Iridoid content and biological activities of Veronica cuneifolia subsp. cuneifolia and V. cymbalaria

The genus Veronica L. (Plantaginaceae) is represented by 79 species, 26 of which are endemic in Turkey. Some Veronica species are used for the treatment of different inflammatory diseases and cancer in traditional medicine. In addition, chemotaxonomy of the genus is important for the reclassification of the family Plantaginaceae after different phylogenetic studies.

Veronica cuneifolia subsp. cuneifolia D. Don and V. cymbalaria Bodard were studied from the view point of iridoid glucosides which are known as chemotaxonomical markers for this genus. Radical scavenging and cytotoxic activities of the extracts were also determined in this study.

Major compounds, isolated from iridoid fractions of V. cuneifolia subsp. cuneifolia were used as the standard compounds for HPLC after determination of their structures, and investigated for their presence in iridoid fractions of V. cymbalaria. Additionally, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and SO radical scavenging and cytotoxic activities against three cancer and a noncancerous cell lines of both extract were also tested using the MTT method.

While aucubin, catalpol, verproside, amphicoside, verminoside, and veronicoside were obtained from V. cuneifolia subsp. cuneifolia, two more iridoid glucosides, 6-O-veratroylcatalposide and 6-O-isovanilloylcatalpol, were isolated from V. cymbalaria. Comparing both species, V. cuneifolia subsp. cuneifolia showed stronger radical scavenging and cytotoxic activities than V. cymbalaria.

Our results demonstrated that the iridoid contents of both species were very close to each other confirming to the chemotaxonomic studies on Veronica species and their different bioactivity range make the plants interesting from the view point of natural drug discovery research.