Variation of the Polyphenolic Composition and Antioxidant Capacity of Freshly Prepared Pomegranate Leaf Infusions over One-Day Storage

In recent decades, an intensive search for natural and novel types of antioxidant polyphenolics has been carried out on numerous plant materials. However, the current literature has very little information on their storage stability in the form of freshly prepared infusions. This study aims to characterize the polyphenolic composition and the antioxidant capacity of pomegranate (Punica granatum L.) leaf infusions over one-day storage (analyzed at 0, 2, 4, 6, 8, and 24 h). Spectrophotometric evaluation demonstrated that the infusion presented no significant changes in the content of total phenols (131.40–133.47 mg gallic acid g(−1)) and ortho-diphenols (239.91–244.25 mg gallic acid g(−1)). The infusion also maintained high stability (over 98% and 82%, respectively) for flavonoids (53.30–55.84 mg rutin g(−1)) and condensed tannins (102.15–124.20 mg epicatechin g(−1)), with stable (>90%) potent antioxidant capacity (1.5–2.2 mmol Trolox g(−1)) throughout 0–24 h storage. The main decrease was observed during 0–2 h storage of flavonoids, 8–24 h storage of tannins, and 0–4 h storage of antioxidant capacity. Chromatographic analysis further revealed that 7 decreased and 11 increased compounds were found within 0–24 h storage. The good stability of the total polyphenolics and antioxidant properties might be related to the complex conversion and activity compensation among these compounds. The findings suggest that pomegranate leaf infusion could be of great interest in the valorization of high added-value by-products and in the application of green and functional alternatives in the food-pharma and nutraceutical industries.