Research Centre for Natural Medicinal Chemistry, College of Sciences, Northwest A & F University, Yangling, 712100, Shaanxi, China.
*Corresponding Author: E-Mail: jinminggaocn@yahoo.com.cn
1College of Resource and Environment, Northwest A&F University, Yangling, Shaanxi, 712100, China
The alcoholic extracts of walnut (Juglans regia L.) leaves showed allelopathic activity against lettuce (Lactuca sativa L.) seed. Activity-guided fractionation of walnut leaves extracts led to the isolation of two major flavonol allelochemicals: kaempferol (H) and kaempferol-3-O- -L-arabinofuranoside (I) and their structures were elucidated by spectroscopic analysis. Compounds H and I stimulated lettuce seed germination at low concentrations, but inhibited the seedling growth of lettuce at high doses. Compound I showed stronger effect on lettuce seed germination and seedling growth than its aglycone H. It was reported for the first time that both flavonols are additional allelopathic substances in walnut plant. No juglone was isolated or detected by GC-MS in the organic extracts of walnut leaves, indicating the absence of juglone in walnut dry leaves.
Allelopathic activity, flavonols, Juglans regia, kaempferol-3-O--Larabinofuranoside, lettuce, walnut
