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Flos Lamii albi has a high biological activity and is widely used in herbal medicine. The aim of the study was to characterize the secretory structures present in Lamium album subsp. album corolla and the location of phenolic compounds. Additionally, we carried out qualitative phytochemical analyses of flavonoids and phenolic acids. Light, fluorescence, and scanning electron microscopy were used to analyze the structure of the floral organs. The main classes of phenolic compounds and their localization were determined histochemically. Phytochemical analyses were performed with high-performance thin-layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC). Six types of glandular trichomes were found which contained flavonoids, phenolic acids, and tannins. The phytochemical studies demonstrated the presence of caffeic, chlorogenic, ferulic, gallic, p-coumaric, protocatechuic, syringic, gentisic, and vanillic phenolic acids as well as rutoside, isoquercetin, and quercetin flavonoids. The corolla in L. album subsp. album has antioxidant properties due to the presence of various polyphenols, as shown by the histo- and phytochemical analyses. The distribution and morphology of trichomes and the content of phenolic compounds in the corolla have taxonomic, pharmacognostic, and practical importance, facilitating the identification of the raw material.

Kalanchoë daigremontiana leaves contain phenolic compounds, which are one of the determinants of plant therapeutic properties. Light and scanning electron microscopes were used to analyse the structure of leaves. The main aims of the study included the analysis of the anatomy of leaves, localisation of phenolic compounds, and identification of phenolic acids. The thickness of the amphistomatic leaf blades, the number, the size of stomata, and the value of stomatal index, as well as the structure of the parenchyma cells have indicated that K. daigremontiana is adapted to arid environments. The histochemical assays revealed the presence of phenolic idioblasts in the leaf blades and petioles. The idioblasts were located in the epidermis, subepidermal layer, a deeper portion of the mesophyll, and in the sheaths of vascular bundles. The phytochemical analyses of leaves demonstrated the presence of gallic, ferulic, caffeic, p-coumaric, and protocatechuic acids in the form of esters. We carried out the research of the anatomical structure of K. daigremontiana leaves, which has been insufficiently documented to date. We have also revealed new localisation of phenolic compounds in the leaf tissues of this species.

Usnic acid (UA) is a compound with multiple biological activities that make it useful in various industries, e.g., pharmaceutical, cosmetic, dentistry, and agricultural sectors. Lichens are the primary source of UA, which is primarily extracted using acetone. This study aimed to investigate the solubility of UA in numerous natural deep eutectic solvents (NADESs) and use a mixture of thymol and camphor as a NADES in the optimization of the UA extraction process with the design of experiments method. For numerical optimization, the following parameters were employed in the experiment to confirm the model: a camphor-to-thymol ratio of 0.3, a liquid-to-solid ratio of 60, and a time of 30 min. The obtained experimental results aligned well with the predicted values, with the mean experimental value falling within the confidence interval, exhibiting deviations between 11.93 and 14.96. By employing this model, we were able to optimize the extraction procedure, facilitating the isolation of approximately 91% of the total UA content through a single extraction, whereas a single acetone extraction yielded only 78.4% of UA.

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