Ginkgo biloba extract and saikosaponin a suppress lipopolysaccharide‐induced inflammatory cytokines in human U‐937 monocytes

Abstract

Ginkgo biloba extract (EGb 761) contains a large number of flavonoids, ginkgolides and bilobalide, and many studies have reported its activities on enhancing antioxidative defense, increasing blood flow, and improving memory. Saikosaponin a (SSa), one of Bupleurum's major active ingredient, was found to have anti‐inflammatory effect. This study investigated the effects of EGb 761 and/or SSa on lipopolysaccharide (LPS)‐induced inflammatory responses in differentiated human monocyte U‐937 cells. The differentiation from monocytes to macrophages was induced by 160 nM phorbol 12‐myristate 13‐acetate for 48 hours. Cells were then incubated with 200 μg/ml EGb 761 (EGb group), 5 μg/ml SSa (SSa group), or 200 μg/ml EGb 761 and 5 μg/ml SSa (combined group) for 24 hours, and 1 μg/ml LPS was added to the medium for another 24 hours to induce inflammation. The results showed that all treatment groups significantly decreased the secretion of LPS‐induced tumor necrosis factor‐α, (TNF‐α), interleukin‐1β (IL‐1β), IL‐10, and prostaglandin E2 and protein expression of cyclooxygenase‐2 (p<0.05). Additionally, EGb treatment alone or combination treatment with SSa significantly scavenged NO compared with the control group (p<0.05). The combined treatment had synergistic inhibitory effect on TNF‐α secretion and NO scavenging ability. In conclusion, 200 μg/ml EGb 761 and 5 μg/ml SSa alleviate inflammation via scavenging NO and inhibiting inflammatory cytokines produced by LPS‐induced U937 macrophages. Combined EGb and SSa have synergistic inhibitory effects on inflammatory responses.Sponsored by the National Science Council (NSC97‐2320‐B‐038‐034‐MY3)