Synthesis of polyaniline zirconium for purification of barberry anthocyanins and stabilization via copigmentation against thermal and gastrointestinal conditions

This study aimed to purify and stabilize anthocyanins from barberry (Berberis vulgaris L.) through a three-phase approach encompassing synthesis of adsorbent composites for purification, copigmentation, and stability assessment. The first phase involved synthesizing zirconium polyaniline as an adsorbent for anthocyanin purification, optimizing parameters such as substrate amount (0.07-0.21 g), solvent volume (1-3 mL), and adsorption duration (15-30 min). The optimal conditions identified were 0.07 g of substrate, 2 mL of solvent, and 15 min of adsorption, yielding an anthocyanin concentration of 76.02 mg/L, characterized using high-performance liquid chromatography. The second phase explored copigmentation with pectin, varying temperature (25-75 °C), time (30-120 min), and molar ratios (0.06-0.1). Optimal conditions for copigmentation were determined to be 25 °C, 30 min, and a molar ratio of 0.06, resulting in significant hyperchromic and bathochromic effects that enhanced color and stability. The final phase assessed the stability of both copigmented and free anthocyanins under thermal treatment and gastrointestinal conditions, revealing that the anthocyanins-pectin complex exhibited resistance to digestion and heat. Although both anthocyanin content and antioxidant activity decreased during copigmentation, this reduction was less significant in copigmented anthocyanins, demonstrating the effective stabilization of barberry anthocyanins through copigmentation as well as its in vitro digestion condition.