| Summary: | 碩士 === 中國醫藥大學 === 生態暨演化生物學研究所 === 98 === Litchi chinensis Sonn., a family of Sapindaceae, is a subtropical commercial orchard crop. Our field observations revealed that the leaves residues of L. chinensis could retard the growth of plants in its surroundings. The objective of this research is to evaluate the allelopathic potential of leaves residues from L. chinensis. Five percent aqueous extract inhibit the radicle growth of Lactuca sativa, Brassica chinensis, Ama- ranthus tricolor, Bidens pilosa, Ageratum houstonianum and Ocimum basilicum by standard sponge bioassay ( SSB ). Aqueous extract of one-week of decomposition from litchi leaves inhibited the radicle growth of L. sativa and B. pilosa; aqueous ex- tract of two-week of decomposition from litchi leaves inhibited the radicle growth of L. sativa, B. chinensis and B.pilosa; aqueous extract of four-week of decomposition from litchi leaves inhibited the radicle growth of the tested seed more than 80 %; aqueous extract of eight-week of decomposition from litchi leaves inhibited the radi- cle growth of the tested seed more than 90 %. As the decomposition period increases, the effect of inhibition decreases accordingly. The result of paper chromatography showed 4 spots which were not pure constituents under UV light. Furthermore, by silica gel colunm and high performance liquid chromatography, the methanolic extract of the leaves from L. chinensis afforded three compounds, including (-)-epicatechin (1), procyanidinA2 (2), kaempferol-3-O-β-D-galactopyranoside (3). The strutures were elucidated by spectroscopic methods and comparison with literatural data. Procyanidin A2 (2) inhibited the radicle growth of L. sativa to 24 % at 100 μΜ, and kaempferol-3-O-β-D-galactopyranoside (3) stimulated the radicle growth of L. sativa to 11.9 % at 1 μΜ. These results indicated that the L. chinensis has significantly alle- lopathic potential and could be used as natural herbicide for weed control.
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