Extraction, Composition and Comparisons–Free Volatile Compounds from Hydrosols of Nine Veronica Taxa
by
, , and
Marija Nazlić
1
,
Dario Kremer
2,
Karla Akrap
1,
Snježana Topić
1,
Nenad Vuletić
1 and
Valerija Dunkić
1,*
1
Faculty of Science, University of Split, Ruđera Boškovića 33, 21000 Split, Croatia
2
Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10000 Zagreb, Croatia
*
Author to whom correspondence should be addressed.
Horticulturae 2023, 9(1), 16; https://doi.org/10.3390/horticulturae9010016
Submission received: 28 October 2022
/
Revised: 14 December 2022
/
Accepted: 17 December 2022
/
Published: 22 December 2022
(This article belongs to the Special Issue Advances in the Extraction of Bioactive Compounds from Horticultural Plants)
Abstract
: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. Introduction
Extraction methods for the isolation of bioactive compounds from plant material are divided into classical and new methods [1,2]. The most common conventional extraction methods include Soxhlet extraction, maceration and hydrodistillation. Soxhlet extraction is named after its inventor, the chemist Franz Ritter von Soxhlet. This extractor was developed primarily for the extraction of lipids from materials with the addition of interesting solvents. It is used as a model for comparing new extraction alternatives [1]. Maceration is a very simple extraction method and is suitable for the extraction of thermolabile compounds. The disadvantages of this extraction are the long duration of the process and the low yield of extracts [3]. In general, the classical extraction methods of steam distillation or hydrodistillation, which include three physico-chemical processes (hydrodiffusion, hydrolysis, and heat decomposition) are the most commonly used [1]. At a high extraction temperature, thermolabile biologically active compounds may be lost. In addition to temperature effects, each of these classical extraction methods has other disadvantages and limitations that affect the quality and quantity of the isolates obtained. For example, the toxicity of the solvent may affect the obtained isolates, as well as the long extraction time, which makes these extractions methods energy-intensive and consume large amounts of water [4]. Therefore, these classical methods can have a negative impact on the environment and the economy.
Precisely because of all the above, new green extraction techniques are increasingly being applied. One of the new extraction methods is supercritical fluid extraction (SFE) which uses solvents such as CO2, propane, butane, or ethylene at low temperatures to prevent thermal degradation of isolated bioactive plant constituents [5].
Ultrasound-assisted extraction (UAE) is also an environmentally friendly technique. The peculiarity of this technique is the effect of ultrasound on the plant cell membranes, which has a positive effect on the quantitative yield of the extracts and on a shorter extraction time [6]. Microwave-assisted extraction (MAE) is also an environmentally friendly extraction whose heating mechanism is based on friction and favorable atmospheric conditions [4,7,8].
Two extraction methods were used in this study, the classical HD and the new MAE. The extraction products of both methods consist of two parts, a lipophilic layer (LL) and an aqueous layer (hydrosol, HY). The main differences between these two extraction methods are the way the plant material is heated and the duration of the extraction process. In MAE extraction, microwave energy heating is based on the effect of microwaves on molecules. In addition, microwave heating is volumetric and the entire sample is heated simultaneously, unlike classical conductive heating, which is relevant to HD. The temperature gradient is reversed compared with classical heating, as MAE heats the center of the material and solvent, while conventional HD extraction heats the surface first [9]. There are studies that confirmed that MAE is faster and less energy consuming when comparing with classical methods of extraction. Ferhat et al. discussed this in their research where they used different extraction methods for EO from Citrus peel and they showed that MAE does not cause considerable changes in its volatile oil composition and properties [10].
The composition of the hydrosol formed during distillation is dominated by polar, oxygenated, hydrophilic components that form hydrogen bonds with water, and the concentration of these volatile compounds is usually less than 1 g/L [11]. Unfortunately, hydrosols are usually treated as wastewater from extraction [12]. Research into the effects of hydrosols has shown significant biological potential, therefore hydrosols should not be considered waste. Among other uses (e.g., antibacterial, antioxidant, antiviral), they can be used in agriculture for soil fertilization and to control fungi, molds, and insects [13,14,15,16,17].
The studied Veronica taxa, family Plantaginaceae (formerly classified in family Scrophulariaceae) are widespread in the Mediterranean region, on the islands, in the lowlands, and on the highest peaks of the Dinaric Mountains in the Republic of Croatia [18,19,20]. They grow in different habitats and are characterized by a great morphological diversity [18], and an abundance of specialized metabolites [21,22,23] that represent an adaptation to different biotic and abiotic stress [24].
Thanks to the attractive appearance of the flowers [18] and the ability to spread rapidly due to metabolic adaptations, the selected Veronica taxa studied in this work can be used in horticulture. In addition, natural bioactive compounds can be extracted from the cultivated Veronica taxa. The hydrosols, which make up a large part of the extracts obtained, can be used as green manure. The hydrosols would therefore not be waste [25], but represent an ecologically acceptable fertilization with the recovery of bioactive compounds. In this way, the natural cycle of Veronica taxa would be closed with minimal consumption of energy and water resources, thus making an important contribution to environmental protection.
The aim of this study is to identify the free volatile components in the composition of hydrosols obtained from HD and MAE of nine selected Croatian Veronica species and to compare and discuss the differences and similarities of these two methods.
In general, the composition of hydrosol compared to the lipophilic part (essential oil) of plant extracts is much less studied scientifically [25,26,27]. The contribution of this research is a complete insight into the composition of free volatile compounds from the water and lipid phases of the hydrodistillation extracts of the studied Veronica taxa. The composition of the lipophilic phases was published in our previous work [28].
2. Materials and Methods
2.1. Plant Material
Plant material of nine Veronica taxa was collected during the flowering period from March to July 2021 at different locations in Croatia. The voucher specimens were deposited in the herbarium of the Laboratory of Botany (HPMF-HR) of the Faculty of Science, University of Split, Croatia, under the designation CROVeS-No-2021 (Table 1) [28]. All plant material was air dried for ten days under controlled conditions: in a single layer, protected from direct sunlight, and in temperatures up to 22 °C. The dried plant material was then stored in paper bags.
