Antioxidant potential of Salvia officinalis L. residues as affected by the harvesting time

• S. officinalis residues constitute a source of natural antioxidants.
• Methanolic extracts were marked by the predominance of rosmarinic acid and phenolic diterpenes.
• The flowering phase revealed the best antioxidant activity.

A field experiment was conducted to valorize Salvia officinalis post-distilled aerial parts as natural antioxidants, at different harvesting times. Total phenolic contents were determined spectrophotometrically, the phenolic constituents were determined using HPLC with UV detection and the antioxidant capacity was assessed by DPPH, ABTS and FRAP assays. S. officinalis residues revealed high contents of rosmarinic acid and phenolic diterpenes as main components. The highest contents of total phenolics identified by HPLC (32204.96, 30035.00 μg/g DW) and phenolic diterpenes (20055.17, 18011.76 μg/g DW), as well as the best antioxidant activities were detected at the flowering phase. Rosmarinic acid (10768.65, 11723.29 μg/g DW) revealed the maximal accumulation at the vegetative phase, while the highest total phenolic contents estimated by the Folin–Ciocalteu assay (142.75, 146.76 mg GAE/g DW) were detected at fruiting. These findings suggest that S. officinalis by-products, particularly at flowering, may be considered as an interesting source of natural antioxidants.