Synthesis and biological evaluation of marine natural product, Cryptoechinuline D derivatives as novel antiangiogenic agents.

Tumor angiogenesis is an important biological process involved in the proliferation and migration of endothelial cells, regulated by Ang/Tie-2 signaling pathways, which is essential for tumor growth and metastasis. Therefore, blocking Ang/Tie-2 signaling pathways is a promising anti-angiogenic strategy for tumor treatment. 2,5-Diketopiperazines (DKPs) are a kind of bioactive compounds derived from marine fungi and they present a wide spectrum of pharmacological properties, particularly in the field of cancer treatment. Herein, a DKP marine natural product, Cryptoechinuline D (Cry D) was applied to structural modification and twelve derivatives were synthesized. Among which, compound 5 showed significant inhibitory activity against HUVECs with an IC50 value of 12.6 µmol/L, which weakened the proliferation, migration and invasion of HUVECs by inhibiting the Ang2/Tie-2 signaling pathway. The results of these evaluations indicated that compound 5 might be a promising anti-angiogeneic agent and worth further optimization and development for cancer therapy.