The analysis of flavonoids and triterpenes extracted from Urtica by LC‐MS and the antimicrobial activity of the extracts

The purpose of this study was to explore the single factors including the time, solid–liquid ratio, choice of organic solvent, and ethanol concentration that influenced the extraction of flavonoids and triterpenoids from Urtica and firstly optimized the ultrasonic-assisted extract conditions using the response surface method. The ethanol extract of Urtica was further purified by polyamide column chromatography and macroporous resin column chromatography. The results showed that flavonoid compounds yield and triterpenoid compounds were 3.432% and 9.184%, respectively. LC-MS analysis was applied for identification and confirmation of flavonoids, triterpenoids, and a small quantity of polyphenols. In addition, the bacteriostasis experiments of the products were conducted. The results showed flavonoid, and triterpenoid compounds from Urtica showed good antibacterial activities. Novelty Impact Statement The ultrasonic-assisted extraction method was used to extract flavonoids and triterpenes from Urtica, and the response surface method was used to optimize the extraction process conditions of triterpenes at the single factor level for the first time. The study found for the first time that there was a large amount of dodemorph and other antimicrobial active substances in the purified flavonoids and triterpene extracts of Urtica through LC-MS analysis. Antimicrobial experiments have confirmed that Urtica on the part of some gram-positive and gram-negative bacteria as well as some plant pathogenic fungus have an excellent inhibitory effect.