Péter Radácsi

Changes in biomass and essential oil profile of four Lamiaceae species due to different soil water levels

Abstract The reactions of Majorana hortensis, Melissa officinalis, Mentha piperita and Thymus vulgaris were investigated in controlled conditions to compare their responses on drought stress concerning yield, essential oil (EO) content and composition. Biomass and essential oil concentration were significantly decreased in each species similarly, if they were grown at 40% level of soil water capacity (SWC) compared to the ones growing at 70% SWC. The largest changes were detected in lemon balm (4.47-fold difference in biomass, 2.78-fold difference in EO content) while the response of marjoram was the modest one (1.95-fold in biomass, 1.21-fold in EO content). We found species specific quantitative modifications in the EO composition. The ratio of terpinene-type components increased in the EO of both thyme and marjoram to the expense of their characteristic compounds thymol, carvacrol and sabinyl compounds, respectively. The composition of lemon balm and peppermint, however, did not show considerable changes.

Studies on Occurence, Essential Oil Data and Habitat Conditions of Hungarian Thymus pannonicus and Thymus glabrescens Populations

Thymus pannonicus and T. glabrescens flowering shoots are gathered from wild populations. Dried aerial parts contain active compounds used in the therapy of coughing and possess strong antimicrobial activity. Eight natural habitats, involving 17 populations of the two species were found in 2010, where the essential oil characteristics of the flowering shoots and soil parameters have been determined. The highest essential oil level (1.079 mL/100 g) have been detected in the T. pannonicus sample collected near Balatongyorok. Concerning average essential oil amounts, T. pannonicus samples accumulated 0.566 mL/100 g, while those of T. glabrescens produced 0.083 ml/100 g. High thymol ratio is an important qualitative trait: fairly high levels (51.1-65.6%) were found in samples of T. pannonicus. T. pannonicus population, growing on rhyolite tuff in Bukk Mountains, had low essential oil content with sesquiterpene chief compounds and without thymol. Regarding essential oils of T. glabrescens, the major compounds were sesquiterpenes (germacrene D, β-caryophyllene, caryophyllene oxide), with low amount of thymol (<5%). Our results approve data of the previous literature, concerning generalist and pioneer characters of both species with eurytopic attitude, tolerating different soil parameters (pH, salt %, NPK and CaCO3 content). Strong positive correlation have been found between the p-cymene and γ-terpinene ratios (r=0.951), while the latter compounds were in medium positive correlation with thymol percentage (r=0.387 and 0.481, respectively). It was also proven statistically that the essential oil content correlated negatively with high ratio of sesquiterpenes.

Effect of water supply on growth and polyphenols of lemon balm (Melissa officinalis L.) and thyme (Thymus vulgaris L.)

A pot experiment was carried out with lemon balm (Melissa officinalis L.) and thyme (Thymus vulgaris L.). Different water supply was applied: 25%, 40% and 70% saturation of soil water capacity (SWC). Morphological traits, biomass and phenolic type active ingredients were investigated. Among the two species, main differences were registered in biomass and TPC. Lower SWC resulted in reduced biomass production of lemon balm, while the applied stress treatments did not effect the biomass of thyme. In lemon balm, highest TPC contents were measured in control plants both in shoots and roots but in thyme, the shoots showed a significantly increased TPC at the 25% SWC conditions. Neither the content of total flavonoids nor that of the rosmarinic acid was affected by the treatments. The antioxidant capacity proved to be in tight connection with the TPC in both species (r = 0.766-0.883). The rosmarinic acid content of lemon balm plants contributed to the antioxidant capacity, as well (r = 0.679-0.869).

Morphological, phytochemical and molecular characterization of intraspecific variability of wormwood ( Artemisia absinthium L.)

