A new quercetin nanocrystals self-stabilized Pickering emulsion(QT-NSSPE) was prepared by high-pressure homogenization combined with probe ultrasonic method. The influences of oil fraction, quercetin(QT) concentration, and pH of water phase on the formation of QT-NSSPE were investigated. On this basis, the QT-NSSPE prepared under optimal conditions was evaluated in terms of microstructure, stability, and in vitro release and the droplet size and drug loading were 15.82 μm and 4.87 mg·mL~(-1), respectively. The shell structure formed by quercetin nanocrystals(QT-NC) on the emulsion droplet surface was observed under a scanning electron microscope(SEM). X-ray diffraction(XRD) showed that the crystallinity of adsorbed QT-NC decreased significantly as compared with the raw QT. There were not significant changes of QT-NSSPE properties after 30 days of storage at room temperature. The in vitro release experiment confirmed that QT-NSSPE has a higher accumulative release rate than the raw QT. All these results indicated that QT-NSSPE has a great stability and a satisfactory in vitro release behavior, which is a promising new oral delivery system for QT.
Emulsions/chemistry* ; Nanoparticles ; Particle Size ; Quercetin ; Water/chemistry*

With an attempt to synthesize high-value isoquercitrin (quercetin-3-O-β-D-glucopyranoside), we carried out the biotransformation of quercetin (1) by Gliocladium deliquescens NRRL 1086. Along with the aimed product quercetin 3-O-β-D-glycoside (2), three additional metabolites, 2-protocatechuoyl-phlorogucinol carboxylic acid (3), 2,4,6-trihydroxybenzoic acid (4), and protocatechuic acid (5), were also isolated. The time-course experiments revealed that there were two metabolic routes, regio-selectivity glycosylation and quercetin 2,3-dioxygenation, co-existing in the culture. Both glycosylation and oxidative cleavage rapidly took place after quercetin feeding; about 98% quercetin were consumed within the initial 8 h and the oxdized product (2-protocatechuoyl-phlorogucinol carboxylic acid) was hydrolyzed into two phenolic compounds (2,4,6-trihydroxybenzoic acid and protocatechuic acid). We also investigated the impact of glucose content and metal ions on the two reactions and found that high concentrations of glucose significantly inhibited the oxidative cleavage and improved the yield of isoquercitrin and that Ca, Fe, Mn, Mg, and Zn inhibited glycosylation. To test the promiscuity of this culture, we selected other four flavonols as substrates; the results demonstrated its high regio-selectivity glycosylation ability towards flavonols at C-3 hydroxyl. In conclusion, our findings indicated that the versatile microbe of G. deliquescens NRRL 1086 maitained abundant enzymes, deserving further research.
Biotransformation ; Gliocladium ; chemistry ; metabolism ; Molecular Structure ; Quercetin ; chemistry ; metabolism

OBJECTIVETo investigate the chemical constituents of Lespedeza virgata.

METHODThe constituents were isolated by column chromatography and their structures were elucidated by chemical properties and spectroscopic evideuce.

RESULTSeven components were isolated and identified as quercetin 3-O-[2"-O-( E'-6"-O-feruloyl)-beta-D-glucopyranosyl]-beta-D-galact opyranoside (1), kaempferol-7-O-L-rhamnopyranoside (2), 7-O-alpha-L-rhamnopyransyl-kaempeferol-3-O-beta-D-glucopyranoside (3), quercetine (4), E-beta-hydroxycinnamic acid (5), protocatechuic acid (6), p-hydroxybenzoic (7).

CONCLUSIONSeven components are isolated from L. virgata for the first time.

Drugs, Chinese Herbal ; chemistry ; Glycosides ; chemistry ; Hydroxybenzoates ; chemistry ; Lespedeza ; chemistry ; Magnetic Resonance Spectroscopy ; Quercetin ; chemistry

The present study is to study the chemical constituents from ethanol extract of Psidium guajava leaves. The constituents were separated and purified by silica gel column chromaiographios over, macroporous resin D-101, Sephadex LH-20, and ODS. Six flavonoids compounds were isolated and identified as quercetin(1), quercetin-3---D-arabinopyranoside(2), quercetin-3---D-ribopyranoside(3), quercetin-3---D-galactopyranoside(4), quercetin-3---D-glucopyranoside(5), and quercetin-3--D-xylpyranoside(6). The antioxidant effects of six flavonoids was evaluated by scavenging ability of DPPH, superoxide anion, ABTS·⁺, and reducing effect of Fe³⁺ as well as total antioxidant capacity(FRAP). Vitamin C was used as positive control. The results indicated that six flavonoids exhibited significant antioxidant effects.
Antioxidants ; chemistry ; Flavonoids ; chemistry ; Phytochemicals ; analysis ; Plant Leaves ; chemistry ; Psidium ; chemistry ; Quercetin ; chemistry

OBJECTIVETo study the water soluble constituents from Amomum villosum.

METHODThe constituents were separated and purified with chromatographic methods, identified by NMR, MS, UV and IR.

RESULTTwo quercetin glycosides: quercitrin (quercetin-3-O-alpha-L-rhamnoside I) and isoquercitrin (quercetin-3-O-beta-D-glucoside II) were isolated and identified.

CONCLUSIONI and II were isolated for the first time from A. villosum.

