Sustainable Recovery of Phenolic Compounds from Distilled Rosemary By-Product Using Green Extraction Methods: Optimization, Comparison, and Antioxidant Activity

Abstract

Rosemary solid distillation waste (SWR), a by-product of the essential oil industry, represents an important source of phenolic antioxidants. Green technologies such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and accelerated solvent extraction (ASE) of phenolic compounds from SWR were optimized as valorization routes to maximize yield, rosmarinic acid (RMA), carnosol (CARO) and carnosic acid (CARA) contents. Response surface methodology was used in this context, with ethanol concentration (X1), extraction temperature (X2), and time (X3) being the independent variables. A second-order polynomial model was fitted to the data, and multiple regression analysis and analysis of variance were used to determine model fitness and optimal conditions. Ethanol concentration was the most influential extraction parameter, affecting phenolic compounds, while the influence of other parameters was moderate. The optimized conditions were as follows: X1: 67.4, 80.0, and 59.0%, X2: 70, 51, and 125 °C, and X3: 15, 10, and 7 min for MAE, UAE, and ASE, respectively. A comparison of optimized MAE, UAE, and ASE with conventional Soxhlet extraction techniques indicated that ASE provided a higher extraction yield and content of phenolic compounds. However, UAE represented the best process from an environmental point of view, allowing an improved extraction of phenolics from SWR with high energy efficiency and low energy costs.

Antioxidant Activity of Carob Tree (Ceratonia siliqua L.) Leaf Extracts Obtained by Advanced Extraction Techniques

“…Custodio et al [45] investigated the antioxidant activity of the extracts obtained by the decoction of various parts of the carob tree and found that the leaves showed the highest activity according to the FRAP and DPPH test, which can be attributed to the high polyphenolic content. Other studies [46,47] that compared the antioxidant activity of plant extracts using the above-mentioned methods also concluded that the highest antioxidant activity was shown by the extracts with the highest level of polyphenols. In order to investigate the effect of polyphenolic content in the optimal extracts obtained in this study and antioxidant activity, Pearson's correlation factors were calculated (Table 4).…”

Evaluation of Polyphenolic Profile and Antioxidant Activity of Sea Buckthorn (Elaeagnus rhamnoides (L.) A. Nelson) Leaf and Berry Extracts Obtained via Optimized Microwave-Assisted and Accelerated Solvent Extraction

“…Flavan-3-ols were only determined in the leaf extracts and epicatechin was present in higher contents. Contradictory results are reported in the literature concerning the extraction efficiency of phenolic compounds using ASE and MAE and some authors have concluded that the extraction method should be selected depending on the target molecules, as not all phenolics follow the same trend [70,71]. Biesaga [72] reported that hydroxyl groups promoted the degradation of flavonoids during MAE, while sugar and methoxyl groups protected them from degradation.…”