Antioxidant properties and electrochemical activity of anthocyanins and anthocyanidins in mulberries

This study analyzed the anthocyanin content and antioxidant properties of five mulberry (Morus spp.) varieties, including black (M. nigra), red (M. rubra) and white (M. alba) types. Anthocyanins were extracted and analyzed using HPLC–MS, which revealed four major pigments: cyanidin-3-glucoside, cyanidin-3-rutinoside, cyanidin-3,5-diglucoside and pelargonidin-3-glucoside. Total anthocyanins were significantly higher in black mulberries Bom irangi (185 mg/100 g) and Kalmi (158 mg/100 g) compared to 28–60 mg/100 g in other varieties, consistent with their dark fruit color. Electrochemical analysis by cyclic voltammetry showed oxidation peak potentials (E_pa) of key anthocyanins: + 368 mV for cyanidin; + 830 mV for cyanidin-3-glucoside; and + 912 mV for pelargonidin-3-glucoside. Lower E_pa indicates easier oxidation and greater antioxidant activity. DPPH radical scavenging assays revealed strongest potency for Bom irangi (EC50 42 μg/mL) and Kalmi (EC50 58 μg/mL), again due to high anthocyanin levels. Further, a negative correlation (R² = 0.923) was demonstrated between E_pa values and EC50, proving excellent predictive ability of electrochemical data for estimating antioxidant capacity. Cyanidin with lowest E_pa (+ 368 mV) and highest hydroxylation exhibited strongest activity (EC50 35 μg/mL). Overall, the study successfully demonstrated the antioxidant potential of mulberry anthocyanins, especially from black varieties, using advanced analytical strategies.