If you are using an extract, then its not just a single molecule its a combination of several compounds, hence unless and until you use a particular compounds it becomes very difficult to say which one is activating the receptor, So i would suggest that if you are looking for a articular compound than you can seperate the compounds using HPLC and then can go for further study on the receptor using western blot, FACS or staining method.
just a some suggessions for you ,first of all try to do some assays that let you know about your cells health or status, for exemple, viability, oxidative stress, proliferation, and after that you can choose some known biomarkers for this status, after that i think it's more easy to know which pathway is activated.