Cytotoxic and EGFR tyrosine kinase inhibitory activities of aglycone derivatives obtained by enzymatic hydrolysis of oleoside-type secoiridoid glucosides, oleuropein and ligustroside

Hydrolysis of oleoside-type secoiridoid glucosides, oleuropein (1) and ligustroside (2), in the presence of beta-glucosidase provided their aglycones, named (5S,8R,9S)-7-3,4-dihydroxyphenethyl elenolate (3) and (5S,8R,9S)-7-4-hydroxyphenethyl elenolate (4), respectively. The structures of 3 and 4 were identified by spectroscopic means and optical rotation measurements. Evaluation of the cytotoxic and epidermal growth factor receptor (EGFR) tyrosine kinase inhibitory activities of compounds 1-4 showed that compounds 3 and 4 exhibited moderate cytotoxicity against a disease-oriented panel of 39 human cancer cell lines in vitro, whereas compound 3 inhibited the enzyme.