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. 2022 May 18;11(5):988.
doi: 10.3390/antiox11050988.

Bioactive Antioxidant Compounds from Chestnut Peels through Semi-Industrial Subcritical Water Extraction

Christian Cravotto  1   2 , Giorgio Grillo  2 , Arianna Binello  2 , Lorenzo Gallina  2 , Mariló Olivares-Vicente  3 , María Herranz-López  3 , Vicente Micol  3   4 , Enrique Barrajón-Catalán  3 , Giancarlo Cravotto  2
Affiliations

Bioactive Antioxidant Compounds from Chestnut Peels through Semi-Industrial Subcritical Water Extraction

Christian Cravotto et al. Antioxidants (Basel). .

Abstract

Chestnut peels are a poorly characterized, underexploited by-product of the agri-food industry. This raw material is rich in bioactive compounds, primarily polyphenols and tannins, that can be extracted using different green technologies. Scaling up the process for industrial production is a fundamental step for the valorization of the extract. In this study, subcritical water extraction was investigated to maximize the extraction yield and polyphenol content. Lab-scale procedures have been scaled up to the semi-industrial level as well as the downstream processes, namely, concentration and spray drying. The extract antioxidant capacity was tested using in vitro and cellular assays as well as a preliminary evaluation of its antiadipogenic activity. The temperature, extraction time, and water/solid ratio were optimized, and the extract obtained under these conditions displayed a strong antioxidant capacity both in in vitro and cellular tests. Encouraging data on the adipocyte model showed the influence of chestnut extracts on adipocyte maturation and the consequent potential antiadipogenic activity. Chestnut peel extracts characterized by strong antioxidant power and potential antiadipogenic activity were efficiently obtained by removing organic solvents. These results prompted further studies on fraction enrichment by ultra- and nanofiltration. The semi-industrial eco-friendly extraction process and downstream benefits reported here may open the door to production and commercialization.

Keywords: adipocytes; bioactivity; chestnut peels; polyphenols; semi-industrial scale; subcritical water extraction; tannins; ultra-nano filtration.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Cellular treatment scheme for ROS quantification. Representative images are shown above the timeline.
Figure 2
Figure 2
Extraction yields at different solid/liquid ratios and temperatures.
Figure 3
Figure 3
TPC, yield, and selectivity.
Figure 4
Figure 4
SWE kinetics at 150 °C for different S/L ratios. (a) 1:20; (b) 1:30.
Figure 5
Figure 5
Peleg model for 1:20 and 1:30 S/L ratios, chestnut peel extractions at 150 °C. (a) TPC selectivity; (b) TPC yield.
Figure 6
Figure 6
LC-MS of chestnut peel extract, DAD chromatograms of extract at 150 °C, 30 min.
Figure 7
Figure 7
(A) ROS reduction levels in 3T3-L1 adipocytes (mean ± SD, n = 6). The untreated sample was considered 100%, and the reduction in the fluorescent signal was normalized against its value. All the values were viability-corrected as described in the methods section. Statistical significance was calculated using untreated samples (black bars) as a reference (* p < 0.05, ** p < 0.01, *** p < 0.001 and **** p < 0.0001). (B) Representative fluorescent images of H2DCFDA staining after treatment with 500 µg/mL extracts in comparison with the untreated sample.
Figure 7
Figure 7
(A) ROS reduction levels in 3T3-L1 adipocytes (mean ± SD, n = 6). The untreated sample was considered 100%, and the reduction in the fluorescent signal was normalized against its value. All the values were viability-corrected as described in the methods section. Statistical significance was calculated using untreated samples (black bars) as a reference (* p < 0.05, ** p < 0.01, *** p < 0.001 and **** p < 0.0001). (B) Representative fluorescent images of H2DCFDA staining after treatment with 500 µg/mL extracts in comparison with the untreated sample.
Figure 8
Figure 8
Triglyceride accumulation levels after AdipoRed™ staining. Undifferentiated control with low glucose is only shown in the left panel. Statistical significance was calculated using the high glucose-treated sample (full mature adipocytes) as a reference (* p < 0.05, ** p< 0.01, *** p < 0.001, and **** p < 0.0001).
Figure 9
Figure 9
Representative microscope images of 3t3-L1 cells treated with different concentrations of the three tested extracts showing the accumulation of lipid droplets.
Figure 10
Figure 10
UF, TPC mass balance, expressed as percentage on TPC.
Figure 11
Figure 11
UF tannins mass balance, expressed as the percentage on TPC. (a) UF total tannin content; (b) tannin composition of retentate (hydrolyzable and nonhydrolyzable).
Figure 12
Figure 12
TPC recovery trend, depending on the different elution fractions.
Figure 13
Figure 13
Purification trend of resin process. Reported values are expressed as percentages (mgGAE on 100 mgEXTR).
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