New Phenylphenalene Derivatives from Water Hyacinth (Eichhornia crassipes)

Water hyacinth (Eichhornia crassipes) is a cause of great concern in terms of environmental and agricultural impacts in many parts of the world. Phytochemical investigation of water hyacinth led to the isolation of six new phenylphenalenes, 2,3-dihydro-3,9-dihydroxy-5-methoxy-4-phenyl-1H-phenalen-1-one (1), 2,3-dihydro-8-methoxy-9-phenyl-1H-phenalene-1,4-diol (2), 2,3-dihydro-4,8-dimethoxy-9-phenyl-1H-phenalen-1-ol (3), 2,3-dihydro-9-(4-hydroxyphenyl)-8-methoxy-1H-phenalene-1,4-diol (4), 2,6dimethoxy-9-phenyl-1H-phenalen-1-one (5), and 7-(4-hydroxyphenyl)-5,6-dimethoxy-1H-phenalen-1one (6), together with the four known compounds 7-10. Their structures were elucidated by spectrometric methods including 1D- and 2D-NMR, and MS analysis. These compounds may be involved in allelopathic interactions of water hyacinth with neighboring plants.