygenase-1 and catalase, as well as their upstream regulator nuclear factor erythroid 2-related factor 2, in HK-2 cells. Taken together, these results suggested that the intraoral administration of RVS induces a therapeutic effect on IRI-induced AKD. These effects are at least partly due to the attenuation of ROS production via upregulation of the antioxidant defense system in renal tubular cells.

Analysis of the pH-Dependent Fe(III) Ion Chelating Activity of Anthocyanin Extracted from Black Soybean [Glycine max (L.) Merr.] Coats

The Fe(III) chelating activity of anthocyanin extracted from black soybean coats was investigated at pH 3.0, 5.0, 6.5, 7.0, and 7.4 with fluorescence spectroscopy and microscale thermophoresis (MST). Cyanidin-3-glucoside (C3G) was determined to be 98% of the total anthocyanin by high-performance liquid chromatography. The binding affinity (Ka) exhibited significant pH-dependent behavior: Ka was 9.7167 × 104, 1.0837 × 104, 1.4284 × 104, 5.4550 × 104, and 3.0269 × 104 M-1 at pH 3.0, 5.0, 6.5, 7.0, and 7.4, respectively (p < 0.05). The MST data showed that ΔG < 0 and ΔH < 0, demonstrating that chelation is spontaneous and exothermic. Because both ΔH and ΔS < 0, the chelation involves hydrogen bonds and/or van der Waals forces for pH 3.0, 5.0, and 6.5. Electrostatic interactions contributed to chelation at pH 7.0 and 7.4 with ΔH < 0 and ΔS > 0. With the formation of chelates, C3G improved the solubility of Fe(III) at pH 6.5, 7.0, and 7.4 to enhance the ferric ion bioavailability, except for aggregation observed at pH 5.0.

A theoretical study on the antioxidant properties of methoxy-substituted chalcone derivatives: A case study of kanakugiol and pedicellin through their Fe (II and III) coordination ability

A theoretical study on the antioxidant properties of two chalcone derivatives, kanakugiol and pedicellin, is performed by considering their Fe[Formula: see text] and Fe[Formula: see text] coordination ability. The objective of the study is to elucidate the factors influencing the stability of the isolated conformers, the nature of the complexes, metal[Formula: see text]ligand stability, metal ion affinities (MIA) and electronic properties of the cations before and after coordination to the ligand. The study is performed using the B3LYP/6–311[Formula: see text]G(2d,p)//B3LYP/6–31[Formula: see text]G(d,p) method. The LANL2DZ pseudopotential is selected to describe the Fe[Formula: see text] ions. Time-dependent density functional theory (TDDFT) method is used to assess the electronic UV–Vis spectra of the isolated chalcones and their complexes with Fe[Formula: see text] ions. The results suggest that the preferred complexes are those in which the Fe ion is coordinated at the hydroxyl-methoxy and hydroxyl-keto sites for kanakugiol and methoxy-keto site for pedicellin. Both kanakugiol and pedicellin have potential to chelate iron ions as demonstrated by their high MIA values in vacuo and in water solution. However, the ability of pedicellin to chelate iron is slightly lower than that of kanakugiol, indicating that the presence of the hydroxyl group has an effect of enhancing the metal binding abilities of the chalcone derivatives. In all the complexes obtained in vacuo, kanakugiol and pedicellin exhibit the ability to reduce the Fe[Formula: see text] ion. In water solution (which mimics the environment in biological systems or studies performed in vivo), Fe[Formula: see text] is reduced to Fe[Formula: see text] upon coordination to the ligand while the oxidation number of Fe[Formula: see text] upon coordination to the ligand remains virtually unchanged.