Several research studies have reported on the pharmacological relevance of the medicinal plants used for treating various gastrointestinal disorders and controlling the dietary glucose uptake in the intestinal tract.

Male rats were used to investigate the pharmacological effects of green oak acorn aqueous extract (GOAE) on gastrointestinal physiological parameters in vivo and in vitro. In this respect, the gastro-intestinal motility and hypersecretion essays were evaluated using a simple test meal (10% charcoal in 5% gum arabic) and castor oil induced diarrhea. However, the effect of GOAE on glucose absorption and homeostasis was assessed by the Ussing chamber system and oral glucose tolerance test (OGTT) measures.

Various doses of the Quercus ilex aqueous extract (125, 250 and 500mgkg⁻¹) administered orally produced a significantly dose-related inhibition of gut meal travel distance in normal rat. The highest intestinal transit reduction of 49.34% was obtained with 500mgkg⁻¹ compared to 58.33% caused by reference drug (clonidine, 1mgkg⁻¹). In castor oil induced diarrhea in rat, Q. ilex extract reduced the frequency of defecation, fluid accumulation and electrolyte transport. These effects were associated with decreased histopathological damage and regulation of intracellular mediators disturbance in the intestinal mucosa. In addition, GOAE treatment improved glucose tolerance and significantly and dose-dependently reduced (>50%) the glucose absorption via intestinal epithelium. Phytochemical screening revealed the presence of many bioactive natural compounds.

These results suggest that the extract was effective towards reducing diarrhea, fluid accumulation, electrolyte transport and glucose absorption, and no toxic effects of the GOAE presented on this study.