HPLC-DAD Analysis, SFE-CO₂ Extraction, and Antibacterial Activity on Bioactive Compounds from Mosla chinensis Maxim

Mosla chinensis Maxim is an annual herb with many potential purposes in agricultural, industrial, and pharmaceutical fields. At present, the extract of the whole plant from M. chinensis has been proven to demonstrate antifungal, antioxidant, and anti-inflammatory activities. Previous studies focused on the enzyme pretreatment in hydrodistillation from M. chinensis. However, organic solvent or supercritical fluid carbon dioxide extraction (SFE-CO₂) methods, which are commonly utilized in industry, have seldom been studied and cannot provide multiple evaluations of yield. In this work, we analysed compounds from M. chinensis by HPLC-DAD, discussed n-hexane extraction, and conducted further investigations on SFE-CO₂ through the design of response surface methodology (RSM). The sample obtained from pilot-scale SFE-CO₂ was also tested against nine kinds of microorganisms. Single-factor results revealed that the extraction rates from M. chinensis by steam distillation, n-hexane extraction, and SFE-CO₂ were 1%, 2.09%, and 3.26%, respectively. RSM results showed a significant improvement in extraction rate through optimising pressure and time, and the interaction of both factors was more important than that of temperature-pressure and temperature-time. A pilot-scale test with an extraction rate of 3.34% indicated that the predicted RSM condition was operable. In addition, samples from the pilot-scale SFE-CO₂ showed antibacterial effects against three previously unreported bacteria (Gardnerella vaginalis, methicillin-resistant Staphylococcus aureus, and Propionibacterium acnes). These results fill the gap in previous research and provide more information for the application and development of M. chinensis in the future.