The aim of the present study was to investigate the effect of the level and timing of watering on the productivity and chemical constituents of lemon balm (Melissa officinalis L. cv. 'Soroksár'). As control 70% soil water capacity was set. In treatments stress1 and stress2 the soil water capacity decreased stepwise from 70% to 30% and sharply from 70% to 30%, respectively. In the strongest and permanent water deficit treatment stress3 30% soil water capacity was applied. Among the production parameters the water deficit reduced the plant height, bush diameter, fresh and dry mass of the plants. Besides, the root:shoot ratio increased, while in the root length, fresh and dry mass no significant differences were detected. Water deficit also influenced the phenolic compounds. Under stress1 and stress2 circumstances decreased accumulation of flavonoids (by 14-22%) was observed while the drought conditions resulted in enhancement in the rosmarinic acid concentration (1-22% compared to the control). The highest antioxidant capacity (201 mg ascorbic acid equivalent g -1 dry mass) and total phenolic content (178 mg gallic acid equivalent g -1 dry mass) were measured in treatment stress3 where permanent 30% soil water capacity was applied, while the stress2 plants produced the lowest antioxidant capacity (66 mg ascorbic acid equivalent g -1 ) and total phenolic content (105 mg gallic acid equivalent g -1 ). The gradually decreasing water supply did not modify antioxidant capacity and total phenolic content. The results show that not only the level of water deficit, but its timing and dynamics may have significant effects on the quantity and quality of lemon balm production.

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Furocoumarins are known for their phototoxic and potential carcinogenic effects. These types of compounds have previously been reported from fennel (Foeniculum vulgare Mill.), a widely used medicinal plant and spice; however, no reliable quantitative data are available on the occurrence of these compounds in fennel fruits. For the first time, we report a comprehensive analysis of fennel fruit samples of different origins, representing a wide range of accessions for their furocoumarin content. Psoralene, 5-methoxypsoralene (bergapten), and imperatorin contents of 33 fennel samples were analyzed using a sensitive liquid chromatography-mass spectrometry (LC-MS) method. When applied at the highest therapeutic dose described in the monograph issued by the European Medicines Agency, the furocoumarin content of the fruits ranged up to 1.22 μg/d, which is below the most restrictive recommendations. Based on our findings, fennel consumption can be considered as safe, at least based on its low furocoumarin content.

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 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 in 2015, respectively). The highest TPC values were measured by PS3 in 2014 (204.320 ± 1.822 mg GAE g) and GB in 2015 (136.450 ± mg GAE g). The 588P produced the highest essential oil content (1.432 ml 100 g DM) while J3 had the lowest (0.144 ml 100 g 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.

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).

The reactions of lemon balm, marjoram, peppermint, thyme were investigated and compared in a pot experiment, adjusting 70% and 40% of soil water capacity (SWC). Biomass, total phenolic content (TPC), rosmarinic acid content (RA) and antioxidant capacity (FRAP, DPPH) of both the shoots and roots were measured. As an universal phenomenon the water stress (40% SWC) decreased the total biomass production of all species drastically. The highest increase was observed in the shoot mass of peppermint and lemon balm (decreased from 52.6 g•plant-1 to 11.3 g•plant-1 and from 236.8 g•plant-1 to 58 g•plant-1 , respectively). The reaction of marjoram was much more moderate. The accumulation level of TPC was accelerated in the aboveground parts of the studied species, universally. The reactions in the roots were less characteristic. The largest increase of TPC was measured in the shoots of lemon balm (from 359.015 mg GAE• g-1 d.w. up to 412.44 GAE•g-1 d.w.). The reaction of marjoram was the less characteristic in this respect, as well. The parallel changes of biomass and TPC level might allow the total phenolic content to function as an adequate marker in predicting the lack of appropriate water supply. RA content showed species characteristics. Thyme, marjoram and peppermint reacted by a significant elevation (by 23-127%) of the RA content to the lack of water. The highest proportions were accumulated in shoots of the stressed thyme plants (3.45% d.w.).

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