The mechanism of action is not entirely understood. In rats, the antiviral properties of sophoridine, an alkaloid constituent, appear to be mediated via up-regulation of the cytokines IL-10 and IFN-gamma (11). Other animal studies suggest that Sophora flavescens flavonoids may promote vasodilation by inhibiting Ca2+ influx through a voltage-gated channel (12). The flavonoids sophoraflavonone G and kurarinone appear to be responsible for antioxidant effects, which are mediated through free radical scavenging (4). Sophoraflavonone G may also play a role in S. flavescens's anti-inflammatory effects, by inhibiting prostaglandin E2 formation via down-regulation of COX-2 (13).
(2S)-2'-Methoxykurarinone, a compound isolated from the S. flavescens root, was shown to inhibit osteoclast differentiation and bone resorption via receptor activator of nuclear factor-κB ligand (RANKL)-induced mitogen-activated protein kinases (MAPKs) and c-Fos-NFATc1 signaling pathways (29).
Most of the reported antineoplastic effects of Sophora flavescens are due to the pro-apoptotic activity of Matrine, the main alkaloid constituent. In human hepatocellular carcinoma cells, matrine inhibits matrix metalloproteinase-9 (MMP-9) by downregulating the NF-kappa B pathway (18). It has also been shown to demonstrate anti-angiogenic effects by inhibiting VEGF and VEGFR-2 (19). Matrine triggers the mitochondrial pathway, in which cytochrome C release induces caspase-9 and -3 activation and subsequently induces apoptosis (2) (3) (10) (21) (2).