Bioactivity guided isolation of iridoid and flavonoid glycosides from four Veronica species
The genus Veronica L. (Plantaginaceae) has been used traditionally for the treatment of a number of diseases. The use of Veronica species for influenza, coughs, inflammation, rheumatic pains and cancer was reported in many countries [1,2]. Earlier investigations performed on Veronica species resulted in the isolation of mainly iridoid glucosides, especially benzoic and cinnamic acid esters of catalpol, some phenylethanoid and flavonoid glycosides [3,4]. It is represented by 79 species in Turkish flora, 26 of which are endemic . In this study, the antioxidative activity of four different Turkish Veronica species were investigated and bioactivity guided isolation was carried out to examine the chemical composition of V. serpyllifolia L. further. 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO) and superoxide (SO) radical scavenging assays were performed for guiding of the bioactivity. V. chamaedrys L. was found to be the most bioactive species, followed by V. serpyllifolia. V. fuhsii Freyn & Sint. was found to be the least active species. Thin layer chromatografies of their water extracts showed V. chamaedrys to contain a large proportion of phenylethanoid glycosides, the remaining species showed the presence of a large proportion of flavonoid glycosides. Chromatography of V. serpyllifolia water extract gave five pure compounds. Their structures were determined as iridoid glucosides verproside, catalposide, veronicoside and flavonoid glycosides 4'-O-methylapigenin-7-O-rhamnopyranosyl-acetylglucopyranoside, 3'-O-methylluteolin-7-O-rhamnopyranosyl-acetylglucopyranoside using different 1D and 2D NMR techniques. Isolation and structure determination studies on bioactive compounds of genus Veronica are still continuing.
Acknowledgement: This study was supported by The Scientific and Technological Research Council of Turkey (TUBITAK) Project No: 108T518.
References: 1. Baytop T (1984) Therapy with Medicinal Plants in Turkey (Past and Present). Publications of Istanbul University. Istanbul.
2. Fujita T et al. (1995) Econ Bot 49: 406–422.
3. Harput US et al. (2003) Z Naturforsch 58c: 481–484.
4. Saracoglu I et al. (2004) Phytochemistry 65: 2379–2385.
5. Davis P. (1978) Flora of Turkey and the East Aegean Islands. Vol. 6. University Press. Edinburgh.