Isolation of ambiguine D isonitrile from Hapalosiphon sp and characterization of its phytotoxic activity

Cyanobacterium Hapalosiphon sp. contains phytotoxic substances. Fractionation of Hapalosiphon sp. crude extract guided by lettuce seedlings bioassay revealed that multiple fractions contained differential plant growth suppression activity. From the most active fraction inhibiting the growth of lettuce, ambiguine D isonitrile was isolated. A physiological study with ambiguine D isonitrile showed that it effectively inhibited mitosis, which resulted in the suppression of root growth. Ambiguine D isonitrile caused increased reactive oxygen species (ROS) generation and was associated with observed lipid peroxidation and cell death. These oxidative processes probably play a key role in the phytotoxic action of ambiguine D isonitrile in plants.