Yanka Karamalakova

Radical scavenging and radiomodulatory effects of Psoralea corylifolia Linn. substantiated by in vitro assays and EPR spectroscopy.

The present study is the first report of the radiomodulatory effects of Psoralea corylifolia Linn. The extract (IBG-RA-26) prepared from P. corylifolia was chemically analysed by HPLC, LC-MS/MS and NMR. The total polyphenolic content of IBG-RA-26 was 0.287 mg/ ml of quercetin equivalents. IBG-RA-26 exhibited a dose-dependent increase in 2,2-diphenyl- 1-picrylhydrazyl (DPPH) radical scavenging activity. It exhibited comparable (> 50%) site-specific and non-site-specific hydroxyl radical scavenging activity in higher concentration ranges (500 - 1000 μg/ml), while at lower concentrations (5 - 50 μg/ml) it exhibited significantly (p < 0.05) higher non-site-specific scavenging ability compared to site-specific activity. Nitric oxide scavenging activity of IBG-RA-26 (5 - 1000 μg/ml) increased in a concentrationdependent manner, while maximum superoxide ion scavenging ability (79%) was observed at 50 μg/ml. The electron donation potential of IBG-RA-26 was found to be higher than that of ascorbic acid at lower concentrations (up to 5 μg/ml). Analysis of the ability of IBGRA- 26 to protect membranes against γ-radiation, utilizing an artificial membrane system (liposome), revealed a significant (p < 0.05) decrease in the formation of malondialdehyde (MDA) as a function of the concentration of IBG-RA-26. Radiation-induced lysis of human erythrocytes was monitored and efficacy of IBG-RA-26 was tested in the concentration range 25 - 1000 μg/ml, with significant protective efficacy observed in the range 25 - 50 μg/ml. IBG-RA-26 rendered significant (p < 0.05) protection against radiation (0.25 kGy)-induced DNA damage. EPR spectroscopy was used to investigate the DPPH radical scavenging capacity of IBG-RA-26. IBG-RA-26 exhibited a good DPPH radical scavenging capacity in a concentration-dependent manner. By direct EPR spectroscopy we have also demonstrated the possible formation of free radical species in a solution of IBG-RA-26. The wide spectrum of radioprotective and antioxidant properties exhibited by IBG-RA-26 indicate that P. corylifolia has potential as a radiomodulatory agent.

Studies on Antioxidant Properties before and after UV- And Γ-Irradiation of Bulgarian Lavender Essential Oil Isolated from Lavandula Angostifolia Mill

ABSTRACT At present there is not enough data about different types of radiation on Bulgarian essential oils isolated from medicinal plants. Here we report for the first time our studies on the effects of UV-radiation (290 nm to 320 nm) and γ-radiation (doses of 5 Gy, 10 Gy, 20 Gy and 30 Gy) on Bulgarian lavender essential oil isolated from Lavandulla angustifolia Mill. A spectrophotometry method was used for evaluation of the changes in the reducing power of the Bulgarian lavender oil before and after radiation. The electron donation potential of non-irradiated oil was found to be lower (0.268 ± 0.0244) than those of both, UV-irradiated (0.336 ± 0.0121) and γ-irradiated, oil samples (0.427 ± 0.0251 at 5 Gy radiation, 0.341 ± 0.0371 at 10 Gy; 0.328 ± 0.0173 at 20 Gy). By direct electron paramagnetic resonance (EPR) spectroscopy, single almost symmetrical EPR signals with different values of the g-factor were registered in non-irradiated (g = 2.0047 ± 0.0002), UV-irradiated (g = 2.01050 ± 0.00005) and γ-irradiated oil samples (g = 2.0017 ± 0.0002), respectively. EPR spectroscopy was used for assessment of the radical scavenging capacity of the non-irradiated and UV- and γ-irradiated samples of the Bulgarian lavender oil towards the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). Excellent DPPH radical scavenging capacities were found for UV- and 30 Gy-irradiated lavender oil samples. Based on these preliminary results, we consider that, after proper UV- or γ-radiation treatment, Bulgarian lavender oil might find application as a good radioprotector and antioxidant in cosmetics and medicine.

Biological evaluation of new potential anticancer agent for tumour imaging and radiotherapy by two methods: 99mTc-radiolabelling and EPR spectroscopy

Recently, a new class of in vitro and ex vivo radiotracers/radioprotectors, the nitroxyl-labelled agent 1-ethyl-1-nitroso–3-[4-(2,2,6,6–tetramethylpiperidine-1-oxyl)]-urea (SLENU), has been discovered. Our previous investigations demonstrated that SLENU is a low-molecular-weight stable free radical which is freely membrane permeable, easily crosses the blood brain barrier and exhibited in/ex vivo the lowest general toxicity and higher anticancer activity against some experimental tumour models. Further investigation was aimed to develop a 99mTc-labelled SLENU (97%) as a chelator and evaluate its labelling efficiency and potential use as a tumour seeking agent and for early diagnosis. Tissue biodistribution of 99mTc-SLENU was determined in normal mice at 1, 2 and 24 h (n = 4/time interval, route of administration i.v.). The distribution data were compared using male albino non-inbred mice and electron paramagnetic resonance investigation. The imaging characteristics of 99mTc-SLENU conjugate examined in BALB/c mice grafted with Ehrlich Ascitis tumour in the thigh of hind leg demonstrated major accumulation of the radiotracer in the organs and tumour. Planar images and auto-radiograms confirmed that the tumours could be visualized clearly with 99mTc-SLENU. Blood kinetic study of radio-conjugate showed a bi-exponential pattern, as well as quick reduced duration in the blood circulation. This study establishes nitroxyls as a general class of new spin-labelled diagnostic markers that reduce the negative lateral effects of radiotherapy and drug damages, and are appropriate for tumour-localization.

