Thymus vulgaris L. (thyme), Origanum majorana L. (marjoram), and Origanum vulgare L. (oregano) were used to determine whether light modification (plants grown under nets with 40% shaded index or in un-shaded open field) could improve the quantity and quality of essential oils (EOs) and antioxidant activity. The yield of EOs of thyme, marjoram, and oregano obtained after 120 min of hydrodistillation was 2.32, 1.51, and 0.27 mL/100 g of plant material, respectively. At the same time under shading conditions plants synthetized more EOs (2.57, 1.68, and 0.32 mL/100 g of plant material). GC/MS and GC/FID analyses were applied for essential oils determinations. The main components of the thyme essential oil are thymol (8.05–9.35%); γ-terpinene (3.49–4.04%); p-cymene (2.80–3.60%) and caryophyllene oxide (1.54–2.15%). Marjoram main components were terpinene 4-ol (7.44–7.63%), γ-terpinene (2.82–2.86%) and linalool (2.04–2.65%) while oregano essential oil consisted of the following components: caryophyllene oxide (3.1–1.93%); germacrene D (1.17–2.0%) and (E)-caryophyllene (1.48–1.1%). The essential oil from thyme grown under shading (EC₅₀ value after 20 min of incubation) have shown the highest antioxidant activity – 0.85 mg mL⁻¹ in comparison to marjoram and oregano (shaded plants EC₅₀ 19.97 mg mL⁻¹ and 7.02 mg mL⁻¹ and unshaded, control plants EC₅₀ 54.01 mg mL⁻¹ and 7.45 mg mL⁻¹, respectively). The medicinal plants are a good source of natural antioxidants with potential application in the food and pharmaceutical industries. For production practice, it can be recommended to grow medicinal plants in shading conditions to achieve optimal quality parameters.

The present study focuses on the yield, chemical composition, and antioxidant activity of essential oils from different parts (flowers or leaves/stems) of cultivated plants grown under pearl shade nets with a 40% shaded index or in nonshaded plants and wild-grown oregano. The chemical composition of isolated essential oils was determined by GC/MS and GC/FID. Antioxidant activity was determined using the DPPH assay. The highest yield of oregano essential oils (OEOs) was obtained in cultivated shaded plants (flowers) at 0.35 mL/100 g p.m., in contrast to nonshaded plants (flowers), where the yield of OEOs was low (0.21 mL/100 g p.m.). Qualitative and quantitative analyses of the OEOs identified 16–52 constituents that varied with origin and plant organs. The oxygenated sesquiterpene caryophylleneoxide (7.4–49.9%) was predominant in all the essential oil samples. Other major constituents were sesquiterpene hydrocarbon-germacrene D (8.4–22.5%) and (E)-caryophyllene (8.5–10.8%), monoterpene hydrocarbon-sabinene (1.6–7.7%), and oxygen-containing monoterpenes-terpinen-4-ol (1.5–7.0%). The plant part has a significant effect on the antioxidant activity of OEOs, while the influenceof modified light under the shade nets is significantly lower. The OEOs from wild flowers showed the highest antioxidant activity, with an EC₅₀ value of 4.78 mg/mL. OEOs from cultivated nonshaded plants (flowers) recorded the lowest antioxidant activity with an EC₅₀ value of 24.63 mg/mL. The results suggest that the yield and quality of OEOs can be scaled-up by optimizing plant production in comparison with wild-growing plants. The content and quality of OEO can be increased by optimizing its production compared to plants from the spontaneous flora. Adequate cultivation techniques, such as shading, can achieve high-quality oregano yields and better quality parameters in terms of specific OEO components and meet the different requirements of the market and industrial sectors.

This study determined the content and composition of dill seed (Anethum graveolens L.) essential oil under varying light conditions: non-shaded plants in open fields and plants covered with pearl shade nets (40% shade index). Essential oil was extracted using Clevenger hydrodistillation. The essential oil content was 4.63% for non-shaded plants and 4.81% for shaded plants. GC/MS analysis revealed twenty-one and twenty-two components in dill seed from non-shaded and shaded plants, respectively. The terpenic fraction of essential oil from non-shaded plants consisted mainly of oxygen-containing monoterpene derivatives (53.6%), with carvone (46.1%) as the primary component, followed by monoterpene hydrocarbons (46.4%), predominantly limonene (43.8%). Essential oil from shaded plants contained a higher content of carvone (49.8%) and a lower content of limonene (37.8%) compared to essential oil from non-shaded plants. Non-shaded plant essential oil exhibited stronger antioxidant activity (EC₅₀ value: 26.04 mg mL⁻¹) than shaded plant essential oil (54.23 mg mL⁻¹). Dill seed essential oil showed the most potent antimicrobial activity (disc diffusion method) against Escherichia coli (inhibition zone: 15–18 mm). Shaded plants demonstrated a positive influence of essential oil against Klebsiella pneumoniae. Carvone and its derivatives, as the main components, hold significant potential in the food industry and alternative medicines. A practical implication of this study could be higher plant densities or intercropping of dill, as it thrives with minimal light.