Evaluation of cytotoxic activity and active compounds from genus Digitalis

In the Flora of Turkey, the genus Digitalis is represented by 9 species (1). Since most of the researches are focused on the cardenolides, other active compounds such as phenolics haven't been investigated for their role in biological activity of Digitalis extracts (2). In this study, comparative biological investigations were performed on the aqueous extracts of D. ferruginea L. subsp. schischkinii (Ivan) Werner and D. lamarckii Ivan on the basis of their cytotoxic activity. Cytotoxic activity was determined through the Hep-2 cancer cell line by MTT method (3). It was found that both extracts showed concentration dependent cytotoxicity. The extract of D. ferruginea subsp. schischkinii has shown 60,09% inhibition, while the inhibition of D. lamarckii is 35,13%, at 200 µg/ml concentration. Since the extract of D. ferruginea subsp. schischkinii was determined to be more active, it was applied to polyamide column chromatography for the bioactivity guided fractionation. The main fractions of the polyamide column were also investigated for their cytotoxic activity against Hep-2 cell line. Fraction, rich in phenylethanoid glycosides, was found as the most active which showed 52% inhibition at 200 µg/ml. Phytochemical studies on the active fraction were resulted in the isolation of seven compounds. Isolated compounds also showed cytotoxic activities against Hep-2 cell line between the IC₅₀:100 – 150 mg/ml. Structures of the isolated three compounds were determined as forsythiaside, calceorioside A, and methyl caffeoate by extensive NMR techniques. Structure determination studies on the other bioactive compounds have still been continuing.

Acknowledgement:This study was supported by TUBITAK Project No:108T518.

References:

[1] Davis PH (1978) Flora of Turkey and East Eagean Islands, University Press, Edinburg, Vol 6.

[2] Calıs I, et al.(1999) Pharmazie, 12,1926 – 1930

[3] Saracoglu I, et al.(1995) Biol Pharm Bull,18,1396 – 1400