Conventional and Enzyme-Assisted Extraction of Rosemary Leaves (Rosmarinus officinalis L.): Toward a Greener Approach to High Added-Value Extracts  
[PERSON]  
1 Laboratory of Organic Chemistry, Zografou Campus, School of Chemical Engineering, National Technical University of Athens, 15780 Athens, Greece; [EMAIL_ADDRESS] (A.R.N.P. ); [EMAIL_ADDRESS] (L.P.T.) [PERSON]  
1 Laboratory of Organic Chemistry, Zografou Campus, School of Chemical Engineering, National Technical University of Athens, 15780 Athens, Greece; [EMAIL_ADDRESS] (A.R.N.P. ); [EMAIL_ADDRESS] (L.P.T.) The  
(ultrasound- and microwave-assisted extractions) [1; 10; 11]. In order to increase the process yield as well as to optimize the bioactivity of rosemary extracts, a variety of pretreatment techniques performed on the plant material prior to extraction have been examined, such as deoiling, grinding, maceration, or pulsed electric fields (PEF) treatment [12; 13]. Moreover, the ability of green solvents to extract bioactive phytochemicals from rosemary has attracted considerable attention recently. To cite the most recent examples, the group of [PERSON] et al. used choline chloride-based deep eutectic solvents to efficiently extract phenolics from rosemary leaves [14; 15]. The deep eutectic solvents acted as protective agents for the extracted phytochemicals. [PERSON] et al. developed an on-line methodology combining supercritical CO\({}_{2}\) extraction with supercritical chromatography [16] to achieve the sequential extraction of carnosic acid, rosmarinic acid, and pigments from rosemary leaves. Enzyme-assisted extraction (EAE) is considered to be a promising, greener alternative to conventional extraction methods. Enzymes catalyze a variety of hydrolytic reactions acting on the existing polymers in the cell wall, such as pectin and hemicellulose. Bioactive components of the plants are usually linked to the cell wall polysaccharides either by hydrogen bonds or by being encapsulated in hydrophobic pockets, resulting in a stable complex. Hence, the enzyme-assisted extraction manages to release the phenolic compounds, rendering them more easily extractable, improving their extraction rate, selectivity, and yield. Moreover, the use of different enzymes, as well as different extraction conditions, strongly affects the outcome, enabling the development of a tailor-made extraction formula to obtain an added-value final product [17; 18]. [PERSON] et al. [19] studied the extraction of polysaccharides from the leaves of lotus with four different enzyme types, namely amylase, cellulose, protease, and pectinase. All extracts showed different chemical compositions with the use of pectinase, resulting in an extract with good immunostimulatory activity. [PERSON] et al. [20] were able, via experimental design and statistical analysis, to determine the optimal conditions of the combined use of polygalacturonase, pectin lyase, cellulose, xylanase for the extraction of carotenoids from tomatoes. It was proved that the experimental conditions play a vital role in the properties of the extract obtained. [PERSON] et al. [21] investigated the optimization of the conditions for the recovery of bioactive compounds from lentils with the use of proteases and cellulases. The results of the study revealed an up to 226% improvement of the antioxidant activity of the extract, compared to a non-enzymatic extraction technique. Recently, [PERSON] et al. [22] reported an enzymatic approach for the extraction of rosemary leaves which was implemented using Cellulase A and four proteases. The results obtained from the experimental design revealed that the highest rosmarinic acid extraction was achieved after 4.6 h of extraction at 36.6 \({}^{\circ}\)C using Cellulase A at concentration 2.56% and a water-to-sample ratio of 28.69 mL/g. The aim of the present work is the identification of the optimum extraction method of rosemary leaves in order to obtain an extract that combined high total phenolic content and antioxidant activity.