2.2. Extractions, Preparation and Analyses of Hydrosols
Extractions of 50 g of each Veronica sample (Table 1) were hydrodistilled (HD) for 2.5 h in a Clevenger apparatus (CL) (Šurlan, Medulin, Croatia) and microwave-assisted extractions (MAE) (Milestone ‘ETHOS X’ microwave laboratory oven, 1900 W maximum). In the inner tube of CL apparatus, volatile compounds were collected in a solution of pentane and diethyl ether (2:1). MAE was performed at atmospheric pressure for 40 min (extraction process started after 10 min) at 500 W (98 °C) and volatile compounds were collected in the same solution as in CL extraction. All extracts consist of two layers: a lipophilic layer collected in a side tube using a pentane/diethyl ether trap, and a water layer (hydrosol). The composition of hydrosols obtained was further investigated.
From each sample, 2 g of the hydrosol was placed in a glass bottle and sealed with a bottle cap. The sample thus prepared was placed in a water bath, and a Solid Phase Micro-Extraction (SPME) needle was injected through the septum of the bottle cap. The first part of the process took place at 40 °C for 20 min to allow the compounds to evaporate from the water. The SPME fiber is positioned directly above the liquid sample being stirred during the next 20 min of the process. The volatile compounds settled on the resin SPME fiber.
The prepared sample was injected into the gas chromatography (GC) inlet and left there for 20 min to ensure that all volatile compounds were reabsorbed from the SPME fiber into the injection liner.
Chromatographic analyses were performed with a GC (model 3900; Varian Inc., Lake Forest, CA, USA) equipped with a flame ionization detector and a mass spectrometer (model 2100 T; Varian Inc., Lake Forest, CA, USA), nonpolar capillary column VF-5 ms (30 m × 0.25 mm i.d., coating thickness 0.25 μm, Palo Alto, CA, USA), and polar CP Wax 52 (30 m × 0.25 mm i.d., coating thickness 0.25 μm, Palo Alto, CA, USA) (Supplementary material: Tables S1 and S2). The chromatographic methods and conditions for the analysis of the hydrosol fraction were the same as described in the article by Dunkić et al. [28] as follows: the conditions for the VF-5-ms column were a temperature of 60 ◦C (isothermal) for 3 min, which was then increased to 246 °C at a rate of 3 °C min−1 and held (isothermal) for 25 min. The conditions for the CP Wax 52 column were a temperature of 70 °C (isothermal) for 5 min, which was then increased to 240 °C at a rate of 3 °C min−1 and held (isothermal) for 25 min. The injected volume was 2 µL and the split ratio was 1:20. The MS conditions were: ion source temperature, 200 °C; ionization voltage, 70 eV; mass scan range, 40–350 mass units.
The individual peaks of all samples were identified by comparing their retention indices of n-alkanes with those of authentic samples and the studies [29,30] by comparison with our libraries from previous work, and by comparison with other previously published material for Veronica species [16,28]. The results are given as the mean of three analyses with standard deviation.
2.3. PCA Analyses
Statistical analysis was performed in GraphPad Prism Version 9 (GraphPad Software, San Diego, CA, USA). All data in the tables are expressed as the mean ± SD (n = 3). Data included in the PCA analyses were obtained from the GC–MS analyses. PCA analyses were performed for volatile compounds with amounts greater than 2%. Significant differences between taxa for the relative percentage of the compounds (identified by GC–MS) were determined using 2-way ANOVA followed by Tukey’s multiple comparisons test (p < 0.05).
3. Results
3.1. Extraction of Hydrosol Components from Veronica Taxa
Extraction of bioactive compounds from the hydrosols of nine selected Croatian Veronica taxa were obtained by classical extraction-hydrodistillation (HD) and novel-microwave-assisted water extraction (MAE). The extracts were analyzed by gas chromatography–mass spectrometry (GC–MS), and the results of the composition of hydrosol are presented in Table 2 and Table 3 and in Figure 1.
3.1.1. Composition of Veronica Hydrosols Obtained by Hydrodistillation
The compounds germacrene D, caryophyllene oxide, α-muurolol, benzene acetaldehyde, (E)-β-damascenone, and β-ionone, were detected in all studied HD Veronica hydrosols (Table 2).
The dominant components identified in the composition of hydrosol V. austriaca ssp. jacquinii taxa are benzaldehyde (10.38%) and benzene acetaldehyde (18.43%). These two components also dominate in V. longifolia taxa with the following proportions: benzene-acetaldehyde, 22.27%, and benzaldehyde, 10.33%. In the hydrosol composition of V. dalmatica, benzaldehyde was identified at a similar percentage as in V. longifolia. The peculiarity of V. dalmatica hydrosol is the content of thymol at 26.72%.
Also, benzene acetaldehyde was identified in a significant percentage in the following taxa: V. beccabunga (13.23%), V. montana (25.33%), V. serpyllifolia (16.44%), and V. urticifolia (18.68%).
Moreover, the compound α-thujene was identified only in the hydrosols of V. urticifolia, V. montana, and V. serpyllifolia. In the composition of V. urticifolia, besides the main components already mentioned (benzene acetaldehyde and α-thujene), linalool is the most represented in this hydrosol with 10.87% compared with all other studied taxa Veronica (Table 2).
Caryophyllene oxide is the most abundant compound of V. serpyllifolia at 37.03% and in hydrosol of V. chamaedrys at 21.11%. Peculiarity of V. chamaedrys hydrosol is the composition of α-muurolol at 23.16%.
The following compounds are most abundant in the V. saturejoides ssp. saturejoides hydrosol: trans-p-mentha-1(7),8-dien-2-ol, 10.24%, and caryophyllene oxide, 21.56%, methyl eugenol, 22.76%, and β-ionone, 13.21%. The compound trans-p-mentha-1(7),8-dien-2-ol at 10.30% was also identified in the hydrosol of V. beccabunga. The dominant compound in this hydrosol is piperitone with an identification percentage of 28.15% (Table 2).
