Moreover, we showed that the flavonoids 5-hydroxy-7,4′-dimethoxyflavone, casticin, apigenin, and penduletin, obtained from Croton betulaster leaves, and the glycosylated flavonoid rutin, obtained from Dimorphandra mollis pods, inhibited the proliferation of a human GBM cell line (GL15); additionally, rutin and casticin also negatively regulated the levels of VEGF and TGF-β1 [29], which involved increases in the migration of glioma cells [30,31,32]. Here, TGFB1 is linked to glioblastoma.