Using HPLC-MS/MS to Assess the Quality of Beet, Mizuna, Lettuce and Corn Salad after Juglone and Walnut Leaf Extract Treatments

The present study was carried out to investigate the yield, quality, and metabolomic responses of four different vegetable crops to treatments with pure juglone standard and walnut (Juglans regia L.) leaf extract at soil concentrations found in walnut orchards. A total of 60 phenolic compounds were identified and quantified, some for the first time in these crop vegetables. Beta vulgaris L. and Lactuca sativa L. were less susceptible to juglone. For crop quality, B. vulgaris showed the least effects of the different treatments. Both Brassica rapa L. var. japonica and Valerianella locusta Laterr. showed lower yields, even at the lower juglone concentration, and reduced quality, so their cultivation in juglone-containing soils should be avoided. This study also investigated leaf quality at different ages and the quality and yield of these crop vegetables grown under the influence of allelochemicals, to determine the influence of allelochemicals on metabolomics and, thus, on the uptake of phenolic compounds considered to be beneficial to human health.