Extraction of essential oils from the residues of two shrub species aiming for their revalorization: chemical characterization and antioxidant, antimicrobial and cytotoxic activities

In recent years, essential oils have been subject of research for their bioactive properties, such as antimicrobial, fungitoxic, anti-viral, anti-inflammatory and antioxidant activities. Owing to these properties they are potentially interesting for diverse industries including the food industry since one of its main problems concerns microbes and associated toxins that are responsible for food spoilage. Although the application of essential oils in the food industry may have some limitations, such as impact on the organoleptic properties and low solubility, different delivery strategies such as nanoencapsulation, active packaging and coatings are promising technologies that may overcome these issues without compromising nutritional properties in food systems [1]. In this view, increased knowledge on the composition and activity of different essential oils is needed, particularly regarding novel potential sources of essential oils such as agricultural wastes or species grown in marginal lands, on a perspective of circular economy. Therefore, in the scope of the BeonNAT project, biomass from different tree and shrub species are being screened as possible sources of essential oils and respective bioactivity evaluated. In this work, the essential oil extracted by steam distillation from the branches (>20mm) of two shrub species grown in Spain, Juniperus communis L. and Cistus ladanifer L., was characterized for their chemical composition by gas chromatography coupled with mass spectrometry (GC-MS) as well as for their antioxidant, antimicrobial, antiinflammatory and cytotoxic activities. GC-MS analysis allowed the identification of 98.1% of compounds in J. communis EO, corresponding to a total of 63 identified compounds, alfa-pinene being the major compound (35.1%), followed by limonene (15.0%), sabinene (6.7%), cis-tujopsene (8.0%), beta-myrcene (3.2%) and beta-caryophyllene (3.5%). In general, the chemical composition is in agreement with that of juniper berry EO, defined in the European Pharmacopoeia and ISO 8897 standard, except for limonene (15.0%) which was slightly higher than the defined range (Eur. Ph of 2-12% and ISO standard of 2-8%). For C. ladanifer EO, 61 compounds were identified corresponding to 92.8% of the total compounds, with viridiflorol being the main compound (24.0%), followed by alfa-pinene (19.3%), ledol (6.9%), camphene (6.7%) and bornyl acetate (5.0%), which is in good agreement with previous data [2]. Both oils showed potential against the panel of bacteria selected according to their importance in public health and foodborne diseases, highlighting the rock-rose EO that showed interesting activity against Escherichia coli, Morganella morganii, Pseudomonas aeruginosa, Enterococcus faecalis, Listeria monocytogenes and methicillin resistant Staphylococcus aureus in a concentration range of 0.039-2.5%(v/v). Regarding the antioxidant activity, both oils showed promising results, with EC50 values of 1.35 ± 0.19 mg/mL and 1.30 ± 0.07 mg/mL in the reducing power assay and 68% and 83% inhibition of oxidation according to the cellular antioxidant activity assay, for J. communis and C. ladanifer, respectively. The essential oils showed antiinflammatory (IC50 of 24±1 µg/mL and 21±2 µg/mL for juniper and rock-rose-rose, respectively) and cytotoxic activity, with the best results obtained with the rock-rose EO in the inhibition of stomach-AGS, colon-CaCo, breast-MCF-7 and lung-NCI-H460 cancer cell lines (GI50 between 47±5 µg/mL and 58±1 µg/mL). Juniper EO did not evidenced cytotoxicity in non-tumoral Vero cells at the highest tested concentration (400 µg/mL) wich can be an indicator of its safety. Overall, the results demonstrated that shrubs biomass can be a source of EO with similar composition to that reported for respective berries and leaves. The EOs showed interesting antibacterial and antioxidant activity thus being potential candidates for further studies on their safety and potential application in food systems.Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES to the CIMO (UIDB/00690/2020). L. Barros and S.A. Heleno (CEECIND/03040/2017) thank the national funding by FCT, P.I., through the institutional and individual scientific employment program-contract for their contracts, respectively. This project has received funding from the Bio Based Industries Joint Undertaking (JU) under grant agreement No 887917 BeonNAT. The JU receives support from the European Union's Horizon 2020 research and innovation programme and the Bio Based Industries Consortium.