Cerebral protective and cognition-improving effects of sinapic acid in rodents.

We previously demonstrated that tenuifoliside B and 3,6'-disinapoylsucrose in Polygalae Radix, the root of Polygala tenuifolia WILLDENOW, inhibited potassium cyanide (KCN)-induced hypoxia and scopolamine-induced memory impairment in mice. Because both ingredients have a common sinapoyl moiety in their structure, we inferred that the sinapoyl moiety could inhibit hypoxia and memory impairment. In the present study to clarify the hypothesis, sinapic acid inhibited KCN-induced hypoxia and scopolamine-induced memory impairment as well as tenuifoliside B and 3,6'-disinapoylsucrose did. In addition, sinapic acid inhibited decompression- or bilateral carotid artery ligation-induced hypoxia (or mortality) and CO2-induced impairment in mice, and basal forebrain lesion-induced cerebral cholinergic dysfunction (decreases in acetylcholine concentration and choline acetyltransferase activity) in rats. These results, taken together, suggest the possibilities that sinapic acid is not only a very important moiety in the pharmacological activities of tenuifoliside B and 3,6'-disinapoylsucrose but also a candidate for a cerebral protective and cognition-improving medicine.