Structural analysis of flavonoids in solution through DFT 1H NMR chemical shift calculations: Epigallocatechin, Kaempferol and Quercetin

Encapsulation of quercetin fraction from Musa balbisiana banana blossom in chitosan alginate solution, its optimization and characterizations

This study comprises the isolation of quercetin from the bhimkol banana (Musa balbisiana) blossom, encapsulation, and its characterizations. An isolated quercetin rich fraction was obtained from HPLC followed by column chromatography and subsequently encapsulated with chitosan-alginate polyelectrolyte complex at optimum encapsulation conditions obtained by ant colony optimization. Quercetin fraction and encapsulated quercetin were characterized for their physicochemical properties (by HPLC, FTIR, NMR, XRD, Dynamic Light Scattering, and release study). The yield and purity of isolated quercetin rich fractions were 2.35 ± 0.08 μg/ml and 83.12 ± 0.31 %, respectively. After the optimization of encapsulation, quercetin 0.2 %, sodium alginate 4 %, chitosan 0.5 %, and agitation at 300 rpm were found to be the optimal conditions resulting in higher encapsulation efficiency (EE, 84.54 %). EE was significantly improved by a slight increase in sodium alginate, and agitation. Encapsulated quercetin revealed good pH resistance by releasing 68.27 mg QE/g quercetin in simulated gastric fluid at 60 min. Microbeads of encapsulated quercetin showed the structural bond stretching of encapsulating materials and quercetin in FTIR spectra (stretching at 1511 cm-1, 1380 cm-1, and 1241 cm-1 are attributed to the stretching vibration of CO in aromatic rings, and bending vibration of OH bond in phenols). An average particle size of 2.71 μm exhibited the microgel behavior of microbeads (by XRD). The present study on the underutilized variety of banana blossoms has diverse applications in the food and pharmaceutical industries that will productively exhibit effective drug delivery properties.

Apoptosis Induction in HepG2 and HCT116 Cells by a Novel Quercetin-Zinc (II) Complex: Enhanced Absorption of Quercetin and Zinc (II)

Quercetin forms complexes with various metals due to its structural attributes. It predominantly exhibits chelating activity at the 3-hydroxy/4-carbonyl group. Previously, coordination in synthetically obtained quercetin-zinc (II) complexes has been limited to this group. However, the expanded coordination observed in quercetin-iron complexes has opened avenues for diverse applications. Thus, synthesizing novel quercetin-zinc complexes with different coordination positions is a significant advance. In our study, we not only synthesized and comprehensively characterized a new quercetin-zinc (II) complex, Zn-Q, but also evaluated the structure and bioactivity of chelate complexes (Q+Zn) derived from co-treatment in cell culture mediums. The structure of the new compound Zn-Q was comprehensively characterized using 1D 1H and 2D correlation spectroscopy (COSY), nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), electrospray ionization mass spectrometer (ESI-MS), and X-ray diffraction analysis (XRD) analysis. Subcellular localization and absorption of these zinc (II) complexes were determined using the ZnAF-2 DA zinc ion fluorescence probe. Throughout the experiments, both Zn-Q and Q+Zn exhibited significant antioxidant, cell growth inhibitory, and anticancer effects in HepG2 and HCT116 cells, with Zn-Q showing the highest potential for inducing apoptosis via the caspase pathway. Tracking intracellular zinc complex absorption using zinc fluorescent probes revealed zinc (II) localization around the cell nucleus. Interestingly, there was a proportional increase in intracellular quercetin absorption in conjunction with zinc (II) uptake. Our research highlights the advantages of quercetin complexation with zinc (II): enhanced anticancer efficacy compared to the parent compound and improved bioavailability of both quercetin and zinc (II). Notably, our findings, which include enhanced intracellular uptake of both quercetin and zinc (II) upon complex formation and its implications in apoptosis, contribute significantly to the understanding of metal-polyphenol complexes. Moving forward, comprehensive functional assessments and insights into its mechanism of action, supported by animal studies, are anticipated.

