Salvia desoleana Atzei et Picci Steam-Distillation Water By-Products as a Source of Bioactive Compounds with Antioxidant Activities

In this study, water residue obtained from Salvia desoleana Atzei et Picci steam distillation was evaluated for its antioxidant activity in vitro using different experimental models. In particular, the study evaluated the antiradical and antioxidant activity of Salvia desoleana extracts using CUPRAC, FRAP, DPPH•, and ABTS•+ assays; and tested ROS scavenging activity in Caco-2 cell cultures. Phenolic compounds were identified by (HR) LC-ESI-QTOF MS/MS and quantified with HPLC-PDA. Furthermore, Keap1-Nrf2, iNOS, and NOX enzymes involved in oxidative stress and antioxidant defences were the targets of molecular docking on key polyphenols. Hydroxycinnamic acids and flavonoids are the most important classes of compounds detected in the extracts. Among these compounds, the most significant was rosmarinic acid, followed by caffeic acid, luteolin glucuronide, and methyl rosmarinate. Although all extracts have shown encouraging results, the ethanolic extract solubilised with water (SEtOHA) was the one with the highest hydroxycinnamic acid content and total phenol content (518.64 ± 5.82 mg/g dw and 106.02 ± 6.02 mg GAE/g dw), as well as the highest antioxidant and antiradical activity. The extracts have shown anti-inflammatory activity by inhibiting NO release in LPS-stimulated Caco-2 cells. Finally, the in silico evaluation against the three selected enzymes showed interesting results for both numerical affinity ranking and predicted ligand binding models. The outcome of this study suggests this by-product as a possible ally in counteracting oxidative stress, as established by its favourable antioxidant compound profile, thus suggesting an interesting future application as a nutraceutical.