3.1.2. Composition of Veronica Hydrosols Obtained by Microwave-Assisted Water Extraction
The compounds E-caryophyllene, caryophyllene oxide and benzene acetaldehyde, were detected in all studied MAE Veronica hydrosols (Table 3).
Other important components of the hydrosol composition are: α-muurolol (18.75%) in V. austriaca ssp. jacquinii and in V. chamaedrys with 22.45%, in V. saturejoides ssp. saturejoides methyl eugenol (24.23%), in V. montana (E)-β-damascenone (36.04%), in V. dalmatica thymol with 38.81%. A peculiarity is the composition of the hydrosol of V. beccabunga, in which piperitone is present with 79.86% identification (Table 3).
Component α-thujene was detected in MAE hydrosol in the same Veronica taxa as HD hydrosol (V. montana, V. serphyllifolia, and V. urticifolia) (Table 2). The highest content α-thujene was found in MAE hydrosol of V. urticifolia, 39.73%.
In the Figure 1, percentages for the groups of compounds are shown for every species and both extractions. Compound groups that prevail in hydrosols are the ones containing more polar compounds, that are common group of acids, alcohols and esters, phenolic compounds, oxygenated monoterpenes and oxygenated sesquiterpenes. There is one exception, V. urticifolia. MAE hydrosols of this species contain high relative percentage of monoterpene hydrocarbons (α-thujene).
3.2. PCA Analyses
PCA analyses were performed for volatile compounds from hydrosols with an amount greater than 2%. Separated analyses were performed for classical (Figure 2) and microwave water extraction methods (Figure 3). Furthermore, PCA analyses for hydrosols from both extraction methods were conducted together to see if there are some major differences for particular species in different extraction methods (Figure 1).
In the first PCA analysis where hydrosols from two methods were compared, PC1 and PC2 explained 51.71% of variance. From the Figure 2a, it can be seen that for only two species, V. beccabunga and V. longifolia, the extracts from Clevenger extraction and microwave extraction differ, therefore they are apart from each other on the PC score plot and are in the different sides of the PC1 and PC2. In the case of V. beccabunga, MAE hydrosol is in the negative region of the PC1 due to its high relative content of piperitone (Figure 2b). In the case of V. longifolia MAE hydrosol is in the positive region of PC1 and near the center for PC2 due to its higher relative percentage of benzaldehyde, β-ionone, and α-muurolol. HD hydrosol is located in the negative region of both PC1 and PC2 due to its higher relative percentage of benzene acetaldehyde and (E)-β-damascenone. For other species the differences between the two extracts are not so major. V. dalmatica is apart from all other hydrosol extracts because of its higher relative content of thymol.
In the comparation of volatile compounds from the hydrosols and the lipophilic layer, PC1 and PC2 for volatile compounds from Clevenger extraction explained 60.74% of the variance. Extracts of volatiles from LL are mostly in the negative side of PC1 and extracts from HY are all on the positive side of PC1 so the differences between between LL and HY extracts are visible (Figure 3a). For the LL volatiles, hexadecanoic acid, hexahydrophanesyl acetone, phytol, pentacosane, and hexacosane prevail in the composition. For HY volatiles, caryophyllene oxide, α-muurolol, benzene acetaldehyde, (E)-β-damascenone, β-ionone, benzaldehyde, and (E)-caryophyllene prevail (Figure 3b).
PC1 and PC2 for hydrosol volatile compounds from microwave extraction explained 56.61% of the variance. All LL extracts are in the positive region of PC2. All HY extracts are in the negative region of PC2. Veronica beccabunga is farther from all the other species, and for this species extracts are in different parts of the PCA score plot (Figure 4a). This is due to its high relative percentage of piperitone in the MAE hydrosol. In the loadings score plot, compounds that prevail in both type of extracts can be detected. For the LL volatiles, hexadecanoic acid, hexahydrophanesyl acetone, phytol, docosane, and heptacosane prevail in the composition. For HY volatiles, caryophyllene oxide, α-muurolol, benzene acetaldehyde, (E)-β-damascenone, β-ionone, and benzaldehyde (Figure 4b).
4. Discussion
Specialized metabolites are important phytochemical compounds formed in plants in response to stressful environmental conditions [31]. These bioactive compounds, which are produced in small amounts in the plant organism, are responsible for the growth and development of the plant. Even in ancient times, people recognized the benefits of these bioactive molecules [32] and “stole” them from plants. The quality and quantity of the isolated compounds depend on the methods of extraction from the plant material. Therefore, it is very important to choose a suitable method for the pretreatment of the plant material [33]. The pretreatment of the plant material of the studied Veronica taxa consisted in drying the collected plants in the air (Table 1). After drying, extractions were carried out. Two extraction methods were used in this study, hydrodistillation (HD) and microwave-assisted water extraction (MAE). For both extraction methods, the same mass of plant material was used for each Veronica taxa, and the solvent was water for both extraction methods. The choice of extraction solvents significantly affects the composition of the isolate [7].
To choose the best extraction technique, it is necessary to subject small samples of the plant material to different extraction techniques. This optimizes the extraction process to obtain the maximum amount of isolated bioactive constituents while consuming as little energy and resources as possible. In our study, each extract consists of two layers, a lipophilic layer (LL) and an aqueous layer (hydrosol, HY). The compounds caryophyllene oxide and benzene acetaldehyde were detected in all HD and MAE hydrosols of the Veronica taxa studied. In addition to these two compounds, the compounds germacrene D, α-muurolol, (E)-β-damascenone, and β-ionone were detected in all HD Veronica hydrosols examined (Table 2), and (E)-caryophyllene was detected in all MAE Veronica hydrosols examined (Table 3). The components β-caryophyllene and β-caryophyllene oxide act as a natural fungicide against various phytopathogenic fungi, with β-caryophyllene oxide being more effective in inhibiting fungal growth [34]. Benzaldehyde and benzene acetaldehyde represent important aldehydes in plants. Benzaldehyde, which is a common component of plant volatiles, attracts many types of insects and can affect their behavior [35].
