Coffee By-Products Studied by the Planar Ames Bioassay with pH Indicator Endpoint Using the 2LabsToGo-Eco

The mutagenic potential of coffee by-products, including <i>Coffea</i> leaves, blossoms, cherries, and silverskin, was studied using thin-layer chromatography (TLC) coupled with the recent planar Ames bioassay via pH indicator endpoint. The 2LabsToGo-Eco allowed for the separation and detection of mutagens in complex samples. Hot water was the most effective extraction solvent in terms of yield and closely simulated the typical human consumption of coffee by-products. Separation was performed on TLC plates with a mixture of ethyl acetate, <i>n</i>-propanol, and water, followed by bioassay detection. The positive control 4-nitroquinoline 1-oxide exhibited clear mutagenic responses, confirming the proper bioassay performance. In the Ames bioautogram, none of the tested coffee by-products showed mutagenic zones, suggesting the absence of strongly acting, acute mutagens under the applied test conditions; however, given the only 5 h short incubation and the use of TA98 strain only, a longer incubation time and testing with additional <i>Salmonella</i> strains is recommended. The results provide new safety data for <i>Coffea</i> leaves and blossoms and are consistent with some previous studies demonstrating the safety of coffee by-products. However, further improvements in the sensitivity and selectivity of the planar Ames bioassay are demanded, and further in vivo and long-term safety studies are recommended. Considering natural variability, the different uses of pesticides and treatments, and the fluctuating supply chains, coffee by-products may differ highly. The planar bioassay technology using the affordable 2LabsToGo-Eco is a powerful toxicological screening option for the coffee industry, considering the increasing interest in utilizing coffee by-products.