Antioxidant and Neuroprotective Xenicane Diterpenes from the Brown Alga Dictyota coriacea .

Five new xenicane diterpenes, including three rare nitrogen-containing derivatives, dictyolactams A () and B () and 9-demethoxy-9-ethoxyjoalin (), a rare diterpene with a cyclobutanone moiety, named 4-hydroxyisoacetylcoriacenone (), and 19--acetyldictyodiol (), were isolated from an East China Sea collection of the brown alga , along with 15 known analogues (-). The structures of the new diterpenes were elucidated by spectroscopic analyses and theoretical ECD calculations. All compounds had cytoprotective effects against oxidative stress in neuron-like PC12 cells. The antioxidant mechanism of 18-acetoxy-6,7-epoxy-4-hydroxydictyo-19-al () was related to the activation of Nrf2/ARE signaling pathway; it also showed significant neuroprotective effects against cerebral ischemia-reperfusion injury (CIRI) . This study provided xenicane diterpene as a promising lead scaffold for the development of potent neuroprotective agents against CIRI.