Effect of solvent extraction on the antioxidant and phytochemical profiles of ellagitannins from 'wonderful' pomegranate peel: an advanced chemometrics analysis

摘要

Ellagitannins are the predominant bioactive tannins present in the peel of pomegranate. Studies have explored different extraction solvents to maximize recovery of the bioactive phytochemicals in pomegranate peel but lack proper statistical correlation between the extraction solvent, phytochemistry and bioactivity. This study employed advanced chemometrics models, including principal component analysis (PCA) and orthogonal projections to latent structures (OPLS) in determining the solvent extraction (among methanol, ethanol, acetone and water) that will yield optimum antioxidant and ellagitannins profiles from "Wonderful" pomegranate peel. Acetone extraction had the highest (p < 0.05) total phenol (TFC) and flavonoid contents and strongest (p < 0.05) Fe3+ reducing effect, while methanol extraction had the strongest (p < 0.05) radical scavenging activity. The oxygen radical absorbance capacity (ORAC) and anti-lipid peroxidative activities of both solvent extractions outperformed that of the ethanol and water extractions. Tannins purified using Amberlite (R) XAD16N resin were highest for acetone and methanol extractions. LCMS-quantified ellagitannins in the tannins varied for the different extractions. PCA and OPLS models adequately characterized, described and predicted the variation and patterns in the antioxidant and ellagitannins datasets (up to 95 for PCA). OPLS bi-plot showed that the high ellagic acid constituents and total tannins yield of the methanol extraction influenced its potent radical scavenging activity, while the ellagitannin constituents including punicalagins, granatin A, geraniin and casuarinin influenced the high TFC, as well as the potent Fe3+ reducing, ORAC and anti-lipid peroxidative activities of acetone extraction. Acetone and methanol extraction of pomegranate peel are promising for optimum ellagitannins recovery and antioxidant profile.