Tetrandrine is a natural, bis-benzylisoquinoline alkaloid isolated from the root of the plant Radix stephania tetrandrae. Tetrandrine non-selectively inhibits calcium channel activity and induces G1 blockade of the G1 phase of the cell cycle and apoptosis in various cell types, resulting in immunosuppressive, anti-proliferative and free radical scavenging effects. This agent also increases glucose utilization by enhancing hepatocyte glycogen synthesis, resulting in the lowering of plasma glucose.