Anti-inflammatory and anticancer effects of flavonol glycosides from Diplotaxis harra through GSK3β regulation in intestinal cells.

Diplotaxis harra (Forssk.) Boiss. (Brassicaceae) is traditionally used as an antidiabetic, anti-inflammatory or anticancer agent. In these pathologies, the glycogen synthase kinase 3 β (GSK3β) is overactivated and represents an interesting therapeutic target. Several flavonoids can inhibit GSK3β and the purpose of this study was to search for the compounds in Diplotaxis harra which are able to modulate GSK3β. Methanol extracts from D. harra flowers were prepared and the bio-guided fractionation of their active compounds was performed using inflammatory [protease-activated receptor 2 (PAR2)-stimulated IEC6 cells] and cancer (human Caco-2 cell line) intestinal cells. 50-100 μg/mL of fractions or compounds purified by HPLC were incubated with cells whose inhibited form of GSK3β (Pser9 GSK3β) and survival were analyzed by Western blot at 1 h and colorimetric assay at 24 h, respectively. LC-UV-MS profiles and MS-MS spectra were used for the characterization of extracts and flavonoids-enriched fractions, and the identification of pure flavonoids was achieved by MS and NMR analysis. The methanol extract from D. harra flowers and its flavonoid-enriched fraction inhibit GSK3β in PAR2-stimulated IEC6 cells. GSK3β inhibition by the flavonoid-enriched D. harra fraction was dependent on PKC activation. The flavonoid-enriched D. harra fraction and its purified compound isorhamnetin-3,7-di-O-glucoside induced a 20% decrease of PAR2-stimulated IEC6 and Caco-2 cell survival. Importantly, normal cells (non-stimulated IEC6 cells) were spared by these treatments. This work indicates that flavonoids from D. harra display cytotoxic activity against inflammatory and cancer intestinal cells which could depend on GSK3β inhibition.