Oxidative stress is closely related with inflammation and development of many diseases. Black soybean seed coat contains high amount of anthocyanins, which are well-known for free radical scavenging activities. This study investigated inflammatory response and action mechanism of black soybean anthocyanins with regard to antioxidant activity in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells.

RAW 264.7 cells were treated with anthocyanins extracted from black soybean seed coats in a concentration range of 12.5 to 100 µg/mL. The production of reactive oxygen species (ROS), secretion of pro-inflammatory mediators and cytokines, and the signaling in the mitogen activated protein kinases (MAPKs) pathway were examined.

Black soybean anthocyanins significantly decreased LPS-stimulated production of ROS, inflammatory mediators such as nitric oxide (NO) and prostaglandin E₂, and pro-inflammatory cytokines, including tumor necrosis factor α and interleukin-6, in a dose-dependent manner without cytotoxicity ( P < 0.001). Black soybean anthocyanins downregulated the expression of inducible NO synthase and cyclooxygenase-2 in LPS-stimulated RAW 264.7 cells ( P < 0.001). Moreover, black soybean anthocyanins inhibited LPS-induced phosphorylation of MAPKs, including extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 ( P < 0.001).

These results suggest that black soybean anthocyanins exert anti-inflammatory activity by inhibiting ROS generation and subsequent MAPKs signaling, thereby inhibiting inflammatory responses.