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Microwave‐assisted extraction of phenolic compounds from Morus nigra leaves: optimization and characterization of the antioxidant activity and phenolic composition
Author(s) -
Radojković Marija,
Moreira Manuela M,
Soares Cristina,
Fátima Barroso M,
Cvetanović Aleksandra,
ŠvarcGajić Jaroslava,
Morais Simone,
DelerueMatos Cristina
Publication year - 2018
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.5541
Subject(s) - gallic acid , oxygen radical absorbance capacity , dpph , chemistry , chlorogenic acid , polyphenol , trolox , caffeic acid , ascorbic acid , antioxidant , extraction (chemistry) , rutin , food science , chromatography , organic chemistry
BACKGROUND Morus nigra (mulberry) fruit has been reported as a source of bioactive compounds, although information about their leaves is very limited. Usually, they are considered wastes and have been traditionally used only for tea preparation. The main objective of this work was to explore the valorization of mulberry leaves by polyphenols microwave‐assisted extraction (MAE) and characterization of their antioxidant activity and phenolic composition. A 2 3 factorial design combined with response surface methodology were applied to characterize the effect of main microwave parameters on total phenolic content (TPC). RESULTS The optimized MAE conditions were 20 mL of ethanol:water (1:1; v/v), 120 °C, 28 min, 0.414 g and medium stirring speed. Under these conditions, TPC was 19.7 ± 2.0 mg gallic acid equivalents (GAE) g ‐1 dry plant (DP), and antioxidant activity was 15.3 ± 1.0 mg ascorbic acid (AA) g ‐1 DP (ferric reduction activity power –FRAP– assay), 18.6 ± 1.3 mg Trolox equivalents (TE) g ‐1 DP (2,2‐diphenyl‐1‐picrylhydrazyl –DPPH– assay) and 186 ± 15 mg TE g ‐1 DP (oxygen radical absorbance capacity –ORAC– assay). When compared with ultrasound extraction and Pharmacopeia reference method, MAE was more efficient, representing a valuable technology. Of the 13 compounds identified by HPLC, the most abundant were rutin, chlorogenic, β‐resorcylic and caffeic acids. CONCLUSION These results indicate that mulberry leaves are of potential interest for agro‐food industries as a new source of natural antioxidants. © 2017 Society of Chemical Industry