Isolation and identification of an allelopathic substance from duckweed (Lemna minor L.)

An aqueous methanol extract of duckweed (Lemna minor L.) inhibited the growth of cress (Lepidium sativum L.). The extract was partitioned by silica gel, Diaion HP20, Sephadex LH-20 and Diaion HP20SS columns, C-18 Sep-Pak cartridges and reverse phase HPLC to isolate phytotoxic substances. The (3R)-(-)-3-hydroxy-beta-ionone was identified as the active ingredient in the extract by its spectral data. (3R)-(-)-3-hydroxy-beta-ionone inhibited growth of cress and Italian ryegrass seedlings at >= 0.1 and >= 5 mu M, respectively. (3R)-(-)-3-Hydroxy-beta-ionone inhibited 50% of cress roots and shoots growth with 0.1 mu M and 50% of Italian ryegrass root and shoot growth at 2.4 and 3.4 mu M, respectively. The presence of (3R)-(-)-3-hydroxy-beta-ionone in duckweed and its growth inhibitory activity suggested that it may contribute to the allelopathic potential of duckweed.