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. 2019 Dec 16;8(12):647.
doi: 10.3390/antiox8120647.

Characterization of Polyphenolic Compounds Extracted from Different Varieties of Almond Hulls (Prunus dulcis L.)

Maher Kahlaoui  1   2 , Stefania Borotto Dalla Vecchia  1 , Francesco Giovine  1 , Hayet Ben Haj Kbaier  2 , Nabiha Bouzouita  2 , Letricia Barbosa Pereira  1   3 , Giuseppe Zeppa  1
Affiliations

Characterization of Polyphenolic Compounds Extracted from Different Varieties of Almond Hulls (Prunus dulcis L.)

Maher Kahlaoui et al. Antioxidants (Basel). .

Abstract

Ultrasound-assisted extraction (UAE) was applied as a pretreatment technique to improve the recovery of polyphenols from the almond hulls of four Tunisian and three Italian almond varieties, followed by the characterization with HPLC-DAD. The operating parameters (solid/liquid ratio, extraction time, and ethanol concentrations) were optimized using a Response Surface Methodology. A polynomial equation was calculated to describe the relationship between the operating parameters and dependent variables as total polyphenolic content (TPC) and antioxidant activity (RSA). A desirability function approach was used to determine the optimum conditions for operating parameters: a solid:solvent ratio of 2 g/100 mL, an extraction time of 13 min, and an ethanol concentration of 51.2%. Among the almond varieties, Pizzuta and Fakhfekh showed the highest polyphenol content and antioxidant activity. HPLC-DAD analysis of almond hull extracts confirmed that chlorogenic acid, catechin, and protocatechuic acid were the most important polyphenols in almond hull. The results highlighted that UAE could be an effective technique for the recovery of phenolic compounds from almond hull, thereby making this byproduct a promising source of compounds with potential applications in food and healthcare sectors.

Keywords: Prunus dulcis L.; almond hull; polyphenols; radical scavenging activity; response surface methodology; ultrasound-assisted extraction.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Response surface plots showing the effect of interaction of solid:solvent ratio (X1; g/100 mL), extraction duration (X2; min), and ethanol concentration (X3; % v/v) on TPC (a–c) and RSA (d–f) values of almond hull extracts obtained using UAE. For each graph, the third variable was fixed at the central value.
Figure 1
Figure 1
Response surface plots showing the effect of interaction of solid:solvent ratio (X1; g/100 mL), extraction duration (X2; min), and ethanol concentration (X3; % v/v) on TPC (a–c) and RSA (d–f) values of almond hull extracts obtained using UAE. For each graph, the third variable was fixed at the central value.
See this image and copyright information in PMC

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