Therapeutic effectiveness of sinensetin against cancer and other human complications: A review of biological potential and pharmacological activities

BACKGROUND

Plant and their active phytoproducts have been used in modern medicine and playing an important role in the health sectors since a very early age. Human beings need a considerable amount of these plant-based phytochemicals for their health. The flavonoidal class phytochemical is an important class of natural products in modern healthcare because of their different pharmacological activities and health benefits. Flavonoidal class phytochemicals have been used to treat diabetes and related secondary complications in humans. Flavonoids have anti-apoptotic, anti-hyperlipidemic, anti-inflammatory, and anti-oxidant potential in the health sectors. Sinensetin, also called 3',4',5,6,7-pentametoksiflavon is a colorless compound with a molecular weight 372.37g/mol and is found to be present in the Orthosiphon stamineus.

METHODS

In the present investigation, we aim to collect scientific information on sinensetin and analyze it for its biological potential and therapeutic benefits against various types of disorders and complications. Medicinal importance and pharmacological activities data have been collected and analyzed in the present work for sinensetin through literature data analysis of different research works. Google Science Direct, PubMed, Scopus, and Google Scholar were mainly searched to collect the scientific information in the present work. The present work analyzed sinensetin's biological potential, pharmacological activities, and analytical aspects.

RESULTS

Literature data analysis of different scientific research works revealed the biological potential of phytochemicals in medicine, including flavonoids. Sinensetin has anti-tumor, anti-inflammatory, anti-oxidant, anti-diabetic, and antibacterial activities through their testing in different in vitro and in vivo models. Sinensetin has physiological functions, including anti-oxidant, anti-inflammation, and anti-cancer potential in medicine. Scientific data analysis signified the biological importance of sinensetin against tumors, gastric cancer, colorectal cancer, breast cancer, diabetes, influenza H1N1 infection, obesity, inflammation, colitis, brain disorders, and microbial infections. Further biological potential of sinensetin on enzymes and angiogenesis has been analyzed in the present work. Sinensetin was isolated through different analytical and extraction techniques, including chromatographic techniques.

CONCLUSION

Literature data analysis signified sinensetin's biological potential and pharmacological activities in medicine.

The discovery of a key prenyltransferase gene assisted by a chromosome-level Epimedium pubescens genome

Epimedium pubescens is a species of the family Berberidaceae in the basal eudicot lineage, and a main plant source for the traditional Chinese medicine "Herba Epimedii". The current study achieved a chromosome-level genome assembly of E. pubescens with the genome size of 3.34 Gb, and the genome guided discovery of a key prenyltransferase (PT) in E. pubescens. Our comparative genomic analyses confirmed the absence of Whole Genome Triplication (WGT-γ) event shared in core eudicots and further revealed the occurrence of an ancient Whole Genome Duplication (WGD) event approximately between 66 and 81 Million Years Ago (MYA). In addition, whole genome search approach was successfully applied to identify 19 potential flavonoid PT genes and an important flavonoid PT (EpPT8) was proven to be an enzyme for the biosynthesis of medicinal compounds, icaritin and its derivatives in E. pubescens. Therefore, our results not only provide a good reference genome to conduct further molecular biological studies in Epimedium genus, but also give important clues for synthetic biology and industrial production of related prenylated flavonoids in future.

Kaempferol: A flavonoid with wider biological activities and its applications

Kaempferol and its derivatives are naturally occurring phytochemicals with promising bioactivities. This flavonol can reduce the lipid oxidation in the human body, prevent the organs and cell structure from deterioration and protect their functional integrity. This review has extensively highlighted the antioxidant, antimicrobial, anticancer, neuroprotective, and hepatoprotective activity of kaempferol. However, poor water solubility and low bioavailability of kaempferol greatly limit its applications. The utilization of advanced delivery systems can improve its stability, efficacy, and bioavailability. This is the first review that aimed to comprehensively collate some of the vital information published on biosynthesis, mechanism of action, bioactivities, bioavailability, and toxicological potential of kaempferol. Besides, it provides insights into the future direction on the improvement of bioavailability of kaempferol for wide applications.

