Inhibition of desmoglein-1 by aspirin leads to synthetic lethality of keratinocytes in Shuanghuanglian-induced cutaneous eruption response.

Cutaneous eruptions caused by the combination of Chinese and Western medicine have attracted widespread attention; however, the underlying mechanism remains unclear. This study aimed to evaluate the potential mechanism of cutaneous eruptions in vivo and in vitro using the combination of Shuanghuanglian injection powder (SHL) and aspirin (ASA) as an example. ASA and SHL co-administration induced inflammatory responses in HaCat cells, as evidenced by marked increases in the expression of IL-4 and TNF-α, and the level of apoptosis. Additionally, histopathological investigation of mice skin tissues showed local inflammatory cell infiltration. Western boltting was used to detect the effects of ASA on desmoglein-1 (DSG1) expression; we found that DSG1 expression was down-regulated in vivo and in vitro. Finally, the key components of SHL were administered to HaCat cells with down-regulated DSG1; it was seen that neochlorogenic acid and rutin have a significant effect on HaCat cell apoptosis. These results demonstrate that DSG1 deficiency is a potential cause of cutaneous eruptions caused by the combination of SHL and ASA, and neochlorogenic acid and rutin are the main allergenic components. This study provides a new research strategy for the safety evaluation of integrated traditional Chinese and Western medicine.

Preclinical safety assessment of the crude extract from Sida rhombifolia L. aerial parts in experimental models of acute and repeated-dose 28 days toxicity in rats.

Sida rhombifolia (Malvaceae) is popularly used as a treatment for several pathological conditions; however, there is a lack of studies that identify its compounds and that evaluate comprehensively the safety of its consumption. Therefore, the aim of this study was to determinate the phytochemical constitution of the crude extract of Sida rhombifolia (CESR), and its safety in models of acute and repeated doses (28 days) toxicity. The tested dose for the model of acute toxicity was 2000 mg/kg doses for the repeated dose model were 150, 300 e 600 mg/kg. Hematological, biochemical, histopathological and oxidative markers were investigated. HPLC-DAD-MS analysis evidenced the presence of caffeic acid, coumarin, and rutin. In the acute toxicity model the only altered parameters were tissue ROS, and AST and BUN in serum. As for the repeated dose experiment both hematological and biochemical markers remained within the values of reference for the species. Obtained results demonstrate that the CESR did not present significant toxic effects when administrated orally to male and female rats in acute and repeated doses.

In vitro genotoxicity assessment of functional ingredients: DHA, rutin and α-tocopherol.

The in vitro genotoxicity of three compounds widely used as functional ingredients, docosahexaenoic acid (DHA), rutin and α-tocopherol, was assessed. A miniaturized version of the Ames test in Salmonella typhimurium TA97a, TA98, TA100, TA102, and TA1535 strains (following the principles of OECD 471), and the in vitro micronucleus test in TK6 cells (OECD 487) were performed. This strategy is recommended by the European Food Safety Authority for the in vitro genotoxicity assessment of food and feed. In addition, this approach was complemented with the in vitro standard and enzyme-modified comet assay (S9-/S9+) using hOGG1, EndoIII and hAAG in order to assess potential premutagenic lesions in TK6 cells. Rutin showed an equivocal response in the in vitro micronucleus test and also was a potent Salmonella typhimurium revertant inductor in the Ames test. DHA showed equivocal results in the in vitro micronucleus test. In this regard, DHA and rutin seemed to interact with the DNA at a chromosomal level, but rutin is also capable of producing frameshift mutations. No genotoxicity was observed in cells treated with α-tocopherol. This article complements the evidence already available about the genotoxicity of these compounds. However, more studies are needed in order to elucidate the consequences of their use as functional ingredients in human health.

The mutagenic potency of onion juice vs. its contents of quercetin and rutin.

In spite of its considerable value as a predictor of in vivo genotoxicity and even for carcinogenicity, false positive cases were reported for the Ames test, e.g., with a number of natural food constituents. Here we analyzed the effects of juice of Allium cepa, the common onion, a staple food and traditional remedy used in many civilizations, in the Ames fluctuation assay. We could find mild mutagenicity with an onion juice extract in Salmonella typhimurium strains TA98 and TA100, the latter being less sensitive towards the extract. Mutagenicity was not influenced markedly by the presence of rat liver S9 mix. Onion juice also exerted some toxicity to the bacteria in the same concentration range. Comparative studies with quercetin and rutin, major flavonoid glycosides in onions, revealed a mutagenic potency of quercetin with an EC50-value of 4 µM in TA98. The contents of quercetin and rutin in onion juice were determined as 0.71 ± 0.20, and 0.71 ± 0.21 mg/kg. Calculations of quercetin and rutin concentrations in mutagenic dilutions revealed that both compounds are highly unlikely to cause the mutagenic effects of onion juice and that other yet undefined constituents must be responsible for these effects.