Hydrosols are very dilute solutions with a volume of water many times that of the dissolved ingredients. As can be seen from our results presented in this paper, they are complex mixtures containing various volatiles and water-soluble secondary metabolites [36]. Veronica plants are known to be a rich source of bioactive compounds [37]. In the search for effective means against certain pathogens, the agricultural industry is increasingly relying on green manures. The aim is to control plant pathogenic organisms without harming non-target organisms [33]. Furthermore, hydrosols can be used in protecting fresh fruit and vegetables from browning when cut, which is indicated in the study by Xiao et al. [38]. Politi et al. even investigated the possibility of producing hydrosols to become the main distillation product, not just a by-product, of the aromatic plant’s manufacture [17].
PCA analysis is often used when differences and similarities within compounds are observed in a large number of species. In support of this statistical tool, in research by Rodriguez et al. PCA was used to discriminate chemical groups of volatiles of sweet orange (juices and fruit) to conclude which ones are the most influential for odor in different transgenic lines [39]. In our research, PCA analyses revealed the differences in the composition of lipophilic layer and hydrosols (Figure 3a and Figure 4a). Furthermore, in most species (except two, V. beccabunga and V. longifolia) the composition of hydrosol volatiles does not differ significantly in the two techniques and therefore we can say that microwave-assisted water extraction is a good extraction technique when extracting free volatile compounds, especially in terms of less energy and water consumption (Figure 2a). This conclusion was also made by Zhao et al. in their research on the separation of polysaccharides and essential oil from Taxus chinensis var. mairei [40]. Another study on the essential oils of Rosmarinus officinalis L. by hydrodistillation and microwave assisted hydrodistillation concluded that MAE hydrodistillation extracts an essential oil with higher amounts of oxygenated compounds with environmentally friendlier method conditions (energy and water savings) [41].
To conclude, hydrosols are not extraction waste. They represent a wealth of dissolved bioactive compounds. Adequate extraction procedures contribute to the preservation of the nature, quality, and quantity of isolates.
5. Conclusions
In this study, free volatile compounds from nine Croatian Veronica taxa (family Plantaginaceae) hydrosols were extracted by two methods: Clevenger hydrodistillation and microwave-assisted water extraction. Gas chromatography-mass spectrometry was used to identify the compositions of volatile compounds: β-ionone and benzene acetaldehyde in all nine Veronica hydrosols studied. Other compounds abundant in all investigated species were germacrene D, α-muurolol, (E)-β-damascenone, and β-ionone. Comparing the compositions of hydrosols and lipophilic phases (published in our previous research) of these nine Veronica species, we conclude that hydrosols should not be considered a waste product, as they often are, but represent a valuable source of compounds with different possible applications that are yet to be investigated (such as using hydrosols as green fertilizers or in the protection from browning of fresh fruit and vegetables).
Future analyses for this Veronica species’ hydrosols should include analyzing potential fruit and food preservation activity (antimicrobial and antifungal) and also other bioactivities such as antiproliferative, antioxidant, and antiphytoviral.
Supplementary Materials
The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/horticulturae9010016/s1, Table S1. Components of the hydrosols (%) obtained by hydro-distillation from the aerial parts of Veronica taxa, Table S2. Components of the hydrosols (%) obtained by microwave-assisted water extraction from the aerial parts of Veronica taxa.
Author Contributions
Conceptualization, V.D. and M.N.; methodology, V.D. and M.N.; software, M.N.; validation, V.D., M.N. and D.K.; formal analysis, V.D., M.N., K.A. and S.T.; investigation, V.D., M.N., K.A., S.T. and N.V.; resources, D.K.; data curation, V.D. and M.N.; writing—original draft preparation, V.D., M.N. and D.K.; writing—review and editing, V.D., M.N. and D.K.; visualization, V.D. and M.N.; supervision, V.D.; project administration, V.D.; funding acquisition, V.D. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by the Croatian Science Foundation, grant number: IP-2020-02-8425, Croatian Veronica Species: Phytotaxonomy and Biological Activity (CROVeS-PhyBA) project.
Data Availability Statement
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to being part of further project research.
Conflicts of Interest
The authors declare no conflict of interest.
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Figure 1.
Relative percentage of volatiles in Veronica species from the hydrosols extracted with Clevenger hydrodistillation and microwave-assisted distillation: monoterpene hydrocarbons (MH), oxygenated monoterpenes (OM), sesquiterpene hydrocarbons (SH), oxygenated sesquiterpenes (OS), phenolic compounds (PD), hydrocarbons (H), a common group (CG) of acids, alcohols, and esters and oxygenated diterpene (OD).
Figure 1.
Relative percentage of volatiles in Veronica species from the hydrosols extracted with Clevenger hydrodistillation and microwave-assisted distillation: monoterpene hydrocarbons (MH), oxygenated monoterpenes (OM), sesquiterpene hydrocarbons (SH), oxygenated sesquiterpenes (OS), phenolic compounds (PD), hydrocarbons (H), a common group (CG) of acids, alcohols, and esters and oxygenated diterpene (OD).
Figure 2.
(a) PCA analyses of volatile compounds of 9 Veronica species–hydrodistillation (HD) and microwave assisted extraction (MAE); (b) PCA loading plots of volatiles from the first and second principal component.
Figure 2.
(a) PCA analyses of volatile compounds of 9 Veronica species–hydrodistillation (HD) and microwave assisted extraction (MAE); (b) PCA loading plots of volatiles from the first and second principal component.
Figure 3.
(a) PCA score plot for LLs (lipophilic layer) and hydrosols (HY) from HD method; (b) PCA loading plots of HD volatiles from the first and second principal component. The color palette represents the same species as in Figure 2a.
Figure 3.
(a) PCA score plot for LLs (lipophilic layer) and hydrosols (HY) from HD method; (b) PCA loading plots of HD volatiles from the first and second principal component. The color palette represents the same species as in Figure 2a.
Figure 4.
(a) PCA score plot for LLs and hydrosols from MAE method; (b) PCA loading plots of MAE volatiles from the first and second principal component. The color palette represents the same species as in Figure 2a.
