Oleuropein/ligstroside isomers and their derivatives in Portuguese olive mill wastewaters

► Phenolic extracts from olive mill wastewaters contain oleuropein and ligstroside isomers and also. ► Diglucoside derivative of the oleuropein isomer (MW 864 Da). ► Mono- and diglucosides of the ligstroside isomer (MW 686 Da and 848 Da, respectively). ► A degradative product of the ligstroside isomer (MW 454 Da). ► An elenoic derivative of the compound with MW 864 Da.