Impact of Metallic Nanoparticles on In Vitro Culture, Phenolic Profile and Biological Activity of Two Mediterranean Lamiaceae Species: Lavandula viridis L’Hér and Thymus lotocephalus G. López and R. Morales

Abstract

Nanoparticles (NPs) recently emerged as new chemical elicitors acting as signaling agents affecting several processes in plant metabolism. The aim of this work was to investigate the impact of the addition of copper oxide (CuO), zinc oxide (ZnO) and iron oxide (Fe3O4) NPs (<100 nm) at different concentrations (1, 5 and 10 mg/L) to the culture media on several morphological, physiological and -biochemical parameters of in vitro shoot cultures of Lavandula viridis L’Hér and Thymus lotocephalus G. López and R. Morales (Lamiaceae), as well as on phenolic profile and bioactivity (antioxidant and enzyme inhibition capacities). Although some decreases in shoot number and length were observed in response to NPs, biomass production was not affected or was improved in both species. Most NPs treatments decreased total chlorophyll and carotenoid contents and increased malondialdehyde levels, an indicator of lipid peroxidation, in both species. HPLC-HR-MS analysis led to the identification of thirteen and twelve phenolic compounds, respectively, in L. viridis and T. lotocephalus extracts, being rosmarinic acid the major compound found in all the extracts. ZnO and Fe3O4 NPs induced an increase in total phenolic and rosmarinic acid contents in T. lotocephalus extracts. Additionally, some NPs treatments also increased antioxidant activity in extracts from this species and the opposite was observed for L. viridis. The capacity of the extracts to inhibit tyrosinase, acetylcholinesterase and butyrylcholinesterase enzymes was not considerably affected. Overall, NPs had a significant impact on different parameters of L. viridis and T. lotocephalus in vitro shoot cultures, although the results varied with the species and NPs type.

Response of Thymus lotocephalus In Vitro Cultures to Drought Stress and Role of Green Extracts in Cosmetics

“…Salvianolic acid F and sagerinic acid, although being identified for the first time in T. lotocephalus , were detected in other Thymus species ( T. zygis , T. pulegioides , T. fragrantissimus , and T. herba-barona ) [ 73 ]. As reported in previous studies with this species [ 6 , 15 , 17 ], rosmarinic acid was the major biocompound identified in the extracts (with a range of 12.5 g/kg in 7% PEG + MeJA to 58.2 g/kg in MeJA) ( Table 4 ). Rosmarinic acid has been demonstrated to have important biological properties, such as antioxidant, anti-inflammatory, antitumor, neuroprotective, and antimicrobial [ 74 , 75 ].…”

“…Moreover, SA treatments showed a positive effect in decreasing H 2 O 2 contents in I. walleriana under 1–4% PEG [ 51 ]. Excessive oxidative stress was also observed in other species subjected to different metal oxide NPs [ 9 , 17 , 58 , 59 ], which denotes the ROS effects induced by metals binding with proteins presenting SH bonds, which are found in plants.…”

“…Results indicated that Fe 3 O 4 NPs improved shoot number and biomass production, in comparison to the control. It is known that iron has a great influence on the growth and development of plants, and its nanoscale application in in vitro cultures facilitates its absorption and plant nutritional balance [ 17 , 48 , 49 ]. Furthermore, the application of these NPs has been demonstrated to improve the uptake of important macronutrients in some plants [ 49 , 50 ].…”

“…5 μm 100 A C18 Kinetex column (Phenomenex, UK) with 1 mL/min of flow rate and with 40 °C of column temperature. The chromatographic conditions were performed according to Gonçalves et al and Mansinhos et al [ 17 , 18 ]. The solvent system was composed of solvent A (distilled water) and solvent B (acetonitrile), both with 0.1% formic acid.…”

“…Thymus lotocephalus López and Morales is a Mediterranean species endemic to the Algarve, a southern region of Portugal, that is listed as Near Threatened in The IUCN Red List of Threatened Species [ 14 ]. Previous studies indicated that this species produces phenolic (e.g., rosmarinic acid, salvianolic acids, luteolin, caffeic acid) and volatile (e.g., linalool, caryophyllene oxide, camphor, borneol) compounds with biological effects, and that in vitro culture is a good alternative for the production of bioactive compounds from this species, without compromising natural populations [ 6 , 15 , 16 , 17 ]. Phenolic compounds, which may be categorized as phenolic acids, flavonoids, tannins, stilbenes, lignans, and coumarins, present a great potential for therapeutic applications to numerous human diseases, such as diabetes, cancer, neurodegenerative and cardiovascular pathologies, due to their multifunctional biological activities, particularly antioxidant [ 18 ].…”