A comparative study on the radioprotective potential of the polyphenolic glycoconjugates from medicinal plants of Rosaceae and Asteraceae families versus their aglycones.

Radioprotective potential of the polyphenolic glycoconjugates, isolated from flowers of Sanguisorba officinalis L. (So) and Erigeron canadensis L. (Ec), and from leaves of Fragaria vesca L. (Fv) and Rubus plicatus Whe. Et N. E. (Rp) as well as their aglycones (SoA, EcA, FvA and RpA, respectively), against γ-radiation-induced lipid peroxidation in human plasma and DNA damage in lymphocytes, were investigated in vitro. These properties were assessed by measuring the concentration of thiobarbituric acid reactive substances (TBARS) and using the alkaline comet assay, and were compared to the protective effects of rutin (R) and quercetin (Q). Cytotoxicity of the glycoconjugates/aglycones towards L929 mouse fibroblasts and human lymphocytes were also measured. Plant products from S. officinalis, similar to Q, were able to reduce the most radiation-induced lipid peroxidation as well as DNA damage and extent of oxidative damage to the DNA basis. Contrary to the pure flavonoids, where Q was shown to be significantly more effective than its glycoside R, the results did not show more benefit with application of SoA/EcA over So/Ec in terms of lipid peroxidation inhibition. Moreover, glycoconjugates Ec and So showed much higher capacity in protecting lymphocytes against radiation-induced genotoxicity which may suggest that between the polyphenolic and polysaccharide parts exist some synergistic effects. There were no significant differences between Fv versus FvA or Rp versus RpA in terms of the provided radioprotection. Summarizing, plant glycoconjugates isolated by the multi-step method offered sufficient radioprotection. In addition, they possess many advantages, compared to the synthetic polyphenolic compounds or the plant extracts, such as water-solubility and minor toxicity.

Polyphenolic glycoconjugates from medical plants of Rosaceae/Asteraceae family protect human lymphocytes against γ-radiation-induced damage.

Radioprotective effects of the water-soluble polyphenolic glycoconjugates, isolated from flowers of Sanguisorba officinalis L.(SO) and Erigeron canadensis L.(EC), and from leaves of Fragaria vesca L. (FV) and Rubus plicatus Whe. Et N. E. (RP), against γ-radiation-induced toxicity in human peripheral blood lymphocytes were investigated. Cell treatment with glycoconjugates (1, 5 and 25µg/mL) prior exposure to 10/15Gy radiation resulted in concentration-dependent reduction of DNA damage including oxidative DNA lesions (comet assay), substantial inhibition of lipid peroxidation (TBARS) and restoration of superoxide dismutase and S-glutathione transferase activities. Glycoconjugates isolated from SO and EC ensured better protection versus these from RP and FV, with the SO product potential comparable to that of the reference quercetin. Strong antioxidant/radioprotective activity of the SO and EC glycoconjugates could be attributed to high abundance of syringol-type and ferulic acid units in their matrices, respectively. Moreover, polyphenolic glycoconjugates (25µg/mL), including RP and FV products, significantly decreased DNA damage when applied post-radiation suggesting their modulating effects on DNA repair pathways. Preliminary data on the glycoconjugate phenolic structural units, based on GLC/MS of the products of pyrolysis and in situ methylation, in relation to application of plant products as potential radioprotectors is promising and deserves further investigation.

Radioprotectors in radiotherapy - advances in the potential application of phytochemicals.

Radiotherapy, in addition to chemotherapy, is currently the primary method of cancer treatment based on destruction of malignant cells by ionizing radiation. Unfortunately, it also affects normal cells, which is associated with negative consequences for a patient. Radioprotectors are compounds used to prevent/protect the non-tumor cells from the harmful effects of radiation. To play their role these compounds should meet several criteria; among others, they should significantly protect normal cells from radiation without changing the tumor cell radiosensitivity. In general, agents used to alter normal tissue toxicity from radiation can be broadly divided into three categories based on timing of delivery in relation to radiation: chemical radioprotectors, mitigators, and treatment. These groups include a diverse range of synthetic compounds in terms of their structure and protective mechanisms. The aminoradiothiol amifostine is the only radioprotectant approved in clinical application. However, its use is limited due to toxicity concerns (it may cause hypotension). Natural compounds, derived from plants, meet all criteria of the ideal radioprotector. They exert their protective actions against adverse effects of ionizing radiation by several mechanisms. Plant compounds that show radioprotective activity include flavonoids and phenolic acids, stilbenes, lycopene, alkaloids, peptides, polysaccharides, and phytohormones. Garlic, green tea, apples, citrus, and ginger are examples of constituents of the human diet that contain radioprotective substances.

