“…The above molecular descriptor values obtained from the total energy method for the investigated compound are displayed in Table 1. The calculated molecular properties clearly confirms that quercetin and its glucosides prefer to act as electron donor rather than electron acceptor in the studied environments 16, 17 . This is also an indication of their antioxidant activity.Figure 1The chemical structure and atom numbering for quercetin and its glucosides.
…”
Among the multiple components of propolis, flavonoids contribute greatly to the antioxidant activities of propolis. Flavonoids mainly exist in the form of sugar-conjugated derivatives. Quercetin glycosides represent the predominant flavonoid fraction in propolis. In this work, density functional theory (DFT) calculations were applied to analyze the antioxidative properties of quercetin and its glucosides in the gas and in the liquid phase (ethanol, water). Three main antioxidant mechanisms, hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) were used to analyze the antioxidative capacity of the investigated compounds. Solvent effects dominantly affect SET-PT and SPLET. Thus, the thermodynamically preferred mechanism can be altered. HAT and SPLET are the thermodynamically dominant mechanisms in gas and solvent phases, respectively. Therefore, in the gas phase, the sequence of the antioxidative capacity is similar with the bond dissociation enthalpy values: quercetin > quercetin-5-O-glucoside > quercetin-7-O-glucoside > quercetin-3-O-glucoside > quercetin-3′-O-glucoside > quercetin-4′-O-glucoside. While, in the solvent phases, the sequence is similar with the proton affinity values: quercetin-4′-O-glucoside > quercetin-5-O-glucoside > quercetin > quercetin-3-O-glucoside > quercetin-7-O-glucoside > quercetin-3′-O-glucoside. OH groups in B-ring and C-ring contribute mainly to the antioxidative activities of quercetin and glucosides compared with A-ring.
“…The above molecular descriptor values obtained from the total energy method for the investigated compound are displayed in Table 1. The calculated molecular properties clearly confirms that quercetin and its glucosides prefer to act as electron donor rather than electron acceptor in the studied environments 16, 17 . This is also an indication of their antioxidant activity.Figure 1The chemical structure and atom numbering for quercetin and its glucosides.
…”
Among the multiple components of propolis, flavonoids contribute greatly to the antioxidant activities of propolis. Flavonoids mainly exist in the form of sugar-conjugated derivatives. Quercetin glycosides represent the predominant flavonoid fraction in propolis. In this work, density functional theory (DFT) calculations were applied to analyze the antioxidative properties of quercetin and its glucosides in the gas and in the liquid phase (ethanol, water). Three main antioxidant mechanisms, hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) were used to analyze the antioxidative capacity of the investigated compounds. Solvent effects dominantly affect SET-PT and SPLET. Thus, the thermodynamically preferred mechanism can be altered. HAT and SPLET are the thermodynamically dominant mechanisms in gas and solvent phases, respectively. Therefore, in the gas phase, the sequence of the antioxidative capacity is similar with the bond dissociation enthalpy values: quercetin > quercetin-5-O-glucoside > quercetin-7-O-glucoside > quercetin-3-O-glucoside > quercetin-3′-O-glucoside > quercetin-4′-O-glucoside. While, in the solvent phases, the sequence is similar with the proton affinity values: quercetin-4′-O-glucoside > quercetin-5-O-glucoside > quercetin > quercetin-3-O-glucoside > quercetin-7-O-glucoside > quercetin-3′-O-glucoside. OH groups in B-ring and C-ring contribute mainly to the antioxidative activities of quercetin and glucosides compared with A-ring.
