Biol. Pharm. Bull. 30(9) 1727—1731 (2007)

farct dementia accompanying the increase in aging populations has become a social problem, the development of effective drugs for treating these conditions is vital. Among the traditional Chinese natural medicines, Polygala root (Japanese name: onji)—the root of Polygala tenuifolia WILLDENOW (family Polygalaceae)—may improve memory, since some Chinese prescriptions containing Polygala root have been used to treat amnesia, neurasthenia, palpitation, and insomnia. Recent studies revealed that P. tenuifolia roots are effective for memory impairment in rats and mice, and scopolamine-induced impairment of passive avoidance response was improved by oral administration of water extract of Polygala root in mice. Park et al. also reported that ethanol extract from Polygala root (BT-11) was effective against scopolamine-induced cognitive impairments in passive avoidance response and water maze tests. Tenuifoliside B, one of the saccharides containing acyl groups isolated from P. tenuifolia, had an ameliorative effect on scopolamine-induced impairment in the performance of passive avoidance tasks in rats. The eight-arm radial maze task is regarded as more useful for studying the effects of drugs on the learning process and memory than other methods such as passive and active avoidance tasks because it estimates the process of spatial cognition. Moreover, drugs used clinically to treat dementia also display effectiveness in the radial maze task. Therefore, we studied the effects of a precipitate fraction (PTB) obtained from an n-BuOH extract of P. tenuifolia on the retrieval process of spatial cognition in rats using the eight-arm radial maze with four-arms baited. We also investigated the effects of cinnamic acid derivatives, which are present as the acyl groups of the constituents of PTB, and a purified saponin-rich fraction (PTBM) on scopolamineinduced memory impairment in this experimental system. MATERIALS AND METHODS