Assessment of allelopathic, cytotoxic, genotoxic and antigenotoxic potential of Smilax brasiliensis Sprengel leaves.

Smilax brasiliensis (Smilacaceae) is a native Brazilian plant found in the Cerrado biome and commonly used in folk medicine. The aim of this study was to evaluate the allelopathic, cytotoxic, genotoxic, and antigenotoxic potential of extract and fractions of Smilax brasiliensis leaves. Quercetin and rutin isomers were observed in the subfractions. The dichloromethane fraction (1000 µg/mL) decreased lettuce (Lactuca sativa) seed vigor, while and ethyl acetate and hydromethanol fractions (1000 µg/mL) affected the germination, and quercetin and rutin affected the vigor and germination of onion seeds. The extract, fractions, quercetin, and rutin inhibited or promoted lettuce hypocotyl and radicle growth. The extract and fractions inhibited onion hypocotyl growth at all concentrations. With regards to radicle growth, the results were diversified: growth was either inhibited or promoted. Rutin and quercetin inhibited onion hypocotyl and radicle growth at all concentrations. The extract and fractions of Smilax brasiliensis, rutin, and quercetin did not cause cytotoxic effect evaluated by mitotic index. The extract and fractions showed genotoxic effects. Quercetin and rutin did not cause genotoxic effects. On the other hand, the extract and fractions showed antigenotoxic effects at all tested concentrations, where they were able to revert chromosomal abnormalities caused by glyphosate. However, additional studies are required to evaluate the possible use of the S. brasiliensis leaf methanol extract and fractions as natural sources of bioherbicides.

In Vivo Hypoglycemic Studies of Polyherbal Phytoceuticals, Their Pharmacokinetic Studies and Dose Extrapolation by Allometric Scaling.

BACKGROUND: This work reports the safety profiling, in vivo hypoglycemic and pharmacokinetic studies of three phytoceuticals viz. conventional and sustained release tablets and microspheres each containing a polyherbal product phytocomposite (PHC) as the active ingredient. PHC is prepared from the leaf extracts of Ficus benghalensis: Syzigium cumini: Ocimum sanctum mixed in the weight ratio of 1:1:2. Further no observed adverse effect level (NOAEL), maximum recommended starting dose (MRSD) in human and prediction of human pharmacokinetic parameters have been accomplished by allometric equations. METHODS: Acute and sub chronic studies of the phytoceuticals were done as per OECD and in vivo hypoglycemic studies in STZ induced diabetic rats. Plasma concentrations of the active constituent rutin (pharmacologically active compound of PHC) were determined by HPLC and other pharmacokinetic parameters using PK Solver. Repeated dose toxicity was carried out to determine the NOAEL value, MRSD estimated using allometric formulas of body surface area and clearance (CL) and volume of distribution (Vd) predicted by allometric equations of single species scaling. RESULTS: Phytoceuticals showed a wide range of safety profile with a significant lowering of blood gluco-lipid level. The values of the pharmacokinetic parameters for different doses of phytoceuticals showed that the active concentration was maintained in plasma level and each formulation complied with their relevant quality criteria. NOAEL value was 5000 mg/kg/body weight and MRSD was 4864.86 mg. CONCLUSION: Phytoceuticals prepared are safe and effectively controlled blood gluco lipid level. Animal to human dose extrapolation and prediction of human pharmacokinetic parameters by allometry was convenient.

Toxicological evaluation of the flavonoid rutin on the reproductive system of wistar rats / Avaliação toxicológica do flavanoide rutina no sistema reprodutor de ratos wistar

Introduction: Rutin, a flavonoid commonly found in nature, has anti-mitotic, vasoprotective, and antihyperlipidemic activity. When hydrolyzed as quercetin, it promotes inhibition of spermatozoa motility, alterations in the prostate, and in the levels of testosterone and dihydrotestosterone. Objective: This study aimed to evaluate the toxicity of rutin in Wistar rats. Methods: Animals were divided into Control (1 ml of distilled water), Treated I, II and III, respectively receiving 5, 10 and 20 mg/kg/day of rutin for seven consecutive days. When euthanasia was performed after 10, 42 and 60 days into the experiment, a laparotomy was performed and the testicles, prostate, seminal vesicles, epididymis, epididymal spermatozoa to be counted, as well as the liver, spleen and kidneys were removed. Hematological and biochemical tests were performed. Results: Hepatomegaly was observed and in the reproductive system, the weight of the epididymis was reduced, not affecting any other organ examined. Conclusion: Except by the reduction of the weight of the epididymis, which is reversible at 42 days of completion of treatment, no suggestive data of the toxicity of rutin on the reproductive system of adult rats were found.

