First review the literature on chemistry of species of Boraginaceae. If you are going to analyse the chemistry of some species from the family you can be specific at least to genus level. Phytochemical analysis of of single species itself might take months together. Boraginaceae is a big family with several plants. How will you restrict your scope? Otherwise chose some medicinally important plants from the family. It will be a good topic for a chemistry researcher working on natural products. Good luck.