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Agronomy 2018, 8(9), 170; https://doi.org/10.3390/agronomy8090170

Antioxidant Capacity and UPLC-PDA ESI-MS Phenolic Profile of Stevia rebaudiana Dry Powder Extracts Obtained by Ultrasound Assisted Extraction

1
Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco (CIATEJ) Unidad Sureste, Mérida 97070, Mexico
2
CIATEJ Unidad Zapopan, Camino Arenero 1227, El Bajio del Arenal, Zapopan Jalisco 45019, Mexico
3
Departamento de Recursos del Mar, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Mérida 97310, Mexico
*
Author to whom correspondence should be addressed.
Received: 24 July 2018 / Revised: 20 August 2018 / Accepted: 27 August 2018 / Published: 31 August 2018
(This article belongs to the Special Issue Functional Metabolism in Crops/Agronomy)
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Abstract

Stevia leaves, which are commonly used as a natural sweetener in food products, have increased in importance for antioxidant delivery due to their high content of phenolic compounds. In this study, the influence of the drying process on stevia leaves, with regards to phenolic content and antioxidant activity during drying kinetics 40 °C for 7 h, was studied. The effect of solvent concentration and extraction time using a 32 factorial design on total phenol content (TPC), and on antioxidant activity of extracts obtained from dried stevia leaves, by ultrasound assisted extraction (UAE) as alternative method was evaluated. Steviol glycosides contents were also evaluated by a conventional and UAE method. Phenols identification, quantification and purification were performed by Ultra Performance Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (UPLC-ESI-MS), Ultra Performance Liquid Chromatography-Photodiode Array (UPLC-PDA) and advanced automated flash purification, respectively. Drying time affected the moisture content of stevia leaves. A constant weight was reached after six hours of drying, and higher antioxidant activity was observed, while the highest TPC was obtained after seven hours of drying. The highest TPC (91.57 ± 8.8 mg GAE/g dw) and antioxidant activity (603.24 ± 3.5 μmol TE/g dw) in UAE method was obtained when ethanol 50% at 5 min was used. Steviol glycosides extracted by UAE were recorded with a content of 93.18 ± 1.36 mg/g dw and 98.97 ± 1.75 mg/g dw for stevioside and rebaudioside A respectively. Six phenolic compounds including four phenolic acids and two flavonoids were identified and quantified by UPLC-PDA, and confirmed by ESI-MS reporting its fragmentation pattern. Diosmin and chlorogenic acid were the most abundant compounds with values of 2032.36 μg/mL and 434.95 μg/mL respectively. As a novelty we found that the antioxidant activity evaluated in partially purified fractions suggested that biological activity might be attributed to the synergistic effect of the six phenols present in the stevia leaves extract. In addition to its sweeting properties, stevia leaves constitute a potential source of polyphenolic compounds, with antioxidant activity that could be used as a food additive. View Full-Text
Keywords: stevia leaves; drying kinetics; UAE; phenols; antioxidant activity; partial purification; UPLC-PDA ESI-MS stevia leaves; drying kinetics; UAE; phenols; antioxidant activity; partial purification; UPLC-PDA ESI-MS
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Covarrubias-Cárdenas, A.G.; Martínez-Castillo, J.I.; Medina-Torres, N.; Ayora-Talavera, T.; Espinosa-Andrews, H.; García-Cruz, N.U.; Pacheco, N. Antioxidant Capacity and UPLC-PDA ESI-MS Phenolic Profile of Stevia rebaudiana Dry Powder Extracts Obtained by Ultrasound Assisted Extraction. Agronomy 2018, 8, 170.

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