[Studies on the flavonoid compounds of Rhododendron anthopogonoides]

OBJECTIVE

To investigate the flavonoid constituents of the Rhododendron anthopogonoides systematically.

METHOD

The chemical components were isolated by sephadex LH-20, polyamide and silica gel column chromatography. The chemical structures were elucidated on the basis of physic-chemical properties and spectral data.

RESULT

Eight compounds were isolated and identified as: Quercetin (I), isorhamnetin (II), hyperoside (III), cacticin (IV), hirsutine (V), kaemferol-3-beta-D-galactoside (VI) myricetin-3-beta-D-Xyloside (VII), (6''-O-(4-Hydroxybenzoyl) hyperoside (VIII).

CONCLUSION

Compounds II, IV, V, VI, VII, and VIII were obtained from this plant for the first time. Compounds VII and VIII were separated from the Ericaceae plant for the first time.

Isolation of flavonol rhamnosides fromloranthus tanakae and cytotoxic effect of them on human tumor cell lines

Loranthus tanakae Fr. et Sav. (Loranthaceae) is a species of mistletoe, a semiparasitic plant growing on the branches of Quercus and Betula species as host trees. In our ongoing search for bioactive compounds from endemic species in Korea, we have investigated to isolate the chemical constituents responsible for the antitumor effect of the MeOH extract of L. tanakae. The ethylacetate soluble part of the MeOH extract demonstrated a marginal inhibition on the proliferation of the tumor cell lines such as A549 (non small cell lung), SK-OV-3 (ovary), SK-MEL-2 (melanoma), XF498 (central nerve system), and HCT-15 (colon) in vitro. Thus, the activity-guided isolation procedure upon the ethylacetate soluble part of the extract has been carried out and finally four flavonoid rhamnopyranosides (1-4) were isolated as active principle. The structures of 1-4 were elucidated by the physicochemical and spectral data as rhamnetin 3-O-alpha-L-rhamnoside (1), quercetin 3-O-alpha-L-rhamnoside (2), rhamnocitrin 3-O-alpha-L-rhamnoside (3), and kaempferol 3-O-alpha-L-rhamnoside (4).

[Isolation and structure identification of chemical constituents from the seeds of Descurainia sophia (L.) Webb ex Prantl]

AIM

To isolate and determine the structures of chemical constituents from the seeds of Descurainia sophia (L.) Webb ex Prantl.

METHODS

The chemical constituents were extracted from the seeds of Descurainia sophia (L.) Webb ex Prantl with 75% ethanol and purified by polyamide, silica gel, RP-C18 and Sephadex LH-20 on column chromatography. Chemical methods and spectroscopic methods, such as 1H and 13CNMR, HSQC, HMBC and TOCSY spectra were used for the structural identification.

RESULTS

Fifteen compounds were obtained. Twelve of them were identified as quercetin-3-O-beta-D-glucopyranosyl-7-O-beta-gentiobioside (I), kaempferol-3-O-beta-D-glucopyranosyl-7-O-beta-gentiobioside (II), isorhamnetin-3-O-beta-D-glucopyranosyl-7-O-beta-gentiobioside (III), quercetin-7-O-beta-gentiobioside (IV), kaempferol-7-O-beta-gentiobioside (V), isorhamnetin-7-O-beta-gentiobioside (VI), quercetin-3,7-di-O-beta-D-glucopyranoside (VII), kaempferol-3, 7-di-O-beta-D-glucopyranoside (VIII), isorhamnetin-3, 7-di-O-beta-D-glucopyranoside (IX), kaempferol-3-O-beta-D-glucopyranosyl-7-O-[(2-O-trans-sinnapoyl)-beta-D- glucopyranosyl(1-->6)]-beta-D-glucopyranoside) (X), sinapic acid ethyl ester (XI) and 3, 4, 5-trimethoxyl-cinnamic acid (XII).

CONCLUSION

Compounds X and VI are new compounds. IV, V, VII, VIII and IX were isolated from Cruciferae family for the first time. I, II, III were obtained from Descurania genus and XI, XII from D. sophia for the first time.

Silymarin extraction from milk thistle using hot water

Hot water is attracting attention as an extraction solvent in the recovery of compounds from plant material as the search for milder and "greener" solvents intensifies. The use of hot water as an extraction solvent for milk thistle at temperatures above 100 degrees C was explored. The maximum extraction yield of each of the silymarin compounds and taxifolin did not increase with temperature, most likely because significant compound degradation occurred. However, the time required for the yields of the compounds to reach their maxima was reduced from 200 to 55 min when the extraction temperature was increased from 100 to 140 degrees C. Severe degradation of unprotected (plant matrix not present) silymarin compounds was observed and first-order degradation kinetics were obtained at 140 degrees C.

