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A comparative study of radioprotection by propolis and its polyphenolic/flavonoids compounds and synthetic protector 2-aminoethylisothiouronium bromide hydrobromide in the mouse.

There is continued interest and a need for the indentification and development of non-toxic, inexpensive and effective radioprotective compounds. Such compounds could potentially protect humans against the genetic damage, mutation, immune system alterations, and teratogenic effects of toxic agents which act through the generation of free radicals. Considering that product of beekeeping possess antiinflamatory, immunomodulative, hemostimulative and antioxidant action, manifestitation of their radioprotective characteristic should be expected. In this study radioprotective effect of two preparation of propolis (water and ethanolic extract of propolis ; WSDP or EEP) and their polyphenolic compounds (caffeic acid, naringin, chrysin, quercetin) and synthetic protector 2-aminoethylisothiouronium bromide hydrobromide (AET) have been compared by examing DNA damage of lymphocytes using the single-cell gel electophoresis assay (comet assay) in irradiated mice.Healthy adult CBA mice were injected intraperitoneally (ip) with dose of 100 mg kg-1 body weight and/or double distilled water or 1% solution of ethanol with water as control, for 3 conecutive days before or after whole body  -irradiation (WBI).Mice were exposed to WBI with 9 Gy of 60Co  -radiation source. Thirty minutes after iradiation and/or treatment with test components we examined DNA damage of lymphocytes using the comet assay. The WBI of mice resulted in a significant elevation of DNA damage of lymphocytes as compared with unradiated mice. Pretreatment of mice with WSDP, EEP and related flavonoids as well as with AET produced the reduction in oxidative DNA damage of lymphocytes as compared with radiation control ; test components were ranked in decreasing order of potency as follows: naringin (2.98%) ; chrysin (16.84%) ; quercetin (33.67%) ; AET (48.52%) ; caffeic acid (49.51%) ; EEP (53.47%) ; and WSDP (54.46%) (Figure 1A). Treatment with preparations of propolis and its polyphenolic/flavonoids compounds and AET after irradiation resulted in a significant reduction of DNA damage as follows: caffeic acid (32.31%) ; AET (75.39%) ; naringin (78.46%) ; EEP (80%) ; chrysin (83.08%) ; quercetin (84.62%) ; and WSDP (89.24%) (Figure 1B). Propolis and its flavonoids (with exeption of caffeic acid) showed better radioprotective effect than AET. The most effective reduction of DNA damage of lymphocytes by WSDP and EEP indicate synergistic antioxidative effect of different polyphenolic flavonoids components present in EEP or WSDP. Neither of test components induced any systemic toxicity, even at dose of 200 mg kg-1. Considering the low dose needed for protection and the high margin between the effective and toxic dose, propolis and its polyphenolic compounds may be promising for human radiation protection and chemprevention of cancer. The clinical potential of these protetors in cancer theraphy needs to be investigated.

propolis; flavonoids; radioprotection; mice; comet assay

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