Analysis of Lamiaceae essential oils (EOs) by GC-FID-MS revealed the presence as the major constituents of linalool (16.8%), linalyl acetate (15.7%) in Lavandula angustifolia, menthol (29.0%), menthone (22.7%), menthyl acetate (19.2%) in Mentha x piperita, terpinen-4-ol (27.1%), (E)-sabinene hydrate (12.1%), γ-terpinene (10.0%) in Origanum majorana, α-thujone (19.5%), camphor (19.0%), viridiflorol (13.5%) in Salvia officinalis, thymol (61.9%), p-cymene (10.0%), γ-terpinene (10.0%) in Thymus vulgaris. Based on the MIC and MBC values (0.09–0.78 mg/mL) and ratio MBC/MIC showed that EO from T. vulgaris (TO) had the strong inhibitory and bactericidal effect against multidrug-resistant Staphylococcus aureus. The bacterial cells were total killed by TO at 2MIC concentration after 6 h. The higher concentrations of other EOs were needed to achieve bactericidal effects. The strong bactericidal effect of TO against these bacteria indicates the possibility of topical use of TO but it requires research under clinical conditions.

The study aimed at comparing the changes in the content of free amino acids, phenolic compounds and the activity of PAL and TAL caused by two piercing-sucking arthropods: the grape mealybug (Pseudococcus maritimus Ehrh.) and the two-spotted spider mite (Tetranychus urticae Koch) in the leaves of orchid and strawberry, respectively. The obtained results show that the amino acid content and the ratio of amino acids to phenolic compounds increased in both plant species infested by the mealybug and the mite. However, such response was weakly dependent on changes in activity of the analysed enzymes. The pest feeding affected accumulation of the phenolic compounds, since the induction of the PAL activity in mealybug-infested orchid leaves during the first 5 h of the experiment preceded the increase in phenolic compounds during the first week of insect feeding. Instead, the increased activity of TAL was accompanied by elevated levels of phenolic compounds in the leaves of strawberry infested by mites. Mechanisms of biochemical plant responses induced by infestation of the studied herbivorous arthropods are discussed.

This study investigated the toxicity of essential oils (EOs) from Santolina chamaecyparissus (L.) and Tagetes patula (L.) towards the green peach aphid Myzus persicae (Sulzer) and the bird cherry-oat aphid Rhopalosiphum padi (L.). The effects of the EOs on aphid population parameters and levels of biochemical markers of oxidative stress within insect tissues were analyzed. In laboratory bioassays, application of the studied EOs at sublethal concentrations reduced daily fecundity and led to a decrease in the intrinsic rate of natural increase in both aphid species. Treatment with EOs also induced generation of reactive oxygen species (ROS) within aphid tissues. The highest levels of superoxide anion and hydrogen peroxide were noted after 24 and 48 h of exposure. Moreover, a significant increase in lipid peroxidation was shown in treated aphids, especially between 48 and 72 h after exposure. The increase was more pronounced after treatment with the essential oil of S. chamaecyparissus, which also exhibited higher aphicidal activity in toxicity tests. The activities of antioxidant enzymes—superoxide dismutase (SOD) and catalase (CAT)—were significantly elevated in both aphid species in response to the tested EOs. The obtained results suggest that oxidative stress evoked by treatment with the studied EOs may be an important factor determining their toxicity towards aphids.