Stimulation of phenolic compounds accumulation and antioxidant activity in in vitro culture of Salvia tebesana Bunge in response to nano-TiO2 and methyl jasmonate elicitors

In the present study, we first attempted to achieve an efficient procedure for optimizing callogenesis from apical meristem and leaf explants of Salvia tebesana on MS media containing different concentrations of BAP alone and in combination with 2,4-D. Then, the inducing effect of nano-TiO₂ (10, 60, and 120 mg L⁻¹) and methyl jasmonate (50, 100, and 200 µM), as abiotic elicitors were studied on the enhancement of phenolic compounds, rosmarinic acid, and some individual flavonoids as well as antioxidant capacity of callus. According to the results, the highest callogenesis rate (100 and 93.33, respectively) and DW (0.55 ± 0.03 and 0.36 ± 0.02 g, respectively) per responsive explant were achieved from apical meristem on MS media containing "BAP₁ + 2,4-D₁" mg L⁻¹ and from leaf explant on the medium supplemented with "BAP₀.₅ + 2,4-D₁" mg L⁻¹. The elicitation with 10 and 60 mg L⁻¹ nano-TiO₂ (respectively for apical meristem and leaf), and 50 µM MeJa could significantly promote the production of predominant phenolic derivatives in S. tebesana calli, where the highest content of total phenolics, O-diphenols, phenolic acid, flavonoid, flavone and flavonol, proanthocyanidin was recorded. As well as results declared that the increasing of rosmarinic acid was more correlated with nano-TiO₂ treatment than MeJa elicitation. Moreover, the highest content of apigenin (0.33 ± 0.02 μg g⁻¹ DW) was detected after MeJa-elicitation (50 µM), while the maximum level of quercetin (2.62 ± 0.09 μg g⁻¹ DW) and rutin (13.79 ± 0.87 μg g⁻¹ DW) were obtained after exposure to 60 mg L⁻¹ nano-TiO₂, both from leaf-derived calli. While a significant positive correlation was recorded between antioxidant assays (DPPH and FRAP) and phenolic derivatives of treated calli; a very strong correlation occurred between the content of rosmarinic acid of apical meristem-derived calli and DPPH and FRAP values (r² = − 0.921 and r² = − 0.913, P < 0.01 respectively). Our results showed that the combination of in vitro culture and elicitation would be a good technique to successfully produce and enhance the content of pharmacologically valuable metabolites in S. tebesana.