Inhibition of Na+,K+-ATPase Activity by (-)-ent-Kaur-16-en-19-oic Acid and its Derivatives - Ngamrojnavanich, Nattaya; Sirimongkon, Supaporn; Roengsumran, Sophon; Petsom, Amorn; Kamimura, Hishashi (Planta Medica, 2003)