Interaction between quercetin and superoxide radicals. Reduction of the quercetin mutagenicity

Interaction between quercetin and superoxide radicals was investigated using xanthine-xanthine oxidase system and potassium superoxide as superoxide radical generators. Superoxide radical scavenging action of quercetin was demonstrated by measurement of the electron spin resonance spectrum of the 5-hydroperoxy-2,2-dimethyl-1-pyrrolidinyloxyl adduct. Degradation of quercetin by the radicals was demonstrated spectrophotometrically. Reduction of the quercetin mutagenicity by the radicals was demonstrated in the Salmonella typhimurium strain TA 98 by the Ames test.

Optical spectroscopy as an in vitro method to monitor aldose reductase inhibitors in the lens

The tricyclic ring structure of several of the aldose reductase inhibitors indicates that they could be detected by optical spectroscopy in certain ocular tissues. Four of these compounds (Quercetin, Quercitrin, AY22-284, and Sorbinil) were investigated with respect to their UV absorption, fluorescence, and phosphorescence characteristics. All absorb in the UV wavelength and have measurable fluorescence (room temperature) and phosphorescence characteristics (77 K). The phosphorescence characteristics were utilized to monitor for the presence of Quercetin, Quercitrin, and AY22-284 in rat, rabbit, and human lenses incubated with each of the inhibitors. Following IP injection, rat and rabbit lenses were removed and subjected to phosphorescence spectroscopy for these three reagents. AY22-284 gave the sharpest and clearest phosphorescence spectra with emission wavelengths well removed from intrinsic lens phosphorescence. It can be detected in the extracted ocular lens within 30 minutes after in vivo IP administration, as well as in vitro lens incubations. The spectral data correlate well with aldose reductase inhibitor levels in such lenses as measured by a biochemical technique. Similar data were obtained with Quercitrin. Sorbinil was best monitored by fluorescence spectroscopy and could be detected in the lens following in vivo administration, as well as in vitro lens incubations.

Mutagenicity of hydrolysates of citrus fruit juices

Hydrolysates of citrus fruit juice were mutagenic according to the Ames test. The citrus fruit juices were hydrolysed with 1 M HCl, hesperidinase, naringinase and human intestinal bacteria. The hydrolysates were successively extracted with n-hexane, chloroform, diethyl ether and ethyl acetate. The mutagenicities of extracts were assayed by the Ames test, and the mutagens were analysed by gas chromatography and mass spectrometry (GC-MS). Mutagenicities of hydrolysates of citrus fruit juice were found in both the chloroform extracts and the ether extracts. The chloroform extracts were mutagenic to TA98 and TA100 with S9 mix, and the ether extracts were mutagenic to TA98 and TA100 with or without S9 mix. Some known flavonols such as kaempferol and quercetin were detected in the extracts of the hydrolysates by GC-MS. It is suggested that the mutagenicity of the extracts originated from those flavonols in the citrus fruit juice.

Presence of trifoliin A, a Rhizobium-binding lectin, in clover root exudate

Trifoliin A, a Rhizobium-binding glycoprotein from white clover, was detected in sterile clover root exudate by a sensitive immunofluorescence assay employing encapsulated cells of Rhizobium trifolii 0403 heat-fixed to microscope slides. Its presence in root exudate was further examined by immunoaffinity chromatography. The binding of trifoliin A to cells was specifically inhibited by the hapten, 2-deoxyglucose. Significantly higher quantities of trifoliin A were detected in root exudate of seedlings grown hydroponically in nitrogen-free medium than in rooting medium containing 15 mM NO-3, a concentration which completely suppressed root hair infection by the nitrogen-fixing symbiont. The presence of trifoliin A in root exudate may make it possible for recognition processes to occur before the microsymbiont attaches to its plant host.

Quercetin, a rat intestinal and bladder carcinogen present in bracken fern (Pteridium aquilinum)

Albino noninbred weanling male and female rats were fed a basic grain diet (Group 1) or a basic diet supplemented with 33% bracken fern [BF (Group 2)] or 0.1% quercetin [purity, > 99% (Group 3)] for 58 weeks. The quantities of quercetin and kaempferol (a close structural analog) in BF as glycosides were determined to be 0.57 and 1.1 g, respectively, per kg of dried BF. Estimated mean total cumulative doses (mmol) per rat were: Group 1, quercetin, males and females < 0.03; kaempferol, males and females < 0.03; Group 2, quercetin, males 5.8, females 5.2; kaempferol, males 11.9, females 10.8; and Group 3, quercetin, males 27.8, females 25.3; kaempferol, males and females < 0.03. Growth of rats fed BF or quercetin was comparable but significantly (p < 0.01) slower after 24 weeks than that of Group 1. Mean survivals (weeks) of rats of all groups were: Group 1, 58 +/- 7 (S.D.); Group 2, 51 +/- 13; and Group 3, 56 +/- 8. They were not significantly different, although rats fed BF tended to die earlier secondary to intestinal tumor-induced intussusception and obstruction. The following incidences of intestinal or bladder neoplasms in male or female rats, respectively, were observed: Group 1, intestinal and bladder, males, 0 of 9, females, 0 of 10; Group 2, intestinal, males, 7 of 8, females, 10 of 11; bladder, males, 6 of 8, females 8 of 11; Group 3, intestinal, males, 6 of 7, females, 14 of 18; bladder, males, 2 of 7, females, 3 of 18. The histopathology of neoplasms of the 2 target organs was identical for rats of Groups 2 and 3. Multiple ileal intestinal neoplasms of rats fed quercetin included: adenoma, 4; fibroadenoma, 7; and adenocarcinoma, 9 (with mesenteric metastases, 3). The 5 bladder tumors were papillary or sessile transitional cell carcinomas.