Figure 4.
(a) PCA score plot for LLs and hydrosols from MAE method; (b) PCA loading plots of MAE volatiles from the first and second principal component. The color palette represents the same species as in Figure 2a.
Table 1.
Details on collection data and origin of investigated Veronica taxa.
| Taxa | Locality | Latitude | Longitude | Altitude a.s.l. (m) | Voucher No. |
|---|---|---|---|---|---|
| V. austriaca ssp. jacquinii | Brač Island | 43°19′07.3″ N | 16°36′08.5″ E | 564 | CROVeS-02-2021 |
| V. beccabunga | Baške Oštarije | 44°31′32.1″ N | 15°10′34.2″ E | 908 | CROVeS-08-2021 |
| V. chamaedrys | Radoboj | 46°09′49.4″ N | 15°55′36.1″ E | 260 | CROVeS-13-2021 |
| V. dalmatica | Dubrovnik | 42°39′19.1″ N | 18°04′56.9″ E | 58 | CROVeS-04-2021 |
| V. longifolia | Oštarije | 45°13′36.1″ N | 15°16′18.2″ E | 311 | CROVeS-10-2021 |
| V. montana | Papuk Mt | 45°30′38.1″ N | 17°39′57.2″ E | 761 | CROVeS-15-2021 |
| V. saturejoides ssp. saturejoides | Dinara Mt | 44°03′11.3″ N | 16°23′29.7″ E | 1697 | CROVeS-05-2021 |
| V. serpyllifolia | Zagreb | 45°49′40.3″ N | 15°58′59.5″ E | 192 | CROVeS-20-2021 |
| V. urticifolia | Plešivica Mt | 45°45′05.7″ N | 15°42′28.3″ E | 350 | CROVeS-21-2021 |
Table 2.
Components of the hydrosols (%) obtained by hydro-distillation from the aerial parts of Veronica taxa.
Table 2.
Components of the hydrosols (%) obtained by hydro-distillation from the aerial parts of Veronica taxa.
| V. austriaca ssp. jacquinii | V. beccabunga | V. chamaedrys | V. dalmatica | V. longifolia | V. montana | V. saturejoides ssp. saturejoides | V. serpyllifolia | V. urticifolia | |||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Component | RI a | LRI | VC ± SD | VC ± SD | VC ± SD | VC ± SD | VC ± SD | VC ± SD | VC ± SD | VC ± SD | |
| Monoterpene hydrocarbons | 1.79 | - | - | - | - | 9.44 | - | 8.65 | 14.58 | ||
| α-Thujene | 924 | 924 | 1.79 ± 0.01 d | - | - | - | - | 9.44 ± 0.01 b | - | 8.65 ± 0.01 c | 14.58 ± 0.01 a |
| Oxygenated monoterpenes | 10.67 | 40.75 | 7.86 | 7.54 | 19.19 | 10.13 | 10.24 | 5.53 | 16.38 | ||
| γ-Terpinene | 1057 | 1054 | - | - | - | 1.15 ± 0.01 b | - | - | - | 0.68 ± 0.01 c | 1.61 ± 0.01 a |
| Linalool | 1095 | 1095 | 1.42 ± 0.1 f | - | 1.03 ± 0.01 g | 3.64 ± 0.01 d | 9.43 ± 0.01 b | 5.45 ± 0.01 c | - | 3.52 ± 0.01 e | 10.87 ± 0.01 a |
| Terpinen-4-ol | 1174 | 1174 | 1.77 ± 0.04 d | 1.87 ± 0.03 c | 1.93 ± 0.1 c | - | 3.82 ± 0.01 a | 1.91 ± 0.01 c | - | 0.32 ± 0.05 e | 3.13 ± 0.01 b |
| Borneol | 1176 | 1165 | 6.72 ± 0.01 | - | - | - | - | - | - | - | |
| α-Terpineol | 1184 | 1186 | 0.76 ± 0.12 c | - | - | - | 0.82 ± 0.05 c | 2.77 ± 0.1 a | - | 1.01 ± 0.01 b | 0.77 ± 0.01 c |
| trans-p-Mentha-1(7),8-dien-2-ol | 1187 | 1187 | - | 10.30 ± 0.01 a | 3.16 ± 0.03 c | - | 5.12 ± 0.01 b | - | 10.24 ± 0.01 a | - | - |
| β-Cyclocitrat | 1233 | 1217 | - | - | 1.74 ± 0.1 | - | - | - | - | - | - |
| Piperitone | 1250 | 1249 | - | 28.15 ± 0.01 | - | - | - | - | - | - | - |
| Menthyl acetate | 1294 | 1294 | - | 0.43 ± 0.07 b | - | 2.75 ± 0.02 a | - | - | - | - | - |
| Sesquiterpene hydrocarbons | 4.06 | 5.65 | 4.11 | 11.34 | 8.55 | 12.57 | 3.16 | 10.24 | 15.59 | ||
| E-Caryophyllene * | 1424 | 1417 | 2.02 ± 0.01 g | 3.41 ± 0.1 f | 2.04 ± 0.01 g | 5.51 ± 0.01 c | 3.95 ± 0.01 e | 5.82 ± 0.01 b | 0.56 ± 0.15 h | 5.12 ± 0.01 d | 9.88 ± 0.01 a |
| allo-Aromadendrene | 1465 | 1458 | 0.76 ± 0.01 d | 0.32 ± 0.01 e | 0.37 ± 0.01 e | - | 0.83 ± 0.01 d | 1.44 ± 0.01 c | - | 1.54 ± 0.01 b | 2.14 ± 0.01 a |
| Germacrene D | 1481 | 1484 | 1.28 ± 0.1 f | 1.92 ± 0.12 e | 0.64 ± 0.01 h | 5.83 ± 0.01 a | 2.32 ± 0.05 d | 4.52 ± 0.01 b | 0.72 ± 0.01 g | 0.66 ± 0.1 h | 2.53 ± 0.01 c |
| δ-Selinene | 1492 | 1492 | - | - | 1.06 ± 0.1 d | - | 1.45 ± 0.01 c | 0.79 ± 0.07 f | 1.88 ± 0.03 b | 2.92 ± 0.01 a | 0.94 ± 0.01 e |
