Characterization of the enzyme activity in barley anthocyanin pathway and reaction of these pigments to electromagnetic irradiation

Abstract

The enzymatic activities were indirectly investigated in the grain anthocyanin synthesis of blue barley by the HPLC data. These results were then evaluated together with absorbed light energy levels of the pigments. In addition, in two photochemical experiments, the change in aleurone pigmentation and the water activation was studied at the dormant grains, using focused sunlight and heat radiation. In the middle stage of the synthesis (at day after flowering, DAF 26), there was a significant cooling period in the weather. Differences of synthesis dynamics were found before and after the cooling period. The anthocyanin production after the cooling period (DAF 26–33) was more intense compared to the beginning of synthesis (17–22). In addition, a more intense degradation was detectable during the cooling period (22–26) than what was observed at the end of seed maturation (33–39). The most efficient light energy binders glucosides (delphinidin- and cyanidin-3-glu.) produced and degraded more dynamically than their more complex forms (malonylglucosides, rutinoside). Furthermore, among the pigments, the cyanidins are able to provide greater energy absorption. Differences in the synthesis dynamism of compounds indicate that individual enzymes and not a multienzyme complex operate in the last phase of the anthocyanin pathway, and by their operation, they can change the energy absorption level of aleurone. In irradiation of blue grains with focused sunlight (~ 400 to ~ 2500 nm, 2–3 min), the aleurone anthocyanins facilitated the vitrified water activation. During intense heat irradiation (~ 8000 nm, 1 min), the laser light scattering associated with water content decreased more intensively within the blue grains compared to the white, indicating the IR absorption surplus for the pigments. Observation suggests that the blue pigments in aleurone can contribute to energy transfer in the direction of water, so they may have role in enhancing energy dissipation.