Innovative UAPLE system coupled with UV-vis detection: a sustainable method for extracting and quantifying phenolics...

Monitoring industrial processes is critical for ensuring consistent product quality, as consumers expect uniformity across different production batches. In the case of herbal extracts, such as rosemary hydroalcoholic extracts, it is essential to control the yield of target compounds to maintain both the expected quality and safety. Typically, these extracts are produced in an extractor and then analyzed separately in a laboratory (offline). By integrating these methods, it is possible to reduce the number of manipulation steps, shorten processing times, and lower solvent and energy consumption; however, combining extraction techniques with quantification analysis remains a challenge.

Accordingly, we designed an innovative method to simultaneously extract and quantify the primary phenolic acids from rosemary using an ultrasound-assisted pressurized liquid extraction (UAPLE) system inline coupled to a UV-vis detector. Jacket temperature (40, 60, 80, 100 °C), nominal power (240, 320, 400 W), and ultrasound time (1, 3, 5 min) were optimized concerning the offline yield of carnosic derivatives (CD) in ethanol 99.5 % (v/v) and rosmarinic acid (RA) in ethanol 30.0 % (v/v). Time and power had minimal impact on the yield of both CD and RA compounds. Temperature was the most significant factor. Increasing temperature favored RA extraction but reduced CD yields above 62.1 °C. Offline optimization yielded 22.7 ± 0.7 mg_CD.g_biomass^-1 (at 62.1 °C, 400 W, 5 min) and 9.9 ± 0.2 mg_RA.g_biomass^-1 (at 100 °C, 240 W, 5 min). In addition, changing solvents during the ongoing process allowed to obtain CD and RA in separated fractions.

This work introduced a green, novel, inline method for selectively UAPLE extracting and quantifying the primary phenolic acids in rosemary. Inline quantification approach successfully matched the offline (conventional) yield for carnosic derivatives and rosmarinic acid. Therefore, our system enabled a quicker and easier quantification of target compounds without compromising the yields.