horticulturae Article Wild Species Veronica officinalis L. and Veronica saturejoides Vis. ssp. saturejoides—Biological Potential of Free Volatiles Marija Nazli´c 1 , Željana Fredotovi´c 1 , Elma Vuko 1 , Lea Fabijani´c 2, Dario Kremer 3, Edith Stabentheiner 4, Mirko Rušˇci´c 1 and Valerija Dunki´c 1,* 1 Faculty of Science, University of Split, Rudera¯ Boškovi´ca33, HR-21000 Split, Croatia; [email protected] (M.N.); [email protected] (Ž.F.); [email protected] (E.V.); [email protected] (M.R.) 2 Bartul Kaši´cHigh School, Ante Starˇcevi´ca9, HR-23250 Pag, Croatia; [email protected] 3 Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovaˇci´ca1, HR-10000 Zagreb, Croatia; [email protected] 4 Institute of Biology, Karl-Franzens University, Schubertstrasse 51, A-8010 Graz, Austria; [email protected] * Correspondence: [email protected]; Tel.: +385-21-619-296 Abstract: Extracts from plants of the genus Veronica have been and continue to be used in traditional medicine to treat various diseases throughout the world. Although often considered a weed, many scientific reports demonstrate that these plants are a source of valuable biologically active compounds and their potential for horticulture should be investigated and considered. In this study, free volatile compounds of essential oils (EO) and hydrosols were extracted from two species: Veronica officinalis, which is most commonly used in traditional medicine, and Veronica saturejoides, an endemic plant that could be obtained by cultivation in horticulture. Volatiles were analyzed by gas chromatography Citation: Nazli´c,M.; Fredotovi´c,Ž.; coupled with mass spectrometry (GC, GC-MS). The most abundant compounds identified in the EOs Vuko, E.; Fabijani´c,L.; Kremer, D.; were hexadecanoic acid in V. officinalis EO and caryophyllene oxide in V. saturejoides EO. The hydrosols Stabentheiner, E.; Rušˇci´c,M.; Dunki´c, were characterized by a high abundance of caryophyllene oxide in V. saturejoides hydrosol and of V. Wild Species Veronica officinalis L. p-vinyl guaiacol for V. officinalis hydrosol. The sites where the volatile compounds are synthesized and Veronica saturejoides Vis. ssp. saturejoides—Biological Potential of and stored were analyzed using SEM (Scanning Electron Microscopy); glandular and non-glandular Free Volatiles. Horticulturae 2021, 7, trichomes were detected on stems, leaves and the calyx. Further, to investigate the activity of the free 295. https://doi.org/10.3390/ volatile compounds against pathogens, isolated volatile compounds were tested on the antiphytoviral horticulturae7090295 activity against tobacco mosaic virus (TMV) infection. The hydrosols of both investigated species and EO of V. officinalis showed significant antiphytoviral activity. To further investigate the biological Academic Editor: Othmane Merah potential of these extracts they were also tested for their antiproliferative and antioxidant activities. The results indicate that these compounds are a valuable source of potential anticancerogenic agents Received: 18 August 2021 that should be investigated in future studies. The presented results are the first report of hydrosol Accepted: 3 September 2021 and EO activity against TMV infection, suggesting that these extracts from Veronica species may be Published: 7 September 2021 useful as natural-based antiphytoviral agents. Publisher’s Note: MDPI stays neutral Keywords: antioxidant activity; antiphytoviral activity; antiproliferative activity; essential oil; free with regard to jurisdictional claims in volatile compounds; GC-MS; hydrosol; speedwell published maps and institutional affil- iations. 1. Introduction The genus Veronica of the family Plantaginaceae grows predominantly in temperate Copyright: © 2021 by the authors. Northern Hemisphere regions, with a smaller number of species growing in Southern Licensee MDPI, Basel, Switzerland. This article is an open access article Hemisphere regions and in Australia [1,2]. The many species of this plant family, about distributed under the terms and 450, show the great ecological adaptability of the genus Veronica. Species of this genus conditions of the Creative Commons grow in wet and dry habitats, as well as in the marine belt and mountains [3]. Attribution (CC BY) license (https:// The studied species Veronica officinalis L. (Figure1b) (common speedwell) and Veronica creativecommons.org/licenses/by/ saturejoides Vis. ssp. saturejoids (Figure1a) (savory leafed speedwell) grow on Dinaric 4.0/). Massif (Republic of Croatia). Both species are perennial herbaceous plants with small Horticulturae 2021, 7, 295. https://doi.org/10.3390/horticulturae7090295 https://www.mdpi.com/journal/horticulturae Horticulturae 2021, 7, x 2 of 19 Horticulturae 2021, 7, 295 2 of 19 The studied species Veronica officinalis L. (Figure 1b) (common speedwell) and Veron- ica saturejoides Vis. ssp. saturejoids (Figure 1a) (savory leafed speedwell) grow on Dinaric Massif (Republic of Croatia). Both species are perennial herbaceous plants with small at- attractive violet flowers. Veronica officinalis is slightly taller (10–50 cm) and has longer tractive violet flowers. Veronica officinalis is slightly taller (10–50 cm) and has longer leaves leaves (1.5–5 cm) than V. saturejoides ssp. saturejoides (stem length 10–30 cm, leaf length (1.5–5 cm) than V. saturejoides ssp. saturejoides (stem length 10–30 cm, leaf length 1–3 cm). 