Protective effects of mustard leaf (Brassica juncea) against diabetic oxidative stress

Of four fractions (CH2Cl2, EtOAc, BuOH and H2O) from mustard leaf (Brassica juncea), the EtOAc fraction showed the strongest inhibitory effects, which were concentration-dependent, on the formation of advanced glycation end products and free radical-mediated protein damage in an in vitro system, indicating that this fraction has a potential protective role against diabetes and/or its complications. Based on these results, we carried out an in vivo study to determine whether the EtOAc fraction protected against diabetic oxidative stress induced by streptozotocin. Oral administration of the EtOAc fraction at doses of 50 and 200 mg/kg body weight/d for 10 d reduced the serum levels of glucose and glycosylated protein, implying that the impaired glucose metabolism due to diabetes had been ameliorated. In addition, the EtOAc fraction significantly reduced the thiobarbituric acid-reactive substance levels of serum and hepatic and renal mitochondria. Furthermore, the elevated levels of superoxide and nitrite/nitrate were reduced in a dose-dependent manner by oral administration of the EtOAc fraction. These findings suggest that the EtOAc fraction from mustard leaf might be beneficial in attenuating the damage caused by oxidative stress involved in diabetes and its complications.