Anthocyanin transformation in Cabernet Sauvignon wine during aging

Anthocyanins in Cabernet Sauvignon grapes and wines were elucidated by HPLC-MS/MS. Major anthocyanins in Cabernet Sauvignon grape extract are malvidin 3-O-glucoside and malvidin 3-O-acetylglucoside. In matured wine, anthocyanins are transformed to anthocyanin-vinyl derivatives, ethyl bridged anthocyanin-flavanol adducts, and anthocyanin-flavanol adducts. The major anthocyanin pigments are malvidin 3-O-glucoside-pyruvate, malvidin 3-O-acetylglucoside-pyruvate, malvidin 3-O-coumaroylglucoside-pyruvate, malvidin 3-O-glucoside-4-vinylphenol, malvidin 3-O-acetylglucoside-4-vinylphenol, and malvidin 3-O-coumaroylglucoside-4-vinylphenol. The presence of syringetin 3-O-glucoside and syringetin 3-O-acetylglucoside has been established for the first time in grape and wine.

Methylation of dihydroquercetin acetates: synthesis of 5-O-methyldihydroquercetin

The major products of methylation of dihydroquercetin (1, dhq) with diazomethane have been identified as 7-O-methyldhq (9), 7,3'-di-O-methyldhq (10), 7,4'-di-O-methyldhq (11), and 7,3',4'-tri-O-methyldhq (2). With dhq 3,7,3',4'-tetraacetate (6), dhq 3,5,3',4'-tetraacetate (5), dhq 3,3',4'-triacetate (7), dhq 7,3',4'-triacetate (8), and dhq 3-acetate (4) the same reaction affords mainly 5-O-methyldhq 3,7,3',4'-tetraacetate (15), 7-O-methyldhq 3,5,3',4'-tetraacetate (13), 7-O-methyldhq 3,3',4'-triacetate (14), 5-O-methyldhq 7,3',4'-triacetate (25), and 7-O-methyldhq 3-acetate (12), respectively. The methylation of 8 is accompanied by intermolecular acetyl migration from phenolic oxygen to the hydroxy group of the heterocyclic ring. 5-O-Methyldhq (28) is accessible by deacetylation of 25. 5,7-Di-O-methyldhq (29), four known methyl ethers, 13 new and three known methyl ether acetates of dhq, and six new isomers with 2,3-cis stereochemistry were spectroscopically identified.

Flavonol glycosides of Warburgia ugandensis leaves

Four new flavonol gycosides: kaempferide 3-O-beta-xylosyl (1-->2)-beta-glucoside, kaempferol 3-O-alpha-rhamnoside-7,4'-di-O-beta-galactoside, kaempferol 3,7,4'-tri-O-beta-glucoside and quercetin 3-O-[alpha-rhamnosyl (1-->6)] [beta-glucosyl (1-->2)]-beta-glucoside-7-O-alpha-rhamnoside, were characterized from a methanolic leaf extract of Warburgia ugandensis. The known flavonols: kaempferol, kaempferol 3-rhamnoside, kaempferol 3-rutinoside, myricetin, quercetin 3-rhamnoside, kaempferol 3-arabinoside, quercetin 3-glucoside, quercetin, kaempferol 3-rhamnoside-4'-galactoside, myricetin 3-galactoside and kaempferol 3-glucoside were also isolated. Structures were established by spectroscopic and chemical methods and by comparison with authentic samples.

Acylated flavonol glycosides from leaves of Planchonia grandis

Three acylated flavonol glycosides have been identified from leaves of Planchonia grandis Ridley. They possess kaempferol as aglycone and two triglycosidic chains substituting hydroxyl groups at the 3- and 7-positions. The first glycosidic unit of each chain is esterified by a cis or trans p-coumaric acid. Structural elucidation was achieved by means of UV, NMR and mass spectrometry.

Constituents from the leaves of Phellodendron amurense var. wilsonii and their bioactivity

Two new dihydroflavonols, phellodensin-A (1) and phellodensin-C (2); three new coumarins, phellodenol-A (3), phellodenol-B (4), and phellodenol-C (5); one new chlorophyll, phellophyll-a (6); and one new phenyllactate, (2R)-sodium 3-phenyllactate (7), in addition to 35 known compounds have been isolated from the leaves of Phellodendron amurense var. wilsonii. The structures of the new compounds were established based on 1D, 2D NMR and mass spectral analyses. The stereochemistry at the C-2, C-3, and C-2' ' positions of new dihydroflavonol 1 was determined by CD spectroscopy. The known compounds were identified by comparison with authentic samples. The antioxidant and antityrosinase activities were also described.

