Reversal of Multidrug Resistance by Kopsiflorine Isolated from Kopsia dasyrachis - Rho, Mun-Chual; Toyoshima, Mitsuhide; Hayashi, Masahiko; Koyano, Takashi; Subramaniam, Gurusamy; Kam, Toh-Seok; Komiyama, Kanki (Planta Medica, 1999)