Rikkunshito (RKT), a Japanese traditional medicine, has been shown to stimulate food intake in rats with cisplatin-induced anorexia: however, the underlying mechanisms remain unknown. In this study, we investigated whether RKT is involved in the degradation of peripheral ghrelin. RKT inhibited decreases in plasma ghrelin level and enhanced acyl- to desacyl-ghrelin (A/D) ratio in cisplatin-treated rats. Several components of RKT demonstrated inhibitory activity against ghrelin deacylating enzymes. In addition, 10-gingerol, a component of RKT, inhibited exogenous ghrelin deacylation. Therefore, RKT may enhance plasma acyl-ghrelin level, at least in part, by inhibiting the circulating ghrelin degrading enzyme. (C) 2011 Elsevier Inc. All rights reserved.