Therapeutic importance and pharmacological activities of karanjin in the medicine for the treatment of Human disorders: A review through scientific data analysis

Backgrounds:

Plant and derived herbal drugs have been used in the traditional system of medicine for the treatment of various forms of human health complications since a very early age. Commercial products prepared from natural herbs have been always valuable for the society in the form of health supplement to medicament. In the ancient time, herbal products were mainly prepared from plants and their derived phytochemical. Plants contain a rich source of pure phytochemical called secondary metabolite and examples are flavonoids, glycosides, tannins and terpenoids etc. Plants and their parts including fruits, flowers, vegetables etc. are the best source of Flavonoid class phytochemicals.

Methods:

Present work summarized the scientific information of karanjin for their health beneficial aspects and pharmacological activities including its analytical aspects. In the present investigation, scientific data of karanjin have been collected from various scientific databases such as Google, Goggle Scholar, Science Direct and PubMed and analyzed to know the health beneficial aspects of karanjin in the medicine. Further pharmacological activity data has been collected and analyzed in the present work to know their biological potential in the medicine. Analytical methods used for the separation, isolation, and identification of karanjin for the standardization of different natural products have been also discussed in the present work.

Results:

Scientific data analysis signified the biological importance of Flavonoid class phytochemicals in the medicine as they are well known for their anti-ischemic, vasodilatory, anti-bacterial, anti-inflammatory, anti-oxidant, anti-viral, and anti-cancer activities. Scientific data analysis revealed the presences of karanjin in numerous medicinal plants such as Fordia cauliflora, Lonchocarpus latifolius, Millettia pinnata, Millettia pubinervis, Pongamia pinnata, and Tephrosia purpurea. Pharmacological activity data revealed the biological potential of karanjin against cancerous disorders, glucose metabolism abnormalities, gastrointestinal disorders, arthritis, inflammatory disorders, colitis, psoriasis and brain related disorders. However, analytical data signified the importance of RP-HPLC, TLC, HPTLC, UPLC-ESI-MS/MS and HSCCC techniques in the medicine for the quantification of karanjin in different samples.

Conclusion:

Presented information about karanjin in this review paper will be beneficial to the scientific peoples of the world to know the health beneficial aspects of karanjin in the medicine.

Pharmacological activities and Therapeutic potential of kaempferitrin in medicine for the treatment of human disorders: A review of medicinal importance and health benefits

BACKGROUND

Herbal drugs and their derived phytochemicals are valuable for human being as a source of vital component of food material and drugs. Flavonoids are naturally occurring phytochemical produced in plants through metabolisms and they are having anti-hyperlipidemia, anti-inflammatory, anti-oxidant and anti-apoptotic activity. Flavonoids have been identified in the fruits, nuts, vegetables, seeds, stem, flowers and tea. Kaempferol is a natural flavonoidal compound present in edible plants such as apples, broccoli, strawberries, beans, grapefruit, propolis and medicinal plants such as Aloe vera, Ginkgo biloba, Rosmarinus officinalis, Crocus sativus L., Hypericum perforatum L. Kaempferol have anti-oxidant, anti-inflammatory, anti-apoptotic, pro-apoptotic, cardio-protective and anti-cancer activities.

METHODS

Glycosides of kaempferol such as kaempferitrin also called kaempferol 3,7-dirhamnoside are known to be more abundant than their flavonoid monomers in plants. Various literature databases have been searched to collect all the scientific information of kaempferitrin in the present investigation and analyzed in order to know the therapeutic benefit and biological potential of kaempferitrin. Moreover all the information has been presented here in two broad sections i.e. pharmacological and analytical.

RESULTS

From the analysis of all the collected and presented information, it was found that kaempferitrin has potent insulin-mimetic potential and could be used for the treatment of diabetes and related complication. However, it has also shown anti-oxidant, anti-inflammatory, anti-convulsant, anti-osteoporotic, anti-depressant, anthelmintic, immunostimulatory and natriuretic properties and inhibits cell proliferation and apoptosis. Kaempferitrin also improves meat quality of broiler chickens.

