Study of the antiangiogenic effect of a terthiophene isolated from Tagetes minuta

Abstract

Angiogenesis is an essential mechanism involved in biological processes such as reproduction, development and wound healing. Imbalances between the factors that regulate angiogenesis have been linked to different diseases that affect human health. Despite the great progress achieved in antiangiogenic therapy, its limited efficacy, severe adverse effects and the development of resistance demands the continuous development of novel therapeutic agents to overcome these obstacles. In this context plant-derived metabolites continue to play a highly significant role in drug discovery. From a screening performed in our laboratory, the ethanol extract of Tagetes minuta arose as a potent antiangiogenic agent. This effect was evaluated by the tube formation assay using bovine aortic endothelial cells (BAEC). Through bio-guided chemical fractionation three compounds identified as: 5´-methyl-5-(4-hydroxybut-1-ynyl)-2,2´-bithiophene (1), 5-(4-hydroxybut-1-ynyl)-2,2´-bithiophene (2) and alfa-terthienylmethanol (3) were obtained. Among these, compound 3 showed a potent antiangiogenic activity (IC50 = 2.69 μM). The influence of 3 over cell proliferation and cell invasion induced by the vascular endothelial growth factor (VEGF) was evaluated. While no effect was observed in the MTT proliferation assays, 3D transwell experiments demonstrated that compound 3 efficiently blocked cell invasion. Additionally, molecular docking experiments showed that 3 overlaps with the tyrosine kinase inhibitor sorafenib (a potent antioangiogenic agent) at the catalytic cleft of VEGF receptor 2 interacting with key aminoacids such as Glu885, Phe1047 and Cys919, extending over Val916 into the adjacent allosteric hydrophobic back pocket resembling a type II inhibition. These studies contribute to position 3 as a potential candidate to be used in antiangiogenic therapy itself or as a lead compound for the development of analogues with improved activity.