Purification and characterization of a flavonol 3-O-beta-heterodisaccharidase from the dried herb of Fagopyrum esculentum Moench

A flavonol-3-O-beta-heterodisaccharide glycosidase (FHG I) was isolated from dried aerial tissues of Fagopyrum esculentum Moench (Fagopyri herba). It has a specific enzyme activity of ca. 3.5 nkat mg(-1) protein in buffered extracts when rutin (quercetin-3-O-rutinoside) was used as substrate and an optimal enzyme activity was seen at around pH 4.8 and 30 degrees C. FHG I was purified about 156-fold to apparent homogeneity by hydrophobic interaction, anion exchange and size exclusion chromatographic steps. The apparent molecular mass of FHG I was 74.5+/-2 kDa as determined by SDS-PAGE and it is a monomeric glycoprotein with a carbohydrate content of 23%. The isoelectric point as determined by isoelectric focusing was 5.7 and the energy of activation was 32 kJ mol(-1). FHG I exhibits a high substrate specificity, preferring flavonol 3-O-glycosides comprising the disaccharide rutinose. The K(m) and V(max) values for the natural substrate rutin were calculated to be 0.561 microM and 745 nkat mg (-1) protein, respectively. Two oligopeptide fragments obtained after enzymatic digestion of FHG I were sequenced and showed similarities to sequences of beta-glucohydrolases from other plant species. Polyclonal antibodies were raised and their specificities determined. Another flavonol 3-O-beta-heterodisaccharide glycosidase (FHG II) could also be detected in buckwheat herb, having a molecular mass of 85.3+/-2 kDa and an isoelectric point between pH 6.0 and 6.5.

Bioactive flavonoids of Tanacetum parthenium revisited

Bio-guided fractionation of an extract from Tanacetum parthenium showing activity as mitotic blocker allowed the isolation and identification of santin 3, jaceidin 2 and centaureidin 1. The latter two closely related flavonols, which, to the best of our knowledge, are isolated here together for the first time, form a mixture difficult to resolve and which is probably the reason for the confusion in the literature regarding their occurrence. Centaureidin 1 had an IC50 of 1 microM while jaceidin 2 and santin 3 were 200 times less active.

Antioxidation properties and mechanism of action of dihydromyricetin from Ampelopsis grossedentata

AIM

To assess the antioxidative properties and the mechanism of action of dihydromyricetin (DMY) from Ampelopsis grossedentata.

METHODS

The antioxidative properties of DMY were measured by scavenging 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and inhibiting lipid peroxidation induced by FeSO4-edetic acid in linoleic acid. The mechanism of antioxidative properties of DMY was tested by measuring the chelating activities of DMY for Fe2+ with ultraviolet spectrum (UV) method.

RESULTS

The specific absorption of DPPH radical solution at 517 nm was reduced 73.3%-91.5% when DMY was added into the reaction solution in the concentration range from 0.01% to 0.04%. DMY was shown to greatly inhibit the increase of lipid peroxidation (LPO) values in linolei acid system catalyzed by FeSO4-edetic acid. The reaction rates (A532.min-1) of lipid peroxidation were 0.0021-0.0004 in the concentration range from 0.01% to 0.04% and the inhibition activities of DMY was found to be in a concentration-dependent manner. The mechanism of antioxidative properties of DMY was chelating Fe2+ in the Fe(2+)-dependent lipid peroxidation system.

CONCLUSION

DMY showed great antioxidative effect and would be a good natural antioxidant.

Identification of lipophilic flavones and flavonols by comparative HPLC, TLC and UV spectral analysis

The identification of lipophilic flavones and flavonols using a combination of high performance liquid chromatography, thin layer chromatography and UV spectral analysis is discussed. Data are provided for the flavones, apigenin, luteolin and tricetin and twelve of their methyl ethers, 8-hydroxyluteolin, 6-hydroxyluteolin and scutellarein and fourteen of their methyl ethers, and some 6,8-dihydroxyapigenin and 6,8-dihydroxyluteolin derivatives. Data for some forty two flavonols with extra 6- and/or 8-hydroxylation, mostly 6-hydroxykaempferol and quercetagetin derivatives, are also presented. The remaining compounds analysed include fourteen 5-deoxyflavones, four 5-methoxyflavones and five 5-deoxyflavonols plus further 5-hydroxylated flavones and flavonols without B-ring oxidation or with 2'-, 5'- or 6'-hydroxylation.

