Isolation and identification of allelochemicals from invasive plant Ipomoea cairica

Ipomoea cairica L. Sweet is an extensively invasive plant in southern China and its allelopathy has been confirmed. However, little is known about its allelochemicals, hence, we did this study to isolate and identify the allelochemicals using ultrasonic extraction and bioactivity guided column chromatography. We isolated 2 allelochemicals: 3–3′-5-Trihydroxy-4′-7-dimethoxyflavone and 3–3′-5-Trihydroxy-4′-7-dimethoxyflavone-3- O-sulfate from the crude extracts of n-butanol. In bioassay, both these allelochemicals independently or jointly inhibited the seed germinations of all 4 test plants [Raphanus sativus, Cucumis sativus, Brassica pekinensis and Ligularia virgaurea (a weed)]. These allelochemicals exhibited selectivity, both strongly inhibited the germination of cucumber seeds but were moderately inhibitory to cabbage seeds. There was antagonism between these allelochemicals and they might be candidates for new natural product based herbicides.