Anti-inflammatory effect of tribulusamide D isolated from Tribulus terrestris in lipopolysaccharide-stimulated RAW264.7 macrophages

Tribulus terrestris (T. terrestris) has been used as a traditional medicine for the treatment of a variety of diseases, including inflammation, edema and hypertension. The aqueous and ethanol extracts of T. terrestris contain alkaloids, flavonoids, tannins, quinines and phenolic compounds. Tribulusamide D is a compound that has been isolated from the ethanol extract of T. terrestris. The present study investigated the anti-inflammatory effect of tribulusamide D on lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Tribulusamide D inhibited the production of LPS-induced nitric oxide and prostaglandin E(2), by reducing the expression of inducible nitric oxide synthase and cyclooxygenase-2 expression, respectively. The expression of these genes associated with inflammation was determined using reverse transcription-polymerase chain reaction and western blot analysis. Furthermore, tribulusamide D reduced the expression of LPS-induced inflammatory cytokines, including interleukin (IL)-6, IL-10 and tumor necrosis factor-α. They were quantified using an enzyme-linked immunosorbent assay. In addition, the present study confirmed that the inhibitory effects of tribulusamide D on the inflammatory response were mediated through inactivation of mitogen-activated protein kinase p38 and inhibition of nuclear localization of nuclear factor-B, which were also determined by western blot analysis. To the best of our knowledge, the current study is the first to demonstrate that tribulusamide D exerts anti-inflammatory activity by altering the expression of inflammatory mediators and cytokines, indicating that tribulusamide D could be developed as a potential therapeutic agent for the treatment of inflammatory disorders.