CONCLUSIONS

The presented information in this work will be valuable to justify the biological importance and therapeutic potential of kaempferitrin in the scientific field.

Phytochemical composition, antisnake venom and antibacterial activities of ethanolic extract of Aegiphila integrifolia (Jacq) Moldenke leaves

Snakebites are considered a major neglected tropical disease, resulting in around 100,000 deaths per year. The recommended treatment by the WHO is serotherapy, which has limited effectiveness against the toxins involved in local tissue damage. In some countries, patients use plants from folk medicines as antivenoms. Aegiphila species are common plants from the Brazilian Amazon and are used to treat snakebites. In this study, leaves from Aegiphila integrifolia (Jacq) Moldenke were collected from Roraima state, Brazil and its ethanolic extract was evaluated through in vitro and in vivo experiments to verify their antiophidic activity against Bothrops atrox crude venom. The isolated compounds from A. integrifolia were analyzed and the chemical structures were elucidated on the basis of infrared, ultraviolet, mass, ¹H and ¹³C NMR spectrometry data. Among the described compounds, lupeol (7), betulinic acid (1), β-sitosterol (6), stigmasterol (5), mannitol (4), and the flavonoids, pectolinarigenin (2) and hispidulin (3), were identified. The ethanolic extract and flavonoids (2 and 3) partially inhibited the proteolytic, phospholipase A2 and hyaluronidase activities of B. atrox venom, and the skin hemorrhage induced by this venom in mice. Antimicrobial activity against different bacteria was evaluated and the extract partially inhibited bacterial growth. Thus, taken together, A. integrifolia ethanolic extract has promising use as an antiophidic and antimicrobial.

Analysis of Conformational, Structural, Magnetic, and Electronic Properties Related to Antioxidant Activity: Revisiting Flavan, Anthocyanidin, Flavanone, Flavonol, Isoflavone, Flavone, and Flavan-3-ol

Understanding the antioxidant activity of flavonoids is important to investigate their biological activities as well as to design novel molecules with low toxicity and high activity. Aromaticity is a chemical property found in cyclic structures that plays an important role in their stability and reactivity, and its investigation can help us to understand the antioxidant activity of some heterocyclic compounds. In the present study, we applied the density functional theory (DFT) to investigate the properties of seven flavonoid structures with well-reported antioxidant activity: flavan, anthocyanidin, flavanone, flavonol, isoflavone, flavone, and flavan-3-ol. Conformational, structural, magnetic, and electronic analyses were performed using nuclear magnetic resonance, ionization potentials, electron affinity, bond dissociation energy, proton affinity, frontier molecular orbitals (highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO)), and aromaticity through nucleus-independent chemical shifts to analyze these seven flavonoid structures. We revised the influence of hydroxyl groups on the properties of flavonoids and also investigated the influence of the aromaticity of these seven flavonoids on the antioxidant activity.

Investigation of supramolecular interaction of quercetin with N,N-dimethylamine-functionalized p-sulfonated calix[4,8]arenes using molecular modeling and their in vitro cytotoxic response towards selected cancer cells

Although quercetin is an effective bioactive compound preventing the progress of several human cancers, its impact is reduced due to low bioavailability.

Targeting the initiation and termination codons of SARS-CoV-2 spike protein as possible therapy against COVID-19: the role of novel harpagide 5-O-β-D-glucopyranoside from Clerodendrum volubile P Beauv. (Labiatae)