| Oxygenated sesquiterpenes | 19.91 | 12.19 | 45.72 | 18.8 | 4.64 | 6.95 | 24.42 | 39.37 | 12.93 | ||
| Spathulenol | 1577 | 1577 | - | - | - | 1.05 ± 0.01 b | 0.74 ± 0.01 c | 1.21 ± 0.01 a | - | - | 0.43 ± 0.01 d |
| Caryophyllene oxide * | 1581 | 1582 | 9.92 ± 0.01 d | 8.21 ± 0.01 e | 21.11 ± 0.01 b | 8.13 ± 0.01 f | 0.66 ± 0.01 h | 4.88 ± 0.01 g | 21.56 ± 0.01 b | 37.03 ± 0.01 a | 10.32 ± 0.01 c |
| Viridiflorol | 1592 | 1592 | 0.43 ± 0.02 e | 1.45 ± 0.01 a | - | 0.78 ± 0.01 c | 0.86 ± 0.05 b | - | 0.57 ± 0.01 d | 0.54 ± 0.01 d | |
| γ-Eudesmol | 1632 | 1630 | 0.45 ± 0.01 | - | - | - | - | - | - | - | - |
| α-Muurolol | 1645 | 1644 | 8.75 ± 0.01 c | 3.55 ± 0.01 d | 23.16 ± 0.01 a | 9.62 ± 0.01 b | 2.76 ± 0.01 e | - | 1.88 ± 0.01 f | 1.24 ± 0.01 h | 1.64 ± 0.01 g |
| α-Bisabolol | 1685 | 1685 | - | - | - | - | - | - | - | 0.83 ± 0.01 | - |
| Hexahydrofarnesyl acetone * | 1839 | - | 0.79 ± 0.03 b | - | - | - | - | - | 0.98 ± 0.1 a | - | - |
| Phenolic compounds | 6.03 | 10.49 | 2.72 | 26.72 | 6.69 | 12.45 | 23.5 | 4.35 | 5.27 | ||
| Thymol * | 1289 | 1289 | - | 4.11 ± 0.01 c | - | 26.72 ± 0.01 a | - | 4.55 ± 0.01 b | - | 1.58 ± 0.01 e | 3.64 ± 0.05 d |
| p-Vinyl guaicol | 1313 | 1309 | - | - | - | - | 4.25 ± 0.01 a | 1.73 ± 0.01 c | - | 2.42 ± 0.1 b | 0.55 ± 0.01 d |
| Methyl eugenol | 1403 | 1403 | 2.31 ± 0.1 e | 5.82 ± 0.01 c | 2.72 ± 0.01 d | - | 2.44 ± 0.01 e | 6.17 ± 0.01 b | 22.76 ± 0.01 a | 0.35 ± 0.01 g | 1.08 ± 0.01 f |
| (Z)-Methyl isoeugenol | 1451 | 1451 | 3.72 ± 0.01 a | 0.56 ± 0.07 c | - | - | - | - | 0.74 ± 0.01 b | - | - |
| Common group | 50.64 | 24.7 | 33.56 | 32.48 | 54.51 | 41.87 | 32.21 | 26.02 | 28.79 | ||
| (E)-2-Hexenal | 846 | 846 | 3.44 ± 0.02 | - | - | - | - | - | - | - | - |
| Isopentyl acetate | 863 | 869 | - | - | - | - | - | - | - | - | - |
| Benzaldehyde | 952 | 952 | 10.38 ± 0.02 a | 1.42 ± 0.02 e | 3.51 ± 0.01 b | 3.53 ± 0.02 b | 10.33 ± 0.01 a | - | 3.25 ± 0.01 c | - | 1.52 ± 0.01 d |
| Benzene acetaldehyde | 1036 | 1036 | 18.43 ± 0.01 c | 13.23 ± 0.01 e | 8.64 ± 0.01 h | 10.46 ± 0.01 f | 22.27 ± 0.01 b | 25.33 ± 0.01 a | 9.13 ± 0.01 g | 16.44 ± 0.01 d | 18.68 ± 0.01 c |
| n-Nonanal | 1100 | 1100 | - | 0.82 ± 0.1 d | 0.34 ± 0.01 g | 5.92 ± 0.01 a | 3.42 ± 0.01 b | 1.56 ± 0.01 c | 0.45 ± 0.01 f | 0.53 ± 0.01 e | 0.38 ± 0.01 fg |
| Hexyl 2-methyl butanoate | 1233 | 1229 | - | - | 1.72 ± 0.01 | - | - | - | - | - | - |
| n-Decanol | 1266 | 1266 | - | - | - | - | 2.86 ± 0.01 | - | - | - | - |
| Bornyl acetate | 1285 | 1287 | - | - | 4.54 ± 0.01 | - | - | - | - | - | - |
| (E)-β-Damascenone | 1384 | 1383 | 8.92 ± 0.01 a | 3.11 ± 0.01 g | 5.01 ± 0.01 d | 5.17 ± 0.01 d | 7.42 ± 0.01 b | 4.43 ± 0.01 e | 6.17 ± 0.01 c | 3.73 ± 0.01 f | 0.39 ± 0.1 h |
| β-Ionone | 1487 | 1487 | 9.49 ± 0.01 c | 6.12 ± 0.01 h | 9.37 ± 0.01 d | 7.40 ± 0.01 g | 8.21 ± 0.01 e | 10.55 ± 0.01 b | 13.21 ± 0.01 a | 5.32 ± 0.01 i | 7.82 ± 0.01 f |
| Hexadecanoic acid * | 1959 | 1959 | - | - | 0.43 ± 0.01 | - | - | - | - | - | - |
| Total identification (%) | 93.1 | 93.73 | 93.97 | 96.88 | 93.58 | 93.41 | 93.53 | 94.16 | 93.54 |
Retention indices (RIs) were determined relative to a series of n-alkanes (C8–C40) on capillary column VF5-ms (RI); Identification method: RI, comparison of RIs with those in a self-generated library and with reported in the literature (LRI) [29] and/or with authentic samples; comparison of mass spectra with those in the NIST02 [30] and Wiley 9 mass spectral libraries; * injection of reference compounds; -, not identified; SD, standard deviation of triplicate analysis. Significant differences were determined using 2-way ANOVA followed by Tukey’s multiple comparisons test. a,b,c,d,e,f,g,h,i, Mean values in the same row with different superscript letters indicate a statistically significant difference between data (p < 0.05).
