Procyanidins from Cranberry Press Residues-Extraction Optimization, Purification and Characterization

Abstract

Procyanidins are a polyphenolic group that can be found in a variety of foods such as chocolate, tea, cranberries and others. Type A procyanidins can be found in a handful of sources and one of the richest sources are American cranberries. These compounds possess antioxidative, anticancer and anti-inflammatory activities and are most widely used as prevention for urinary tract infections. Cranberries are utilized for jam and juice production, and the latter produces industrial food waste press residues. Press residues contain free and bound procyanidins which can be extracted for use as nutraceuticals. In this study, the extraction of cranberry press residues has been optimized using RSM and the resulting extracts have been purified and fractionated. The obtained procyanidin fractions have been investigated for their antioxidative potential and analyzed using LC-ESI-FTICR-HRMS to determine individual procyanidins. The optimization showed that the optimal extraction can be conducted using acetone in a concentration of 53% without the addition of an acidifying agent. Strong correlation was observed for procyanidin contents and their antioxidative activity using DPPH, ABTS and FRAP methods. The purified fractions contained 78 individual (65 Type A) procyanidins with the degree of polymerization of up to 9.

Keywords: American cranberry; Vaccinium macrocarpon; antioxidants; optimization; press residues; procyanidins; response surface methodology; valorization.

Figure 1

Screening of solvent compositions used for the extraction of procyanidins (TPCA) from American cranberry press residues. Additional measurements of total polyphenolics (TPC) and anthocyanins (ACN) have been conducted. The extractions were performed in triplicate. The means have been compared using ANOVA with post-hoc Tukey’s LSD test. Connecting letters above bars represent statistically different results (n = 3).

Figure 2

Response surface graphs showing the effect of acetone (X₁) and added acid (X₂) concentration on the measured response (total procyanidins): (a) shows the effects of adding acetic acid; (b) formic acid; (c) hydrochloric acid; (d) shows the effects of adding acetic acid and acetone concentration on the yield of total polyphenolics.

Figure 3

The purification of the prepared optimal procyanidin extract from cranberry press residues. Solvents indicated on the arrows are the solvents used for the elution of the specific fraction. The number indicated in green boxes are the fraction (purification steps) numbers represented in Table 3 with representative quantitative data.

Figure 4

Multivariate correlation analysis of total group parameters (TPCA, ACN, TPC) and the measured antioxidative activity (DPPH, ABTS, FRAP) of extract fractions. The asterisk (*) next to the correlation coefficient R represents a statistically significant correlation (pairwise correlations, α = 0.05, n = 76 for each parameter).

Figure 5

(a) Base peak chromatogram and (b) extracted ion chromatograms of procyanidin oligomers found in Vaccinium macrocarpon purified press residue extract by LC-HRMS. The numbers above peaks represent the identified procyanidins in Table 4.

Figure 6

LC-HRMS peak area profiles of procyanidin oligomers found in Vaccinium macrocarpon extract, expressed as a percentage of the total peak area.