Flavonoids from Cleome droserifolia suppress NO production in activated macrophages in vitro

The effect of an Egyptian medicinal plant, Cleome droserifolia (Forssk.) De l. on nitric oxide (NO) production in bacillus Calmette-Guerin-induced mous e peritoneal macrophages activated by lipopolysaccharide was investigated i n vitro. The methanol extract of C. droserifolia reduced the NO production, and two flavonoids were isolated as the active components. The new one was determined to be 5,4'-dihydroxy-6,7,8,3',5'-pentamethoxyflavone (1) and th e other was identified as 5,4'-dihydroxy-6,7,8,3'-tetramethoxyflavone (8-me thoxycirsilineol; 2). Compound 1 concentration-dependently suppressed the N O production and was effective at a non-toxic concentration (12.5 mu g/ml). The suppressive activity of 2 was weaker than that of 1.