Quercetin, a flavonoid compound which is widely distributed in plants are considered ass beneficial physiologically due to attributed bioactivity such as anti-cancer, immunomodulatory, antidiabetic, and anti-inflammatory. In this study, the quercetin content from the dried Blumea balsamifera L. DC dried leaf was macerated with 95% ethanol and the concentrated extract was purified using Modified Kupchan method and flash chromatography. All fractions were tested for the presence of flavonoids using phytochemical screening and the selected dichloromethane fraction were further purified using another round of flash chromatograph. All resulting fractions and pooled samples were tested for the antioxidant property using the developed Thin Layer Chromatography (TLC)-Bioautography and separated compounds were derivatized with DPPH. Using the optimized TLC-Bioautography method, the quercetin content in the dichloromethane fraction was analyzed and compared with a reversed phase high performance liquid chromatography hyphenated with photodiode array detector (RP-HPLC-PDA). The calculated quercetin content from the pooled sample using TLC-bioautography method is 2.25 mg/ml and from RP-HPLC-PDA is 2.02 mg/ml which was not comparable statistically using unpaired t-test (p<0.05, α=0.05
Quercetin

Myricetin and its glycosides are important flavonols commonly found in plants, and they are natural organic compounds with diverse pharmacological activities. Numerous studies have demonstrated that myricetin and its glycosides are strong antioxidants that have great potential in preventing, alleviating and assisting the treatment of chronic non-infectious diseases such as cancer, diabetes, and cardiovascular diseases. In addition, myricetin and its glycosides also have antiviral, antibacterial, anti-inflammatory, analgesic, liver protection and other pharmacological activities. Myricetin contains more hydroxyl groups in the parent ring structure than other flavonoids, so myricetin and its glycosides have stronger pharmacological activities than other flavonols or flavonoids such as quercetin and kaempferol. Therefore, myricetin and its glycosides have great development and application prospects. In this paper, the classification and distribution of myricetin and its glycosides, their pharmacological activity and mechanism, as well as comparison with other flavonoids were reviewed. In addition, limitations of the current research and application of myricetin and its glycosides were analyzed, and the further studies on pharmacological activities as well as their dose-activity relationship, structure-activity relationship, chemical modification, biosynthesis and application prospects of myricetin and its glycosides were discussed and proposed.
Flavonoids ; Flavonols ; Glycosides ; Quercetin

This study explored the chemical constituents of the aerial part of Hypericum curvisepalum. Sixteen compounds were isolated from the 95% ethanol extract of H. curvisepalum with various chromatographic techniques, including a new prenylated phenyl polyketide, mysorenone D(1). Other compounds were mysorenone-A(2), mysorenone-C(3), mysorenone-B(4), peplidiforone A(5), 4-methoxy-3-(2-methylbut-3-en-2-yl)-6-phenyl-2H-pyran-2-one(6), hyperenone-A(7), 4-(3,3-dimethylallyl)oxy-6-phenyl-α-pyrone(8), peplidiforone B(9), elegaphenone(10), hypercohin A(11), hyperisampsin G(12), spathulenol(13), quercetin(14), β-sitosterol(15), and β-amyrin(16).
Benzophenones ; Hypericum ; Quercetin

Chemical investigation of the plant Tristemma hirtum P. Beauv (Melastomataceae) resulted to the isolation of a new flavonol glycoside named quercetin-7-O-α-D-arabinofuranoside (1), together with nine known compounds including 3′-hexadecanoyl-2′-(9aZ)-tetradecanoyl-glycerol 1′-O-[β-D-galactopyranosyl-(1″ → 6″)-α-D-galactopyranoside] (2), arjunolic acid (3), β-sitosterol-3-O-β-D-glucopyranoside (4), terminolic acid (5), quercetin (6), asiatic acid (7), maslinic acid (8), 1β-O-galloylpedunculagin (9) and 6-hydroxyapigenin 7-O-β-D-glucopyranoside (10) from the methanol extract using normal and reversed phase column chromatography. The structures of these compounds were determined by comprehensive interpretation of their spectral data mainly including 1D- 2D-NMR (¹H-¹H COSY, HSQC, and HMBC) spectroscopic and ESI-TOF-MS mass spectrometric analysis.
Chromatography ; Melastomataceae ; Methanol ; Plants ; Quercetin

Studies on the interaction between small organic molecules and DNA are important means to explore drug mechanism and new drugs. Quercetin is a polyhydroxy flavone compound with activities such as anti-cancer, anti-inflammatory, antibacterial, antiviral, hypoglycemic and anti-hypertensive, immunomodulation and cardiovascular protection. Experimental studies aim at confirming if an interaction exists between quercetin and DNA, and determining the type of interaction. The interaction between quercetin and herring DNA can be detected by fluorescence spectrometry and resonance scattering fluorescence spectrometry analysis. The mode of the interaction between quercetin and herring DNA can be detected by UV-Vis spectrophotometry and fluorescence polarization analysis. This review helps understand the in vitro interaction between quercetin and DNA, and assist the development of drugs for corresponding diseases.
DNA/genetics* ; Quercetin ; Spectrometry, Fluorescence

