Yerba mate waste: A sustainable resource of antioxidant compounds

• Published in: Industrial crops and products 2018-03, Vol.113, p.398-405
• Main Authors: Gullón, Beatriz, Eibes, Gemma, Moreira, María Teresa, Herrera, René, Labidi, Jalel, Gullón, Patricia
• Format: Article
• Language: English
• Subjects: Antioxidant activity; Bioactive compounds extraction; Solvent efficiency; Yerba mate waste
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2018.01.064

•Valorization of yerba mate waste as a source of antioxidant phenolics.•The extraction process was optimized using one factor at a time method.•Extraction conditions were optimized: liquid/solid ratio, solvents and time.•Obtained extracts exhibited high antioxidant activity.•Chemical composition, structural characterization and thermal stability of the optimal extract. The infusion of yerba mate (Ilex paraguariensis St. Hil.) is the most popular tea-like beverage of southern Latin American countries, and its health benefits such as stimulating effect and antioxidant activity are well known. The exhausted mate leaves are managed as waste and are not currently exploited or valorized as a bio-resource. In this work, a cost-effective alternative for extracting antioxidant compounds from this type of residue as a possible valorization route was investigated. Accordingly, different liquid/solid ratios, solvents and extraction times were evaluated with the aim of maximizing extraction performance, total phenolic (TPC) and flavonoid (TFC) content and antioxidant activity (AA) of the extracts. The optimal conditions allowed the recovery of high level of phenolics (TPC 63.13 mg gallic acid equivalents/g) and flavonoids (TFC 148.45 mg rutin equivalents/g) in the extract, with remarkable content in AA (111.18 mg Trolox equivalents/g). Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analysis identified that the main compounds in the extract were terpenes (phenol, guaiacol, 4-vinylguaicol and eugenol), caffeine, 4-ethyl-resorcinol, hydroquinone, palmitic acid, and stearic acid. Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) analyses provided the functional characteristics and thermal stability of the extract. From the results obtained, it can be concluded that the residue of yerba mate after the infusion of the original yerba mate still possesses high antioxidant potential, mainly associated with its phenolic and flavonoid composition. Furthermore, the content of antioxidant phenolic compounds reported here was higher than most of those reported for agro-industrial residues. Therefore, this type of waste, that is generally discarded, can be valorized as a source of high added-value compounds.