An efficient method for quantitative analysis of the lipophilic rosemary extract applied in vegetable oils

Abstract Rosemary extract (RE) is a natural antioxidant, which has been widely used for preservation of oils. The main lipophilic components of RE are carnosic acid (CA) and carnosol (CN). However, the reports on the method for determining CA and CN in vegetable oils are really rare. Herein, a highly efficient method for quantitative analysis of CA and CN in vegetable oils was developed. The vegetable oil samples were dissolved in n-hexane saturated using acetonitrile and extracted with acetonitrile saturated using n-hexane, followed by HPLC analysis using UV detector. Qualitative and quantitative determinations were performed by external standard method. Under the optimised conditions, limit of detection (LOD) and limit of quantitation (LOQ) of CA were 0.11 μg mL−1 and 0.55 μg mL−1, respectively; LOD and LOQ of CN were 0.05 μg mL−1 and 0.20 μg mL−1, respectively. When the method was applied to determine CA and CN in vegetable oils spiked with standards, good recoveries (83.98% ~ 102.80% for CA and 98.29% ~ 114.74% for CN) and RSDs (0.61% ~ 7.36% for CA and 0.40% ~ 2.88% for CN, n = 2) were achieved. Accordingly, this work would efficiently identify and monitor lipophilic RE in vegetable oils, as this advanced method showed sensitive, quantitative, and reliable results suited for vegetable oils.