Table 3.
Components of the hydrosols (%) obtained by microwave-assisted water extraction from the aerial parts of Veronica taxa.
Table 3.
Components of the hydrosols (%) obtained by microwave-assisted water extraction from the aerial parts of Veronica taxa.
| V.a austriaca ssp. jacquinii | V. becabunga | V. chamaedrys | V. dalmatica | V. longifolia | V. montana | V. saturejoides ssp. saturejoides | V. serpyllifolia | V. urticifolia | |||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Component | RI | LRI | VC ± SD | VC ± SD | VC ± SD | VC ± SD | VC ± SD | VC ± SD | VC ± SD | VC ± SD | VC ± SD |
| Monoterpene hydrocarbons | 5.13 | - | - | - | 0.75 | 7.09 | - | 1.72 | 44.37 | ||
| α-Thujene | 924 | 924 | - | - | - | - | - | 6.38 ± 0.01 b | - | 1.72 ± 0.01 c | 39.73 ± 0.01 a |
| α-Pinene * | 935 | 932 | 5.13 ± 0.01 a | - | - | - | 0.75 ± 0.01 c | 0.71 ± 0.01 c | - | - | 4.64 ± 0.1 b |
| Oxygenated monoterpenes | 10.17 | 80.76 | 7.35 | - | 17.03 | 8.82 | 24.5 | 7.51 | 4.46 | ||
| γ-Terpinene | 1057 | 1054 | 9.54 ± 0.01 a | - | - | - | - | - | 3.96 ± 0.02 b | 1.49 ± 0.01 c | - |
| Linalool | 1095 | 1095 | - | - | 3.15 ± 0.01 c | - | 7.74 ± 0.01 a | 4.64 ± 0.01 b | - | 4.84 ± 0.01 b | 2.31 ± 0.01 d |
| Terpinen-4-ol | 1174 | 1174 | 0.63 ± 0.1 g | 0.77 ± 0.01 f | 2.45 ± 0.01 d | - | 4.22 ± 0.03 a | 3.91 ± 0.1 b | 3.43 ± 0.01 c | 0.43 ± 0.01 h | 2.15 ± 0.01 e |
| α-Terpineol | 1184 | 1186 | - | - | - | - | 0.43 ± 0.01 b | 0.27 ± 0.01 c | - | 0.75 ± 0.01 a | - |
| trans-p-Mentha-1(7),8-dien-2-ol | 1187 | 1187 | - | 0.13 ± 0.04 d | 1.75 ± 0.01 c | - | 4.64 ± 0.01 b | - | 17.11 ± 0.01 a | - | - |
| Piperitone | 1250 | 1249 | - | 79.86 ± 0.01 | - | - | - | - | - | - | - |
| Menthyl acetate | 1294 | 1294 | - | - | - | - | - | - | - | - | |
| Sesquiterpene hydrocarbons | 8.04 | 5.79 | 6.32 | 1.1 | 4.82 | 7.15 | 9.56 | 16.4 | 4.96 | ||
| E-Caryophyllene * | 1424 | 1417 | 3.54 ± 0.01 e | 4.43 ± 0.01 d | 3.31 ± 0.01 f | 0.42 ± 0.01 i | 2.33 ± 0.01 g | 6.24 ± 0.01 b | 8.49 ± 0.01 a | 5.25 ± 0.01 c | 0.75 ± 0.01 h |
| allo-Aromadendrene | 1465 | 1458 | 1.31 ± 0.01 b | 0.81 ± 0.01 d | 0.42 ± 0.01 g | 0.68 ± 0.07 f | 1.10 ± 0.01 c | 0.71 ± 0.05 ef | 0.75 ± 0.01 e | 3.77 ± 0.01 a | 0.48 ± 0.01 g |
| Germacrene D | 1481 | 1484 | 1.67 ± 0.01 b | 0.55 ± 0.01 e | 0.76 ± 0.01 c | - | 0.65 ± 0.07 d | 0.56 ± 0.01 e | 0.32 ± 0.1 f | 0.24 ± 0.01 g | 3.73 ± 0.01 a |
| δ-Selinene | 1492 | 1492 | 1.52 ± 0.1 c | - | 1.83 ± 0.01 b | - | 0.74 ± 0.01 e | 1.64 ± 0.01 d | - | 5.12 ± 0.01 a | - |
| δ-Cadinene | 1517 | 1522 | - | - | - | - | - | - | - | 2.02 ± 0.1 | - |
| Oxygenated sesquiterpenes | 28.63 | 2.55 | 44.32 | 23.36 | 19.44 | 11.3 | 5.08 | 32.96 | 9.76 | ||
| Spathulenol | 1577 | 1577 | 0.43 ± 0.01 d | - | 1.15 ± 0.01 a | - | 0.63 ± 0.01 c | 0.82 ± 0.01 b | - | 0.57 ± 0.01 c | 0.33 ± 0.04 e |
| Caryophyllene oxide * | 1581 | 1582 | 5.75 ± 0.01 e | 1.79 ± 0.01 h | 18.16 ± 0.01 a | 13.72 ± 0.02 b | 2.27 ± 0.01 g | 8.14 ± 0.01 d | 2.43 ± 0.01 f | 18.83 ± 0.01 a | 9.08 ± 0.01 c |
| Viridiflorol | 1592 | 1592 | 1.17 ± 0.01 b | - | 0.78 ± 0.01 c | - | 2.65 ± 0.1 a | 0.34 ± 0.05 d | - | - | - |
| α-Muurolol | 1645 | 1644 | 18.75 ± 0.01 b | - | 22.45 ± 0.02 a | 9.64 ± 0.01 e | 13.11 ± 0.01 d | - | 1.88 ± 0.01 f | 10.36 ± 0.01 c | - |
| α-Bisabolol | 1685 | 1685 | 1.56 ± 0.01 b | - | 0.83 ± 0.01 c | - | - | - | - | 2.42 ± 0.01 a | 0.35 ± 0.1 d |
| α-Bisabolol oxide | 1748 | 1748 | - | - | - | - | - | - | 0.78 ± 0.01 | - | |
| Hexahydrofarnesyl acetone * | 1839 | - | 0.97 ± 0.01 a | 0.76 ± 0.01 b | 0.95 ± 0.01 a | - | 0.78 ± 0.1 b | - | 0.77 ± 0.05 b | - | - |
