Free volatile compounds were isolated from 21 Croatian Veronica species studied by hydrodistillation (HD) and microwave extraction (ME) and analyzed by gas chromatography coupled with mass spectrometry. Principal Component Analysis (PCA) distinguished some clusters based on the relative proportion of major compounds, such as hexadecanoic acid, hexahydrofarnesyl acetone, phytol, E-caryophyllene, and caryophyllene oxide, which were identified in all species studied by both isolation methods. In addition to these compounds, germacrene D, δ-selinene, and eicosane were also identified in five samples from dry habitats isolated using ME. Allo-aromadendrene and β-ionone are particularly abundant in five species from wet habitats isolated by both methods. The peculiarities of Veronica species from moderate habitats isolated with HD are benzene acetaldehyde, n-nonanal, and the identification of significant compounds from the hydrocarbon class, while the peculiarity of ME is (E)-β-damascenone. In this article, we present new results on the phytochemical characterization of Veronica species from different habitats. The biological potential of these compounds should be further investigated for a better understanding and utilization of the specialized plant metabolites.

In this study, free volatile compounds (FVCs) were isolated from the water fractions (hydrosols) of 10 Croatian Veronica species obtained by hydrodistillation (HD) and microwave-assisted extraction (MAE). The use of different isolation techniques is important for the analysis of the influence of extraction conditions on the qualitative and quantitative composition of the isolated constituents. The composition of the hydrosols was analyzed using gas chromatography and mass spectrometry. The compounds β-ionone and benzene acetaldehyde were detected in all 10 Veronica hydrosols studied. E-caryophyllene was also identified in all isolates except the MAE isolate of V. arvensis L. Caryophyllene oxide was isolated in all isolates apart from the HD isolate of V. catenata Pennell. (E)-β-Damascenone is significantly present in all isolates except the MAE isolates of V. catanata and V. cymbalaria Bodard. In these two species, α-muurolol was identified in a high percentage. The same basic phytochemical constituents and compounds characteristic of a given Veronica species suggest the importance of further research. Antioxidant activity was tested for all extracts using two methods, ORAC and DPPH. Therefore, it is crucial to identify as many specialized metabolites from Veronica species as possible, especially hydrosols, which are natural products of potential pharmacological interest.

The extraction of bioactive plant components, which belong to specialized metabolites, is carried out by conventional and novel extraction methods. In this study, a classical (hydrodistillation, HD) and a novel technique (microwave-assisted water extraction, MAE) were used to isolate free volatile compounds from nine Croatian Veronica taxa (family Plantaginaceae). Each of these extracts consists of a lipophilic phase and an aqueous phase (hydrosol). Gas chromatography-mass spectrometry was used to identify the compounds in the hydrosol phase studied taxa Veronica. The compounds β-ionone and benzene acetaldehyde were detected in all nine Veronica hydrosols studied. Other compounds abundant in all investigated species are germacrene D, α-muurolol, (E)-β-damascenone, and β-ionone. Also, the compositions of hydrosols and lipophilic phases (published in our previous research) of these nine Veronica species were compared. Identification of the compounds in both extract parts is important for selecting the extract part for further biological research. According to the distribution of species in the PCA analyses comparing two methods, only two species showed a greater difference in the composition of the hydrosol by the two methods, therefore our conclusion is that for most species there is no significant difference in the composition. Microwave water extraction is a better choice with regards to more environmentally friendly working conditions. Furthermore, we conclude that hydrosol extracts are not waste products, but are a valuable source of compounds with great potential applications.

(1) Background: The conservation of plant resources is important because many wild plant populations are threatened by various influences. Growing plants from seeds is one way to ensure their survival. Comparing the biological potential of extracts between plants cultivated from seeds and wild plants provides information about their specialized metabolites. For this reason, this study compared the biological potential of phenolic extracts from four wild-collected species of the genus Veronica and the same four cultivated species. The studied species of the genus Veronica are V. anagallis-aquatica L., V. persica Poir., V. polita Fr. and V. hederifolia L. (2) Methods: The phenolic composition was investigated with LC-QTOF (Liquid Chromatography-Quadrupole Time-of-Flight). The main methods for biological activities were as follows: ORAC (Oxygen Radical Absorbance Capacity) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical for antioxidant activity, the disk diffusion test for antibacterial activity and the MTS test of cytotoxic activity. (3) Results: The major compound in all extracts was apigenin. Cultivated species showed higher antioxidative activity. Phenolic compounds isolated from the V. anagallis-aquatica species showed the highest cytotoxic effect on all tested lines. The extracts showed antibacterial activity on three bacterial strains: Streptococcus pyogenes, Listeria monocytogenes and L. innocua. Extracts of V. anagallis-aquatica showed the highest antibacterial activity, both from the natural habitat and cultivated habitat. (4) Conclusions: A comparison of the different activities tested for phenolic extracts between wild and cultivated species of the genus Veronica showed that cultivated species also have significant biological activity and are suitable for further research and applications.