Abstract: Aichasu (Ⅰ) was isolated from the Chinese herb Ardisia japonica. It shows antitussive activity in mice (cough induced by ammonium hydroxide spray), and has been used clinically for the treatment of chronic bronchitis with beneficial effect. Through spectroscopic analyses (UV, IR, NMR, MS) and the determination of physico-chemical constant as well as periodate degradation, aichasu (Ⅰ)was identified as bergenin formerly isolated from the root of Bergenia crossefolia.Aichasu (Ⅰ)was synthesized by the reaction of methyl 4-O-methylgallate with acetobromoglucose in the presence of sodium methoxide in methanol. A by-product was separated from the reaction mixture and determinted to be methyl 3-β-glucosyl-4-methoxy-5-hydroxybenzoate (Ⅵ-1).