Radical Scavenging Capacity of Seeds and Leaves Ethanol Extracts of Cynara Scolymus L.—A Comparative Study

ABSTRACT Artichoke with scientific name Cynara scolymus L. is an herbal medicinal plant widely used in traditional European medicine. This medicinal plant possesses many properties, including hepatoprotective ability and antioxidant effect. It has been reported that seeds and leaves of the artichoke contain different constituents such as caffeoylquinic acid derivatives, mono- and di- caffeoylquinic acids, bitter sesquiterpene such as cynatriol and cynaropicrin and flavonoids glycosides like apigenin, luteolin cynaroside, scolimoside, quercitine and others. The aim of the present study was by an Electron Paramagnetic Resonance (EPR) method and visible spectrophotometry to evaluate and compare the radical scavenging capacity towards 1,1 -diphenyl-2-picrylhydrazyl (DPPH) of ethanol extracts prepared from Cynara scolymus L. seeds and leaves. By both methods we have demonstrated that at any studied concentration of the seeds extract the percent of the scavenged DPPH radicals was considerably higher than that calculated for the leaves extract.

Oxidative-protective effects of Tinospora cordifolia extract on plasma and spleen cells after experimental ochratoxicosis

The importance of Tinospora cordifolia extract was investigated for its possible protective effect in spleen and blood in male ICR albino mice against ochratoxin A-induced toxicity (OTA). OTA instigates oxidative changes and results in the overproduction of free radicals, changes in body/organ weight, and the food consumption and is considered as a risk factor for animals and humans. Reactive oxygen species (ROS), reactive nitrogen species (RNS), and consequent lipid-peroxidative damages caused by OTA are considered to be the main mechanisms leading to oxidative stress disorders in organs and blood. TC oral administrations prevent the physiological status of animals and improve the biochemical parameters of the urine and plasma. Moreover, EPR analysis show that TC administration decreased Asc• and NO• radicals and ROS productions in the spleen and serum, even in OTA-treated group. The significant decrease in MDA formation in the spleen and serum and the increased expression of SOD activity in TC and TC + OTA groups confirm the positive modulatory effect of TC extract on the cellular antioxidant system. TC and TC + OTA treatment caused significant reduction of genotoxic potential (8-OHdG) of OTA, followed by a decreased oxidative activity and gradual recovery of ROS-induced DNA damage. The results suggested that TC extract protect against OTA-induced oxidative disorders and other abnormalities. As typical antioxidant TC could protect splenic macrophages and regain intracellular antioxidant capacity.

Effect of antigen stimulation on the oxidative stress parameters in sperm of outbred and inbred rabbits

ABSTRACT The presence of an increased oxidative stress during antigen stimulation was established in the sperm of inbred rabbits by evaluation of the level of real-time free radical formation (ROS and Asc•), final products of oxidation of lipids (MDA) and the activities of antioxidant defence enzymes superoxide dismutase (SOD) and catalase (CAT). There was not a significant difference between levels of ROS, Asc• and MDA in inbred and outbred rabbits before immunization. The immune response, represented by levels of ROS and Asc• of inbread and outbread rabbits were statistically significantly higher compared to those before immunization (p = 0.0001 and p = 0.00001) Moreover, the levels of ROS in the sperm of inbread rabbits were statistically significantly higher compared to outbread rabbits (p < 0.05). Oxidative stress was accompanied by an adaptive increase of SOD and CAT activities during the immune response, compared to those before immunization. Furthermore, the increased SOD and CAT activities appeared to be sufficient to inactivate the oxidative stress. We measured reduced levels of ROS, Asc• and MDA 30 days after immunization. When immune response reduced, the observed SOD and CAT activities tended to return to the values before immunization. That might have been connected with the decreased oxidative burden. However, CAT activities remained about 1.5 times higher than that before immunization. In conclusion, our results indicate that the administered antigen stimulation induces oxidative stress in both groups inbred and outbred rabbits.

Comparative Investigation on Radical Scavenging Activity and Protective Properties of Natural Isolated and Synthetic Antioxidants

ABSTRACT The purpose of this study is to evaluate and compare the free radical scavenging activity and protective properties of the natural product SQGD-IBG-21 isolated from a radioresistant bacterium Bacillus sp. INM-1 and synthetic nitroxyl free radical containing antioxidant 1-ethyl-1-nitroso-3-[4-(2,2,6,6-tetramethylpiperidine-1-oxyl)]-urea (SLENU). It was found a higher reducing power potential for SQGD (1.336±0.03357 Uabs) comparing to that of SLENU (0.196±0.002273Uabs); a higher nitric oxide radical scavenging activity 35.645 ±1,122% for SQGD in comparison with SLENU (19.964±2.233%). Total antioxidant capacity of SQGD was found to be 75±0.06%, while for SLENU it was only 22±0.03%. Maximum protection to the liposomes calculated in % inhibitory activity of two agents was found to be 50.04±0.037% for the natural agent and 27.54±0.33% for nitroxyl-labeled agent. By direct EPR spectroscopy stable radical structures were recorded in the solutions of both studied antioxidants: an o-semiquinone radical structure was recorded in aqueous solution of SQGD and nitroxyl free radical struture in the ethanol solution of SLENU, respectively. It should be mentioned that the natural antioxidant possesses higher protective properties in comparison with the synthetic antioxidant. In conclusion, because of well expressed free radical scavenging and antioxidant activities of both studied agents they might be used in the combination anticancer chemotherapy for reduction the toxicity caused by anticancer drugs and/or radiation therapy.