Evaluation of the hypoglycemic effects of extracts and diterpenoids from Azorella compacta (llareta)

Aqueous or ethanol infusions of llareta have been used as antidiabetics in the popular medicine in the Chilean highlands. A previous report [1] demonstrated the hypoglycemic effect of some compounds on a type 1 diabetic rat model. In order to determine the compounds responsible for this effect, we evaluated the hypoglycemic activity of llareta crude extract and some of its constituents, on the C2C12 cell line. The leaves of Azorella compacta were collected in Tatio, Antofagasta region, Chile. The plant extract was prepared using petroleum ether, dichloromethane and methanol. The extract was fractionated using chromatographic techniques with Sephadex LH-20 and silica gel. Three diterpenes were isolated and identified by NMR analysis. The crude extract and diterpenes were incorporated into micelles using an aqueous solution of the polymer Pluronic F127 (1mM) for solubilisation. C2C12 myotubes were incubated with different concentrations of Azorella crude extract and the 3 diterpenes (Y1, Y2 and Y5) for 4h, in glucose uptake medium. The crude extract and Y5 diterpene stimulated glucose uptake in C2C12 myotubes up to 50%. The effect was also evaluated using a cell line model of insulin resistance. C2C12 insulin-resistant cells were established by adding palmitic acid (0.75mM) to the culture medium and then cells were treated with the crude extract or Y5. Both treatments increased glucose uptake in C2C12 insulin-resistant cells and displayed an effect similar to metformin, used as a positive control. Glucose consumption of C2C12 cells was determined by a glucose oxidase method. The findings of this study are in agreement with the traditional use of the leaves of llareta as a hypoglycemic agent. We have shown that one of the substances responsible for the effects is a diterpene that significantly stimulated glucose uptake in C2C12 under conditions of insulin resistance.

Acknowledgment: This research was supported by Fondecyt project N° 1120199 and Sistema General de Regalias Colombia No. 2013000100177.

Keywords: Azorella compacta, anti-diabetic, diterpenes, C2C12 myotubes, insulin resistance.

References:

[1] Fuentes NL, Sagua H, Morales G, Borquez J, San Martin A, Soto J, Loyola LA. Experimental antihyperglycemic effect of diterpenoids of Llareta Azorella compacta (Umbelliferae) Phil in rats. Phytother Res 2005; 19: 713 – 716