A comparative analysis of the effects of different drying and storage techniques on the phenolic content of Pistacia atlantica leaves

This study presents a comparative analysis of the effects of different drying and storage techniques on the phenolic content of Pistacia atlantica leaves in both whole and ground states. Four drying methods were evaluated: direct sunlight, a ventilated drying chamber, shade, and obscurity. Additionally, three storage conditions were assessed: direct sunlight, shade, and freezing. The concentrations of total phenolics, total flavonoids, and tannins were quantified, and antioxidant activity was evaluated using the DPPH radical scavenging assay. Our findings indicate that drying in obscurity and shade yielded the highest levels of total phenolics (369.45±2.12 and 362.78±1.36 mg GAE/g DM), total flavonoids (54.34±0.95 and 55.68±1.25 mg QE/g DM), and tannins (36.35±0.91 and 33.80±0.79 mg CE/g DM), correlated with strong antioxidant activity (1.85±0.01 and 1.92±0.01 µg/mL, respectively), particularly when the leaves were stored whole. The results emphasize that controlled drying methods (ventilated chambers and darkness), along with storing the leaves whole and under freezing conditions, are optimal for preserving the antioxidant activity and phenolic content of P. atlantica leaves. Freezing proved to be the most effective storage condition for preserving phenolic compound concentrations and their associated antioxidant properties. Overall, the study highlights that the strategic selection of drying techniques and storage conditions is critical for optimizing the preservation of phenolic compounds and antioxidant activity in plant materials.