Use of Microwave Assited Extraction to obtain anthocyanins and total phenolic compounds rich extracts in myrtle (Myrtus communis L.)

Abstract

Myrtle (Myrtus communis L.), is a wild shrub, typical of the Mediterranean flora. Myrtle is an evergreen plant with very aromatic dark green leaves, white, delicate flowers and small, round, dark blue/purple fruit. As a member of the aromatic plants and being typical ofthe Mediterranean flora, myrtle has been the object of a number of studies which have shown that it also possesses very interesting medicinal properties being referred to as an antiseptic, antimicrobial, disinfectant and hypoglycaemic agent. Studies have shown high antioxidant capacity in plant extracts obtained both by conventional extraction and by supercritical fluid extraction. The applicability of microwave assisted extraction has never been evaluated before for extraction of anthocyanins and phenolic compounds in myrtle. Microwave Assisted Extraction has been used to extract both anthocyanins and total phenolic compounds in myrtle pulp. The optimization of the extraction variables (% methanol, pH, temperature and ratio mass/solvent) was performed using the Box-Behnken methodology considering the total amount of anthocyanins on the one hand and total phenolic compounds on the other hand as independent variables. The anthocyanins identified in Myrtle pulp using UHPLC-Q-ToF-MS were delphinidin-3-O-glucoside, cyanidin-3-O-glucoside, petunidin-3-O-glucoside, peonidin-3-O-glucoside, malvidin-3-O-glucoside, delphinidin-3-Oarabinoside, cyanidin-3-O-arabinoside, petunidin-3-O-arabinoside, peonidin-3-O-arabinoside and malvidin-3-O-arabinoside. Anthocyanins were analyzed by UHPLC-UV-Vis and total phenolics by the Folin-Ciocalteu spectrophotometric method. The percentage of methanol is the most critical variable in extracting anthocyanins and the extraction temperature and the percentage of methanol are the most critical for the total phenolics. The extraction kinetic was also studied using the best extraction conditions. Five minutes of extraction was sufficient to extract the maximum amount both the total phenolic compounds and the total anthocyanins. The methods developed have a good repeatability and reproducibility (RSD < 5%). The two methods developed have been employed for the analysis of anthocyanins and total phenolic compounds in different myrtles collected in different zones of the province of Cadiz (South of Spain).