Gastroprotective activity of kaempferol glycosides from Malvaviscus arboreus Cav

Malvaviscus arboreus is traditionally used in Mexico and Central America for culinary and medicinal purposes. Leaves and flowers of this species are commonly used for preparation of salads, herbal teas and herbal dyes. Panamanian, Guatemalan and Mexican healers use this medicinal plant for the management of fever, respiratory complications, dysentery, liver and gallbladder problems, stomachache and gastritis between other health troubles.

Considering the traditional use of M. arboreous as well as its content in flavonoids and other polyphenols, the objective of this work was to evaluate the gastroprotective effect of an aqueous extract and identify the potential bio-active principles from flowers of this species.

Fresh flowers of Malvaviscus arboreus were collected, dried, and macerated with water. The aqueous extract (ExAq) was partitioned using an immiscible mixture of water and ethyl acetate, giving an aqueous (MaAq) and organic (MaEA) fractions. The gastroprotective effect was carried out using an ethanol-induced gastric ulcer experimental test in male rats. While tween 20 was used as a negative control, famotidine (10 mg/kg) and L-arginine (300 mg/kg) were used as positive controls. Compounds 1 and 2 were isolated by several chromatographic techniques and the chemical characterization was carried out by means of the analysis of the NMR spectra in one and two dimensions.

The integrate extract (ExAq) to 250, 500 and 750 mg/kg showed gastroprotective effect with high levels of 97.8%, 79.5% and 91.1% respectively. The organic fraction (MaEA) displayed a protection of 91.2%, 96.0% and 99.4% when it was evaluated at 125, 250 and 500 mg/kg respectively. Comparison of these results with famotidine at 10 mg/kg (83% of gastroprotection) indicated that ethyl acetate fraction showed a better gastroprotection. The bio-guided separation of this organic mixture, allowed obtaining the most active fraction (C1F4, 60 mg/kg) which was finally purified to obtain two glycosylated flavonols: kaempferol 3-O-D-sophoroside (1) and kaempferol 3-O-D-sambubioside (2). This mixture of flavonoids (40 y 60 mg/kg) showed 93.7 and 92% of gastroprotective activity respectively.

This study allowed demonstrating that an aqueous extract and its organic fraction (MaEA) from M. arboreous contain glycosylated flavonoids (1 and 2) which are responsible of the gastroprotective properties of M. arboreous. These results will be used in the future development of a standardized treatment useful in the therapeutic management of gastric ulcers.