A New Indole Alkaloid, 7 α-Hydroxy-7H-mitragynine, from Mitragyna speciosa in Thailand - Ponglux, Dhavadee; Wongseripipatana, Sumphan; Takayama, Hiromitsu; Kikuchi, Masae; Kurihara, Mika; Kitajima, Mariko; Aimi, Norio; Sakai, Shin-ichiro (Planta Medica, 1994)