Research - Radiation
Radioprotective Potential of Plants and Herbs against the Effects of Ionizing Radiation
Ganesh C. Jagetia*
Ionizing radiations produce deleterious effects in the living organisms and the rapid technological advancement has increased human exposure to ionizing radiations enormously. There is a need to protect humans against such effects of ionizing radiation. Attempts to protect against the deleterious effects of ionizing radiations by pharmacological intervention were made as early as 1949 and efforts are continued to search radioprotectors, which may be of great help for human application. This review mainly dwells on the radioprotective potential of plant and herbal extracts. The results obtained from in vitro and in vivo studies indicate that several botanicals such as Gingko biloba, Centella asiatica, Hippophae rhamnoides, Ocimum sanctum, Panax ginseng, Podophyllum hexandrum, Amaranthus paniculatus, Emblica officinalis,Phyllanthus amarus, Piper longum, Tinospora cordifoila, Mentha arvensis, Mentha piperita, Syzygium cumini, Zingiber officinale, Ageratum conyzoides, Aegle marmelos and Aphanamixis polystachya protect against radiation-induced lethality, lipid peroxidation and DNA damage. The fractionation-guided evaluation may help to develop new radioprotectors of desired activities.
Source : J Clin Biochem Nutr.
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Vitamin E Analogs as Radiation Response Modifiers
Pankaj K. Singh and Sunil Krishnan
Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
The potentially life-threatening effects of total body ionizing radiation exposure have been known for more than a century. Despite considerable advances in our understanding of the effects of radiation over the past six decades, efforts to identify effective radiation countermeasures for use in case of a radiological/nuclear emergency have been largely unsuccessful. Vitamin E is known to have antioxidant properties capable of scavenging free radicals, which have critical roles in radiation injuries. Tocopherols and tocotrienols, vitamin E analogs together known as tocols, have shown promise as radioprotectors. Although the pivotal mechanisms of action of tocols have long been thought to be their antioxidant properties and free radical scavenging activities, other alternative mechanisms have been proposed to drive their activity as radioprotectors. Here we provide a brief overview of the effects of ionizing radiation, the mechanistic mediators of radiation-induced damage, and the need for radiation countermeasures. We further outline the role for, efficacy of, and mechanisms of action of tocols as radioprotectors, and we compare and contrast their efficacy and mode of action with that of another well-studied chemical radioprotector, amifostine.
......Taken together, these promising findings of preclinical radioprotective activity of newer tocols beyond α-tocopherol warrant continued evaluation of their pharmacokinetics, bioavailability, pharmacodynamics, tolerability, and efficacy in large animal models. A greater understanding of mechanisms of action may facilitate adoption of newer strategies such as alpha-tocopherol succinate-mobilized cellular therapy as a bridge to recovery of innate hematopoietic cells after radiation injury or design of synthetic analogs based on analysis of structure-function relationships critical for specific activity. Collectively, recent advances in our knowledge of vitamin E derivatives provide a framework for the advancement of such agents as viable radiation countermeasures.
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Radioprotective Activities of Podophyllum hexandrum: Current Knowledge of the Molecular Mechanisms
Raj Kumar, Pankaj Kumar Singh, Rajesh Arora, Raman Chawla, Rakesh Kumar Sharma*
Institute of Nuclear Medicine and Allied Sciences, Brig S.K. Mazumdar Road, Delhi-110 054, INDIA.
Radiation mediated free radical flux interferes with oxidation/reduction-based physiological mechanisms. These free radicals react with a number of biomolecules including Deoxyribonucleic acid (DNA), lipids and proteins. The rate and selectivity of these free radical mediated reactions depend upon the concentration, half-life and state of delocalization of electrons in the free radicals and the free radicals’ oxidizing ability.
Podophyllum hexandrum Royle (Himalayan Mayapple) was known as Aindri (“a divine drug”) in ancient times. It has been reported to be used through the ages and in modern times as a cure for allergic and inflammatory conditions of the skin; biliary fever; burning sensation; cold; constipation; cancer of the brain, bladder and lung; erysipelas; Hodgkin’s disease; insect bites; mental disorders; monocytoid leukemia; non-Hodgkin’s lymphoma; rheumatism; septic wounds; plague; and venereal warts. It has served as a commercial source of podophyllotoxin and related aryltetralin lignans and several other bioactive constituents. Podophyllotoxin finds use as a precursor for the semi-synthetic topisomerase inhibitors in the treatment of leukemias, lung and testicular cancers, dermatological disorders like warts, rheumatoid arthritis, psoriasis and malaria. It also has numerous applications in modern medicine by virtue of its free radical scavenging capacity. An extract of P. hexandrum has been shown to provide approximately 80% whole-body radioprotection in mice.
The present review highlights the state of knowledge about the radioprotective mechanism of P. hexandrum at different levels of organization in living organisms. Further, an insight into its mode of action at the molecular level, including the studies of the expression patterns of various proteins associated with inhibition of apoptosis in the spleen of male Swiss albino strain ‘A’ mice by immunoblotting, has been presented. In conclusion, the studies clearly demonstrated that P. hexandrum extract provides protection from gamma-radiation by the modulation of expression of proteins associated with cell death attributed to its ability to modulate free radical flux.
Source : Trees for Life Journal
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Role of Rosemary Leaf Extract Against Various Doses of Gamma Radiation
Garima Sancheti and P. K. Goyal*
Radiation & Cancer Biology Laboratory, Department of Zoology, University of Rajasthan, Jaipur – 302 004 (India)
The present investigation reports the radiomodulatory effect of Rosmarinus officinalis (rosemary) leaf extract against radiation-induced hematological alterations in Swiss albino mice at various post-autopsy intervals (i.e., between 24 hours to day 30). Treatment of animals with rosemary extract (1000 mg/ kg body wt) prior to irradiation was found to delay the onset of mortality and reduced the symptoms of radiation sickness such as ruffled hairs, lethargy, anorexia and diarrhea in comparison to radiation alone treated animals. Rosemary treated experimental groups exhibited a dose dependent rise (9 < 6 < 3 Gy) in the number of leucocytes (i.e., lymphocytes, monocytes, basophils, eosinophils and neutrophils) by the 30th day post autopsy interval in comparison to the control. Irradiation resulted in a significant increase in lipid peroxidation levels (p< 0.01, p< 0.001) and a reduction in glutathione levels (p<0.05, p<0.001) in blood as observed in radiation alone treated animals. Conversely, treatment of mice with rosemary extract exhibited a significant decrease (p< 0.01, p< 0.001) in lipid peroxidation level and an increase (p< 0.05, p<0.001) in glutathione content.
......The mechanism of the radioprotective action of Rosmarinus officinalis leaf extract in this animal model may thus be its free radical scavenging activity and its ability to thus protect cellular molecules from oxidative damage. Furthermore, it inhibited lipid peroxidation and modulated GSH levels in blood of these Swiss albino mice. The activity of rosemary may also be attributed to stimulating or protecting hematopoiesis in bone marrow and a subsequent increase of hematological constituents in the peripheral blood. Since significant protection was obtained at a non-toxic low dose, RE may have an advantage over the known radioprotectors. Further investigations are in progress to study the exact mechanism of action and clinical applicability of R. officinalis in radioprotection.
Source : Trees For Live Journal
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