Flavones isolated from Pseudognaphalium liebmannii with tracheal smooth muscle relaxant properties.

The inflorescences of Pseudognaphalium liebmannii are used as folk medicine to treat various respiratory diseases. In this work, we report the isolation of seven known flavones: 5-hydroxy-3,7-dimethoxyflavone 1, 5,8-dihydroxy-3,7-dimethoxyflavone 2, 5,7-dihydroxy-3,8-dimethoxyflavone 3 (gnaphaliin A), 3,5-dihydroxy-7,8-dimethoxyflavone 4 (gnaphaliin B), 3,5-dihydroxy-6,7,8-trimethoxyflavone 5, 3,5,7-trimethoxyflavone 6 and 3-O-methylquercetin 7. All these flavones except 1 and 6 showed a relaxant effect on guinea pig tracheal preparation with EC50 between 69.91 ± 15.32 and 118.72 ± 7.06 µM. Aminophylline (EC50 = 122.03 ± 7.05 µM) was used as a relaxant reference drug. The active flavones shifted the concentration-response curves of forskolin and nitroprusside leftward, and significantly reduced the EC50 values of these drugs. Furthermore, these flavones dose-dependently inhibited phosphodiesterase (PDE) in an in vitro assay. This reveals that the inflorescences of P. liebmannii contain several flavones with relaxant effect on airway smooth muscle and with PDEs inhibition that contribute to supporting the anti-asthmatic traditional use.

Development and validation of a column high-performance liquid chromatography method for quantification of ganaphaliin A and B in inflorescences of Gnaphalium liebmannii Sch. Bp ex Klatt.

An HPLC method was developed for the simultaneous determination of gnaphaliin A and B, active compounds of Gnaphalium liebmannii Sch. Bp ex Klatt. The HPLC separation was performed on an Inertsil ODS-3 (150 x 4.6 mm id, 5 microm) RP C18 column operated at 40 degrees C; the isocratic mobile phase was 0.02% aqueous orthophosphoric acid-methanol-acetonitrile (50 + 30 + 20, v/v/v), with a run time of 20 min and flow rate of 1.5 mL/min. Detection with a photodiode array detector (PDAD) was at 270 nm. The method was validated for linearity, repeatability, LOD, and LOQ. The LOD and LOQ for gnaphaliin A and B were found to be in the range of 0.4-0.5 and 1.0-1.4 microg/mL, respectively. This is the first report of an analytical method developed for the quantitative analysis of flavones from Gnaphalium species by HPLC-PDAD with applications for raw material and commercial products.

Carbenoxolone gastroprotective mechanism: participation of nitric oxide/(c) GMP/K(ATP) pathway in ethanol-induced gastric injury in the rat.

Carbenoxolone, a semi-synthetic triterpenoid, exhibits gastroprotective activity related to the participation of nitric oxide (NO); however, the complete NO/(c) GMP/K(ATP) channels pathway for carbenoxolone is unknown. Therefore the aim of this study was to examine the NO/(c) GMP/K(ATP) channels pathway as the gastroprotective mechanism of carbenoxolone in the ethanol-induced gastric injury model in the rat. Oral administration of carbenoxolone (30 mg/kg, p.o.) exhibited gastroprotective effect against ethanol-induced gastric injury in rats. Pretreatment with N(G) -nitro-l-arginine methyl ester (L-NAME, 70 mg/kg, i.p.); 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ, guanylate cyclase inhibitor, 10 mg/kg, i.p.); or glibenclamide (K(ATP) channels inhibitor, 1 mg/kg, i.p.) reversed the gastroprotective effect of carbenoxolone for ethanol-induced gastric injury. Furthermore, gastric prostaglandins and NO levels increased after carbenoxolone administration in ethanol-induced gastric injury in rats. In conclusion, our results suggest that the increase of NO levels in gastric tissue after pretreatment with carbenoxolone activates the NO/(c)GMP/K(ATP) channels pathway, the principal gastroprotective mechanism of carbenoxolone.

Inhibition of endogenous hydrogen sulfide synthesis by PAG protects against ethanol-induced gastric damage in the rat.

Hydrogen sulfide (H(2)S) is a gaseous mediator involved in a multitude of physiological functions; however the role of H(2)S in the gut is far from being understood completely. The aim of this study was to determine the effect of d-l-propargylglycine (PAG), an inhibitor of H(2)S synthesis, on ethanol-induced gastric injury in rat and to examine the role of l-cysteine, exogenous H(2)S, prostaglandins, non-protein sulphydryls groups, nitric oxide and K(ATP) channels in the gastroprotective effect of PAG. Administration of PAG (3.12 to 75mg/kg i.p.) or l-cysteine (0.3 to 300mg/kg, p.o.) exhibited a dose-dependent protective effect after intragastric administration of 1ml of ethanol to induce gastric injury. The gastroprotective effect of PAG (25mg/kg i.p.) was maintained after post-treatment with l-cysteine (10mg/kg p.o.), while NaHS (8.4mg/kg p.o.) inhibited this effect. The levels of gastric hydrogen sulfide were increased after ethanol-induced gastric damage and they were reverted by PAG while prostaglandin E(2) levels in gastric tissue were decreased by ethanol and PAG did not revert to this effect. Pretreatment with indomethacin (10mg/kg i.p.) and N-ethylmaleimide (NEM, 10mg/kg s.c.) resulted in a reversion of the gastroprotective effect of PAG while N(G)-nitro-l-arginine methyl ester (L-NAME, 70mg/kg s.c.), glibenclamide (1mg/kg i.p.) or diazoxide (3mg/kg i.p.) did not induce any changes. These results suggest that ethanol-induced gastric injury is related with an increment of endogenous H(2)S levels, and therefore a decrement of H(2)S levels by PAG is a benefit to protect gastric injury caused by ethanol.