A trial with nine wormwood accessions was installed to carry out a systematic evaluation of intraspecific diversity. Six morphological features, essential oil (EO) yield and thujone content were measured. Besides, 11 RAPD and 15 ISSR molecular markers were tested to determine the genetic diversity of the accessions. The experiment was carried out in open field in 2016.Accession “Pakozd” exhibited largest growth (64.9 cm) and genotype “Norwegen” was the smallest (29.9 cm). This latter accession had also the smallest but thickest leaves. Concerning morphological features, the Norwegian population was the most homogenous one (CV%: 10.6-20.1) while “Belgin” brought about largest variability (CV%: 18.4-45.3).Based on EO yield, the studied accessions were divided into three significantly diverse groups. The highest yield was produced by “Spanish” accession (3.215 ml/100 g), “Norwegen” and “Belgien” produced medium values (1.569-1.892 ml/100 g) and six accessions showed EO yields below 1% (0.349-0.832 ml/100 g). Three acces-sions (“Leipzig”, “Belgien” and “Norwegen”) had high amount of thujone in the oil (50-89%) while in all other accessions thujones were absent or present only below 1%. “Belgien” accession had balanced ratio of α- and β-thujones while in the other ones β-thujone was the absolute main component.High polymorphism was found among the wormwood accessions also by molecular markers: 81.15% for RAPD and 73.10% for ISSR primers. Based on the Nei’s genetic distances the three groups of genotypes were identical to those in the case of EO yield.The study confirmed the large intraspecific variability of wormwood but revealed that it is not definitely connected to geographical origin of the populations.

Influence of water supply and fluctuations on yield and quality of lemon balm (Melissa offici-nalis L.)

The response of lemon balm (Melissa officinalis) on drought stress was investigated in a pot experiment in 2015-16. In treatment S1, plants grew in 40% saturation of soil water capacity (SWC) for six weeks. In treatment S2, the same level of water supply was used for three weeks, while the control plants received irrigation up to 70% SWC throughout the experimental period. In the second year, after the stress period, a 3 week re-hydration phase was also carried out. Growth, morphology, biomass, active components and antioxidant capacity of the plants were measured. Six weeks growth at reduced soil water content (40% soil water capacity) resulted in a significant decrease of all morphological features of lemon balm as well as the fresh mass of shoots, as compared to the control (70% SWC). The effect of the shorter drought treatment (3 weeks) was less characteristic. After the three week recovery period no significant difference concerning number of branches, leaf length and fresh shoot mass was detectable among the plants. Thus, the retarding effect of even the 6 week drought stress (S1) was reversible in lemon balm. The changes in active components (volatile compounds, phenolics, rosmarinic acid) and antioxidant capacity did not show meaningful changes due to the treatments. After a three-week re-hydration period a significant increase was found in each parameter. It was established that a six week period of water shortage (water content of 40% SWC) could threaten the yield of lemon balm, although re-hydration by regular irrigation may induce significant recovery. The impact of water shortage on the quality of the drug was less critical.

Comparison of the production and chemical constituents of five Perilla frutescens (L.) Britt. accessions

An open field experiment was carried out with five purple Perilla frutescens accessions (588P, GB, J3, JTD3, PS3) in 2014 and 2015. Morphological traits, production, total phenolic content (TPC), essential oil content (EOC) and composition as well as the antioxidant capacity (AOC) were investigated. Highest biomass was produced by JTD3 in both years. The antioxidant capacity and total phenolic content in the stems was lower than in the leaves in all accessions. Leaves of accession GB produced the highest AOC values (215.594 ± 1.437 in 2014 and 86.609 ± 3.602 mg AAE g-1 in 2015, respectively) while the strain 588P showed the lowest values (139.544 ± 1.934 in 2014 and 38.966 ± 4.569 mg AAE g-1 in 2015, respectively). The highest TPC values were measured by PS3 in 2014 (204.320 ± 1.822 mg GAE g-1) and GB in 2015 (136.450 ± mg GAE g-1). The 588P produced the highest essential oil content (1.432 ml 100 g-1 DM) while J3 had the lowest (0.144 ml 100 g-1 DM) in both years. Strong positive correlation was found between the density of glandular hairs and the essential oil content. Three accessions (588P, J3, JTD3) belong to the perillaldehyde chemotype while GB and PS3 to the dehydro elsholtzia ketone chemotype. All studied accessions can be cultivated in Hungary. For the biomass production the JTD3, while for the essential oil production the 588P can be recommended.