The test compound, 6-gingerol (98.7% purity; chemical structure illustrated in Fig. 1), was purchased from Chengdu Biopurify Phytochemicals Ltd. Piracetam, the positive control, was obtained from Glaxosmithkline (Thailand) Ltd. and DMSO, the vehicle, was obtained from Thermo Fisher Scientific, Inc. (product code: D/4121/PB15).