Flavonoids and triterpenoids from Callistemon citrinus and their inhibitory effect on no production in LPS-stimulated RAW264.7 macrophages

Phytochemical investigation of the leaves and stems of Callistemon citrinus (Curtis) Skeels led to the isolation of 12 flavonoid and triterpenoid compounds,  including one new flavonoid, callistine A (1) and six known flavonoids 6,7- dimethyl-5,7-dihydroxy-4’-methoxy flavone (2), astragalin (3), quercetin (4), catechin (5), eucalyptin (6), and 8-demethyleucalyptin (7), along with 5 triterpenoids, 3-β-acetylmorolic acid (8), 3β-hydroxy-urs-11-en-13(28)-olide (9), betulinic acid (10), diospyrolide (11) and ursolic acid (12). Their chemical structures were determined from the spectroscopic evidences counting 1D- and 2D-NMR and HR-MS data. All the isolated compounds were examined for their anti-inflammatory activity against LPS-activated NO production in macrophage RAW264.7 cells. Among them, quercetin (4) and 3β-hydroxy-urs-11-en-13(28)-olide (9) showed potential inhibition activity in nitric oxide (NO)  production in RAW264.7 cells exposed to LPS.