Acteoside from Rehmannia glutinosa nullifies paraquat activity in Cucumis sativus

A natural substance that nullifies paraquat activity was isolated from paraquat-tolerant Relumannia glutinosa and identified. The active component was characterized by spectral analysis as 3,4-dihydroxy-beta-phenethyl-O-alpha-rhamnopyranosyl-(1 --> 3)-4-O-caffeoyl-beta-D-glucopyranoside (acteoside). Phytotoxic injury of paraquat on the leaves of paraquat-susceptible cucumber was greatly decreased when paraquat was applied in combination with the isolated acteoside. No necrosis was observed in the cucumber leaves treated with 0.2 mM paraquat in 0.2% acteoside solution. Acteoside also decreased the levels of chlorophyll loss and malondialdehyde production caused by paraquat in a concentration-dependent manner. These results imply that the acteoside detected in R glutinosa is associated with paraquat tolerance. (C) 2002 Elsevier Science (USA). All rights reserved.