The focus of this work was to develop a simple electrochemical method for the determination of vitamin C (VitC) by using a specially constructed microelectrode made from pyrolytic graphite sheet (PGS). A procedure for quantifying VitC in a real sample was established. VitC shows a single quasi-reversible reaction. The method was optimized, and analytical determination was performed by using cyclic voltammetry and square wave voltammetry for electroanalytical purposes. The obtained results show a linear response of the PGS electrode in a wide concentrations range. For the lower concentration range, 0.18–7.04 µg L⁻¹, the sensitivity is 11.7 µAcm⁻²/mgL⁻¹, while for the higher concentration range, 10.6–70.4 µg L⁻¹, the sensitivity is 134 µAcm⁻²/mgL⁻¹, preserving the linearity of 0.998 and 0.999. The second objective was to determine the effect of the addition of five different types of “green” biowaste on plant growth, VitC content, and antioxidant activity in arugula (Eruca sativa L.) using the developed method. After three weeks of cultivation, small differences in growth and large differences in certain nutritional characteristics were observed. The addition of black coffee makes the soil slightly alkaline and causes a significant increase in VitC content and antioxidant activity.

Summary: Research background. Plant Tropaeolum majus L. belongs to the family Tropaeolaceae, and contains benzyl glucosinolate. The breakdown product of benzyl glucosinolate, benzyl isothiocyanate (BITC), exhibits various biological activities such as antiproliferative, antibacterial, and antiinflammatory activities. In order to optimize the content of biologically active volatile compounds in plant extract and essential oil, the use of appropriate extraction technique has a crucial role. Experimental approach. The current study investigated the effect of two modern extraction methods (microwave-assisted distillation (MAD) and microwave hydrodiffusion and gravity (MHG)) on the chemical composition of volatile components present in essential oil and extract of T. majus L. var. altum seeds. The biological activity of samples (essential oil, extract and pure compounds) was focused on the antiproliferative effect against different cancer cell lines: cervical cancer cell line (HeLa), human colon cancer cell line (HCT116), and human osteosarcoma cell line (U2OS), and the antibacterial activity which was evaluated against growth and adhesion to polystyrene surface of Staphylococcus aureus and Escherichia coli. Results and conclusions. Essential oil and extract of T. majus seeds were isolated by two extraction techniques: MAD and MHG. BITC and benzyl cyanide (BCN) present in extract were identified by GC-MS. Essential oil of T. majus showed higher antiproliferative activity (IC50<5 µg/mL) than T. majus extract (IC50<27 µg/mL) against three cancer cell lines: HeLa, HCT116, and U2OS. BITC showed much higher inhibitory effect on all tested cells in contrast to BCN. Essential oil and extract of T. majus showed strong antimicrobial activity against S. aureus and E. coli. Novelty and scientific contribution. This work represents the first comparative report on the antiproliferative activity of essential oil and extract of T. majus seeds, BITC and BCN against HeLa, HCT116, and U2OS cells as well as their antimicrobial activity against S. aureus and E. coli. This study demonstrated that essential oil of T. majus seeds exhibits stronger antiproliferative and antimicrobial activity than plant extract.

Tropaeolum majus L. is a traditional medicinal plant with a wide range of biological activities due to the degradation products of the glucosinolate glucotropaeolin. Therefore, the goals of this study were to identify volatiles using gas chromatography–mass spectrometry analysis (GC-MS) of the hydrosols (HYs) isolated using microwave-assisted extraction (MAE) and microwave hydrodiffusion and gravity (MHG). Cytotoxic activity was tested against a cervical cancer cell line (HeLa), human colon cancer cell line (HCT116), human osteosarcoma cell line (U2OS), and healthy cell line (RPE1). The effect on wound healing was investigated using human keratinocyte cells (HaCaT), while the antibacterial activity of the HYs was tested against growth and adhesion to a polystyrene surface of Staphylococcus aureus and Escherichia coli. Antiphytoviral activity against tobacco mosaic virus (TMV) was determined. The GC-MS analysis showed that the two main compounds in the HYs of T. majus are benzyl isothiocyanate (BITC) and benzyl cyanide (BCN) using the MAE (62.29% BITC and 15.02% BCN) and MHG (17.89% BITC and 65.33% BCN) extraction techniques. The HYs obtained using MAE showed better cytotoxic activity against the tested cancer cell lines (IC₅₀ value of 472.61–637.07 µg/mL) compared to the HYs obtained using MHG (IC₅₀ value of 719.01–1307.03 μg/mL). Both concentrations (5 and 20 µg/mL) of T. majus HYs using MAE showed a mild but statistically non-significant effect in promoting gap closure compared with untreated cells, whereas the T. majus HY isolated using MHG at a concentration of 15 µg/mL showed a statistically significant negative effect on wound healing. The test showed that the MIC concentration was above 0.5 mg/mL for the HY isolated using MAE, and 2 mg/mL for the HY isolated using MHG. The HY isolated using MHG reduced the adhesion of E. coli at a concentration of 2 mg/mL, while it also reduced the adhesion of S. aureus at a concentration of 1 mg/mL. Both hydrosols showed excellent antiphytoviral activity against TMV, achieving100% inhibition of local lesions on the leaves of infected plants, which is the first time such a result was obtained with a hydrosol treatment. Due to the antiphytoviral activity results, hydrosols of T. majus have a promising future for use in agricultural production.

Extracts from Veronica species (speedwells) are known for the various biological activities they show, such as cytotoxic, antimicrobial, anti-inflammatory, and antioxidant activities. Also, the plants from this genus are known as medicinal plants used in traditional medicine worldwide. Phenolic compounds are specialized metabolites that contribute to biological activity the most. Therefore, the aim of this research is identification and quantification of phenolic compounds present in three Veronica species (Veronica anagallis-aquatica L., Veronica persica Poir., and Veronica polita Fr.) using the liquid chromatography-mass spectrometry (LC-MS/MS) technique. All extracts were tested for antioxidant activity with two methods: DPPH (2,2-diphenyl-1-picrylhydrazyl) and ORAC (oxygen radical absorbance capacity). Also, standards for compounds that were detected in the highest amount in all species were also tested for antioxidant activity. Three different solvents (pure methanol, 80% ethanol, and water) were used for the extraction of phenolic components and their comparison in order to test their antioxidant activity as a final goal. The main compounds present in the tested Veronica extracts were: p-hydroxybenzoic acid, vanillic acid, caffeic acid, gentisic acid, and apigenin. V. anagallis-aquatica contained the highest amount of phenolic components in comparison with the two other tested species, V. persica and V. polita. Caffeic acid showed the highest antioxidant activity in both studied methods with an IC₅₀ value for DPPH activity of 1.99 µg/mL. For the plant extracts, in general, methanolic/ethanolic extracts showed higher activity than water extracts in both methods which was expected, as organic solutions extract more phenolic compounds. This research points to the potential application of extracts of different Veronica species for antioxidant activity.