Extraction Methods for Plant-derived Antimicrobial Phytochemicals and Their Testing Techniques: A Scoping Review

Abstract

Plant-derived antimicrobials have demonstrated significant potential for therapeutic applications. However, the extraction of antimicrobial compounds from plants is a complex process involving various methods used to isolate and concentrate bioactive molecules responsible for antibacterial, antifungal, and antiviral activities. This review study aims to thoroughly investigate and evaluate the process of extracting antibacterial substances from plants and the many techniques used to assess their antimicrobial effectiveness in recent studies. This scoping review study was carried out in accordance with the PRISMA-ScR 2018 checklist guidelines. Google Scholar, PubMed, and PubMed Central were the electronic databases utilised in the search for articles. 84 articles published from January 2020 to December 2024 were included for the review. Among the conventional extraction methods, crude solvent extraction was the most prevalent extraction method, followed by maceration, Soxhlet extraction 11 (11.7%), distillation, and the conventional shaking process. The most predominantly applied advanced extraction techniques were ultrasonification-assisted extraction, followed by the microwave-assisted extraction technique. Assessing the most applied antimicrobial assay technique, Agar well diffusion was the most employed technique, followed by disc diffusion, Broth dilution, Microwell dilution, and time-kill assay. The bacterial and fungal isolates used for testing across the study are of pathological importance and readily available, including bacterial species such as Staphylococcus sp., Escherichia sp., Salmonella sp., Klebsiella sp., and Pseudomonas sp., as well as Shigella sp. Fungal isolates used across the studies included Candida sp., Aspergillus sp., Penicillium, Fusarium, and Rhizopus, among others. While conventional methods are mainly utilised for small-scale research purposes due to their less cost-intensive nature, advanced methods of extraction are gradually taking over the scene; it is important to ascertain in further studies to what extent the method of extraction affects the efficacy of the antimicrobial substances.