Abstract
In this work, essential oils (EOs) and hydrolates (Hys) of Rosmarinus officinalis L. and Lavandula angustifolia Mill., grown in Tuscany (Italy), were studied to describe their chemical composition and biological activities. The aromatic profile of the EOs liquid phase was carried out by gas chromatography–mass spectrometry (GC–MS), while the volatile composition of vapor phase EOs and Hys was performed by headspace (HS)/GC–MS. The obtained results show that monoterpene hydrocarbons (71.5% and 89.5%) were the main compounds, followed by oxygenated monoterpenes (26.0% and 10.5%) in the liquid and vapor phase of R. officinalis EO, respectively. The oxygenated monoterpenes were the main components of L. angustifolia EO, reaching 86.9% in the liquid phase and 53.7% in the vapor phase. Regarding Hys, they consisted only of oxygenated monoterpenes, and 1,8-cineole (56.2%) and linalool (42.9%), were the main components of R. officinalis and L. officinalis Hys, respectively. Their cytotoxicity was investigated on an SHSY5Y neuroblastoma cell line by thiazolyl blue tetrazolium bromide (MTT) test, showing a notable effect of the EOs with a time-independent manner of activity and half maximal effective concentration (EC50) values quite similar for the two plant species (from 0.05% to 0.06% v/v for the three time points evaluated). A measurable activity of Hys was also obtained although with higher EC50 values. The antibacterial activity against Escherichia coli ATCC® 25922, Pseudomonas fluorescens ATCC® 13525, Acinetobacter bohemicus DSM 102855 as Gram-negative bacteria and Kocuria marina DSM 16420, Bacillus cereus ATCC® 10876 as Gram-positive bacteria, was evaluated by the agar disk-diffusion method and the VPT (vapor phase test) to determinate the MIC (minimal inhibitory concentration) and the MBC (minimal bactericidal concentration) values. Both EOs possessed a high activity against all the bacterial strains with MIC values ranging from 0.19% to 3.13% v/v. Unlike EOs, Hys did not show an inhibition of the bacterial growth at the tested concentrations. Furthermore, antioxidant power was measured by 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt-based (ABTS•+) and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, showing a remarkable ability to reduce radicals by both EOs; Hys were slightly less active. The findings highlighted that R. officinalis and L. angustifolia EOs and Hys have a chemical composition rich in bioactive molecules, which can exert different biological activities.
Highlights
Since historic times, spices and herbs have been used as food flavors, and their effects on human health are still being investigated to understand the roles of their chemical components [1,2]
essential oils (EOs) obtained from L. angustifolia and R. officinalis grown in different countries such as China, Siria, India, Iran, Romania, Canada, Spain, France and others were investigated and linalool, borneol, linalyl acetate and 1,8-cineole as well as camphor, camphene and α-pinene resulted as predominant compounds, in different proportions according to the vegetative stage and climatic conditions of the origin area [27,28]
For the first time, to better describe the vapor phase chemical profiles of Hys and EOs obtained from flowers and inflorescences of R. officinalis and inflorescences of L. angustifolia growing in Tuscany, we used the automated headspace sampler directly coupled with gas chromatography–mass spectrometry (HS/GC–mass spectrometer (MS)) [32,33]
Summary
Spices and herbs have been used as food flavors, and their effects on human health are still being investigated to understand the roles of their chemical components [1,2]. There are far fewer studies concerning the volatile chemical composition of hydrolates (Hys), known as hydrosols They are aqueous solutions obtained as by-products of distillation [29] containing a certain number of bioactive molecules, with marked quantitative and qualitative differences compared to EOs [30]. For the first time, to better describe the vapor phase chemical profiles of Hys and EOs obtained from flowers and inflorescences of R. officinalis and inflorescences of L. angustifolia growing in Tuscany, we used the automated headspace sampler directly coupled with gas chromatography–mass spectrometry (HS/GC–MS) [32,33] This sampling technique is conservative and non-destructive and does not require the use of solvent for the extraction process, avoiding a possible loss of components.
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