“…As strong antioxidants, C, Q, and its glycosides might protect endothelial cells by oxidation defense mechanism (Lenz and Monaghan ). C ameliorated oxidant‐induced endothelial damage via increased production of nitric oxide and induction of Hmox‐1 (Jiang and others ). Q suppressed ochratoxin‐induced toxicity and oxidative stress through activation of Nrf2 pathway (Ramyaa and Padma ).…”
Section: Resultsmentioning
confidence: 97%
“…Recently, Li and others () reported that Q could protect human brain microvascular endothelial cells from fibrillar β‐amyloid 1‐40 ‐induced toxicity. In addition, Jiang and others () noted that C could improve vessel function and protects human aortic endothelial cells against HOCl‐induced damage. These phenolic molecules are effective in cell protection based on different bioactivities, such as antiinflammatory, antimicrobial, anticarcinogenic, anticoagulant, and antioxidant properties (Utesch and others ), so they are widely distributed among plants and play an important role in biological defense for plants.…”
Section: Resultsmentioning
confidence: 99%
“…In this study, these 3 phenolics of rabbiteye blueberry leaves, Q, H, and C could reduce oxidative stress by directly decreasing the level of ROS in endothelial cells and influencing protein expression of several key oxidation‐reduction enzymes. SOD and HO‐1 play an important role in vascular protection in response to oxidative stress (Raychaudhuri and Deng ; Jiang and others ). On the contrary, XO‐1, as a major source of superoxide, leads to endothelial dysfunction (Landmesser and others ).…”
In recent years, the blueberry cultivation and processing industry developed quickly because blueberries are super-fruit with healthy function. Blueberry leaves are byproducts of the blueberry industry, which are rich in bioactive phenolics, such as quercetin (Q), hyperin (H), and chlorogenic acid (C). This study investigated protective effects of 3 phenolics (Q, H, and C) from leaves of rabbiteye blueberry Vaccinium ashei on human umbilical vein endothelial cells. The results showed that all these 3 phenolics could improve endothelial function by inhibiting oxidative damage and proinflammatory cytokines caused by tumor necrosis factor-α (TNF-α). The cell vitalities of endothelial cells pretreated with Q, H, and C were higher than those stimulated with TNF-α only. These phenolics could decrease reactive oxygen species and xanthine oxidase-1 levels and increase superoxide dismutase and heme oxygenase-1 levels in endothelial cells. They also could decrease the protein expressions of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and monocyte chemotactic protein-1 induced by TNF-α. In addition, Q, H, and C also exhibited vasodilatory effect by reducing the angiotensin I-converting enzyme (ACE) protein levels in endothelial cells. Mostly 3 phenolics exhibited bioactivities as a function of concentration, but the effects not always depended on the concentration. The antioxidant and antiinflammatory effects of Q seemed to be more pronounced than H; however, H exhibited higher cell vitalities. The results indicated that phenolics from rabbiteye blueberry leaves could be potential antioxidants, inflammation and ACE inhibitors, and rabbiteye blueberry leaves provide a new resources of phytochemicals beneficial for cardiovascular health.
“…Calculated χ and ω values show that more polar the solvent is, more it contributes to accentuate the parametric representation of antioxidant property. The calculated ω properties clearly confirm that quercetin prefers to act as electron donor rather than electron acceptor in the studied environments [ 14 , 15 ]. With these results the antioxidant activity levels of quercetin molecule have been quantitatively parameterized.…”
In this study, a Flavobacterium sp. is isolated from natural spring, and identified using molecular techniques. Extracellular and intracellular secondary metabolites are identified using solid phase microextraction gas chromatography-mass spectrometry and ultra performance liquid chromatography. Cytotoxic activity of the extracellular compounds produced by the Flavobacterium sp. and quercetin as the standard are measured using ECV304 human endothelial cells in vitro. Our results show that Flavobacterim sp. isolate has the highest percentage of similarity with Flavobacterium cheonhonense strain ARSA-15 (99%). Quercetin is detected as the major extracellular compound produced by the Flavobacterium sp. Methanol extract of Flavobacterium sp. resulted in a higher cell viability results when compared to DMSO extracts. Computational chemistry approach was used and it has been found that polar solvent (methanol) contributed to higher antioxidant activity. In conclusion, Flavobacterium sp. can be used to produce quercetin for industrial purposes.
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