UPTAKE AND ACCUMULATION OF THE ALKALOIDS QUININE AND CINCHONAMINE IN CULTURED-CELLS OF CINCHONA-ROBUSTA AND CATHARANTHUS-ROSEUS

The uptake and accumulation of the indole alkaloid cinchonamine and the quinoline alkaloid quinine in suspension cultured cells of Cinchona robusta and Catharanthus roseus were studied. Both alkaloids are endogenous to Cinchona and are not found in Catharanthus. Uptake in Cinchona appeared to be the resultant of two processes: rapid uptake with an equilibrium after 2 h, and slow and steady uptake with equilibrium after about 6 h. Occasionally, the cells of Cinchona lost their brownish-orange colour. During this physiological state of the cells only rapid uptake was observed. Steady uptake in these (white) cells could be induced by vanadate. The time course of rapid uptake in Cinchona was almost identical to the time course of uptake in Catharanthus, and had characteristics of free diffusion of non-protonated alkaloids in combination with ion-trapping of protonated alkaloids. Slow and steady uptake of quinine in Cinchona cells was determined and simultaneously the time course of the pH of the vacuoles was measured with in vivo P-31-NMR. The slow and steady uptake appeared to be correlated with a steady decrease in vacuolar pH. The results demonstrate that a strong basic alkaloid, like quinine, can be accumulated by free diffusion of its neutral form in combination with ion-trapping of its charged form. Slow and steady uptake, which is often observed in alkaloid transport, is not caused by additional accumulation mechanisms or alkaloid carriers, but is the effect of slow acidification of the vacuoles.