Amomum ; chemistry ; Fruit ; chemistry ; Plants, Medicinal ; chemistry ; Quercetin ; analogs & derivatives ; chemistry ; isolation & purification

OBJECTIVETo investigate the chemical constituents from the aerial parts of Hyperricum monogynum.

METHODCompounds were isolated by various column chromatography and identified by spectral analysis.

RESULTTen compounds were isolated and identified as quercetin, quercitrin, hyperoside, rutin, (-)-epicatechin, 3,5-dihydroxy-1-methoxy-xanthone, 3,4-O-isopropylidenyl shikimic acid, shikimic acid, daucosterol, and oleanoic acid.

CONCLUSIONAll compounds were isolated from this plant for the first time.

Hypericum ; chemistry ; Plant Components, Aerial ; chemistry ; Plants, Medicinal ; chemistry ; Quercetin ; analogs & derivatives ; chemistry ; isolation & purification

OBJECTIVETo study the chemical constituents of the seeds of Cuscuta chinensis.

METHODThe separation was carried out by polyamide and silica gel chromatography, and the compounds were identified by means of physico-chemical and spectroscopic methods.

RESULTSEight compounds were isolated from the plant and identified as quercetin 3-O-beta-D-galactoside-7-O-beta-D-glucoside (I), quercetin 3-O-beta-D-apiofuranosyl-(1-->2)-beta-D-galactoside (II), hyperoside (III), isorhamnetin (IV), kaempferol (V), quercetin (VI), d-sesamin (VII) and 9(R)-hydroxy-d-sesamin (VIII).

CONCLUSIONCompounds IV and VII were isolated from Cuscuta for the first time, and I, II and VIII were characteristic constituents for this vegetable drug.

Cuscuta ; chemistry ; Flavonols ; Plants, Medicinal ; chemistry ; Quercetin ; analogs & derivatives ; chemistry ; isolation & purification ; Seeds ; chemistry

OBJECTIVETo study the chemical constituents of Gueldenstaedtia stenophylla.

METHODVarious chromatographic techniques were used to separate and purify the constituents and structure determination was mainly based on the analysis of the spectroscopic data.

RESULTSeven compounds, including 2', 4, 7-trihydroxy-4'-methoxyisoflavans (1), genkwanin (2), quercetin (3), rutin(4), 12-oleanen-3beta, 22beta, 24-triol (5), betulinic acid (6), and 3, 4-dihydroxybenzoic acid (7) were isolated and identified.

CONCLUSIONAll these compounds were isolated from the genus Gueldenstaedtia for the first time.

Asteraceae ; chemistry ; Benzoic Acid ; chemistry ; Drugs, Chinese Herbal ; chemistry ; Flavones ; chemistry ; Magnetic Resonance Spectroscopy ; Quercetin ; chemistry ; Triterpenes ; chemistry

OBJECTIVETo study the chemical constituents from Centipeda minima.

METHODThe compounds were separated and purified by silica gel, reserved phase silica gel and Sephadex LH-20 gel column chromatography. Their structures were identified on the basis physicochemical property and spectral analysis.

RESULTFour chemical constituents were separated from ethyl acetate extracts and five chemical constituents were separated from n-butanol extracts of C. minima and identified as (2R,3R)-(+)-7,4'-di-O-methyldihydrokaempferol (1), iristectorin A (2), 4',5,8-trihydroxy-7-methoxyisoflavone (3), 3-trimethoxyquercetin (4), 3-O-caffeoyl-alpha-glueopyranose (5), 3-O-caffeoyl-beta-glucopyranose (6), quercetin (7), epipinoresinol (8) and hispidulin (9).

CONCLUSIONCompounds 1-3, 5-6, 8 and 9 are separated from this genus for the first time.

Asteraceae ; chemistry ; Drugs, Chinese Herbal ; chemistry ; isolation & purification ; Molecular Structure ; Quercetin ; chemistry ; isolation & purification

OBJECTIVETo prepare quercetin nanostuctured lipid carriers (QT-NLC), and detect their physicochemical properties.

METHODQT-NLC was prepared by emulsification ultrasonic dispersion method, and the optimum prescription was screened out by orthogonal design. Transmission electron microscope was used to observe QT-NLC morphology. Granulometer was applied to determine zeta potential, particle size and distribution. DSC was adopted for phase analysis. Centrifugal ultra-filtration method was used to determine entrapment efficiency. Dialysis method was adopted to detect drug release in vitro of preparations.

RESULTQT-NLC prepared under optimum conditions was mostly spherical grains, with the average particle size of (175 +/- 25) nm, which were distributed evenly, and zeta potential was (-23 +/- 0.3) mV. DSC results indicated that the drug was dispersed in nano-particles in a non-crystalline state, with an entrapment efficiency of (95.43 +/- 0.23)% and a drug-loading capacity of (2.38 +/- 0.24)%. The in vitro drug release was 32.2% in 2 hours, which was followed by a sustained release.

CONCLUSIONEmulsification ultrasonic dispersion method is applicable for preparing QT-NLC, as nano-particles are distributed evenly, with good reliability. This processing technology is safe, reliable and highly reproducible.

Delayed-Action Preparations ; Drug Carriers ; Emulsions ; Lipids ; chemistry ; Nanoparticles ; chemistry ; ultrastructure ; Particle Size ; Quercetin ; chemistry