Abstract
Epilobium parviflorum Schreb. is used in folk and modern medicine for the treatment of prostate diseases. It is also known to alleviate gastrointestinal ailments. The aim of the present study is to define the chemical composition of diverse extracts from the herb, to test their inhibitory properties toward post-proline-specific peptidases and to elucidate the mechanisms of their antitumor activity on colorectal carcinoma cells in vitro. The extractions were performed using mono- or biphasic systems of solvents. Their chemical compositions were defined by LC-HRMS. Inhibitory properties towards prolyloligopeptidase (POP) and fibroblast activation protein (FAP) were studied by kinetic assays on human recombinant enzymes. Antioxidant activity was measured by three methods. Genotoxicity to HT-29 colorectal carcinoma cells was analyzed with the comet assay. FACS analyses and flow cytometry were used to evaluate the extracts effect on the cell cycle and their pro-apoptotic properties on HT-29 cells. The extract derived using 80% ethanol was chosen for the next studies due to its efficient and selective inhibition of POP. It contains mainly oenotein B and myricetin-3-O-rhamnoside. Its antioxidant and moderate genotoxic activities can contribute to the antitumor effect on HT-29 cells. The extract has a small effect on the cell cycle but a pronounced pro-apoptotic action on those cells. In conclusion, the 80% ethanol extract of E. parviflorum concentrates the ellagitannin oenotein B, which is a selective inhibitor of POP. Antitumor activity of the extract towards HT-29 cells may be due to the inhibition of POP, the antioxidant, genotoxic and pro-apoptotic activities.