Isolation of a novel substrate-competitive tyrosine kinase inhibitor, desmal, from the plant Desmos chinensis

In the course of a screening program for tyrosine kinase inhibitors, the chloroform extract of a tropical plant, Desmos chinensis, strongly inhibited the enzyme activity. The active substance was purified by silica gel, gel filtration, and finally crystallized. The structure was elucidated by mass spectrometry and X-ray crystallography to be 8-formyl-2,5,7-trihydroxy-6-methylflavanone, and we named it desmal. Desmal competed with peptide substrate and non-competed with ATP. It inhibited tyrosine kinase in situ in epidermal growth factor (EGF) receptor-overexpressing NIH3T3 (ER 12) cells. It also inhibited EGF-induced inositol phosphate formation and morphological changes.