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Polyphenols in plant foods
higher than previously estimated Fall 2009, ONLINE ONLY 
Researchers in this featured study make an
important discovery regarding the total
content of polyphenols in plant foods.
In recent years investigators have
compiled increasing data on these
bioactive compounds and their potential health
effects, including data on flavanols,
proanthocyanidins, anthocyanidins, flavones,
flavonols and tannins, among others.
However, Arranz et al, note that most reports only include
data on "extractable polyphenols (EPP);" food
compounds extracted in aqueous organic solvents
before undergoing high performance liquid
chromatography (HPLC) analysis. Meanwhile,
cite researchers, significant amounts of
bioactive polyphenols may remain unaccounted for in
the residues from such extractions. These
"nonextractable polyphenols (NEPP)" require
a different chemical or enzymatic treatment
process in order to be extracted from the
food matrixes before undergoing an HPLC
analysis. Given the many potential
antioxidant activities of
nonextractable polyphenols
(largely comprised of
hydrolysable tannins and proanthocyanidins),
together with the absence of data in the
literature, Arranz et al sought to extract
and quantify NEPP and compare the
concentrations to EPP.
To determine total content of polyphenols in apple, peach and nectarine, researchers conducted a common analysis of EPP in aqueous-organic extracts together with a NEPP analysis in acidic hydrolysates of extraction residues using HPLC-MS and spectrophotometry. All fruits were purchased at optimal maturity from markets in Madrid, Spain. The results for EPP and NEPP were determined as mg per 100 g of fresh fruit. EPP determination included concentrations of chlorogenic acids, epicatechins, quercetin-3-glucosides and several other polyphenols. Arranz et al's data for EPPs is consistent with previous findings in the literature. Though there is no other data on HPLC quantification of NEPP in the literature, researchers note the concentrations of NEPP in this study (epicatechins, ellagic acid, gallocatechins and others) are "consistent with other reported data from spectrophotometric analyses." The most significant findings of this study was that NEPP content of apples, peaches and nectarines were significantly higher that the EPP content of these fruits (112-126 mg/100g to 18.8-28 mg/100 g). Investigators elaborated on the significance of their findings, noting, for instance, that concentrations of proanthocynanidins may be very underestimated if nonextractable proanthocynanidins are not considered. Arranz et al cite previous research attributing "antimicrobial properties, antimutagenic activity, and cardioprotective effects" to proanthocynanidins. Given the absence of data of NEPP in the literature, the findings of this featured study contribute greatly to the growing knowledge base of bioactive compounds in fruits and plant foods, and in turn, their potential biological and clinical significance. Study: Arranz, S., et al, J. Agric. Food Chem., 57: 7298-7303, (2009) RETURN HOME from polyphenols higher than estimated |
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