Hydrazone-flavonol based oxidovanadium(V) complexes: Synthesis, characterization and antihyperglycemic activity of chloro derivative in vivo.

Wet synthesis approach afforded four new heteroleptic mononuclear neutral diamagnetic oxidovanadium(V) complexes, comprising salicylaldehyde-based 2-furoic acid hydrazones and a flavonol coligand of the general composition [VO(fla)(L-ONO)]. The complexes were comprehensively characterized, including chemical analysis, conductometry, infrared, electronic, and mass spectroscopy, as well as 1D 1H and proton-decoupled 13C(1H) NMR spectroscopy, alongside extensive 2D 1H1H COSY, 1H13C HMQC, and 1H13C HMBC NMR analyses. Additionally, the quantum chemical properties of the complexes were studied using Gaussian at the B3LYP, HF, and M062X levels on the 6-31++g(d,p) basis sets. The interaction of these hydrolytically inert vanadium complexes and the BSA was investigated through spectrofluorimetric titration, synchronous fluorimetry, and FRET analysis in a temperature-dependent manner, providing valuable thermodynamic insights into van der Waals interactions and hydrogen bonding. Molecular docking was conducted to gain further understanding of the specific binding sites of the complexes to BSA. Complex 2, featuring a 5-chloro-substituted salicylaldehyde component of the hydrazone, was extensively examined for its biological activity in vivo. The effects of complex administration on biochemical and hematological parameters were evaluated in both healthy and diabetic Wistar rats, revealing antihyperglycemic activity at millimolar concentration. Furthermore, histopathological analysis and bioaccumulation studies of the complex in the brain, kidneys, and livers of healthy and diabetic rats revealed the potential for further development of vanadium(V) hydrazone complexes as antidiabetic and insulin-mimetic agents.

Using Quercetin to Construct Molecularly Imprinting Polymer in the Preparation and Enrichment of Flavonol and Flavonoid Compounds.

Flavonol and flavonoid compounds are important natural compounds with various biomedical activities. Therefore, it is of great significance to develop a strategy for the specific extraction of flavonol and flavonoid compounds. Quercetin is a well-studied flavonoid possessing many health benefits. This compound is a versatile antioxidant known to possess protective abilities against body tissue injury induced by pathological situations and various drug toxicities. Although quercetin is widely distributed in many plants, its content generally is not very high. Therefore, the specific extraction of quercetin as well as other flavonol and flavonoid compounds has profound significance. In this work, the quercetin molecularly imprinting polymer (QMIP) was successfully prepared, in which a typical flavonol quercetin was selected as the template molecule. QMIP was synthesized by performing the surface molecular imprinting technology on the surface of NH2-MIL-101(Fe). Our study results showed that QMIP exhibited quick binding kinetic behavior, a high adsorption capacity (57.04[Formula: see text]mg/g), and the specific recognition ability toward quercetin compared with structurally distinct compounds (selective [Formula: see text]). The specific adsorption ability of quercetin by QMIP was further explained using computation simulation that molecules with non-planar 3D conformations hardly entered the molecularly imprinted cavities on QMIP. Finally, QMIP was successfully used for the specific extraction of quercetin and five other flavonol and flavonoid compounds in the crude extracts from Sapium sebiferum. This study proposes a new strategy to synthesize the molecularly imprinted polymer based on a single template for enriching and loading a certain class of active ingredients with similar core structures from variable botanicals.

Health-Promoting Properties of Natural Flavonol Glycosides Isolated from Staphylea pinnata L.

