Pitted keratolysis (PK) is a bacterial skin infection mostly affecting the pressure-bearing areas of the soles, causing unpleasant symptoms. Antibiotics are used for therapy, but the emergence of antiobiotic resistance, makes the application of novel topical therapeutic agents necessary. The antibacterial effects of 12 EOs were compared in the first part of this study against the three known aetiological agents of PK (Kytococcus sedentarius, Dermatophilus congolensis and Bacillus thuringiensis). The results of the minimal inhibitory concentration, minimal bactericidal concentration and spore-formation inhibition tests revealed that lemongrass was the most effective EO against all three bacterium species and was therefore chosen for further analysis. Seventeen compounds were identified with solid-phase microextraction followed by gas chromatography–mass spectrometry (HS-SPME/GC-MS) analysis while thin-layer chromatography combined with direct bioautography (TLC-BD) was used to detect the presence of antibacterially active compounds. Citral showed a characteristic spot at the Rf value of 0.47, while the HS-SPME/GC-MS analysis of an unknown spot with strong antibacterial activity revealed the presence of α-terpineol, γ-cadinene and calamenene. Of these, α-terpineol was confirmed to possess an antimicrobial effect on all three bacterium species associated with PK. Our study supports the hypothesis that, based on their spectrum, EO-based formulations have potent antibacterial effects against PK and warrant further investigation as topical therapeutics.

Spearmint ( Mentha spicata L. var. crispa ) is a widely cultivated aromatic herb valued both as a culinary ingredient and as a source of bioactive compounds, such as essential oils and phenolics, which contribute to its traditional uses and potential medicinal applications. In this work, we provided the first evidence of natural etiolation with etioplast and prolamellar body formation in leaves and stems of spearmint shoots emerging in the soil from underground rhizomes. Soil‐grown and hydroponically dark‐forced shoots exhibited comparable etiolation symptoms, plastid ultrastructure, and chlorophyll biosynthesis as revealed by 77 K fluorescence emission spectroscopy, establishing laboratory etiolated plants as reliable models for natural skotomorphogenetic processes. Comparison of 14‐day‐old light‐grown and dark‐forced shoots developing from the rhizomes of hydroponically cultured adult plants revealed that the slightly smaller etiolated leaves had significantly smaller peltate glandular hairs than light‐grown ones (diameter: 54–56 μm vs. 59 μm, respectively), but their number and density were not influenced by light and they were always present in much higher numbers on the abaxial side than on the adaxial side of the leaf surfaces. Principal component analysis of the volatile organic compound and phenolic profiles distinctly separated light‐grown and dark‐forced shoots, with fewer compounds being present and in lower relative abundance in etiolated tissues, and more pronounced differences observed in the phenolic composition. These data underscore the value of etiolation and greening research, provide new models for studying development and environmental interactions under naturally light‐deprived conditions, and offer novel insights into primary and secondary metabolism in hidden spearmint organs.

Background: Rosmarinic acid (RA) is a major phenylpropanoid constituent of many medicinal plants belonging to the Nepetoideae subfamily of the Lamiaceae family and contributes significantly to their biological activities. Traditionally, RA-containing extracts have been prepared using organic solvents or hot-water extraction. Methods: In addition to conventional extraction techniques, the phenylpropanoid composition of medicinally important tissues from 13 Nepetoideae species was investigated following incubation in an aqueous medium at room temperature. Phenylpropanoids in the differently prepared extracts were identified by extensive HPLC-UV-HR-MS/MS and NMR analyses. The antioxidant and cytostatic activities of isolated phenylpropanoids were evaluated using DPPH and Alamar Blue assays, respectively. Results: In tissues of all investigated species, RA underwent rapid enzyme-catalyzed conversion during aqueous incubation through oxidative decarboxylation, accompanied by the transient accumulation of nepetoidins A and B. The RA-related phenylpropanoid salvianolic acid K was identified in the roots of three Salvia species, while a previously undescribed isomer, designated salvianolic acid O, was discovered in the roots of Salvia verticillata. Both compounds underwent enzymatic transformations analogous to those of RA in aqueous medium, yielding two previously undescribed phenylpropanoids, salvianolic acids P and Q. Optimized aqueous incubation conditions enabled the high-yield accumulation of these conversion products. Together with their parent compounds, seven phenylpropanoids were isolated from selected plant tissues and were found to exhibit structure-dependent antioxidant and metabolic inhibitory activities in vitro. Conclusions: Aqueous incubation of Nepetoideae plant tissues markedly alters their phytochemical composition and provides access to previously unavailable bioactive phenylpropanoids.