Composition of the Essential Oils ofThymus leucostomusHausskn. et Velen var.gypsaceusJalas andThymus pubescensBoiss. et Kotschy ex Celak var.cratericolaJalas

LC-MS/MS and GC-MS profiling, antioxidant, enzyme inhibition, and antiproliferative activities of Thymus leucostomus H ausskn. & V elen. extracts

The chemical composition as well as antioxidant, antiproliferative, and enzyme inhibition activities of extracts from aerial parts of Thymus leucostomus H ausskn. & V elen. obtained with hexane, methanol, and water were evaluated. Results showed that the methanol extract had significantly (p < 0.05) the highest total phenolic content (TPC; 107.80 mg GAE/g) and total flavonoids content (TFC; 25.21 mg RE/g) followed by the aqueous extract (102.72 mg GAE/g and 20.88 mg RE/g, respectively). LC-MS/MS-guided profiling of the three extracts revealed that rosmarinic acid (34.8%), hesperetin (42.9%), and linoleic acid (18%) were the dominant compounds in the methanol, aqueous and hexane extracts, respectively. GC-MS analysis of the hexane extract showed that ɣ-sitosterol (29.9%) was the major constituent. The methanol extract displayed significantly (p < 0.05) the highest Cu++ , Fe+++ , and Mo(VI) ions scavenging and reducing properties while the aqueous extract exerted significantly (p < 0.05) the highest metal chelating power (42.51 mg EDTAE/g). Both the hexane and methanol extracts effectively inhibited the acetylcholinesterase enzyme (2.63 and 2.65 mg GALAE/g, respectively) while the former extract exerted significantly (p < 0.05) the highest butyrylcholinesterase (2.32 mg GALAE/g), tyrosinase (19.73 mg KAE/g), and amylase (1.16 mmol ACAE/g) inhibition capacity. The aqueous extract exhibited the best glucosidase inhibition property (0.49 mmol ACAE/g). The methanol and hexane extracts exerted a higher cytotoxic effect on HT-29 (IC50 : 8.12 µg/mL) and HeLa (IC50  = 8.08 µg/mL) cells, respectively. In conclusion, these results provide valuable insight into the potential use of T. leucostomus bioactive extracts in different pharmaceutical applications.

Exploring the Ecological Preferences and Essential Oil Variability in Wild-Growing Populations of the Endangered Local Greek Endemic Thymus holosericeus (Lamiaceae)

Thymus holosericeus Čelak. (Lamiaceae) is a taxonomically isolated and endangered local endemic thyme species which is geographically isolated in four Ionian Islands (West Greece). The present study investigated the essential oil (EO) composition, the ecological preferences, and their correlations in three T. holosericeus wild-growing populations from Zakynthos (ΤH-Z), Cephalonia (ΤH-C) and Lefkada (ΤH-L). The variations in essential oil yield and the composition of T. holosericeus populations were evaluated using hydrodistillation, GC/MS, TLC and NMR analysis. The climatic conditions of each sample were organized and analyzed in RStudio with the raster package and in SPSS with Pearson's Canonical Correlation Analysis (CCA), respectively. The aerial parts of the plants varied in EO yields from 1.92 to 2.28% w/v. The analysis of EO constituents revealed noteworthy qualitative and quantitative inter-population variation. The composition of EOs revealed the presence of linalool (82.77%) and borneol (5.95%) as major compounds in ΤH-Z, while carvacrol (35.34%), geraniol (23.98%), linalool (14.37%), borneol (5.66%), thymol (4.27%) and p-cymene (4.08%) were the main compounds in ΤH-C and linalool (40.37%), geraniol (39.42%) and borneol (5.20%) were dominant components in ΤH-L. The results of the gas chromatography procedure have also been confirmed by ¹H and ¹³C-NMR and TLC analysis. The ecological profile showed an average annual precipitation of 942 ± 18.33 mm and the temperature limits in which T. holosericeus seems to adapt to are 6.80± 1.08 °C 27.70 ± 0.70 °C. Regarding the examined samples, TH-C was adapted to the driest summer and coldest winter conditions, TH-Z was adapted to the lowest annual precipitation with the most complex climatic conditions, and TH-L was adapted to the highest summer temperatures with the lowest precipitation in the wettest period of the year. For each sampled population, the CCA identified the association of the samples' EOs composition with the prevailing local environmental conditions.

Chemical Composition of the Essential Oil of Thymus longicaulis C. Presl. subsp. longicaulis

In this study, the chemical composition of the essential oils obtained from the aerial parts of Thymus longicaulis subsp. longicaulis naturally grown in Turkey were analyzed by GC and GC-MS and chemical differences in terms of chemotaxonomy were discussed. The main compounds in the essential oils of T. longicaulis subsp. longicaulis essential oils were 1,8-cineole (30.1%), linalool (18.0%), β-pinene (17.3%) and (E)-β-ocimene (%12.6%) Hierarchical cluster analysis was performed by examining essential oil studies of 34 samples belonging to the genus Thymus, including the Sinop sample. The results of the study were discussed with other taxa belonging to the genus.

Evaluation of the antioxidant capacity and phenolic content of three Thymus species

Thymus species are known to have significant amounts of phenolic and flavonoid compounds and exhibit strong antioxidant activities. This work was designed to evaluate the antioxidant activities of three endemic Iranian Thymus species (including T. daenensis, T. kotschyanus, and T. pubescens) in different test systems [namely DPPH() (2,2'-diphenyl-1-picrylhydrazyl), ABTS(+) [2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid], and linoleic acid/β-carotene bleaching assays] to determine the total phenolic and flavonoid contents of the species (assayed by colorimetric techniques) and to study the possible composition-activity relationship. All the tested plants exhibited concentration-dependent antioxidant and free radical scavenging activities. T. pubescens showed the highest free radical scavenging activities in both DPPH() and ABTS(+) methods, while T. daenensis and T. kotschyanus were the most active species in the β-carotene bleaching inhibition test. Alternatively, T. pubescens exhibited a significantly higher level of the total flavonoid content compared with those of the other species, while no significant statistically differences were found among the tested plants regarding the total phenolic content. In addition, significant correlations were found between the flavonoid content and DPPH()/ABTS(+) radical scavenging activities, but not between the β-carotene bleaching inhibition system and the flavonoid content.