Dear it is very important to characterise immunological relevance of many natural products as such will help in reducing side effects of the orthordox drugs.
Yes, quite a number of plant compounds have been found to have good immune-modulatory actions. Curcumin, resveratrol, epigallocatechol-3-gallate, quercetin, colchicine, capsaicin, andrographolide, and genistein are among the most interesting plant-derived compounds with a range of immue-modulations. A pyrrolizidine alkaloid from Heliotropium indicum, indicine N-oxide has been tested in clinical trials.