Evaluation of Biologically Active Extractives in Different Morphological Parts of Walnut Trees for Bioherbicide Applications

This study evaluates various morphological parts of the walnut tree (Juglans regia)—especially, green husks—as potential raw materials for extracting biologically active compounds to develop biodegradable bioherbicides. Accelerated Solvent Extraction (ASE) and maceration were optimized by varying solvents, temperatures, and cycle parameters to maximize the yield of total phenolic compounds (TPC) and antiradical activity. Findings indicate that while water extraction via ASE at 130°C provides the highest overall extractive yield (62.58%) from husks, an extraction temperature of 90°C prevents the thermal degradation of phenolic compounds. Analytical techniques, including UHPLC-DAD-qToF-MS/MS, confirmed the thermal stability of target allelochemicals (juglone) and identified 26 active compounds in the extracts. The research demonstrates that walnut processing waste can be effectively valorized into high-value bioherbicides, promoting sustainable agriculture and a circular economy.