Staphylea, also called bladdernuts, is a genus of plants belonging to the family Staphyleaceae, widespread in tropical or temperate climates of America, Europe, and the Far East. Staphylea spp. produce bioactive metabolites with antioxidant properties, including polyphenols which have not been completely investigated for their phytotherapeutic potential, even though they have a long history of use for food. Here, we report the isolation of six flavonol glycosides from the hydroalcoholic extract of aerial parts of Staphylea pinnata L., collected in Italy, using a solid-phase extraction technique. They were identified using spectroscopic, spectrometric, and optical methods as three quercetin and three isorhamnetin glycosides. Among the flavonol glycosides isolated, isoquercetin and quercetin malonyl glucoside showed powerful antioxidant, antimicrobial, and wound healing promoting activity and thus are valuable as antiaging ingredients for cosmeceutical applications and for therapeutic applications in skin wound repair.

α-Glucosidase inhibitory flavonol glycosides from Cyclocarya paliurus (Batalin) Iljinskaja and their kinetics characteristics.

Seven previously undescribed flavonol glycosides including four rare flavonol glycoside cyclodimers, dicyclopaliosides A-C (1-3) with truxinate type and dicyclopalioside D (4) with truxillate type, as well as three kaempferol glycoside derivatives cyclopaliosides A-C (5-7), were obtained from the leaves of Cyclocarya paliurus. Their structures were elucidated by extensive spectroscopic methods and chemical analyses. All compounds were evaluated for their inhibitory α-glucosidase activities. Among them, compounds 1-4 display strong inhibitory activities with IC50 values of 82.76 ± 1.41, 62.70 ± 4.00, 443.35 ± 16.48, and 6.31 ± 0.88 nM, respectively, while compounds 5-7 showed moderate activities with IC50 values of 4.91 ± 0.75, 3.64 ± 0.68, and 5.32 ± 0.53 µΜ, respectively. The structure-activity relationship analysis assumed that the cyclobutane cores likely contribute to the enhancement of α-glucosidase inhibitory activities of dimers. Also, the interaction mechanism between flavonol glycoside dimers and α-glucosidase were explored by the enzyme kinetic assay, indicating that compounds 1-3 exhibited mixed-type inhibition, while 4 showed uncompetitive inhibition. Additionally, the active compounds have also undergone molecular docking evaluation.

Synthesis of Flavonols and Assessment of Their Biological Activity as Anticancer Agents.

A series of flavanols were synthesized to assess their biological activity against human non-small cell lung cancer cells (A549). Among the sixteen synthesized compounds, it was observed that compounds 6k (3.14 ± 0.29 µM) and 6l (0.46 ± 0.02 µM) exhibited higher potency compared to 5-fluorouracil (5-Fu, 4.98 ± 0.41 µM), a clinical anticancer drug which was used as a positive control. Moreover, compound 6l (4'-bromoflavonol) markedly induced apoptosis of A549 cells through the mitochondrial- and caspase-3-dependent pathways. Consequently, compound 6l might be developed as a candidate for treating or preventing lung cancer.

Effect of Flavonols of Aronia melanocarpa Fruits on Morphofunctional State of Immunocompetent Organs of Rats under Cyclophosphamide-Induced Immunosuppression.

Aronia melanocarpa berries contain many compounds with potential benefits for human health. The food flavonoids quercetin and rutin, found in significant amounts in the fruits of A. melanocarpa, are known to have favourable effects on animal and human organisms. However, data on the effect of flavonols isolated from black chokeberry on immune functions during immunosuppression are not available in the literature. Thus, the aim of this study was to evaluate the effect of flavonol fraction isolated from A. melanocarpa fruits, in comparison with pure quercetin and rutin substances, on the dysfunctional state of rat thymus and spleen in immunodeficiency. The study was performed on Wistar rats. The animals were orally administered solutions of the investigated substances for 7 days: water, a mixture of quercetin and rutin and flavonol fraction of A. melanocarpa. For induction of immunosuppression, the animals were injected once intraperitoneally with cyclophosphamide. Substance administration was then continued for another 7 days. The results showed that under the influence of flavonols, there was a decrease in cyclophosphamide-mediated reaction of lipid peroxidation enhancement and stimulation of proliferation of lymphocytes of thymus and spleen in rats. At that, the effect of the flavonol fraction of aronia was more pronounced.

