The effect of the extraction method on the antibacterial activity of white mulberry extracts

Introduction: The Polish cultivar of white mulberry (Morus alba L.) “Żółwińska wielkolistna” is a sourceof many bioactive substances with a wide spectrum of activities. The leaves of the plant are consideredto be a raw material richest in bioactive substances. The unique properties of the plant are primarily dueto polyphenols, in particular flavonoids, including: rutin, albanon, kuwanone, which make it possible touse white mulberry as an agent with a wide spectrum of activities, from anti-inflammatory, diaphoretic,antioxidant to antimicrobial. Objective: The aim of the study was to determine the effect of the method of extracting substances fromdried white mulberry leaves on the antibacterial activity of the obtained extracts. Four extraction methodswere used to obtain the extracts, and then their antimicrobial activity against selected Gram-positive andGram-negative bacteria was determined. Methods: Mulberry leaves were collected in September 2021 from an ecological plantation located at theExperimental Station, Institute of Natural Fibers and Medicinal Plants in Poznań – National ResearchInstitute in Pętkowo. Leaves were dried at 60C for 12 hours, then laboratory analyses were performed.The extraction was carried out by the following methods: 1.) carbon dioxide extraction, 2.) carbon dioxideextraction using a cosolvent, 3.) maceration with carbon dioxide extraction using a cosolvent, 4.) solventextraction. Then, the antimicrobial activity of the obtained extracts against selected strains of Grampositiveand Gram-negative bacteria was determined. MIC (minimum inhibitory concentration) and MBC(minimum bactericidal concentration) were determined. Results: As a result of the conducted research it was found that there are differences in the antibacterialactivites of extracts from dried white mulberry leaves depending on the extraction method used. Thehighest antibacterial activity both against Gram-positive and Gram-negative bacteria was shown by extractsobtained using a supercritical carbon dioxide extractor without the use of cosolventa, with more effectivegrowth-inhibiting and bactericidal effects observed against Gram-positive bacteria compared to Gramnegativebacteria. Conclusions: Extracts obtained from dried leaves of white mulberry (Morus alba L.) of the Polish variety“Żółwińska wielkolistna” have antibacterial properties. This leads to the possibility of using white mulberryin herbal medicine and pharmacology as an antimicrobial agent.