Effects of glycoalkaloids from Solanum plants on cucumber root growth

The phytotoxic effect of four glycoalkaloids and two 6-O-sulfated glycoalkaloid derivatives were evaluated by testing their inhibition of cucumber root growth. The bioassays were performed using both compounds singly and in equimolar mixtures, respectively. Cucumber root growth was reduced by chaconine (C), solanine (S), solamargine (SM) and solasonine (SS) with IC(50) values of 260 (C), 380 (S), 530 (SM), and 610 microM (SS). The inhibitory effect was concentration-dependent. 6-O-sulfated chaconine and 6-O-sulfated solamargine had no inhibitory effects, which indicated that the carbohydrate moieties play an important role in inhibiting cucumber root growth. The equimolar mixtures of paired glycoalkaloids, both chaconine/solanine and solamargine/solasonine, produced synergistic effects on inhibition of cucumber root growth. By contrast, mixtures of unpaired glycoalkaloids from different plants had no obviously synergistic effects. The growth inhibited plant roots lacked hairs, which implied that inhibition was perhaps at the level of root hair growth.