Chemical constituents were isolated and purified from the water extract of Artemisia annua by column chromatography of HP-20 macroporous resin, silica gel, ODS, Sephadex LH-20, HW-40, and semi-preparative RP-HPLC. Their structures were elucidated by physicochemical properties and spectral analyses. As a result, Fifteen compounds were isolated and identified as vitexnegheteroin M(1), sibricose A5(2), securoside A(3), citrusin D(4), annphenone(5), E-melilotoside(6), esculetin(7), scopoletin-7-O-β-D-glucoside(8), eleutheroside B_1(9), chrysosplenol D(10), patuletin-3-O-β-D-glucopyranoside(11), quercetin-7-O-β-D-glucoside(12), rutin(13), apigenin 6,8-di-C-β-D-glucopyranoside(14), isoschaftoside(15), among them, compounds 1-4 were identified from Artemisia for the first time. Additionally, the isolates were evaluated for their inhibitory effects on the production of PGE_2 in LPS-simulated RAW264.7 macrophages. The results showed that compounds 1, 2, 8, and 10-15 could reduce PGE_2 levels, to a certain extent.
Apigenin ; Artemisia annua ; Quercetin ; Rutin

Quercetin, a flavonol, has been reported to exhibit a wide range of biological properties including anti-oxidant and anti-inflammatory activities. However, pharmacological properties of quercetin-3-O-β-D-glucuronide (QG), a glycoside derivative of quercetin, have not been extensively examined. The objective of this study is to elucidate the anti-inflammatory property and underlying mechanism of QG in lipopolysaccharide (LPS)-challenged RAW264.7 macrophage cells in comparison with quercetin. QG significantly suppressed LPS-induced extracellular secretion of pro-inflammatory mediators such as nitric oxide (NO) and PGE2, and pro-inflammatory protein expressions of iNOS and COX-2. To elucidate the underlying mechanism of the anti-inflammatory property of QG, involvement of MAPK signaling pathways was examined. QG significantly attenuated LPS-induced activation of JNK and ERK in concentration-dependent manners with a negligible effect on p38. In conclusion, the present study demonstrates QG exerts anti-inflammatory activity through the suppression of JNK and ERK signaling pathways in LPS-challenged RAW264.7 macrophage cells.
Dinoprostone ; Macrophages ; Nitric Oxide ; Phosphorylation* ; Quercetin

Taxifolin glycoside is a new drug candidate for the treatment of atopic dermatitis (AD). Many drugs cause side effects such as long QT syndrome by blocking the human ether-a-go-go related gene (hERG) K+ channels. To determine whether taxifolin glycoside would block hERG K+ channels, we recorded hERG K+ currents using a whole-cell patch clamp technique. We found that taxifolin glycoside directly blocked hERG K+ current in a concentration-dependent manner (EC50=9.6+/-0.7 microM). The activation curve of hERG K+ channels was negatively shifted by taxifolin glycoside. In addition, taxifolin glycoside accelerated the activation time constant and reduced the onset of the inactivation time constant. These results suggest that taxifolin glycoside blocks hERG K+ channels that function by facilitating activation and inactivation process.
Dermatitis, Atopic ; Humans ; Long QT Syndrome ; Quercetin

(2S)-taxifolin is an important flavonoid that has anti-inflammatory and anti-oxidation effects. It is widely used in pharmaceutical and nutraceutical industries. Flavone 3-hydroxylase (F3H) can catalyze the synthesis of (2S)-taxifolin and other 3-hydroxylated flavonoids from (2S)-eriodictyol. Due to the low catalytic efficiency of F3H, the titer of many 3-hydroxyflavones, such as taxifolin, synthesized by microbial method is relatively low. In this study, a SmF3H was identified from the transcriptome of Silybum marianum (L.) Gaertn. The results of fermentation showed that SmF3H can catalyze the flavone 3-hydroxylation reaction, and its catalytic efficiency was significantly higher than that of commonly used SlF3H from Solanum lycopersicum. Six promoters with different transcription strength were selected to optimize the synthesis pathway from the flavonoid precursor (2S)-naringenin to (2S)-taxifolin. The results showed that the highest titer of (2S)-taxifolin (695.90 mg/L in shake flask) could be obtained when the P(GAL7) promoter was used to control the expression of SmF3H. The titer of (2S)-taxifolin was further improved to 3.54 g/L in a 5-L fermenter, which is the highest titer according to current available literatures.
Antioxidants ; Flavonoids ; Milk Thistle ; Quercetin/analogs & derivatives*

OBJECTIVE: To investigate the effects of quercetin on the apoptosis of platelets and to analyze the intrinsic mechanism. METHODS: Firstly, the effects of quecetin on the apoptosis of platelets was detected by flow cytometry. Secondly, Western blot was used to detect the expression of apoptosis-related proteins in the platelets treated with quercetin for 2 and 4 day. RESULTS: By flow cytometry, it was found that the apoptosis of platelets in the quercetin-treated group (2, 4 and 8 μmol/L) was inhibited, the apoptosis rate of platelets in 2, 4 and 8 μmol/L quercetin group was 3.12%±0.32%, 2.89%±0.15% and 2.31%±0.28%, respectively, which were signigicantly lover than that in control group (P＜0.01). With the increase of quecetin concentration, the proportion ratio of platelets significantly decreased in a concentration-dependent manner（r=-0.9985）. Similar results were observed on the 4th day. Western blot showed that the treatment with quercetin (2, 4 and 8 μmol/L) promoted the expression of anti-apoptotic protein BCL-2, inhibited the expression of pro-apoptotic protein BAX, resulting in a significant increase in the ratio of BCL-2/BAX (P＜0.01), thereby inhibiting the apoptosis of platelets. Similar results were observed on the 4th day. CONCLUSION Quercetin can inhibit platelet apoptosis by increasing the ratio of apoptosis-related protein BCL-2/BAX in a concentration-dependent manner.
Apoptosis ; Apoptosis Regulatory Proteins ; Blood Platelets ; Quercetin