Photostabilization of phycocyanin and anthocyanin in the presence of biopterin-α-glucoside from Spirulina platensis under ultraviolet ray

Biopterin-α-glucoside purified from Spirulina platensis is stable to irradiation by visible and ultraviolet light. Its absorption spectrum shows maxima at 268 nm and 340 nm and a fluorescence band appears at 447 nm. Although cyanidin-3-galactoside with an absorption maximum at 514 nm (red colour) is unstable and is decolourized by UV light, the pigment becomes stable in the presence of biopterin-α-glucoside. Similar photostabilization phenomenon was observed for phycocyanin (λ max 614 nm) consisting of phycocyanobilin as chromophore and protein subunits α 3 β 3 in the presence of biopterin-α-glucoside. Although the chromophore of phycocyanin is related to phycocyanobilin and protein conformation, the chromophore can be stabilized to UV light in the presence of biopterin-α-glucoside.