Identification and characterization of six cytochrome P450 genes belonging to CYP4 and CYP6 gene families in the silkworm, Bombyx mori.

It was predicted that the genome of silkworm, Bombyx mori, has at least 79 P450 genes; however, P450 genes that are related to the catabolism of exogenous compounds were not reported. In this study we cloned two CYP4 (named CPY4M5 and CYP4M9) and four CYP6 (named CYP6AB5, CYP6AE9, CYP6AE22 and CYP6AU1) genes by using both bioinformatics and RT-PCR approaches. Sequence analysis showed that these genes contained conserved P450 gene sequence regions and one conserved intron. CYP4M5 and CYP4M9 genes were clustered together in a mode of "head-to-tail" possibly due to gene duplication. Blast analysis showed that these P450 genes shared significant similarity with CYP4 and CYP6 genes that are involved in the catabolism and detoxification of exogenous compounds in other insect species. RT-PCR results showed that these P450 genes were highly expressed in the midgut and fat body of B. mori. As the instar age increased, these P450 genes exhibit different expression patterns. When B. mori was exposed to 1.75 × 10(-5)% of cypermethrin, 3.5 × 10(-6)% of cypermethrin and 0.1% of rutin, expression of CYP6AB5 was increased by 2.3-fold, 2.2-fold and 1.9-fold, respectively. Exposure of B. mori to 0.1% quercetin does not change the expression of CYP6AB5. In contrast, expression of the other five P450 genes was inhibited after exposed to these compounds.

Rutin decreases lipopolysaccharide-induced acute lung injury via inhibition of oxidative stress and the MAPK-NF-κB pathway.

Acute lung injury (ALI) is a serious disease with unacceptably high mortality and morbidity rates. Up to now, no effective therapeutic strategy for ALI has been established. Rutin, quercetin-3-rhamnosyl glucoside, expresses a wide range of biological activities and pharmacological effects, such as anti-inflammatory, antihypertensive, anticarcinogenic, vasoprotective, and cardioprotective activities. Pretreatment with rutin inhibited not only histopathological changes in lung tissues but also infiltration of polymorphonuclear granulocytes into bronchoalveolar lavage fluid in lipopolysaccharide (LPS)-induced ALI. In addition, LPS-induced inflammatory responses, including increased secretion of proinflammatory cytokines and lipid peroxidation, were inhibited by rutin in a concentration-dependent manner. Furthermore, rutin suppressed phosphorylation of NF-κB and MAPK and degradation of IκB, an NF-κB inhibitor. Decreased activities of antioxidative enzymes such as superoxide dismutase, catalase, glutathione peroxidase, and heme oxygenase-1 caused by LPS were reversed by rutin. At the same time, we found that ALI amelioration by chelation of extracellular metal ions with rutin is more efficacious than with deferoxamine. These results indicate that the protective mechanism of rutin is through inhibition of MAPK-NF-κB activation and upregulation of antioxidative enzymes.

A novel phytochemical, digoxigenin-3-O-rutin in the amelioration of isoproterenol-induced myocardial infarction in rat: a comparison with digoxin.

INTRODUCTION: The commonly used cardiac glycoside, digoxin (DIG), has a narrow therapeutic window. Although some investigations were made to counteract its toxic effects, no alternate phytochemical is available till date that is more potent and safer than DIG. AIMS: Our main aim was to isolate a novel cardenolide from the seeds of Trigonella foenum graceium and to evaluate its relative potential in comparison to that of DIG. EXPERIMENTAL DESIGN: In one experiment effects of the isolated compound at 2.5, 5.0, and 10 mg/kg (p.o.) were evaluated in isoproterenol (ISO)-induced cardiovascular problems in rats. As the test drug (TDR) reversed most of the ISO-induced changes, it was subjected to the phytochemical analyses and was identified as digoxigenin-3-O-rutin. In another experiment effects of DIG and rutin (Rtn) were compared with those of TDR or DIG alone. The hydroxyl radical scavenging activity was also measured by electron spin resonance (EPR). RESULTS: digoxigenin-3-O-rutin at 10 mg/kg markedly reduced the ISO-induced increase in cardiac lipid peroxidation and in the levels of serum creatinine phosphokinase-MB, glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, lactate dehydrogenase, and creatinine. It also reversed the ISO-induced changes in the cardiac histomorphology. Interestingly TDR appeared to be more effective than DIG alone or DIG and Rtn in combination. CONCLUSION: The newly isolated digoxigenin-3-O-rutin appears to be more potent and safe than digoxin. Its higher efficacy could be due to its structural specificity and might have been mediated through its better free radical scavenging action.