Silver Nanoparticles Encapped by Dihydromyricetin: Optimization of Green Synthesis, Characterization, Toxicity, and Anti-MRSA Infection Activities for Zebrafish (Danio rerio).

To achieve the environmentally friendly and rapid green synthesis of efficient and stable AgNPs for drug-resistant bacterial infection, this study optimized the green synthesis process of silver nanoparticles (AgNPs) using Dihydromyricetin (DMY). Then, we assessed the impact of AgNPs on zebrafish embryo development, as well as their therapeutic efficacy on zebrafish infected with Methicillin-resistant Staphylococcus aureus (MRSA). Transmission electron microscopy (TEM) and dynamic light-scattering (DLS) analyses revealed that AgNPs possessed an average size of 23.6 nm, a polymer dispersity index (PDI) of 0.197 ± 0.0196, and a zeta potential of -18.1 ± 1.18 mV. Compared to other published green synthesis products, the optimized DMY-AgNPs exhibited smaller sizes, narrower size distributions, and enhanced stability. Furthermore, the minimum concentration of DMY-AgNPs required to affect zebrafish hatching and survival was determined to be 25.0 µg/mL, indicating the low toxicity of DMY-AgNPs. Following a 5-day feeding regimen with DMY-AgNP-containing food, significant improvements were observed in the recovery of the gills, intestines, and livers in MRSA-infected zebrafish. These results suggested that optimized DMY-AgNPs hold promise for application in aquacultures and offer potential for further clinical use against drug-resistant bacteria.

Study on the stability of molecular chirality and the configuration protection of dihydromyricetin in vine tea.

This study aims to investigate the impact of four key factors, namely, temperature, water source, metal ion, and pH, on the stability of molecular chirality of dihydromyricetin (DMY) and proposed effective strategies for configuration protection. The findings reveal that temperatures exceeding 80°C could accelerate the racemization process of DMY, with a significant increase in racemization observed at 100°C. In addition, DMY exhibited heightened stability in ultrapure water as compared to various water sources, including pure water-1, pure water-2, mineral water, and running water. Notably, the presence of Fe2+ displayed an inhibitory effect on the racemization of DMY, whereas Mg2+, Ca2+, and Mn2+ showed a substantial promotional effect. Additionally, acidic conditions (pH < 5.0) were found to be protective for maintaining the stability of DMY, whereas alkaline conditions (pH > 9.0) were observed to be detrimental. Meanwhile, we first identified the presence of another pair of DMY isomers in this work.

The structural, antioxidant and emulsifying properties of cellulose nanofiber-dihydromyricetin mixtures: Effects of composite ratio.

In this work, effects of cellulose nanofiber/dihydromyricetin (CNF/DMY) ratio on the structural, antioxidant and emulsifying properties of the CNF/DMY mixtures were investigated. CNF integrated with DMY via hydrogen bonding and the antioxidant capacity of mixtures increased with decreasing CNF/DMY ratio (k). The oxidative stability of emulsions enhanced as the DMY content increased. Emulsions formed at Φ = 0.5 displayed larger size (about 25 µm), better viscoelasticity and centrifugal stability than those at Φ = 0.3 (about 23 µm). The emulsions at k = 17:3 and Φ = 0.5 exhibited the most excellent viscoelasticity. In conclusion, the DMY content in mixtures and the oil phase fraction exhibited distinct synergistic effects on the formation and characteristics of emulsions, and the emulsions could demonstrate superior oxidative and storage stability. These findings could provide a novel strategy to extend the shelf life of cellulose-based emulsions and related products.

Characterization of CsUGT73AC15 as a Multifunctional Glycosyltransferase Impacting Flavonol Triglycoside Biosynthesis in Tea Plants.

