Free radical scavenging and metal chelation by Tinospora cordifolia, a possible role in radioprotection.

Aqueous extract of T. cordifolia inhibited Fenton (FeSO4) reaction and radiation mediated 2-deoxyribose degradation in a dose dependent fashion with an IC50 value of 700 microg/ml for both Fenton and radiation mediated 2-DR degradation. Similarly, it showed a moderate but dose dependent inhibition of chemically generated superoxide anion at 500 microg/ml concentration and above with an IC50 value of 2000 microg/ml. Aqueous extract inhibited the formation of Fe2+-bipiridyl complex and formation of comet tail by chelating Fe2+ ions in a dose dependent manner with an IC50 value of 150 microg/ml for Fe2+-bipirydyl formation and maximally 200 microg/ml for comet tail formation, respectively. The extract inhibited ferrous sulphate mediated lipid peroxidation in a dose-dependent manner with an IC50 value of 1300 microg/ml and maximally (70%) at 2000 microg/ml. The results reveal that the direct and indirect antioxidant actions of T. cordifolia probably act in corroboration to manifest the overall radioprotective effects.

Protective effect of butylated hydroxytoluene (BHT) against the clastogenic acitivity of cadmium chloride and potassium dichromate in hamster ovary cells

The effect of butylated hydroxytoluene (BHT), a widely used food additive, on chromosomal alterations induced by cadmium chloride (CC) and potassium dichromate (PD) in Chinese hamster ovary (CHO) cells was studied both at metaphase and anaphase-telophase. CHO cells were cultured for 15-16 h in the presence of PD (6.0, 9.0 or 12.0 mM), BHT (1.0 mg/ml), or PD plus BHT as well as CC (0.5, 1.0 and 2.0 mM), BHT or CC plus BHT for the analysis of chromosomal aberrations. To perform the anaphase-telophase test, cells were cultured in cover glasses and treated 8 h before fixation with the same chemicals. An extra dose of CC (4 mM) was used in this test. Both metal salts significantly increased chromosomal aberration frequencies in relation to untreated controls, and to DMSO- and BHT-treated cells. Post-treatment with BHT decreased the yield of chromosomal damage in relation to treatments performed with CC and PD. However, chromosomal aberration frequencies were significantly higher than those of the controls. In the anaphase-telophase test, CC significantly increased the yield of lagging chromosomes with the four doses employed and the frequency of lagging fragments with the highest dose. In combined treatments of CC and BHT, frequencies of the two types of alterations decreased significantly in relation to the cells treated with CC alone. No significant variation was found in the frequencies of chromatin bridges. Significant increases of numbers of chromatin bridges, lagging chromosomes and lagging fragments were found in cells treated with PD. The protective effect of BHT in combined treatments was evidenced by the significant decrease of chromatid bridges and lagging chromosomes in relation to PD-treated cells. Whereas BHT is able to induce chromosomal damage, it can also protect against oxidative damage induced by other genotoxicants.

Inhibition of expression of P-selectin by antioxidant in cholesterol-fed rats

Butylated hydroxytoluene (BHT) can inhibit experimental atherosclerosis in animals. Although the agent is an antioxidant, the exact mechanism of the reaction in atherosclerosis is still unknown. To investigate the effects of BHT on expression of P-selectin (PADGEM, GMP-140), intercellular adhesion molecule-1 (ICAM-1) and class II MHC (Ia) antigen, we proposed an experiment on rats. Male rats (n=18 per group) were fed either a normal cholesterol control diet, a normal cholesterol diet containing 0.5% BHT (BD), a high cholesterol diet containing 1.5% cholesterol and 0.1% sodium cholate (CD), or the CD diet containing 0.5% BHT (BCD). Rats were sacrificed after 3 days, and after 1, 2, 4, 10, and 17 weeks of dietary treatment. Although there was no gross or light microscopic atherosclerotic lesions, scanning electron microscopy revealed monocytic adhesion to aortic endothelium and mild endothelial injuries in CD and BCD groups. Immunohistochemically, the addition of BHT to a high cholesterol diet inhibited P-selectin expression but not in ICAM-1 and Ia antigen. These findings suggest that in rats, high cholesterol diets induce expression of ICAM-1, P-selectin and Ia antigen. In addition, the antiatherogenic effect of BHT may play a role in the inhibition of P-selectin.

Induction of prophage lambda by nitrofurantoin and its modulation by butylated hydroxytoluene, sodium arsenite and alpha tocopherol.

Nitrofurantoin induced prophage-lambda in E. coli K12 strain GY5027(lambda) in a dose dependent manner, the maximum induction being 10-fold the spontaneous induction level and the maximum efficiency of induction 74%. The lever extract used as a metabolizing mixture enhanced the induction level significantly. Chloramphenicol at a concentration of 20 micrograms/ml inhibited the prophage induction by nitrofurantoin, indicating that the induction required concomitant protein synthesis. Butylated hydroxytoluene(BHT) and sodium arsenite enhanced the nitrofurantoin induced prophage-lambda induction in E. coli GY 5027(lambda) cells in a dose dependent manner. The maximum modulations in induction level (I/Io) were achieved with 100 micrograms/ml BHT and 250 micrograms/ml sodium arsenite corresponding to a nitrofurantoin concentration of 15 micrograms/ml and were found significant on statistical analysis. alpha-tocopherol, however, did not produce any effect on the prophage-lambda induction by nitrofurantoin.

Enhancement of O-dealkylation in Mouse Liver by Dietary Administrations of BHA and BHT: Studies with Isolated Perfused Livers and Hepatic Microsomes

Effects of feeding 2(3)-tert-butyl 4-hydroxyanisole (BHA) and 3, 5-di-tert-butyl 4-hydroxytoluene (BHT) on the rates of mixed function oxidation and conjugation enzyme reactions have been determined using isolated hepatic microsomal fractions and isolated perfused livers of mice. The treatments with either of the antioxidants have increased the rates of O-demethylation for p-nitroanisole and of O-deethylation for 7-ethoxycoumarin up to 2-fold, both in microsomes and in perfused liver. Analysis of the perfusate showed that the increased amounts of p-nitrophenol and 7-hydroxycoumarin produced by the elevated mixed-function oxidase activities were reflected by the increase in the amounts of glucuronide conjugates and not in the increase for the amounts of the sulfate ester conjugates. Comparison of results also indicated that in the perfused liver, the maximal rate of metabolite conjugation is limited by the maximal rates of the initial mixed function oxidase activities.