The global spread of the coronavirus infections disease − 2019 (COVID-19) and the search for new drugs from natural products particularly from plants are receiving much attention recently. In this study, the therapeutic potential of a new iridoid glycoside isolated from the leaves of Clerodendrum volubile against COVID-19 was investigated. Harpagide 5-O-β-D-glucopyranoside (HG) was isolated, characterised and investigated for its druglikeness, optimized geometry, and pharmacokinetics properties. Its immunomodulatory was determined by chemiluminescence assay using polymorphonuclear neutrophils (PMNs) in addition to T-cell proliferation assay. In silico analysis was used in determining its molecular interaction with severe acute respiratory syndrome coronavirus-2 (SARS-COV-2). HG displayed potent druglikeness properties, with no inhibitory effect on cytochrome P₄₅₀ (1A2, 2C19, 2C9, 2D6 and 3A4) and a predicted LD₅₀ of 2000 mg/kg. Its ¹H-NMR chemical shifts showed a little deviation of 0.01 and 0.11 ppm for H-4 and H-9, respectively. HG significantly suppressed oxidative bursts in PMNs, while concomitantly inhibiting T-cell proliferation. It also displayed a very strong binding affinity with the translation initiation and termination sequence sites of spike (S) protein mRNA of SARS-COV-2, its gene product, and host ACE2 receptor. These results suggest the immunomodulatory properties and anti-SARS-COV-2 potentials of HG which can be explored in the treatment and management of COVID-19.

Communicated by Ramaswamy H. Sarma

Calculating nuclear magnetic resonance chemical shifts in solvated systems

The nuclear magnetic resonance (NMR) chemical shift is extremely sensitive to molecular geometry, hydrogen bonding, solvent, temperature, pH, and concentration. Calculated magnetic shielding constants, converted to chemical shifts, can be valuable aids in NMR peak assignment and can also give detailed information about molecular geometry and intermolecular effects. Calculating chemical shifts in solution is complicated by the need to include solvent effects and conformational averaging. Here, we review the current state of NMR chemical shift calculations in solution, beginning with an introduction to the theory of calculating magnetic shielding in general, then covering methods for inclusion of solvent effects and conformational averaging, and finally discussing examples of applications using calculated chemical shifts to gain detailed structural information.

Conformational Analysis of 5,4'-Dihydroxy-7,5',3'-trimethoxyisoflavone in Solution Using 1H NMR: A Density Functional Theory Approach

Among 20 compounds isolated from the extracts of Ouratea ferruginea the 5,4'-dihydroxy-7,5',3'-trimethoxyisoflavone (9) showed the best inhibitory effect on glutathione S-transferase (GST) and so deserves our attention. In this work we investigated the preferred molecular structure of 9 in chloroform solution using the density functional theory (DFT) and molecular dynamics simulation. Comparison between experimental ¹H NMR data in CDCl₃ solution and calculated chemical shifts enabled us to precisely determine the conformation adopted by 9 in solution, which can be used in further theoretical studies involving interaction with biological targets. Moreover, the experimental NMR data were used as reference to assess the ability of DFT based methods to predict ¹H NMR spectrum in solution for organic compounds. Among various DFT functionals the hybrid B3LYP was the most adequate for the calculation of chemical shifts in what CH_n protons are concerned. Regarding the OH hydrogen, inclusion of explicit CHCl₃ solvent molecules adequately placed around the solute led to good agreement with the experimental chemical shifts (in CDCl₃). It is a well-known fact that theoretical prediction of chemical shifts for OH hydrogens poses as a challenge and also revealed that the way the solvent effects are included in the DFT calculations is crucial for the right prediction of the whole ¹H NMR spectrum. It was found in this work that a supermolecule solute-solvent calculation with a minimum of four CHCl₃ molecules is enough to correctly reproduce the ¹H NMR experimental profile observed in solution, revealing that the calculated solvated structure used to reproduce the NMR chemical shifts is not unique.

Determination of Anticancer Zn(II)-Rutin Complex Structures in Solution through Density Functional Theory Calculations of 1H NMR and UV-VIS Spectra

