Chemophenetics of Azorean Leontodon taxa (Cichorieae, Asteraceae)

Seasonal variations in phenolic natural products in Fagus sylvatica (European beech) leaves

Fagus sylvatica L. (Fagaceae), European beech, is one of the most important deciduous tree species in Central Europe and the most common broadleaved tree species in Germany. We investigated the leaves of six individual Fagus sylvatica trees growing in a beech forest in Kiel, Schleswig-Holstein, Germany, for seasonal variations in the content of phenolic natural products over three consecutive growing seasons. The investigated compound classes comprised hydroxycinnamic acid and flavonoid derivatives. The content of phenolic compounds showed clear trends in all years. A sharp decline in the total content of phenolic substances was observed from mid-April to the end of May. During the summer months, the content of phenolic compounds remained stable with only slight fluctuations until fall. The values for individual trees deviated more pronouncedly from one another in spring, but converged during the course of the growing period. These trends, despite differences in absolute values, were identical in three consecutive growing seasons (2016-2018). Our results contribute to a better understanding of the dynamics of plant natural products of deciduous trees in temperate climates caused by seasonal variations.

Application of Box-Behnken design for optimization of phenolics extraction from Leontodon hispidulus in relation to its antioxidant, anti-inflammatory and cytotoxic activities

To the best of our knowledge, there have been no phytochemical studies concerning the wild plant Leontodon hispidulus Boiss. (Asteraceae). Optimization of the green extraction process of the plant aerial parts, identification of main phenolic compounds, evaluation of antioxidant, anti-inflammatory and anticancer activities of the optimized extract have been carried out. HPLC-analysis was performed using 95% ethanolic extract. 3-Level Box-Behnken Design was applied for optimization of extraction yield and total phenolic content using 3-factors (ethanol/water ratio, material/solvent ratio and extraction time). Antioxidant, anticancer and anti-inflammatory activities were evaluated by ABTS-assay, prostate and cervical carcinoma human cell lines and carrageenan-induced rat paw edema model, respectively. HPLC-analysis showed the presence of quercetin, rutin, kaempferol, chlorogenic and ρ-coumaric acids. Increasing both ethanol/water ratio and material/solvent ratio decreased the yield, while, it increased by prolongation of the extraction time. High material/solvent ratio increased the phenolic content. The optimized extract showed high total phenolic content (104.18 µg/mg) using 201 ml of 74.5% ethanol/water at 72 h and good biological activities. Antioxidant activity was found to be 41.89 mg Trolox-equivalent/gm, with 80% free radicals inhibition. For anti-inflammatory activity, 100 mg/kg of the extract inhibited the edema in rats by 83.5% after 4 h of carrageenan injection as compared to 81.7% inhibition by indomethacin. Prostate carcinoma cell line was more sensitive to the anticancer activity of the extract than cervical carcinoma cell line (IC50 = 16.5 and 23 μg/ml, respectively). The developed extraction procedure proved to be efficient in enriching the extract with phenolic compounds with promising anticancer, anti-inflammatory and antioxidant activities.

Cytotoxic constituents and a new hydroxycinnamic acid derivative from Leontodon saxatilis (Asteraceae, Cichorieae)

In our ongoing research for the discovery of new constituents with antimyeloma activity, we investigated 15 compounds present in the aerial parts of Leontodon saxatilis for their cytotoxic potential against NCI-H929, U266, and OPM2 cell lines. One of the isolated compounds displayed a new natural product and was identified as 5-feruloyl-2α-hydroxyquinic acid after LC-MS and NMR experiments. Of the remaining compounds, cichoric acid and three flavone glycosides, apigenin 4′-O-β-d-glucoside, luteolin 7-O-β-d-glucoside and luteolin 4′-O-β-d-glucoside, showed moderate cytotoxic activity, whereas the effects of two aglyones apigenin and luteolin were more pronounced. Though the cytotoxic potential of the two aglycones (against other cell lines) was reported in various studies, our work moreover showed that cooccurrence of these two compounds with similar components of lower activity led to comparable results and at the same time minimized the damage of healthy fibroblast cells. Thus, our work could be a starting point for additional studies on the synergistic effect of similar components against myeloma cell lines.

Phytochemical investigation of the aerial parts of Leontodon saxatilis yielded six compounds with antimyeloma activity as well as crepidiaside A as a chemophenetic marker and 5-feruloyl-2α-hydroxyquinic acid as a new hydroxycinnamic acid derivative.