Cantharidin derivatives from the medicinal insect Mylabris phalerata

Abstract Thirteen new cantharidin derivatives including six cantharimide-amino acid adducts ( 1 – 6 ), five cantharimide dimers ( 7 – 11 ) and two cantharimide-aromatic compound hybrids ( 12 – 13 ) were isolated from Mylabris phalerata Pallas. Compounds 1 – 5 represent the first natural products combined through cantharimide and neutral amino acids. Compounds 7 – 11 are the first cantharimide dimers consisting of two different cantharimide cores. Their structures with absolute configurations were elucidated by means of NMR spectroscopy, single-crystal X-ray diffraction, and semi-synthesis. Compound 6 showed weak cytotoxicity against HepG2, A549 and MDA-MB-231 cells with IC 50 values of 15.70 ± 3.06, 20.67 ± 4.05 and 23.79 ± 4.54  μ M, respectively.