Barberry (Berberis vulgaris) is a well known medicinal plant in Iran and has also been used as food. The antihistaminic and anticholinergic activity of aqueous extract of barberry fruits were investigated on isolated guinea-pig ileum, and dose response curves of histamine and acetylcholine with and without extract were plotted. The results indicated antihistaminic and anticholinergic activity of extract that seems to be of the competitive type.
– J Ethnopharmacol 1999 Feb;64(2):161-6 — Antihistaminic and anticholinergic activity of barberry fruit (Berberis vulgaris) in the guinea-pig ileum. — Shamsa F, Ahmadiani A, Khosrokhavar R.

The plants under study suppressed as well as intensified the processes of lipid peroxidation, depending on the concentration of the phytopreparation and the type of the model systems. In in vivo experiments the drugs of plant origin suppressed lipid peroxidation, reducing the parameters induced by iron and chemoluminescence and the malonic dialdehyde level in the liver.
– Eksp Klin Farmakol 1999 Mar-Apr;62(2):36-8 — The effect of aqueous extracts of hepatotropic medicinal plants on free-radical oxidation processes — Ryzhikova MA, Farkhutdinov RR, Sibiriak SV, Zagidullin ShZ.

Side-effects can result from high dosages and may include gastrointestinal discomfort, dyspnea, lowered blood pressure, flu-like symptoms, and cardiac damage. Berberine usage should be avoided in pregnancy, due to potential for causing uterine contractions and miscarriage, and in jaundiced neonates because of its bilirubin displacement properties.
– Birdsall TC, Kelly GS. — Berberine: Therapeutic potential of an alkaloid found in several medicinal plants. — Altern Med Rev 1997;2:94-103.