Stable Antioxidant Activity of Maral Root, Rose Root, and Oregano Extracts and Their Application in Alginate-Based Coatings for Extending the Shelf Life of Red Bell Peppers

• Maral root, rose root, and oregano have strong and stable antioxidant activity. • Herb extracts improved the barrier properties of the alginate films. • Coating reduced respiration rate and weight loss in red bell peppers. • Coated peppers maintained higher firmness and phenolic content during storage. • Maral root and rose root delivered the most effective preservation outcomes. Red bell peppers ( Capsicum annuum L.) are highly perishable vegetables prone to rapid post-harvest deterioration due to moisture loss, oxidative degradation, and microbial spoilage. This study evaluated the effect of alginate-based coatings enriched with maral root (MRA), rose root (RRA), and oregano (ORA) in preserving the quality and extending the shelf life of red bell peppers. All herb extracts showed strong antioxidant activity, which remained stable during storage, regardless of the storage temperature. Alginate films incorporated with herbal extracts exhibited significantly improved barrier properties. The MRA films showed the lowest water vapor (187 g·m⁻²·day⁻¹) and oxygen transmission rate (9 mL O₂·m⁻²·day⁻¹). Coated samples showed lower respiration rates than uncoated controls, although no significant differences were observed among the extracts. ORA-coated samples showed higher weight loss, likely due to elevated respiration. Total phenolic content was best preserved in MRA and RRA-coated peppers (45 μg GAE/g fresh fruit), while coated samples also maintained lower total soluble solids (∼7.3%) and higher firmness after 16 days of storage. Microbial analysis confirmed that the total mold and yeast in coated samples remained below acceptable beyond 14 days, unlike the uncoated control. These findings suggest that alginate coatings enriched with maral root and rose root extracts effectively enhance the physicochemical and microbial stability of red bell peppers, offering a promising natural alternative to synthetic preservatives for post-harvest management.