I'm doing extraction of alkaloid from plant leaves. There is a step where I need to dissolve the extract residue from rotavap in 10% acetic acid...

I tried but the extract can't dissolve in the acid. May I know what is the best method to dissolve the extract in the acid?

Can I add some methanol into the residue flask to dissolve the extract first (maybe sonication), then mixed with 10% acetic acid, and rotavap to remove the methanol in the mixture?