The stability test in storage of "Rokumi-gan" powders was carried out under accelerated (40°C, 75%RH, in the dark) and low-temperature conditions (10°C, in the dark). Morroniside (1), loganin (2), paeoniflorin (3), paeonol (4), γ-aminobutyric acid (5) and 50% (v/v) ethanol extract (Extract) were selected as quality indicators. The powder preparation was confirmed to be stable for six months in tight storage under 10°C because the contents of 1, 2, 3, 5 and Extract did not change and that of 4 decreased by 7%. During six-month tight storage under the accelerated condition, the contents of 2, 3 and Extract did not change and that of 4 decreased by 12%. Those of 1 and 5 decreased according to apparent one and two-stage firstorder disappearance, respectively. In open storage, the contents of 1-5 and Extract decreased faster than in tight storage according to apparent two-stage first-order disappearance. These results indicated that temperature was one of the critical factors for good storage and that the stability of the powder preparation in storage under room temperature was not validated.
