Unusual Cycloartane Saponins with Cytotoxic Activity from Astragalus stereocalyx Bornm.

The genus Astragalus L., which is included 10 subgenera and approximately 150 sections, today it contains about 2500–3000 species and subspecies according to some sources (1–2). In Turkish folk medicine, the aqueous extracts of some Astragalus species (declared by the healer) are used to treat leukaemia as well as for wound healing (3). Six new cycloartane-type triterpene glycosides (1–6) were isolated from Astragalus stereocalyx Bornm. along with six known cycloartane-type glycosides (Figure). Their structures were established by the extensive use of 1D and 2D-NMR experiments along with ESIMS and HRMS analysis. Compounds 1-3 are based on a new aglycon characterized by the occurrence of an unusual hydroxyl group at position 20, whereas compounds 4-6 are based on cycloasgenin C as aglycon, so far reported from Astragalus spp. All of the compounds tested for their cytotoxic activities against a number of cancer cell lines. Among the compounds, only 10 exhibited activity versus human cervical cancer (Hela) at 10µM concentration. References: 1. Heywood VH (1978) Flowering Plants of the World. Oxford University Press. London. 2. Maassoumi AA (1998) Astragalus in the Old World, Check-List. Islamic Republic of Iran Ministry of Jahad-e-Sazandegi Research Inst of Forests and Rangelands. Iran. 3.Calis I, Yuruker A, Tasdemir D, Wright AD, Sticher O, Luo YD, Pezzuto JM (1997) Planta Med 63: 183–186.