Perovskia atriplicifolia Benth (Russian Sage), a Source of Diterpenes Exerting Antioxidant Activity in Caco-2 Cells

Perovskia atriplicifolia Benth., a perennial aromatic plant widespread in Iran’s Sistan and Baluchestan region, is known for its essential oil composition, rich in aromatic and non-aromatic sesquiterpenes. To the best of our knowledge, limited information exists on the composition of its non-volatile extracts. Herein, the phytochemical investigation of the EtOH extract of P. atriplicifolia aerial parts was performed, guided by an analytical approach based on LC-(-)ESI/QExactive/MS/MS. This led to the identification of phenolics, flavonoids, diterpenes (mainly carnosic acid derivatives), and triterpenes. Structural elucidation was performed via NMR and HRMSMS analysis. Furthermore, considering the occurrence of diterpenes closely related to carnosic acid and carnosol, known for their antioxidant properties, the antioxidant activity of the extract (0.5–5.0 μg/mL) and selected pure compounds (0.5–25 μM; compounds 5, 7, 9, 10, 12, 16) was evaluated in Caco-2 intestinal cells, showing significant reduction in free radical levels. The quantitative results highlighted that the above cited compounds occurred in concentrations ranging from 1.73 to 520.21 mg/100 g aerial parts, with carnosol (12) exhibiting the highest concentration (520.21 mg/100 g aerial parts), followed by 1α-hydroxydemethylsalvicanol (9) (91.73 mg/100 g aerial parts) and carnosic acid (16) (88.16 mg/100 g aerial parts).