Amaranthus viridis L. belongs to the Amaranthaceae family. It is a rich source of numerous phytochemicals and amino acids. The objective of this work was to optimize Ultrasound-Assisted Extraction (UAE) based on the extraction yield and Thin-Layer Chromatography (TLC) profile under different conditions, to compare the optimized UAE to the Soxhlet extraction method and evaluate the cytotoxic effects of the ethyl acetate fraction of the 80 % ethanolic extract on the SKGT-4 (human esophageal adenocarcinoma), AGS (human gastric adenocarcinoma) and A431 (human epidermoid carcinoma). A one-factor at a time experiment was carefully designed to assess the influence of the following factors on the extraction: time, frequency, solid-to-solvent ratio and aqueous ethanol concentration. Soxhlet extraction using 80 % aqueous ethanol was done for defatted plant material, then fractionation using chloroform, ethyl acetate and n-butanol. Cytotoxicity of ethyl acetate fraction was evaluated using the MTT assay on AGS, A431 and SKGT-4 cell lines. The results indicated that in the UAE, the solid-to-solvent ratio has the most significant effect on yield. Soxhlet extraction proved to be more efficient than UAE in terms of TLC profiles. The cytotoxicity of the ethyl acetate fraction exhibited cytotoxic activity against the tested cell lines in a concentration-dependent manner. Thus, selecting a particular extraction method depends on the target compounds. Soxhlet is preferred for gaining certain compounds that require heat for their extraction. The ethyl acetate fraction showed a cytotoxic effect on various cell lines related to cell components and their interactions with phytochemicals present in this fraction.
