Exploring essential oils of Slovak medicinal plants for insecticidal activity: The case of Thymus alternans and Teucrium montanum subsp. jailae.

Thymus alternans and Teucrium montanum subsp. jailae are medicinal and aromatic plants, typical of Slovakian flora, producing bioactive essential oils. In the present study, we evaluated the insecticidal potential of the essential oils, obtained by hydrodistillation from the plant aerial parts and analysed by GC-MS, as insecticidal agents. For the purpose, they were assayed against three insect species acting as agricultural pests or vectors of medical relevance, such as the common housefly, Musca domestica L., the lymphatic filariasis vector, Culex quinquefasciatus and the Egyptian cotton leafworm Spodoptera littoralis; α-cypermethrin was tested as positive control. The two essential oils exhibited a different chemical profile, with monoterpenes and sesquiterpenes being the main fractions in the essential oils from Th. alternans and T. montanum subsp. jailae, respectively. Insecticidal tests showed that the T. montanum essential oil was effective against S. littoralis (LD50(90) = 56.7 (170.0) µg larva-1) and Cx. quinquefasciatus larvae (LC50(90) = 180.5 (268.7) mg L-1), whereas T. alternans essential oil displayed good toxicity against M. domestica adults (LD50(90) = 103.7 (223.9) µg adult-1). Overall, our results add useful knowledge about the potential of Slovakian flora as a source of botanicals for the eco-friendly management of insect pests and vectors.

Phytochemical investigations and antiproliferative secondary metabolites from Thymus alternans growing in Slovakia.

CONTEXT: Thymus alternans Klokov (Lamiaceae) is a neglected species of the genus Thymus (Sect. Serpyllum) endemic to Carpathian area, where it is used as a flavouring agent and for medicinal purposes. OBJECTIVE: The aim of the work was to identify antiproliferative constituents from the flowering aerial parts of this plant. MATERIALS AND METHODS: Thymus alternans extracts were analyzed by HPLC-MSn and subjected to extensive chromatographic separations. The isolated compounds (phenolics and triterpenes) were structurally elucidated by MS and 1D and 2D NMR experiments. Essential oil (EO) composition was determined by GC-FID and GC-MS. Six purified triterpenes and EO were assayed for in vitro antiproliferative activity against a panel of human cancer cells, namely, breast (MDA-MB 231), colon (HCT-15 and HCT116), lung (U1810), pancreatic (BxPC3), melanoma (A375) and cervical carcinoma (A431) cells. RESULTS: The structures of the isolated compounds were achieved on the basis of H-NMR and MS experiments. Luteolin-4'-O-ß-d-glucopyranoside (P1), chrysoeriol-7-O-ß-d-glucopyranoside (P2), chrysoeriol-5-O-ß-d-glucopyranoside (P3), apigenin-7-O-ß-d-glucopyranoside (P4), rosmarinic acid (P5), rosmarinic acid-3'-O-ß-d-glucopyranoside (P6), caffeic acid-3-O-ß-d-glucopyranoside (P7), 3α-hydroxy-urs-12,15-diene (T1), α-amyrin (T2), ß-amyrin (T3), isoursenol (T4), epitaraxerol (T5), and oleanolic acid (T6). GC-MS analysis revealed that the EO of T. alternans was devoid of phenols and belonged to the nerolidol-chemotype, that is typical of the Sect. Serpyllum. The six purified triterpenes (T1-T6) were active with IC50 ranging from 0.5 to 5 µM being comparable or better than those of reference compounds betulinic acid and cisplatin. The EO exhibited significant effects on A375, MDA-MB 231 and HCT116 cell lines with IC50 in the range of 5-8 µg/mL. CONCLUSION: The reported results suggest that T. alternans can be considered as a good source of phytoconstituents with possible importance in the pharmaceutical field.

Antimicrobial and antioxidant activity of the essential oil from the Carpathian Thymus alternans Klokov.

The genus Thymus includes several species that are used as flavouring, food preservative as well as in cosmetics. Their secondary metabolites have been extensively studied for pharmacological effects. Nonetheless, some species are neglected and deserve to be explored for chemical composition and biological activities. This is the case with Thymus alternans, a Carpathian bush used as a food additive and for the preparation of a traditional herbal medicine. In this work, we have analysed the chemical composition of T. alternans essential oil by GC and GC-MS and evaluated its antimicrobial and antioxidant activity by disc diffusion, DPPH, ABTS and FRAP methods, respectively. Results showed that T. alternans belongs to the nerolidol chemotype, being rich of this sesquiterpene alcohol (15.8%) which might contribute to the antimicrobial (particularly effective on C. albicans growth) and antioxidant (weak inhibition on ABTS radical and reducing power) activities observed.

Two New Isomers of Palmityl-4-hydroxycinnamate from Flowers of Taraxacum Species.

Two isomers, (Z)- and (E)-palmityl 4-hydroxycinnamate [hexadecyl(2Z)-3-(4-hydroxyphenyl)prop-2-enoate and hexadecyl(2E)-3-(4-hydroxyphenyl)prop-2-enoate] were isolated for the first time from ligulate flowers of Taraxacum linearisquameum Soest (sect. Taraxacum). The highest amount of these compounds was detected in pollen grains; 0.26 mg/100 mg DW of the (E)-isomer and 0.096 mg/100 mg DW of the (Z)-isomer. The structures of these compounds were elucidated by a combination of HPLC-ESI-Qtof-MS and 1D and 2D NMR spectroscopy. Their presence was confirmed in other species of Taraxacum, but they were not found in the male - sterile triploid agamospermous taxon T. parnassicum.

Volatile components of whole and different plant parts of bastard balm (Melittis melissophyllum L., Lamiaceae) collected in Central Italy and Slovakia.

The aim of this work was to trap the volatiles released from whole frozen and dry aerial parts, and, separately, from different organs (leaves, stems, corolla and calyx) of bastard balm (Melittis melissophyllum L., Lamiaceae) populations collected in Italy and Slovakia by HS-SPME, and to identify the headspace constituents responsible for the characteristic aroma impression by GC/FID and GC/MS techniques. Among more than 100 volatile components detected, the C(8) alcohol oct-1-en-3-ol, responsible for the typical mushroom-like odor, and the phenolic coumarin, with a characteristic sweet and creamy vanilla bean odor, played a major role in the aroma of whole aerial parts and different plant organ samples. In particular, dry calyx parts could be proposed as flavoring agent in food products as mushroom aroma enhancer. Multivariate chemometric techniques, such as cluster analysis and principal component analysis, were used to characterize the sample populations according to the geographical origin and processing of plant material.