Flavonol glycosides, contributing to the health benefits and distinctive flavors of tea (Camellia sinensis), accumulate predominantly as diglycosides and triglycosides in tea leaves. However, the UDP-glycosyltransferases (UGTs) mediating flavonol multiglycosylation remain largely uncharacterized. In this study, we employed an integrated proteomic and metabolomic strategy to identify and characterize key UGTs involved in flavonol triglycoside biosynthesis. The recombinant rCsUGT75AJ1 exhibited flavonoid 4'-O-glucosyltransferase activity, while rCsUGT75L72 preferentially catalyzed 3-OH glucosylation. Notably, rCsUGT73AC15 displayed substrate promiscuity and regioselectivity, enabling glucosylation of rutin at multiple sites and kaempferol 3-O-rutinoside (K3R) at the 7-OH position. Kinetic analysis revealed rCsUGT73AC15's high affinity for rutin (Km = 9.64 µM). Across cultivars, CsUGT73AC15 expression inversely correlated with rutin levels. Moreover, transient CsUGT73AC15 silencing increased rutin and K3R accumulation while decreasing their respective triglycosides in tea plants. This study offers new mechanistic insights into the key roles of UGTs in regulating flavonol triglycosylation in tea plants.

A novel colormetric and light-up fluorescent sensor from flavonol derivative grafted cellulose for rapid and sensitive detection of Hg2+ and its applications in biological and environmental system.

Mercury ion (Hg2+) is one of harmful heavy metal ions that can accumulate inside the human organism and cause some health problems. In the article, a highly effective fluorescent probe named EC-T-PCBM was prepared by grafting flavonol derivatives onto ethyl cellulose for the specific recognition of Hg2+. EC-T-PCBM exhibited a remarkable fluorescence light-up response toward Hg2+ with excellent sensitivity. EC-T-PCBM possessed several prominent sensing properties for Hg2+, such as low detection limit (43.9 nM), short response time (5 min), and wide detection pH range (6-9). The response mechanism of EC-T-PCBM to Hg2+ has been verified through 1H NMR titration and DFT computation. Additionally, EC-T-PCBM not only can be used for accurately determining trace amount of Hg2+ in actual environmental water samples, but also can serve as a portable and rapid device by loading it on test strips for sensitive and selective visualization of Hg2+. More importantly, the confocal fluorescence imaging of onion cells suggested the favorable cell membrane permeability of EC-T-PCBM and its prominent ability to continuously monitor the enrichment from Hg2+ within fresh plant tissues.

Mechanism of Dihydromyricetin-Induced Reduction of Furfural Derived from the Amadori Compound: Formation of Adducts between Dihydromyricetin and Furfural or Its Precursors.

Dihydromyricetin (DMY) was employed to reduce the yield of furfural derived from the Amadori rearrangement product of l-threonine and d-xylose (Thr-ARP) by trapping Thr-ARP, 3-deoxyxyosone (3-DX), and furfural to form adducts. The effect of different concentrations of DMY at different pH values and temperatures on the reduction of furfural production was studied, and the results showed that DMY could significantly reduce furfural production at higher pH (pH 5-7) and lower temperature (110 °C). Through the surface electrostatic potential analysis by Gaussian, a significant enhancement of the C6 nucleophilic ability at higher pH (pH ≥ 5) was observed on DMY with hydrogen-dissociated phenol hydroxyl. The nucleophilic ability of DMY led to its trapping of Thr-ARP, 3-DX, and furfural with the generation of the adducts DMY-Thr-ARP, DMY-3-DX, and DMY-furfural. The formation of the DMY-Thr-ARP adduct slowed the degradation of Thr-ARP, caused the decrease of the 3-DX yield, and thereby inhibited the conversion of 3-DX to furfural. Therefore, DMY-Thr-ARP was purified, and the structure was identified by nuclear magnetic resonance (NMR). The results confirmed that C6 or C8 of DMY and carbonyl carbon in Thr-ARP underwent a nucleophilic addition reaction to form the DMY-Thr-ARP adduct. In combination with the analysis results of Gaussian, most of the DMY-Thr-ARP adducts were calculated to be C6-DMY-Thr-ARP. Furthermore, the formation of DMY-furfural caused furfural consumption. The formation of the adducts also shunted the pathway of both Thr-ARP and 3-DX conversion to furfural, resulting in a decrease in the level of furfural production.