1–3 cm). The latter species is a plant endemic to Croatia [4]. The latter species is a plant endemic to Croatia [4]. (a) (b) Figure 1. InvestigatedInvestigated plants plants in in their their natural natural habitat habitat:: (a) (Veronicaa) Veronica saturejoides saturejoides ssp. ssp.saturejoidessaturejoides on on Dinara Mountain Mountain;; ( b)) Veronica officinalis officinalis L. on Kamešnica Mountain. In general, the the study of of chemical chemical compounds compounds produced produced by by wild wild plants plants is is extremely extremely important because because these these compounds compounds ultimately ultimately affect affect not not only only the theplant plant in which in which they theyare found,are found, but also but alsoindirectly indirectly other other plants plants in the in vicinity the vicinity as well as as well the environment as the environment as a whole as a whole[5]. These [5]. compounds These compounds are important are important factors in factors plant in adaptation plant adaptation to abiotic to stresses. abiotic stresses. More- over,Moreover, neighboring neighboring plants plants detect detect other other plant plant volatiles volatiles as ‘messages’ as ‘messages’ about about herbivore herbivore or pathogenor pathogen attacks, attacks, and and consequently consequently adapt adapt their their metabolism metabolism responses responses [6]. Plants [6]. Plants of the of genusthe genus VeronicaVeronica are areused used in intraditional traditional medicines medicines in incountries countries around around the the world, world, which which sparked interest in the studying these these plants plants in in terms terms of of their their chemical chemical composition composition and and biological activity. Many Many dif differentferent biological biological activities activities of of the the various various extracts extracts have have been been reported in in recent recent studies studies [7,8] [7,8.]. For For example, example, methanolic methanolic and and ethyl ethyl-acetate-acetate extracts extracts of V. of V.spicata spicata werewere tested tested for forantimicrobial antimicrobial activity activity and andMIC MIC values values were were between between 1.25 and 1.25 5.00 and mg/mL.5.00 mg/mL This. plant This plantextract extract has also has shown also shown substantial substantial antioxidant antioxidant activity, activity, especially especially the methanolthe methanol extracts extracts of flowers of flowers and andleaves leaves with with IC50 ICand50 DPPHand DPPH values values of 8.21 of 8.21µg/mLµg/mL and 8.69and 8.69µg/mL,µg/mL, respectively respectively [9]. Ertas [9]. Ertas et al.et reported al. reported antimicrobial antimicrobial activity activity for phenolic for phenolic ex- tractsextracts of Veronica of Veronica thymoides thymoides subsp.subsp. pseudocinereapseudocinerea and theand MIC the value MIC valuedetermined determined was 31.25 was mg31.25/mL mg/mL for methanol for methanol extract extract against against EscherichiaEscherichia coli [10] coli. [10]. Veronica officinalis, officinalis, whichwhich is isthe the subject subject of this of thisstudy, study, is traditionally is traditionally used in used the inmed- the icinemedicine of Balkan of Balkan peoples. peoples. Mocan Mocan et al. reported et al. reported antioxidant antioxidant activity activityfor ethanol for ethanolextracts of ex- phenolictracts of phenoliccompounds compounds for V. officinalis for V.officinalis to be 157.99to be ± 6.58 157.99 mg± Trolox6.58 mg equivalents/g Trolox equivalents/g d.w [11]. Valyovad.w [11]. et Valyova al. also etconfirmed al. also confirmed antioxidant antioxidant activity of activityphenolic of extracts phenolic for extracts the V. offici for thenalisV. inofficinalis their studyin their [12] study. The [aerial12]. The parts aerial of speedwells parts of speedwells are used to are treat used liver, to treat spleen, liver, kidney, spleen, andkidney, bladder and diseases, bladder diseases,as well as as snakebites well as snakebites wound healing, wound skin healing, lesions, skin eczema lesions, and eczema ulcers [9,1and0 ulcers,13]. [9,10,13]. Green prevention strategies