荔枝為無患子科,亞熱帶經濟果樹。在果園中,發現荔枝葉殘體會抑制其林下植物生長。本研究目的為驗證荔枝葉殘體的植物相生相剋潛力,並鑑定出其相生相剋物質。研究中發現以5 %荔枝葉水萃液對小白菜、萵苣、莧菜、大花咸豐草、紫花藿香薊、九層塔的種子幼根生長抑制大於70 %。而在荔枝殘體分解實驗中,分解一週的水萃液對萵苣、大花咸豐草的種子幼根生長有最大的抑制,分解二週水萃取液對萵苣、小白菜及大花咸豐草有最大的抑制,分解四週水萃取液對實驗植物種子幼根生長抑制能力皆大於80 %,分解八週水萃取液對實驗植物種子幼根生長抑制能力皆大於90 %,隨著萃取次數增加,荔枝葉水萃液抑制種子幼根生長能力降低。在紙色層層析中,以紫外光燈照射下顯示有4個點,但並非純化合物。另外,利用矽膠管柱層析、高壓液相層析方法在甲醇萃取物中得到三個化合物,經過光譜分析與文獻比對後,確定其結構,分別為(-)-epicatechin(1)、procyanidin A2(2)、kaempferol-3-O-β-D-galactopyranoside(3),其中procyanidin A2(2)在濃度100 μΜ能抑制萵苣種子幼根生長24 %,kaempferol 3-O-β-D-galactopyranoside(3)在濃度1 μΜ能促進萵苣種子幼根生長11.9 %。這些結果顯示荔枝葉具有植物相剋潛能,有待繼續研究做為雜草控制的天然除草劑。
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.