Plants from Lamiaceae family as a source of essential oils with bioactive properties

Aromatic and medicinal plants have been used worldwide for culinary purposes aiming to modify, enhance or improve the flavour of foods. In addition, several aromatic plants are also recognized for their empiric use in folk medicine due to their beneficial health effects1. The secondary metabolites of aromatic plants could have diverse applications in industry, and several essential oils have a Generally Recognized as Safe (GRAS) status attributed by the Food and Drug Administration (FDA). In this sense, presently, the possibility of replacing synthetic additives, which can cause adverse effects on consumer health over time, with natural compounds, is attracting the attention of the food industry2. Species of the Lamiaceae family are known to contain antioxidant active components such as phenolic acids and flavonoids. These compounds reveal important information about the quality of food and have potential benefits in the human health3. Therefore, plants of this family have been screened for their potential use as alternative remedies mainly due to their bioactive compounds and antimicrobial properties4. In addition, studies focusing on different aromatic plants have suggest the use of their essential oils and some constituents as promising alternatives to obtain natural preservatives. The present work reports a study on the bioactivity of essential oils obtained from several aromatic plants, namely Origanum vulgare subsp. virens (oregano), Rosmarius officinalis L. (rosemary), Salvia officinalis L. (salvia) and Thymus vulgaris L. (thyme), which are strong flavour aromatic plants belonging to the Lamiaceae family that have long been used in culinary and food industry. The essential oil was obtained by hydrodistillation using a Clevenger apparatus and volatile compounds were analyzed by GC-MS equipped with DB-5MS fused-silica column. The antimicrobial activity was determined by broth microdilution assay against several Gram-positive and Gram-negative ATCC bacterial strains and 2 fungi4. The bioactive potential was evaluated through several in vitro assays, namely antioxidant activity using two different in vitro assays: DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity and reducing power; cytotoxic activity using three tumour cell-lines: CaCo (colorectal adenocarcinoma), MCF-7 (breast adenocarcinoma) and NCI-H460 (non-small cell lung carcinoma) and a non-tumor cell line of monkey kidney (VERO), by applying the sulforhodamine B assay; anti-inflammatory activity was assessed using RAW 264.7 macrophage cells. The results revealed the bioactive potential of all studied extracts. In particular, all essential oils tested in this study were capable of inhibiting the growing of A. brasiliensis and A. fumigatus fungus, presenting minimum inhibitory concentration (MIC) values under 0.3% (v/v) and minimum fungicidal concentration (MFC) under 0.6% (v/v); results highlighted the sample of O. vulgare essential oil which showed the best results against gram-positive and negative bacteria. In the antioxidant activity O. vulgare subsp. virens and T. vulgaris presented values of EC50 for DPPH assay between 9.23 and 10.69 mg/ml respectively, while the other species showed EC50 above 39 mg/mL; for reducing power, T. vulgaris presented the best results with EC50 of 1.69 mg/mL, followed by O. vulgare subsp. virens, R. officinalis and S. officinalis, with values of 1.69 mg/mL, 2.80 mg/mL and 6.50 mg/mL, respectively. In the cytotoxic activity O. vulgare subsp. virens presented the best results with GI50 values of 45 g/mL against CaCo and MCF-7 cell lines; in the anti-inflammatory assay the lowest GI50 value was observed with the essential oil extracted from T. vulgaris L. (8 g/mL). In general, the results revealed a high antimicrobial potential of the essential oils against the tested strains, as well as a very promising antioxidant and anti-inflammatory activities. In addition, it was also possible to verify the absence of toxicity of both extracts. Therefore, essential oils extracted from the studied plants of the Lamiaceae family can be appealing alternatives to the currently used synthetic additives, with potential application in the food and pharmaceutical industries for their relevant bioactive properties.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020) and R.M. Spréa (2020. 08092.BD) grant. M.I. Dias, R.C. Calhelha and L. Barros would like to thank the national funding by FCT, P.I., through the institutional scientific employment program-contract. To the project AllNat for the contract of C. Caleja (Project AllNat POCI-01-0145-FEDER-030463) and to the Project Mobilizador Norte-01-0247-FEDER-024479: ValorNatural® for the contract of E. Pereira. This research was conducted under the project “BIOMA – Bioeconomy integrated solutions for the mobilization of the Agro-food market” (POCI-01-0247-FEDER-046112), by “BIOMA” Consortium, and financed by European Regional Development Fund (ERDF), through the Incentive System to Research and Technological development, within the Portugal2020 Competitiveness and Internationalization Operational Program. This work has been supported by the Ministry of Education, Science and Technological Development of Republic of Serbia (451-03-68/2020-14/200007).