Isoscutellarein 8, 4′-Dimethyl ether glycosides as cytotoxic agents and chemotaxonomic markers in Kickxia aegyptiaca

Abstract

Abstract Two new isoscutellarein methyl ether derivatives were isolated and identified from Kickxia aegyptiaca (L.) Nabělek; isoscutellarein 8, 4′- di-OCH3 7-O-rutinoside-4‴-acetate; isolinariin (1) and isoscutellarein 8, 4′-di-OCH3 7-O-rutinoside; isopectolinarin (2), together with eight known flavonoid compounds; ladenine (3), pectolinarigenin (4), pectolinarin (5), linariin (6), pectolinarigenin 7-O-robinobioside (7), scutellarein 7-O-rutinoside (8), scutellarein 4′-OCH3-7-O-rutinoside (9) and linarin (10). These structures were elucidated on the basis of chromatographic and spectral analysis. Furthermore, the LC-ESI-MS technique was performed and revealed the tentative identification of trihydroxy-dimethoxy flavone glycosides for the first time. In addition, the plant extract and the isolated flavonoids were screened against two human tumor cell lines; breast (MCF-7) and colon (HCT-116). Compound (4) showed the highest % of cytotoxicity at100 μg/ml with 91.1 and 37.9 against MCF-7 and HCT-116, respectively, while compounds 1, 2, 3 and 5 showed moderate activities against MCF-7 as 68.2%, 57.5%, 65.8% and 58.8%, respectively. Also, the chemotaxonomic study revealed that K. aegyptiaca is the most advanced species in tribe Antirrhineae and is closely related chemically to Veronica species.