Green Extraction Tree: A Novel Tool to Greenness Metric for Green Extraction of Natural Products

A comprehensive and intuitive evaluation tool, termed the Green Extraction Tree (GET), has been developed to assess the greenness of the sample preparation process in the green extraction of natural products. The assessment criteria integrate the 10 principles of green sample preparation with the 6 principles of green extraction of natural products, encompassing the entire natural product extraction process, including samples, solvents and reagents, energy consumption, byproducts and waste, process risk, and extract quality. The GET employs a "tree" pictogram to classify and evaluate the greenness of various aspects of the natural product extraction process, using three different color markers (green, yellow, red) to represent three distinct levels of environmental impact (low, medium, high) across different processes. In terms of quantitative analysis, the values 2, 1 and 0 are assigned to green, yellow, and red respectively, the final scores are used to conduct a horizontal comparison of the greenness of different processes. The evaluation procedure was conducted using an open-access toolkit that generates the GET pictogram corresponding to each extraction method, facilitating a visual assessment of the greenness of natural product extraction methods. Through five different extraction methods as case studies, the difference of greenness and extraction process to be improved of each method were successfully identified by GET. Additionally, compared to the other representative green assessment tools, GET presents a unique novel perspective and exhibits greater applicability to the natural product green extraction process.