Polyphenolic-polysaccharide conjugates from plants of Rosaceae/Asteraceae family as potential radioprotectors.

Polyphenolic-polysaccharide macromolecular, water-soluble glycoconjugates, isolated from the selected medicinal plants of Rosaceae/Asteraceae family: from leaves of Fragaria vesca L., Rubus plicatus Whe. et N. E., and from flowering parts of Sanguisorba officinalis L., and Erigeron canadensis L., were investigated for their ability to protect proteins and lipids of human plasma against γ-radiation-induced oxidative damage. Treatment of plasma with plant conjugates (6, 30, 150 µg/ml) prior exposure to 100 Gy radiation resulted in a significant inhibition of lipid peroxidation, evaluated by TBARS levels; conjugates isolated from E. canadensis and R. plicatus and a reference flavonoid quercetin showed similar high potential (approx. 70% inhibition, at 6 µg/ml). The conjugates prevented radiation-induced oxidation of protein thiols and significantly improved plasma total antioxidant capacity, estimated with Ellman's reagent and ABTS(.+) assay, respectively. The results demonstrate by the first time a significant radioprotective capability of the polyphenolic-polysaccharide conjugates isolated from E. canadensis, R. plicatus, S. officinalis and to the less extent from F. vesca. The abilities of these substances to inhibit radiation-induced lipid peroxidation and thiol oxidation in plasma seems to be mediated, but not limited to ROS scavenging activity.

Does quercetin protect human red blood cell membranes against γ-irradiation?

OBJECTIVES: Radioprotective potential of quercetin, a powerful free radical scavenger, was investigated in human red blood cells (RBCs) and in isolated RBC membranes exposed to γ-irradiation-induced oxidative stress. METHODS: RBCs and RBC membrane suspensions were irradiated (50 Gy) in the presence of quercetin (2-50 µM). Oxidative damage of the membranes was analysed by protein carbonyl measurement (enzyme-linked immunosorbent assay). In RBCs, the concentration of glutathione (GSH) was determined. Lipid peroxidation in RBCs, and for comparison in plasma and peripheral lymphocytes, was quantified by the amount of thiobarbituric acid-reactive substances (TBARS). Radiation-induced damage of the RBC membrane integrity was evaluated by the degree of haemolysis. RESULTS: Quercetin (50 µM) brought back the level of carbonyls to normal in γ-irradiated RBC membrane proteins and inhibited radiation-induced lipid peroxidation in plasma and lymphocytes, by 75 and 96%, respectively. However, it moderately decreased reduced/oxidized glutathione (GSH/GSSG) ratio and significantly increased TBARS concentrations, by 60 and 28% in irradiated and non-irradiated RBCs, respectively. Haemolysis rate was much higher in RBCs irradiated in the presence of quercetin vs. non antioxidant. DISCUSSION: In non-cellular systems (RBC membranes or plasma) and in lymphocytes, quercetin shows antioxidative/radioprotective activity but in whole RBCs it acts as a pro-oxidant and a cytotoxic substance. The possible mechanisms of such action are discussed.

A moderate protective effect of quercetin against γ-irradiation- and storage-induced oxidative damage in red blood cells for transfusion.

PURPOSE: To investigate the extent of γ-irradiation-induced oxidative membrane damage and antioxidant activity of quercetin in long-term, cold stored (4°C) acid-citrate-dextrose- preserved human red blood cells (RBC). MATERIALS AND METHODS: The extracellular activity of lactate dehydrogenase (LDH) was measured to assess RBC membrane integrity. Lipid peroxidation and reduced glutathione (GSH) levels were quantified by thiobarbituric acid-reactive substances (TBARS) and Ellman's reagent, respectively. RESULTS: During storage of non-irradiated RBC (up 21 days) the LDH activity in the supernatant increased with time. In contrast to a low dose of ionizing radiation (30 Gy), irradiation at higher, but still clinically relevant doses, of 40-50 Gy resulted in elevation of the post-storage extracellular LDH activity. Quercetin (2-50 µM) dissolved in dimethyl sulfoxide (DMSO) significantly increased the LDH release in the irradiated and non-irradiated RBC, reflecting an increase of RBC membrane permeability. In the presence of ethanol as a solvent quercetin protected RBC against storage-induced oxidative damage - it inhibited the LDH release, GSH depletion, and lipid peroxidation. CONCLUSION: The level of protection offered by quercetin against the radiation- and storage-induced oxidative damage to RBC does not seem to be sufficient to warrant its application as an additive for conservation purposes. The findings indicate that the solvent can modulate a response of RBC to water-insoluble antioxidants changing their properties from anti-oxidative to pro-oxidative.