Investigation of cytotoxic, apoptosis-inducing, genotoxic and protective effects of the flavonoid rutin in HTC hepatic cells.

Rutin is a flavonoid with antioxidant, vasodilatory, anti-inflammatory and immune-stimulating activities. To study the toxicity of rutin and its protective effect, this work investigated the cytotoxic, apoptosis-inducing, genotoxic and protective effects of rutin in HTC cells. In the MTT assay, the highest concentration tested (810 µM) showed cytotoxicity after 72 h of treatment, where cell viability and cell proliferation was diminished. None of the concentrations of rutin tested induced apoptosis after 24h treatment. The highest concentration of rutin after 24h treatment induced DNA damage, shown in the comet assay, but did have a genotoxic effect in the micronucleus test. Rutin was tested against the pro-carcinogenic agent benzo(a)pyrene, at concentrations of 90, 270 and 810 µM, and was found to reduce induced DNA damage significantly. This protective effect of rutin against a pro-carcinogen, suggests an important biological activity for this compound, which can contribute to human health through the diet.

Evaluation of antigenotoxic effects of plant flavonoids quercetin and rutin on HepG2 cells.

The flavonoid quercetin and its derivative rutin were investigated for genotoxicity/antigenotoxicity activity in human hepatoma HepG2 cells using the comet assay. The extract cytotoxicity was evaluated using the trypan blue exclusion dye method with quercetin and rutin concentrations ranging from 0.1 to 200.0 µg/mL of culture medium. Three minor non-cytotoxic concentrations were chosen to evaluate the genotoxicity and antigenotoxicity of the flavonoids (0.1, 1.0 and 5.0 µg/mL) through comet assay. The cultures were treated with three different concentrations of rutin or quercetin (genotoxicity) or their association with Aflatoxin B1 (AFB1), methyl methanesulfonate (MMS) or doxorubicin (DXR) (antigenotoxicity test) in three protocols: pre-treatment, simultaneous treatment and post-treatment. The cell cultures were also treated with 1% DMSO (control group), AFB1, MMS and DXR (positive-control). Statistical analyses were performed using ANOVA and Dunnett's test (p ≤ 0.05). Quercetin at concentrations higher than 10.0 µg/mL or rutin higher than 50.0 µg/mL exhibited a cytotoxic effect on the cells, showing that quercetin is more cytotoxic than rutin. Furthermore, neither compound was able to induce genotoxicity in the concentrations evaluated. On the other hand, both flavonoids reduced DNA damage induced by AFB1, MMS and DXR in all treatment protocols.

Do different casein concentrations increase the adverse effect of rutin on the biology of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae)?

The flavonoid rutin is recognized as playing an important role in the protection of plants against lepidopterans. Bioassays with this compound are generally carried out using artificial diets. Proteins of high energy value, such as casein, are important ingredients of insect artificial diets as a source of essential amino acids. However, such proteins can generally increase the allelochemical activity. Our objective was to evaluate the effects of rutin on larvae of the velvetbean caterpillar Anticarsia gemmatalis Hübner by incorporating this allelochemical into diets with different concentrations of casein. Three casein concentrations (0, 7 g, or 14 g) combined with none, 0.65%, or 1.30% of rutin were added to the rearing diet and offered to the larvae from hatching to pupation. Rutin negatively affected larval development, the amount of food consumed, and pupal weight of A. gemmatalis. These negative effects were clearly seen in insects fed on diets with 7 g of casein to which any concentration of rutin was added. The effects of rutin when added to the diets without casein were stronger than in diets containing a suitable amount of casein (14 g). The greater negative effects of rutin in diets containing suboptimal concentrations of casein indicate that casein can increase the effects of rutin only when the diets are nutritionally unsuitable for insect development.

Do different casein concentrations increase the adverse effect of rutin on the biology of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae)?

