Iridoid glucosides from Scutellaria glaphyrostachys Rech. f.

Genus Scutellaria (Lamiaceae), commonly known as skullcaps, is widespread in all over the world, has 25 taxa in Turkey. Among them 14 taxa are endemic [1,2]. Infusions of most of the species are used as stimulant, tonic, antidiarrheic, and hemostatic, for wound healing, in gastric disorders, nausea and allergies [3,4]. Earlier phytochemical investigations performed on the genus were resulted isolation of flavonoids, iridoid glucosides, phenylethanoid glycosides, diterpenes, triterpenoids, alkaloids and essential oils [2]. The genus Scutellaria is composed of three sections: Galericularia, Scutellaria and Salviifoliae[1]. During our ongoing systematic studies on the genus Scutellaria, we have formerly studied on S. salviifolia Benth. included in section Salviifoliae, and isolated several phenolic compunds, but not terpenic ones, such as iridoids [5]. In the present study, from section Scutellaria, S. glaphyrostachys Rech. f., is an endemic plant of Turkey, has been investigated for its secondary metabolites. Our preliminary studies on the MeOH extract of S. glaphyrostachys indicated that the species was rich in iridoid glucosides, but not in phenolics, which is different from S. salviifolia. Repeated column chromatografies of the extract resulted in the isolation of four iridoid glucosides. Structures of the isolated compounds were identified as catalpol (1), scutelloside (2), 6′-O-E-p-coumaroyl-mussaenosidic acid (albidoside) (3), and 6′-O-E-caffeoyl-mussaenosidic acid (4) on the basis of 1D- and 2D-NMR data. Catalpol was the major compound with the yield of 1.10%. Isolation studies of the constituents are still in progress. Since, the secondary metabolite profiles of these two sections are different from each other, our findings may be useful for chemotaxonomy of the genus Scutellaria. These species together with other Scutellaria species from different sections should be investigated in detail for the future studies.

Acknowledgements: This study was supported by The Scientific and Technological Research Council of Turkey. Program No: 2211-C. The authors are grateful to Prof. Dr. Toshiaki Makino and Dr. Ishiuchi Kan'ichiro (Nagoya City University, Faculty of Pharmaceutical Sciences, Nagoya, Japan) for recording NMR spectra.

Keywords: Scutellaria glaphyrostachys, Lamiaceae, iridoid glucosides.

References:

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