Simultaneous preparation of water- and lipid-soluble antioxidant and antibacterial activity of purified carnosic acid from Rosmarinus offoccnalis L.

Rosemary is an widely used plant in processed foods and cosmetics due to its high antioxidant activity and fascinating flavor. However, complicated production processes and high price of rosemary antioxidant place restrictions on its commercial application. In this research, a simple, highly efficient procedure for simultaneous preparation of water- and lipid-soluble rosemary extracts was developed. Rosemary leaves were macerated with 1 minimum volume (MV) of 70 % acidic ethanol-water solution for 3 h. Next, column chromatographic extraction method (CCE) designed in our laboratory was employed for simultaneous extraction of carnosic acid and rosmarinic acid, and their extraction rates were 96 % and 94 %, respectively. After the removal of ethanol, the supernatant and precipitate were separately collected as water-soluble extract containing 6.84 % rosmarinic acid and lipid-soluble extract containing 31.18 % carnosic acid. Then, the lipid-soluble extract was separated through dissolution with n-hexane, liquid–liquid extraction with NaHCO3, and precipitation at a pH of 1.0; this yielded a carnosic acid product with 90 % purity. After crystallization with cyclohexane, carnosic acid with > 98 % purity was obtained. The prepared carnosic acid could effectively suppress the growth of Gram-positive bacteria and Edwardsiella tarda growth. This study made complete use of rosemary resources, greatly reducing rosemary extract preparation and carnosic acid extraction costs. Further investigation of the antibacterial effectiveness of carnosic acid could promote its industrial applications as antimicrobial agent in food and aquaculture.