Investigating the Combined Toxicity of Cu(II) and Carbon Monoxide (CO); Cellular CO Delivery Using a Cu(II) Flavonolato Complex.

Carbon monoxide (CO) delivery molecules are of significant current interest as potential therapeutics, including for anticancer applications. A recent approach toward generating new types of materials-based anticancer agents involves combining the Fenton reactivity of a redox active metal ion with CO delivery. However, small molecule examples of these types of entities have not been systematically studied to evaluate the combined effect on cellular toxicity. Herein we describe a Cu(II) flavonolato complex which produces anticancer effects through a combination of copper-mediated reactive oxygen species (ROS) generation and light-induced flavonol CO release. Confocal microscopy studies provide evidence of enhanced flavonol uptake in the copper flavonolato system relative to the free flavonol, which leads to an increased amount of CO delivery within cells. Importantly, this work demonstrates that a metal flavonolato species can be used to produce enhanced toxicity effects resulting from both metal ion-induced Fenton reactivity and increased cellular uptake of a flavonol CO donor.

Comparison of binding sites and affinity of flavonol-Cu(II) complexes with the same parent nucleus: Synthesis, DFT prediction, and coordination pattern.

This study explores the coordination dynamics between dietary polyphenols, specifically kaempferol, quercetin, and myricetin, and Cu ions in aqueous environments. A novel synthesis method for flavonol-Cu(II) coordination compounds is introduced, effectively reducing interference from free metal ions. Our results reveal consistent binding patterns of Cu ions with flavonols (2:1 ratio of flavonol to Cu(II)), predominantly at the 4,5 sites. Various analytical techniques are used to validate these coordination ratios and sites. The binding affinity of the flavonols for Cu ions follows a descending sequence: myricetin > quercetin > kaempferol. Notably, coordination with Cu ions enhances the free-radical scavenging activities of these flavonols. These findings hold substantial importance for food chemistry, biology, and medicine, providing crucial insights into the way dietary flavonols form stable structures in environments similar to human body fluids and their interactions with metal ions, opening new possibilities for their application and understanding in diverse scientific domains.

Design of flavonol-loaded cationic gold nanoparticles with enhanced antioxidant and antibacterial activities and their interaction with proteins.

In this work, four structurally similar flavonols (galangin, kaempferol, quercetin and myricetin) were coated on the surface of (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide (MUTAB)­gold nanoparticles (AuNPs) by two-step phase transfer and self-assembly, and the cationic MUTAB- AuNPs coated with flavonols (flavonol-MUTAB-AuNPs) were designed. Free radical scavenging and antibacterial experiments show that flavonol-MUTAB-AuNPs greatly improve the scavenging effect on DPPH, hydroxyl and superoxide anion radicals, and significantly enhance the inhibition effect on Staphylococcus aureus and Escherichia coli compared with flavonols and AuNPs. Then γ-globulin, fibrinogen, trypsin and pepsin were selected as representative proteins and their interaction with flavonol-MUTAB-AuNPs were investigated by various spectroscopic techniques. The fluorescence quenching mechanism of these four proteins by flavonol-MUTAB-AuNPs is static quenching. The binding constants Ka between them are in the range of 103 to 106. The interaction between them is endothermic, entropy-driven spontaneous process, and the main non-covalent force is the hydrophobic interaction. The effect of flavonol-MUTAB-AuNPs on the structure of the four proteins were investigated using UV-vis absorption spectra, synchronous fluorescence spectra and circular dichroism spectra. These results offer important insights into the essence of the interaction between flavonol-MUTAB-AuNPs and γ-globulin/fibrinogen/trypsin/pepsin. They will contribute to the development of safe and effective flavonol-MUTAB-AuNPs in biomedical fields.

