In Vitro Investigation of the Cytotoxic and Antiproliferative Effects of Haberlea rhodopensis Total Extract: A Comparative Study

Haberlea rhodopensis Friv., known also as Rhodope silivryak and the Orpheus flower, is a Balkan endemic “resurrecting” plant belonging to the Gesneriaceae family. In folk medicine, the leaves of Haberlea rhodopensis Friv. were widely used to treat wounds and some infectious diseases of stock such as foot-and-mouth disease and hoof rot, while the herb of Haberlea rhodopensis Friv. is still used to cleanse the stomach, liver, kidneys, and blood vessels. Because of the content of myconoside, during the last decade, Haberlea rhodopensis Friv. extracts have been recognized as valuable cosmetic ingredients. In the present study, we aim to (i) evaluate the cytotoxic and antiproliferative activity of two herb extracts of Haberlea rhodopensis Friv. that are commercially used for the preparation of cosmetic ingredients on different cancer cells, with one normal cell line used as a reference, and (ii) compare the investigated effects with those observed for the reference anticancer, non-selective compound doxorubicin. Herein, we observed a decrease in the inhibitory activity of both extracts compared to those of doxorubicin against all tested cell lines. However, the myconoside-enriched Haberlea rhodopensis Friv. plant Extract 2 (designated also as M2) showed increased inhibitory activity (cytotoxicity and antiproliferative effects) compared to the Haberlea rhodopensis Friv. plant Extract 1 (designated also as E1). Moreover, the Haberlea rhodopensis Friv. plant Extract 2 showed a significant increase in cytotoxicity (at 24 h) and antiproliferative activity (at 48 and 72 h post-treatment) at its highest-tested concentration of 100 µg/mL compared to Haberlea rhodopensis Friv. plant Extract 1.