| Phenolic compounds | - | 0.85 | 2.01 | 38.81 | 7.87 | 1.68 | 26.65 | 9.63 | 1.56 | ||
| Thymol * | 1289 | 1289 | - | 0.85 ± 0.01 d | - | 38.81 ± 0.01 a | - | 1.03 ± 0.03 c | - | 2.54 ± 0.01 b | 0.65 ± 0.12 e |
| p-Vinyl guaicol | 1313 | 1309 | - | - | 1.15 ± 0.01 c | - | 3.11 ± 0.01 a | 0.65 ± 0.01 e | 2.42 ± 0.01 b | 0.66 ± 0.01 e | 0.91 ± 0.05 d |
| Methyl eugenol | 1403 | 1403 | - | - | 0.86 ± 0.05 d | - | 4.76 ± 0.01 c | - | 24.23 ± 0.01 a | 6.43 ± 0.01 b | - |
| Common group | 42.97 | 3.42 | 32.66 | 31.1 | 44.51 | 60.2 | 27.73 | 25.09 | 27.99 | ||
| Isopentyl acetate | 863 | 869 | 5.25 ± 0.03 a | - | - | - | - | - | - | - | 4.93 ± 0.01 b |
| Benzaldehyde | 952 | 952 | 7.86 ± 0.01 e | 1.51 ± 0.01 g | 2.11 ± 0.13 f | 15.32 ± 0.01 b | 13.05 ± 0.01 d | - | 18.52 ± 0.01 a | - | 13.32 ± 0.01 c |
| Benzene acetaldehyde | 1036 | 1036 | 19.02 ± 0.01 b | 0.43 ± 0.1 h | 5.43 ± 0.01 e | 5.77 ± 0.01 e | 10.23 ± 0.01 c | 19.52 ± 0.01 a | 3.77 ± 0.01 f | 4.33 ± 0.01 g | 6.15 ± 0.03 d |
| n-Nonanal | 1100 | 1100 | 1.57 ± 0.01 b | - | - | 0.26 ± 0.01 d | 0.65 ± 0.01 c | - | - | 3.93 ± 0.01 a | - |
| Hexyl-2-methyl butanoate | 1233 | 1229 | - | - | 2.76 ± 0.01 | - | - | - | - | - | - |
| n-Decanol | 1266 | 1266 | - | - | - | - | 0.72 ± 0.01 c | 4.64 ± 0.01 a | - | 0.42 ± 0.01 d | 1.47 ± 0.01 b |
| Bornyl acetate | 1285 | 1287 | - | - | 11.85 ± 0.01 | - | - | - | - | - | - |
| (E)-β-Damascenone | 1384 | 1383 | 0.45 ± 0.01 e | - | 3.35 ± 0.01 d | - | 8.32 ± 0.01 b | 36.04 ± 0.01 a | - | 4.95 ± 0.01 c | - |
| β-Ionone | 1487 | 1487 | 7.04 ± 0.01 c | 1.48 ± 0.01 f | 7.16 ± 0.01 c | 9.75 ± 0.01 b | 11.54 ± 0.01 a | - | 5.44 ± 0.02 d | 11.46 ± 0.01 a | 2.12 ± 0.01 e |
| Hexadecanoic acid * | 1959 | 1959 | 0.78 ± 0.07 | - | - | - | - | - | - | - | |
| Total identification (%) | 93.94 | 93.37 | 92.66 | 94.37 | 94.42 | 96.04 | 93.52 | 93.31 | 93.1 |
Retention indices (RIs) were determined relative to a series of n-alkanes (C8–C40) on capillary column VF5-ms (RI); Identification method: RI, comparison of RIs with those in a self-generated library and with reported in the literature (LRI) [29] and/or with authentic samples; comparison of mass spectra with those in the NIST02 [30] and Wiley 9 mass spectral libraries; *, injection of reference compounds; -, not identified; SD, standard deviation of triplicate analysis. Significant differences were determined using 2-way ANOVA followed by Tukey’s multiple comparisons test. a,b,c,d,e,f,g,h,i, mean values in the same row with different superscript letters indicate a statistically significant difference between data (p < 0.05).
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Nazlić, M.; Kremer, D.; Akrap, K.; Topić, S.; Vuletić, N.; Dunkić, V. Extraction, Composition and Comparisons–Free Volatile Compounds from Hydrosols of Nine Veronica Taxa. Horticulturae 2023, 9, 16. https://doi.org/10.3390/horticulturae9010016
AMA Style
Nazlić M, Kremer D, Akrap K, Topić S, Vuletić N, Dunkić V. Extraction, Composition and Comparisons–Free Volatile Compounds from Hydrosols of Nine Veronica Taxa. Horticulturae. 2023; 9(1):16. https://doi.org/10.3390/horticulturae9010016
Chicago/Turabian StyleNazlić, Marija, Dario Kremer, Karla Akrap, Snježana Topić, Nenad Vuletić, and Valerija Dunkić. 2023. "Extraction, Composition and Comparisons–Free Volatile Compounds from Hydrosols of Nine Veronica Taxa" Horticulturae 9, no. 1: 16. https://doi.org/10.3390/horticulturae9010016
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