The case for an oxidopyrylium intermediate in the mechanism of quercetin dioxygenases.

The quercetin dioxygenases (QDOs) are unusual metalloenzymes in that they display ring-opening dioxygenase activity with several different first-row transition metal ions which do not undergo redox changes during turnover. The QDOs are also unique in that the substrate binds as an η1-flavonolate rather than the η2 -bidentate mode seen in all reported model complexes. The flavonol substrates were early examples of excited state intramolecular proton transfer (ESIPT) phenomena, in which photoexcitation causes an H-atom exchange between the adjacent hydroxyl and ketone, generating an oxidopyrylium emissive state. These oxidopyryliums undergo ring-opening dioxygenations analogous to the enzymatic reactions. Our hypothesis is that lability of the divalent metal ion may allow access to a reactive oxidopyrylium intermediate via coordination switching from the oxy to ketone position, which allows reaction with O2. In this report, we use a straight-forward methylation strategy to generate a panel of flavonol and thioflavonol derivatives modeling several η1- and η2-coordination modes. Methylation of 3-hydroxythioflavone generates an air stable η1 hydroxopyrylium salt, which undergoes rapid ring-opening dioxygenation by deprotonation or photoexcitation. By comparison, the η1-methoxyflavonol does not react with O2 under any condition. We find that any of the studied flavonol derivatives, η1 or η2, which demonstrates ESIPT-like oxidopyrylium emissions undergo QDO-like ring-opening reactions with dioxygen. The implications of these results concerning the mechanism of QDOs and related dioxygenases is discussed.

GABase and glutaminase inhibitory activities of herbal extracts and acylated flavonol monoglycosides isolated from the leaves of Laurus nobilis L.

This study was to compare GABase [a mixture of γ-aminobutyric acid (GABA) aminotransferase and succinic semialdehyde dehydrogenase] and glutaminase inhibitory activities of 20 herbal extracts and investigate the isolation, structural elucidation and those inhibitory activities of three acylated flavonol monoglycosides from the selected extract of Laurus nobilis L. (laurel). On the basis of the NMR spectroscopic data and the ESI MS spectra together with the comparison with the literature values, three compounds were identified as kaempferol-3-O-(4″-E-p-coumaroyl)-α-l-rhamnopyranoside (1), kaempferol-3-O-(3″,4″-di-E-p-coumaroyl)-α-l-rhamnopyranoside (2) and kaempferol-3-O-(2″,4″-di-E-p-coumaroyl)-α-l-rhamnopyranoside (3), respectively. The IC50 values of GABase inhibitory activity of 1-3 and p-hydroxybenzaldehyde (HBA) as control were 0.24 mM, 0.14 mM, 0.12 mM and 0.43 mM, respectively. Additionally, the IC50 values of glutaminase inhibitory activity of 1-3 and 6-diazo-5-oxo-l-norleucine (DON) as control were 0.34 mM, 0.13 mM, 0.14 mM and 0.33 mM, respectively. The results suggest that the extract from laurel shows the strongest biological activities among 20 herbal extracts and three acylated flavonol monoglycosides may serve as potential lead compounds for the prevention and treatment of neurodegenerative and lifestyle-related diseases by targeting GABase and glutaminase. This is the first report on GABase and glutaminase inhibitory activities of 1-3.

An efficient cocrystallization strategy for separation of dihydromyricetin from vine tea and enhanced its antibacterial activity for food preserving application.

