In the present experiment, sour orange and pomegranate wood as well as the main petiole and palm leaflets were soaked in water for 24 and 48 hours and some biochemical indices and biochemical compounds were measured and the allopathic effects was evaluated. The results showed a significant difference in electrical conductivity (EC), pH, soluble solids as well as some biochemical compounds including total phenols, flavonoids and tannin index between plant sample extracts in both successive washing stages. In all three plant samples, the amount of biochemical compounds in the second stage was significantly reduced compared to the first stage. Evaluation of allopathic effects of the extract prepared from the samples using lettuce seed germination test (as a model plant) showed that seed germination percentage, germination index, root length and shoot length in lettuce under the influence of the extract prepared from washing the sample Orange, pomegranate and date leaves had a significant decrease compared to the control (distilled water) treatment. These results indicate the importance of biochemical compounds in wood of fruit trees and measuring the changes of these compounds in cases such as the preparation of wood mulch, compost and leaf litter and other products that are prepared from wood waste of fruit trees.