One thing to research, curcumin is not found as an isolate in nature and its various cofactors most likely add synergy, boost bioavailability and buffer side effects.
Vanadium (Vanadyl Sulfate)- Monograph Alternative Medicine Review 2009 (Jun); 14 (2): 177 — 180 ~ FULL TEXT Nutritionally, vanadium is thought to be a cofactor in various enzymatic reactions.