Sequential high-pressure extraction of caffeine and bioactive compounds from caferana seeds (Bunchosia glandulifera)

https://doi.org/10.1016/j.supflu.2020.104958Get rights and content

Highlights

  • 3-steps sequential extraction of caferana seeds using ScCO2, ethanol, and water.

  • High overall yield of 62.4 % was achieved from the sequential extraction.

  • Highest caffeine concentration was obtained in sequential extraction.

  • Higher monounsaturated fatty acids content was obtained using supercritical CO2.

  • Enhanced antioxidant activity was related to higher phenolic content values.

Abstract

Caferana (Bunchosia glandulifera) is a Brazilian plant that produces small red fruits with high nutritional value and possible anti-aging effects. This study aimed to evaluate the composition of caferana seed extracts obtained by sequential extractions with supercritical carbon dioxide in the first step, followed by pressurized liquid extractions using ethanol (second step) and water (third step) as solvents. Obtained extracts were characterized in terms of global yield, caffeine, tocols, fatty acids contents, and total phenolics, as well as their antioxidant activity, and results were thus compared with the conventional extraction method. Sequential extraction showed the best global yield (62.4 %). Supercritical carbon dioxide extract was more concentrated in caffeine (8.44 mg/g), and ethanolic one was more concentrated in total phenolic compounds with higher antioxidant activity capacity, whereas aqueous extract contained low levels of all monitored compounds. Overall, sequential extraction reveled increased selectivity and efficiency in obtaining extracts enriched with different compounds.

Introduction

Caferana (Bunchosia glandulifera) is a plant species typical from the south region of Brazil, which produces small reddish fruit with a sweet and slightly spicy pulp. Its fruit pulp is a natural source of bioactive compounds with antioxidant potential, whereas the seed contains a high concentration of minerals and polyunsaturated fatty acids (PUFAs) [1,2]. The fruit pulp is consumed in natura or in preparations, whereas the seeds are consumed after being roasted and grounded. Studies using conventional extraction methods (ethanolic maceration) revealed that caferana root and leaves contain high levels of total phenolic compounds (TPC) [3]. Besides that, studies reporting the high content of caffeine in roasted and green caferana seeds can also be found in the literature [4] Therefore, further research in extraction and characterization of caferana fruit and seed extracts can corroborate to the expansion of industrial applications of caferana plant. However, extraction methods need to provide compounds with the highest purity as possible, avoiding solvent contamination and a production with environmental friendly and commercially viable concepts.

Studies report that sequential extractions of bioactive compounds have been used with certain advantages. Since carbon dioxide (CO2) is a non-polar compound, extraction of compounds considered to be polar with supercritical CO2 is thus limited. For this reason, water and ethanol become significant to extract substances of high and medium polarity, respectively. In this sense, sequential extraction can be applied, in which supercritical CO2 (SFE) extracts with non-polar compounds and further extraction with pressurized liquids (PLE) as ethanol and/or water withdraw polar compounds from the same raw material [[5], [6], [7], [8], [9], [10]].

In this context, the use of Generally Recognized as Safe (GRAS) solvents with different polarities has been recommended by several researchers [5,8,9,11,12], particularly in sequential extraction processes. Because of polarity features of some bioactive compounds found in several raw materials, the use of sequential extraction may provide selective extraction of molecules of interest, with potential application in pharmaceutical, nutraceutical, and food products [13].

This study aimed to obtain caferana seed extracts rich in caffeine and bioactive compounds, such as total phenolic compounds, tocols, and fatty acids using the sequential high-pressure extractions with supercritical carbon dioxide (SFE) extraction technique, followed by two pressurized liquid extractions (PLE) using ethanol and water as solvents, consecutively. Obtained extracts were characterized in terms of global extraction yield, caffeine, tocol, and fatty acids contents, total phenolics, as well as antioxidant activity.

Section snippets

Chemicals

Carbon dioxide (CO2, 99.0 % purity) was purchased from White Martins (Brazil), whereas ethanol (99.8 % v/v), hexane (98.5 % v/v), and isopropanol (98.5 % v/v), acquired from Synth (Brazil), were used as solvents in the extractions. The following chemicals were used for the extracts characterization: helium gas (99.0 % purity, White Martins, Brazil); fatty acids standard (99−99,9 % purity, FAME mix C8-C24; Sigma-Aldrich, U.S.A.); α-, β/ γ- and δ- tocopherols (Supelco, 99.5 % purity, U.S.A.); α-,

Characterization of the raw material

In order to evaluate the raw material quality, caferana seeds were submitted to a complete characterization which includes moisture, total lipids, mean particle diameter, density, and bed porosity (Table 1). A difference of 3.31 % between the volatile + moisture (VM%) and moisture (M%) was found. This result can be explained by the evaporation of volatiles other than water contained in caferana seeds. Other authors have also found similar gaps when measuring the moisture of plant raw materials [

Conclusions

The comparative study between sequential and conventional extraction showed that the combination of sequential extraction processes was more efficient to obtain extracts with greater selectivity in compounds of interest, using the same plant matrix. Experimental results revealed that the first step with supercritical CO2 provided an extract with high concentrations of caffeine, tocols, and fatty acids. Meanwhile, the second step with pressurized ethanol resulted in extracts with higher caffeine

Declaration of Competing Interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The authors wish to express their sincere gratitude to São Paulo Research Foundation (FAPESP) (2014/21252-0; 2017/16979-7, 2018/13207-6), National Council for Scientific and Technological Development (CNPQ) (429873/2018-2; 132690/2018-7; 406963/2016-9, 305870/2014-9; 140702/2017-2), and the Coordination for the Improvement of Higher Education Personnel (CAPES - 001) for their financial support.

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