Antioxidant capacity of a 3-deoxyanthocyanidin from soybean.

Soybean cotyledons directly exposed to UV-C (190-280 nm) contained a colored pigment in those areas of the epidermis directly exposed to UV-C. Ethanolic extracts from UV-C irradiated cotyledons showed a significant peak at 532 nm at pH=10, but not seen at pH=6, successive changes in pH were accompanied by reversible changes in the spectra. The identity of the pigment isolated from soybean cotyledons was established as apigeninidin by comparing the features of standard of a apigeninidin (from sorghum) previously characterized by FAB-MS, UV, HPLC, 1H NMR, and IR spectroscopy. To characterize antioxidant activity of this compound, its ability to scavenge radical species in vitro was tested. In the concentration range tested (up to 200 microg ml (-1)), apigeninidin did not show any scavenger activity towards hydroxyl radical, quinones or NO. However, ascorbyl radical and lipid radicals were effectively quenched in a dose-dependent manner. Overall, UV-C radiation triggers molecular signals that lead in soybean cotyledons to the synthesis and accumulation of an antioxidant pigment, apigeninidin, that shows scavenger activity against ascorbyl and lipid radicals in in vitro studies.

Effect of nitric oxide and plant antioxidants on microsomal content of lipid radicals.

The antioxidant ability of nitric oxide (NO) generated by a chemical donor and of commercially available antioxidant preparations was assayed. SNAP (S-Nitroso-N-acetylpenicilamine) was used as the NO donor, and Ginkgo biloba, wheat and alfalfa preparations were tested. Lipid peroxidation was assayed by EPR employing a reaction system consisting of rat liver microsomes, ADP, FeCl3, NADPH and POBN in phosphate buffer, pH=7.4. In vitro NO exposure decreased microsomal lipid peroxidation in a dose-dependent manner. The dose responsible for inhibiting the microsomal content of lipid radical adducts by 50% (LD50) for SNAP was 550 microM (NO generation rate 0.1 microM/min). The addition of 50 microM hemoglobin to the incubation media prevented NO effect on lipid peroxidation. The addition of an amount of the antioxidant preparations equivalent to the LD50 doses inhibited lipid peroxidation by 21, 15, and 33% for wheat, alfalfa, ginkgo biloba preparations respectively in the presence of 550 microM SNAP. We detected a decrease in the content of lipid radical adducts after simultaneous supplementation, although it was less than 50%, even when LD50 doses of the products were added. This suggests that NO and the natural antioxidants inhibit lipid peroxidation by a mechanism that has both common and non-shared features.

Effect of nitric oxide and plant antioxidants on microsomal content of lipid radicals

The antioxidant ability of nitric oxide (NO) generated by a chemical donor and of commercially available antioxidant preparations was assayed. SNAP (S-Nitroso-N-acetylpenicilamine) was used as the NO donor, and Ginkgo biloba, wheat and alfalfa preparations were tested. Lipid peroxidation was assayed by EPR employing a reaction system consisting of rat liver microsomes, ADP, FeCl3, NADPH and POBN in phosphate buffer, pH=7.4. In vitro NO exposure decreased microsomal lipid peroxidation in a dose-dependent manner. The dose responsible for inhibiting the microsomal content of lipid radical adducts by 50% (LD50) for SNAP was 550 microM (NO generation rate 0.1 microM/min). The addition of 50 microM hemoglobin to the incubation media prevented NO effect on lipid peroxidation. The addition of an amount of the antioxidant preparations equivalent to the LD50 doses inhibited lipid peroxidation by 21, 15, and 33% for wheat, alfalfa, ginkgo biloba preparations respectively in the presence of 550 microM SNAP. We detected a decrease in the content of lipid radical adducts after simultaneous supplementation, although it was less than 50%, even when LD50 doses of the products were added. This suggests that NO and the natural antioxidants inhibit lipid peroxidation by a mechanism that has both common and non-shared features.