Coordination compounds formed by flavonoid ligands are recognized as promising candidates as novel drugs with enhanced antioxidant and anticancer activity. Zn(II)-Rutin complexes have been described in the literature and distinct coordination modes proposed based on ¹H NMR/MS and IR/UV-VIS experimental spectroscopic data: 1:1/1:2 (Zn(II) binding to A-C rings) and 2:1 (Zn(II) binding to A-C-B rings) stoichiometry. Aiming to clarify these experimental findings and provide some physical insights into the process of complex formation in solution, we carried out density functional theory calculations of NMR and UV-VIS spectra for 25 plausible Zn(II)-Rutin molecular structures including solvent effect using the polarizable continuum model approach. The studied complexes in this work have 1:1, 1:2, 2:1, and 3:1 metal-ligand stoichiometry for all relevant Zn(II)-Rutin configurations. The least deviation between theoretical and experimental spectroscopic data was used as an initial criterion to select the probable candidate structures. Our theoretical spectroscopic results strongly indicate that the experimentally suggested modes of coordination (1:2 and 2:1) are likely to exist in solution, supporting the two distinct experimental findings in DMSO and methanol solution, which may be seen as an interesting result. Our predicted 1:2 and 2:1 metal complexes are in agreement with the experimental stoichiometry; however, they differ from the proposed structure. Besides the prediction of the coordination site and molecular structure in solution, an important contribution of this work is the determination of the OH-C5 deprotonation state of rutin due to metal complexation at the experimental conditions (pH = 6.7 and 7.20). We found that, in the two independent synthesis of metal complexes, distinct forms of rutin (OH-C5 and O^(-)-C5) are present, which are rather difficult to be assessed experimentally.

Structure of the flavonoid catechin in solution: NMR and quantum chemical investigations

DFT-PCM statistical index scan curves and ¹H-NMR profiles reveal conformational changes when a solid catechin sample is dissolved in acetone solvent.

Structural Determination of Antioxidant and Anticancer Flavonoid Rutin in Solution through DFT Calculations of 1H NMR Chemical Shifts

As the knowledge of the predominant molecular structure of antioxidant and anticancer flavonoid rutin in solution is very important for understanding the mechanism of action, a quantum chemical investigation of plausible rutin structures including solvent effects is of relevance. In this work, DFT calculations were performed to find possible minimum energy structures for the rutin molecule. ¹H NMR chemical shift DFT calculations were carried out in DMSO solution using the polarizable continuum model (PCM) to simulate the solvent effect. Analysis of the experimental and theoretical ¹H NMR chemical shift profiles offers a powerful fingerprint criterion to determine the predominant molecular structure in solution. Therefore, our aim is to find the best match between experimental (in DMSO‐d) and theoretical (PCM–DMSO) ¹H NMR spectrum profiles. Among 34 optimized structures located on the potential energy surface, we found that structure 32, with a B‐ring deviated 30° from a planar configuration (geometry usually assumed for polyphenols), showed an almost perfect agreement with experimental the ¹H NMR pattern when compared to the corresponding fully optimized planar geometry. This structure is also predicted as the global minimum based on room‐temperature Gibbs free energy calculations in solution and, therefore, should be experimentally observed. This is new and valuable structural information regarding structure–activity relationship studies, and such information is hard to obtain by experimentalists without the aid of the X‐ray diffraction technique.

Binding forces between a novel Schiff base palladium(II) complex and two carrier proteins: human serum albumi and β-lactoglobulin

Ligand binding studies on carrier proteins are crucial in determining the pharmacological properties of drug candidates. Here, a new palladium(II) complex was synthesized and characterized. The in vitro binding studies of this complex with two carrier proteins, human serum albumin (HSA), and β-lactoglobulin (βLG) were investigated by employing biophysical techniques as well as computational modeling. The experimental results showed that the Pd(II) complex interacted with two carrier proteins with moderate binding affinity (K_b ≈ .5 × 10⁴ M^-1 for HSA and .2 × 10³ M^-1 for βLG). Binding of Pd(II) complex to HSA and βLG caused strong fluorescence quenching of both proteins through static quenching mechanism. In two studied systems hydrogen bonds and van der Waals forces were the major stabilizing forces in the drug-protein complex formation. UV-Visible and FT-IR measurements indicated that the binding of above complex to HSA and βLG may induce conformational and micro-environmental changes of two proteins. Protein-ligand docking analysis confirmed that the Pd(II) complex binds to residues located in the subdomain IIA of HSA and site A of βLG. All these experimental and computational results suggest that βLG and HSA might act as carrier protein for Pd(II) complex to deliver it to the target molecules.