Growth Stage-Dependent Polyphenol Profiles and Antioxidant Properties in Medicinal Plants of Iraqi Kurdistan

Abstract

Medicinal plants, rich in polyphenolic compounds, play a crucial role in traditional and modern medicine due to their antioxidant, anti-inflammatory, and disease-preventing properties. This study investigated the polyphenol content and antioxidant activity across various growth stages (preflowering, flowering, and post-flowering) of four medicinal plants: Primula auriculata L., Stachys vulgaris L., Verbascum spp., and Ajuga oblongata L., cultivated in the Soran region, Erbil Province, Iraqi Kurdistan. Using high-performance liquid chromatography (HPLC), nine types of polyphenols were identified and quantified, including gallic, caffeic, and chlorogenic acids. The results showed significant variations in polyphenol concentrations across different plant species and growth stages. For example, Primula exhibited the highest levels of gallic acid (41.91 mg/kg) during pre-flowering, while Ajuga showed peak chlorogenic acid content (827.62 mg/kg) postflowering. Antioxidant activity was highest in Ajuga during flowering (75.33%) and lowest during postflowering. Overall, polyphenol content was positively correlated with antioxidant activity, highlighting the importance of growth stage in optimizing the medicinal benefits of these plants. These findings contribute to the ethnobotanical knowledge of Kurdish medicinal plants and offer insights into the optimal harvest times for maximizing bioactive compounds.