Couldn't it have the same ROS potential that dopamine and other catecholamines have?
while hydroxytyrosol, ( lets call it HT because I can't keep spelling that ) is a catechol, it lacks the amine of dopamine. Dopamine gets metabolized to an aldehyde, this aldehyde can form schiff bases with amines on proteins. The catechol can also react with thiols on proteins. So in addition to dopamine's oxidative damage potential, it can crosslink proteins. HT doesn't have the amine, so it probably doesn't get metabolized in the same way.
Here's a paper with more information on dopamine metabolism and toxicity. Look up other papers by that group for more.