Superoxide Radical

Myrica gale L. (sweet gale) fruit leachate contains myrigalone A (MyA), a rare C-methylated dihydrochalcone and putative allelochemical, which is known to be a phytotoxin impeding seedling growth. We found that MyA inhibited Lepidium sativum L. seed germination in a dose-dependent manner. MyA did not affect testa rupture, but inhibited endosperm rupture and the transition to subsequent seedling growth. MyA inhibited micropylar endosperm cap (CAP) weakening and the increase in the growth potential of the radical/hypocotyl region (RAD) of the embryo, both being key processes required for endosperm rupture. We compared the contents of abscisic acid (ABA) and gibberellins in the tissues and found that the major bioactive forms of gibberellin in L. sativum seed tissues were GA(4) and GA(6), while GA(8) and GA(13) were abundant inactive metabolites. MyA did not appreciably affect the ABA contents, but severely interfered with gibberellin metabolism and signaling by inhibiting important steps catalyzed by GA3 oxidase, as well as by interfering with the GID1-type gibberellin signaling pathway. The hormonally and developmentally regulated formation of apoplastic superoxide radicals is important for embryo growth. Specific zones within the RAD were associated with accumulation of apoplastic superoxide radicals and endoreduplication indicative of embryo cell extension. MyA negatively affected both of these processes and acted as a scavenger of apoplastic reactive oxygen species. We propose that MyA is an allelochemical with a novel mode of action on seed germination.

Myrica gale L. (sweet gale) fruit leachate contains myrigalone A (MyA), a rare C-methylated dihydrochalcone and putative allelochemical, which is known to be a phytotoxin impeding seedling growth. We found that MyA inhibited Lepidium sativum L. seed germination in a dose-dependent manner. MyA did not affect testa rupture, but inhibited endosperm rupture and the transition to subsequent seedling growth. MyA inhibited micropylar endosperm cap (CAP) weakening and the increase in the growth potential of the radical/hypocotyl region (RAD) of the embryo, both being key processes required for endosperm rupture. We compared the contents of abscisic acid (ABA) and gibberellins in the tissues and found that the major bioactive forms of gibberellin in L. sativum seed tissues were GA 4 and GA 6 , while GA 8 and GA 13 were abundant inactive metabolites. MyA did not appreciably affect the ABA contents, but severely interfered with gibberellin metabolism and signaling by inhibiting important steps catalyzed by GA3 oxidase, as well as by interfering with the GID1-type gibberellin signaling pathway. The hormonally and developmentally regulated formation of apoplastic superoxide radicals is important for embryo growth. Specific zones within the RAD were associated with accumulation of apoplastic superoxide radicals and endoreduplication indicative of embryo cell extension. MyA negatively affected both of these processes and acted as a scavenger of apoplastic reactive oxygen species. We propose that MyA is an allelochemical with a novel mode of action on seed germination.

Context: The snail hemolymph is a multi-component mixture comprising various substances with pharmacological activity. Aims: To evaluate the antioxidant activity of hemocyanin and fractions isolated of hemolymph from garden snail Helix lucorum. Methods: The antioxidant activity was tested in chemical systems generating superoxide radicals (O2 •-) and hydroxyl radicals (• OH) and was presented as percent inhibition. The fractions' composition was analyzed by MALDI-TOF/TOF mass spectrometry. Results: At concentration of 90 µg/mL the hemolymph fraction with compounds with molecular weight (MW) <100kDa demonstrated the strongest O2 •-scavenger effect (82%), followed by the hemocyanin (58%), and hemolymph fraction with compounds with MW<1kDa (15%). The most powerful • OH scavenger effect at concentration of 90 µg/mL showed hemocyanin (43%) followed by MW<100kDa fraction (26%). No • OH scavenger effect was observed by the MW<1kDa fraction. The highest chelation properties (55%) were demonstrated by the MW<100kDa fraction at concentration of 130 µg/mL; both the hemocyanin and MW<1kDa hemolymph fraction showed 33% inhibitory effect at the same concentration. The analysis of the composition of the tested fractions revealed high content of hydrophobic surfaces in MW<1kDa fraction and presence of antioxidant enzymes-catalase, superoxide dismutase and glutathione peroxidase in MW<100kDa fraction that contribute to the overall antioxidant effect of H. lucorum hemolymph. Conclusions: The complex antioxidant effect of hemolymph from H. lucorum is thought to be related to the presence of low molecular weight peptides in the MW<1 kDa fraction including glutathione and mainly to the antioxidant enzymes in the MW<100 kDa fraction.