Activity of three cytotoxic isoflavonoids from Erythrina excelsa and Erythrina senegalensis (neobavaisoflavone, sigmoidin H and isoneorautenol) toward multi-factorial drug resistant cancer cells - Kuete, V; Sandjo, L P; Kwamou, G M; Wiench, B; Nkengfack, A E; Efferth, T (Phytomedicine, 2014)