The flavonoid rutin is recognized as playing an important role in the protection of plants against lepidopterans. Bioassays with this compound are generally carried out using artificial diets. Proteins of high energy value, such as casein, are important ingredients of insect artificial diets as a source of essential amino acids. However, such proteins can generally increase the allelochemical activity. Our objective was to evaluate the effects of rutin on larvae of the velvetbean caterpillar Anticarsia gemmatalis Hübner by incorporating this allelochemical into diets with different concentrations of casein. Three casein concentrations (0, 7 g, or 14 g) combined with none, 0.65 percent, or 1.30 percent of rutin were added to the rearing diet and offered to the larvae from hatching to pupation. Rutin negatively affected larval development, the amount of food consumed, and pupal weight of A. gemmatalis. These negative effects were clearly seen in insects fed on diets with 7 g of casein to which any concentration of rutin was added. The effects of rutin when added to the diets without casein were stronger than in diets containing a suitable amount of casein (14 g). The greater negative effects of rutin in diets containing suboptimal concentrations of casein indicate that casein can increase the effects of rutin only when the diets are nutritionally unsuitable for insect development.

Fifty-two week chronic toxicity of enzymatically decomposed rutin in Wistar rats.

The chronic toxicity of enzymatically decomposed rutin, which consists mainly of isoquercitrin, was evaluated in male and female Wistar rats with dietary administration at concentrations of 0%, 0.04%, 0.2%, 1% and 5% for 52 weeks. No toxicological findings were found in the mortality, body weights, food consumption, hematology, clinical biochemistry or organ weights in either sex. Obvious clinical signs were chromaturia that could be attributed to the color of test substance in the 5% groups of both sexes. Coloration of the urine collected over 24h in the 1% and 5% groups of both sexes was noted. Increased daily urinary calcium excretion was observed in the 5% groups of both sexes and an increase in urinary calcium concentration was observed in the male 5% group. On histopathological examination, incidences of mineralization, inflammatory cell debris, inflammatory cell infiltration and/or transitional cell hyperplasia in the renal pelvis were increased in the 5% male group, whereas treated females showed no apparent difference in these incidences. Based on the above findings, the no observed adverse effect level (NOAEL) was estimated to be 1% in both sexes (542.4 mg/kg body weight/day for males and 674.0mg/kg body--weight/day for females).

Evaluation of the genotoxic and antioxidant effects of two novel feed additives (ethoxyquin complexes with flavonoids) by the comet assay and micronucleus test.

The complexes of antioxidant ethoxyquin (1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline; EQ) with rutin or quercetin (EQ-R and EQ-Q, respectively) were studied in human lymphocytes for genotoxic and antioxidant activities with the use of the comet assay and micronucleus test. The study was undertaken to search for new potential antioxidants, and was motivated by reports of unfavourable side-effects observed in animals fed with feeds containing EQ, which is allowed up to 150 mg kg(-1) (0.015%) in complete animal feed. It was shown that EQ-R induced DNA damage in human lymphocytes when used at all the concentrations studied (1-25 microM), while after EQ-Q treatment, the genotoxic effect was observed mainly after higher doses (10 and 25 microM). An increase in the number of micronuclei was observed only for EQ-Q after a dose of 50 microM. The studied compounds decreased the degree of DNA damage induced by hydrogen peroxide (10 microM) in the comet assay. The results obtained in both tests showed that the antioxidant activity of EQ-Q was comparable with that of EQ, so further detailed studies are necessary to estimate its possible usefulness as a feed preservative.

In vitro anti-HIV and -HSV activity and safety of sodium rutin sulfate as a microbicide candidate.

Sodium rutin sulfate (SRS) is a sulfated rutin modified from the natural flavonol glycoside rutin. Here, we investigated its in vitro anti-HIV and -HSV activities and its cytotoxic profile. Fifty percent inhibitory concentration (IC(50)) values of SRS against HIV-1 X4 virus IIIB, HIV-1 R5 isolates Ada-M and Ba-L were 2.3+/-0.2, 4.5+/-2.0 and 8.5+/-3.8 microM with a selectivity index (SI) of 563, 575 and 329, respectively. Its IC(50) against primary R5 HIV-1 isolate from Yunnan province in China was 13.1+/-5.5 microM, with a SI of 197. In contrast, unsulfated rutin had no activity against any of the HIV-1 isolates tested. Further study indicated that SRS blocked viral entry and virus-cell fusion likely through interacting with the HIV-1 envelope glycoprotein. SRS also demonstrated some activity against human herpes simplex virus (HSV) with an IC(50) of 88.3+/-0.1 microM and a SI of 30. The 50% cytotoxicity concentration (CC(50)) of SRS was >3.0 mM, as determined in human genital ME180, HeLa and primary human foreskin fibroblast cells. Minimum inhibitory concentration of SRS for vaginal lactobacilli was >3.0 mM. These results collectively indicate that SRS represents a novel candidate for anti-HIV-1/HSV microbicide development.

