Isolation of Secondary Metabolites from Achillea grandifolia Friv. (Asteraceae) and Main Compounds' Effects on a Glioblastoma Cellular Model.

This study aims at the isolation and structural determination of the secondary metabolites of the herbaceous perennial plant Achillea grandifolia Friv. (Asteraceae). The examination of the non-volatile content of the leaves and flowers of A. grandifolia afforded the isolation of sixteen secondary metabolites. On the basis of NMR spectra, the identified compounds included ten sesquiterpene lactones; three guaianolides-rupicolin A (1), rupicolin B (2), and (4S,6aS,9R,9aS,9bS)-4,6a,9-trihydroxy-9-methyl-3,6-dimethylene-3a,4,5,6,6a,9,9a,9b-octahydro-3H-azuleno [4,5-b]furan-2-one (3); two eudesmanolides-artecalin (4) and ridentin B (5); two sesquiterpene methyl esters-(1S,2S,4αR,5R,8R,8αS)-decahydro-1,5,8-trihydroxy-4α,8-dimethyl-methylene-2-naphthaleneacetic acid methylester (6) and 1ß, 3ß, 6α-trihydroxycostic acid methyl ester (7); three secoguaianolides-acrifolide (8), arteludovicinolide A (9), and lingustolide A (10); and an iridoid-loliolide (11). Moreover, five known flavonoids, i.e., apigenin, luteolin, eupatolitin, apigenin 7-O-glucoside, and luteolin 7-O-glucoside (12-16) were also purified from the aerial parts of the plant material. We also investigated the effect of rupicolin A (1) and B (2) (main compounds) on U87MG and T98G glioblastoma cell lines. An MTT assay was performed to define cytotoxic effects and to calculate the IC50, while flow cytometry was employed to analyze the cell cycle. The IC50 values of reduced viability during the 48 h treatment for compound (1) and (2) were 38 µM and 64 µM for the U87MG cells and 15 µM and 26 µM for the T98G cells, respectively. Both rupicolin A and B induced a G2/M cell cycle arrest.

Therapeutic Potential of Linearol in Combination with Radiotherapy for the Treatment of Glioblastoma In Vitro.

Glioblastoma is one of the most malignant and lethal forms of primary brain tumors in adults. Linearol, a kaurane diterpene isolated from different medicinal plants, including those of the genus Sideritis, has been found to possess significant anti-oxidant, anti-inflammatory and anti-microbial properties. In this study, we aimed to determine whether linearol could exhibit anti-glioma effects when given alone or in combination with radiotherapy in two human glioma cell lines, U87 and T98. Cell viability was examined with the Trypan Blue Exclusion assay, cell cycle distribution was tested with flow cytometry, and the synergistic effects of the combination treatment were analyzed with CompuSyn software. Linearol significantly suppressed cell proliferation and blocked cell cycle at the S phase. Furthermore, pretreatment of T98 cells with increasing linearol concentrations before exposure to 2 Gy irradiation decreased cell viability to a higher extent than linearol or radiation treatment alone, whereas in the U87 cells, an antagonistic relationship was observed between radiation and linearol. Moreover, linearol inhibited cell migration in both tested cell lines. Our results demonstrate for the first time that linearol is a promising anti-glioma agent and further studies are needed to fully understand the underlying mechanism of this effect.

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

Thymus holosericeus Celak. (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.