Neuroprotective Effects of Salidroside and its Analogue Tyrosol Galactoside Against Focal Cerebral Ischemia In Vivo and H2O2-Induced Neurotoxicity In Vitro

Salidroside (Sal) is a natural antioxidant extracted from the root of Rhodiola rosea L. that elicits neuroprotective effects in vivo and in vitro. Tyrosol galactoside (Tyr), an analog of Sal, was recently synthesized in our laboratory. The purpose of the current study was to investigate and compare the neuroprotective effects of Sal and Tyr against focal cerebral ischemia in vivo and H2O2-induced neurotoxicity in vitro. Sal and Tyr significantly prevented a cerebral ischemic injury induced by a 2 h middle cerebral artery occlusion and a 24 h reperfusion in rats in vivo. Furthermore, the oxidative insult was markedly attenuated by treatments of Sal and Tyr in the cultured rat cortical neurons after a 30 min exposure to 50 mu M of H2O2. Western blot analysis revealed that Sal and Tyr decreased the expression of Bax and restored the balance of pro- and anti-apoptotic proteins. The neuroprotective effects of these two analogues show that Tyr has a better antioxidative action compared with Sal both in vivo and in vitro, and suggest that the antioxidant activity of Sal and Tyr may be partly due to their different substituents in their glycosyl groups. This gives a new insight into the development of therapeutic natural antioxidants against oxidative stress.