Influence of quercetin and rutin on growth and antioxidant defense system of a human hepatoma cell line (HepG2).

BACKGROUND: Dietary polyphenols like quercetin and rutin are considered beneficial because of their potential protective role in the pathogenesis of multiple diseases associated to oxidative stress such as cancer, coronary heart disease and atherosclerosis. However, many of these effects may depend on the concentration of the polyphenol utilized since high doses of some phenolic compounds may be prooxidant and negatively affect cell growth and viability. AIM OF THE STUDY: To test the potential chemoprotective effects of quercetin and rutin, two flavonols with high antioxidant capacity, on cell growth, viability and the response of the antioxidant defense system of a human hepatoma cell line (HepG2). METHODS: Cell growth was measured by diaminobenzoic acid and bromodeoxyuridine assays, cell toxicity by lactate dehydrogenase leakage assay, reduced glutathione was quantified by a fluorimetric assay, cellular malondialdehyde was analyzed by high-performance liquid chromatography, reactive oxygen species were quantified by the dichlorofluorescein assay, antioxidant enzyme activities were determined by spectrophotometric analysis and their gene expression by northern blot. RESULTS: Short-term exposure (4 h) to these flavonols had no antiproliferative nor cytotoxic effect. High doses of quercetin (50-100 microM) increased glutathione concentration and gene expression of Cu/Zn superoxide dismutase and catalase inhibiting the activity of the latter enzyme, whereas lower doses (0.1-1 microM) decreased gene expression of Cu/Zn superoxide dismutase and increased that of glutathione peroxidase. All doses of quercetin and rutin diminished reactive oxygen species and high doses (10-100 microM) decreased malondialdehyde concentration. CONCLUSION: The results indicate that both natural antioxidants induce favorable changes in the antioxidant defense system of cultured HepG2 that prevent or delay conditions which favor cellular oxidative stress.

In vitro basal and metabolism-mediated cytotoxicity of flavonoids.

The purpose of this study was to compare the basal cytotoxicity and metabolism-mediated cytotoxicity of kaempferol, quercetin and rutin. McCoy cells were exposed to various concentrations of the flavonols with and without the S9 system. The neutral red uptake assay was used to determine viability after 24 h at 35-37 degrees C. Dose-response curves were established for each flavonol in the presence and absence of external metabolizing systems. Kaempferol and quercetin were cytotoxic and provoked a dose-dependent decrease in cell viability, without the S9 system. The hepatic S9 microsomal fraction metabolized these compounds to less cytotoxic metabolites. In contrast, rutin at 500 microg/ml failed to produce any overt signs of toxicity in either assay.

In vitro pollen tube growth reveals the cytotoxic potential of the flavonols, quercetin and rutin.

Flavonols are phytochemicals widely found in commonly consumed foods. In spite of their beneficial effects on human health, however, cytotoxicity and even suspected genotoxicity have also been reported for the flavonol, quercetin. This points to the need for preventive studies to identify any cytotoxic effects associated with pure flavonol intake. This work was performed with the aim of verifying whether a plant-based in vitro system, the pollen tube, could be used to evaluate the cytotoxic potential of exogenous flavonols. Increasing concentrations of the aglycone, quercetin, and its glycoside, rutin, were assayed with regard to tube growth of kiwifruit pollen, determined by applying the pollen tube growth test protocol. This test, based on the photometric quantification of pollen tube mass production in suspension cultures, has already been applied in the sensitive and reliable toxicological evaluation of a wide range of chemicals. Whereas 60-800 microM rutin promoted kiwifruit pollen tube elongation, 10-50 microM quercetin strongly inhibited growth, and also produced irreversible malformations, such as screw-like tube growth, abnormal vacuolation, alteration of organelle streaming, and nuclear positioning. Thus, the cytotoxic potentials of the two flavonols have been confirmed to differ. Pollen tubes seem to afford a promising test system for a preventive, rapid in vitro biosafety assessment of antioxidant nutritional supplements, without using laboratory animals.