Background: Astragalus hamosus L. (Fabaceae) is used in herbal medicine as emollient, demulcent, phrodisiac, diuretic, laxative, and good for inflammation, ulcers, and leukoderma. It is useful in treating irritation of the mucous membranes, nervous affections, and catarrh. Objective: Rhamnocitrin 4-β-D-galactopyranoside (RGP), isolated from A. hamosus, was investigated for its possible protective effect on different models of toxicity in vitro on sub-cellular and cellular level. Materials and Methods: The effects of RGP were evaluated on isolated rat brain synaptosomes, prepared by Percoll reagent and on rat hepatocytes, isolated by two-stepped collagenase perfusion. Results: In synaptosomes, RGP had statistically significant protective effect, similar to those of silymarin, on 6-hydroxy (OH)-dopamine-induced oxidative stress. These results correlate with literature data about protective effects of kempferol and rhamnocitrin on oxidative damage in rat pheochromocytoma PC12 cells. In rat hepatocytes, we investigate the effect of RGP on two models of liver toxicity: Bendamustine and cyclophosphamide. In these models, the compound had statistically significant cytoprotective and antioxidant activity, similar to those of silymarin. Conclusion: According to these results, we can suggest that such cytoprotective effect of RGP might be due to an influence on bendamustine and cyclophosphamide metabolism in rat hepatocytes. In isolated rat hepatocytes, in combination with bendamustine and cyclophosphamide and in 6-OH-dopamine-induced oxidative stress in isolated rat synaptosomes, RGP, isolated from A. hamosus, was effective protector and antioxidant. The effects were closed to those of flavonoid silymarin-the classical hepatoprotector and antioxidant.