Characterization of mutagenic principles and carcinogenicity of dill weed and seeds

Among the various kinds of spices tested, the aqueous extracts of dill weed from Anethum graveolens L. and dill seeds from A. sowa D.C. (Umbelliferae), exhibited a mutagenicity to Salmonella typhimurium, strains TA98 and TA100. The aqueous methanol extracts were fractionated by the mutation assay using the strain TA98 with S-9 Mix. Isorhamnetin 3-sulfate (persicarin) and quercetin 3-sulfate were characterized as the mutagenic principles. Carcinogenicity was not observed for dill weed and seeds when the diets containing these in 33% were administered for 450 and 410 days, respectively, to the inbred strain ACI rats.

[Flavonol glycosides of leaves and fruits of dill (Anethum graveolens L.). II. Phenolics of spices (author's transl)]

From the leaves of dill (Anethum graveolens L.) ten flavonol glycosides have been isolated by means of polyamide, paper and thin-layer chromatography and could be identified by the usual procedures. The two major flavonoids, quercetin 3-O-beta-D-glucuronide and isorhamnetin 3-O-beta-D-glucuronide, were obtained crystalline. The minor components were found to be the 3-glucosides, 3-galactosides and 3-rhamnoglucosides of quercetin and isorhamnetin. Two other 3-glycosides of quercetin and isorhamnetin occur with the component sugars galactose, xylose, and arabinose. Besides these there are probably other two flavonoids present in trace amounts. In addition, the fruits of dill contain kaempferol 3-glucuronide as main component thought this component is completely absent in leaves.--This is probably the first time that isorhamnetin 3-O-beta-D-glucuronide has been obtained crystalline from a plant.

[Analysis of flavonoid glycosides by high pressure liquid chromatography (author's transl)]

The development of a qualitative and quantitative method of determination for glycosides of flavones, flavonols and flavanones and their aglycones by means of high pressure liquid chromatography is described. Silicagel LiChrosorb Si 60 is used as stationary phase, as well as various eluents at different temperatures. The compounds are acetylated. An extract of plum leaves serves as example of application.

[Flavonols and flavones of vegetables. VI. On the changes of the flavonols of onions (authors transl)]

The epidermis of onion scales exclusively contains glucosides of quercetin as flavonols, while the dry outer skins contain quercetin in the free state mainly. First spiraeoside (quercetin-4'-glucoside) is built; the formation of diglucosides follows during storage and increases continously. The mesophyll appears to be free of flavonols. The flavonol concentration decreases from the outer to the inner scales, with higher levels in the outer than in the inner epidermis. In the green leaves the flavonol synthesis is light-dependent and also kaempferol glucosides are formed beside quercetin glucosides, but not spiraeoside and the known diglucosides of the scales. During drying on the field an accumulation of flavonols takes place in the drying leaves. This production is associated with the formation of free quercetin and spiraeoside, but not of free kaempferol.

[The phenolics of fruits. VIII. Changes in flavonol concentrations during fruit development (authors transl)]

In black currants the contents of quercetin- and especially of myricetin glycosides increased during ripeness very considerably. The myricetin level in ripe fruits of cultivated blueberries and the quercetin level in ripe berries of privet was higher than in unripe. However, the concentrations of kaempferol and quercetin glycosides were in most of the fruits (e.g. red and white currants, sour cherries, plums, cultivated blueberries, elderberries) smaller than in unripe fruits. Anthocyanin formation is therefore not combined with an accumulation of flavonols (perhaps with the exception of myricetin).

[Flavonols and flavones of vegetables. V. Flavonols and flavones of root vegetables (author's transl)]

Root vegetables contain flavon(ol) glycosides in tracers up to small amounts, while the level of their leaves are in part considerable (to more than 1 g/kg, calculated as aglycon). Radish, rutabagas, scorzoneras, and beets contain less than 1 mg/kg kaempferol and/or quercetin; carrots less than 1 mg/kg apigenin and luteolin; celery roots ca. 75 mg apigenin/kg and 14 mg luteolin/kg; horseradish about 20 mg kaempferol/kg and small radish 1-10 mg kaempferol/kg, whereby all these flavones and flavonols occur as glycosides in the vegetables. In leaves of small radish, variety "Eiszapfen", we found besides isoquercitrin (quercetin-3-glucoside) a quercetin-3-0-diglycoside and a kaempferol-0-diglycoside, both with the sugars rhamnose and arabinose, by tlc.