The objective of this study was to optimize the separation and purification of dihydromyricetin (DMY) from vine tea to obtain high purity, antibacterial and antioxidant crystal forms. We developed a cocrystallization approach for separation of DMY from vine tea with easy operation and high efficiency. The type and concentration of co-formers as well as solvent for separation have been investigated in detail. Under the optimal conditions, DMY with a purity of 92.41% and its two co-crystal forms (purity >97%) can be obtained. Three DMY crystal forms had consistent and good antioxidant activities according to DPPH radical scavenging results. DMY had effective antibacterial activity against the two kinds of drug-resistant bacteria including CRAB and MRSA, and DMY co-crystals had a greater advantage than DMY itself on CRAB. This work implies that cocrystallization can be used for the DMY separation and enhanced its anti-drug-resistant bacteria activity in food preservation.

Comparative analysis of the reactivity of anthocyanidins, leucoanthocyanidins, and flavonols using a quantum chemistry approach.

Anthocyanidins, leucoanthocyanidins, and flavonols are natural compounds mainly known due to their reported biological activities, such as antiviral, antifungal, anti-inflammatory activities, and antioxidant activity. In the present study, we performed a comparative structural, conformational, electronic, and nuclear magnetic resonance analysis of the reactivity of the chemical structure of primary anthocyanidins, leucoanthocyanidins, and flavonoids. We focused our analysis on the following molecular questions: (i) differences in cyanidin catechols ( +)-catechin, leucocyanidin, and quercetin; (ii) the loss of hydroxyl presents in the R1 radical of leucoanthocyanidin in the functional groups linked to C4 (ring C); and (iii) the electron affinity of the 3-hydroxyl group (R7) in the flavonoids delphinidin, pelargonidin, cyanidin, quercetin, and kaempferol. We show unprecedented results for bond critical point (BCP) of leucopelargonidin and leucodelphirinidin. The BCP formed between hydroxyl hydrogen (R2) and ketone oxygen (R1) of kaempferol has the same degrees of covalence of quercetin. Kaempferol and quercetin exhibited localized electron densities between hydroxyl hydrogen (R2) and ketone oxygen (R1). Global molecular descriptors showed quercetin and leucocyanidin are the most reactive flavonoids in electrophilic reactions. Complementary, anthocyanidins are the most reactive in nucleophilic reactions, while the smallest gap occurs in delphinidin. Local descriptors indicate that anthocyanidins and flavonols are more prone to electrophilic attacks, while in leucoanthocyanidins, the most susceptible to attack are localized in the ring A. The ring C of anthocyanidins is more aromatic than the same found in flavonols and leucoanthocyanidins. METHODS: For the analysis of the molecular properties, we used the DFT to evaluate the formation of the covalent bonds and intermolecular forces. CAM-B3LYP functional with the def2TZV basis set was used for the geometry optimization. A broad analysis of quantum properties was performed using the assessment of the molecular electrostatic potential surface, electron localization function, Fukui functions, descriptors constructed from frontier orbitals, and nucleus independent chemical shift.

Dysosmaflavonoid A-F, new flavonols with potent DPPH radical scavenging activity from Dysosma versipellis.

Six new flavonols, including four glucosylated flavonols (dysosmaflavonoid A-D), one phenylpropanoid-substituted flavonol (dysosmaflavonoid E), and one phenyl-substituted flavonol (dysosmaflavonoid F), together with five known analogues, were isolated from the roots and rhizomes of Dysosma versipellis. Their structures were elucidated by comprehensive analysis of their NMR, IR, UV, HRESIMS, and HPLC data. The antioxidant activities of all isolated compounds were examined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. Compounds 2, 3, 5-8, and 12 exhibited significant DPPH scavenging capacity with IC50 values of 33.95, 39.02, 31.17, 32.79, 31.85, 30.48, and 23.75 µM, respectively, in comparison with Trolox (IC50, 15.80 µM). Compound 12 displayed more potent DPPH radical scavenging activity than prenylated and (or) glucosided derivatives (2-4, or 10). The preliminary structure-activity relationship showed that the catechol structure in flavonol is essential for DPPH radical scavenging effect.