4.6. The Photostabilities of Various Isolated Anthocyanin Monomers

The photodegradation of pure anthocyanin was evaluated using a previously reported protocol [6]. The methanol solutions of various anthocyanins were prepared with the same concentration. The solutions were then kept in the dark, under simulated solar light, and under natural indoor light, all at room temperature. The solutions were analyzed using HPLC to track the concentration change during the storage process. The stability of anthocyanins is highly dependent on light conditions, and thus, the photostability evaluation was performed using three different conditions: natural indoor light, darkness, and simulated solar light. The temperatures for the three different light conditions were at the same room temperature. The simulated solar light was provided by a simulated solar light irradiation cabinet using a 50 watt xenon lamp. All anthocyanin solutions were prepared in methanol with hydrochloric acid (0.01 M) at a 1 mg/mL concentration. The degradation of anthocyanins was determined with HPLC and compared to the peak areas. The freshly prepared anthocyanin solutions were used as 100%, and thus, the trend line of anthocyanins is highly related to their stability.