Papyriflavonol A from Broussonetia papyrifera inhibits the passive cutaneous anaphylaxis reaction and has a secretory phospholipase A2-inhibitory activity

Papyriflavonol A, a new prenylated flavonol isolated from Broussonetia papyrifera, selectively inhibits recombinant human secretory phospholipase A(2)s (sPLA(2)s). Papyriflavonol A was found to inhibit human group IIA and V sPLA(2)s potently and irreversibly in a dose-dependent manner, with respective IC(50) values of 3.9 and 4.5 microM. The inhibitory effects of papyriflavonol A against bovine group IB (IC(50) of 76.9 microM) and the human group X (IC(50) of 225 microM) sPLA(2)s were weaker than those against human group IIA and V sPLA(2)s, and human group IIF sPLA(2) was not inhibited. In addition, papyriflavonol A potently inhibited the stimulus-induced production of leukotriene C(4) with an IC(50) value of approximately 0.64 microM in mouse bone marrow-derived mast cells. In addition, papyriflavonol A significantly reduced IgE-dependent passive cutaneous anaphylaxis in rats. These results indicate that papyriflavonol A provides a basis for novel types of antiinflammatory drugs.

[Studies on chemical constituents of Choerospondias axillaris]

Ten compounds were isolated from the dry fruit of Choerospondias axillaris (Roxb.) Burtt et Hill. Their structures were elucidated as dihydroquercetin(1), quercetin(2), protocatechuic acid(3), gallic acid(4), 3,3'-di-o-methylellagic acid(5), beta-sitosterol(6), daucosterol (7), stearic acid(8), triacontanoic acid(9), octacosanol(10) by IR, EI-MS and NMR.

Cytotoxic activity of flavonoids and extracts from Retama sphaerocarpa Boissier

Seven flavonoids isolated from chloroform, ethyl acetate and butanol extracts, obtained from the aerial parts of Retama sphaerocarpa, have been assessed for cytotoxic activity against three human cancer cell lines: TK-10 (renal adenocarcinoma), MCF-7 (breast adenocarcinoma) and UACC-62 (melanoma), using the SRB assay. All of them, extracts and flavonoids, were actives in, at least, one of the three cell lines at the recommended National Cancer Institute doses. They produce a dose-dependent inhibition of cell growth at concentrations in the 10(-6)-10(-4) M and 25-250 microg/ml range for the flavonoids and extracts respectively, being the flavonol rhamnazin the most cytotoxic.

Antioxidant flavonols from fruits, vegetables and beverages: measurements and bioavailability

Flavonols are polyphenolic secondary plant metabolites that are present in varying levels in commonly consumed fruits, vegetables and beverages. Flavonols have long held an interest for nutritionists, which has increased following a Dutch study in the early 1990's showing that dietary intake of flavonols was inversely correlated with the incidence of coronary heart disease. The main factors that have hindered workers in the field of flavonol research are (i) the accurate measurement of these compounds in foods and biological samples, and (ii) a dearth of information on their absorption and metabolism. This review aims to highlight the work of the authors in attempting to clarify the situation. The sensitive and selective HPLC procedure to identify and quantify common flavonols and their sugar conjugates is described. In addition, the results of an on-going screening program into the flavonol content of common produce and beverages are presented. The bioavailability of dietary flavonols is discussed with reference to an intervention study with onions, as well as pilot studies with tea, red wine and cherry tomatoes. It is concluded that flavonols are absorbable and accumulate in plasma and that consuming high flavonol-containing varieties of fruits and vegetables and particular types of beverages could increase their circulatory levels.

[Separation of flavonol isomers by packed column supercritical fluids chromatography]

Flavonol isomers, which differ only in the position of hydroxyl group substitute on their chemical structures, showed different chromatographic behaviors. These polar compounds, in general, can be analyzed by high performance liquid chromatography. In this paper, the separation of flavonol isomers by home-set up packed column supercritical fluid chromatograph with carbon dioxide modified by ethanol containing 0.5% (V/V) phosphoric acid as mobile phase is described. The effects of temperature, pressure, composition of mobile phase and packed column type on the separation were studid. The addition of phosphoric acid to the mobile phase, which can not result in corrosion on the chromatographic system, enabled flavonol to elute from the column, and showed that the composition of the mobile phase was the most pronounced factor influencing the separation. Three columns were evaluated for the separation. It showed that the phenyl-bonded silica column was the best and the ODS column was the worst for the isomers separation. Increasing pressure shortened the retention time of each compound with good resolution, and higher temperature led to longer retention time.

[Flavonoids in Arabis Caucasica Willd. (Cruciferae). Part I. Heterozygote similar to quercetin and isorhamnetin]

From flowering herb of Arabis caucasica Willd. have been isolated crystalline flavonoid compounds. They have been identified as quercetin 3-glucoside, isorhamnetin 3-glucoside, quercetin 3-beta-glucoside-7-alpha-rhamnoside and isorhamnetin 3-beta-glucoside-7-alpha-rhamnoside. As chromatographically homogenous, in amorphous form have been isolated: quercetin 3-diglucoside-7-glucoside and isorhamnetin 3-diglucoside-7-glucoside.