I do not think it's worth trying to produce such kind of compunds in protoplasts. Protoplast is a special state of cell, when there's no cell wall around and this stage lasts only a few days in case of plant protoplast (or few hours if we talk about bacteria). On the other hand you can try to produce secondary metabolite in plant cell culture, as alkaloids, glycosides, natural phenols, stc. For more information see the review of Ramachandra Rao & Ravishankar, 2002 (http://www.sciencedirect.com/science/article/pii/S0734975002000071)
But if you try in protoplast you might harvest some compounds if you optimise the culture conditions...