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A Targeted UHPLC‐MS Approach to Quantify Phenolics in Muscadine Grape Supplements
Author(s) -
Duncan A'ja V.,
Pirro Nancy T,
Tallant Ann,
Gallagher Patricia E,
Chappell Mark C.
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.646.1
Subject(s) - gallic acid , chemistry , catechin , grape seed extract , polyphenol , chromatography , formic acid , food science , biochemistry , antioxidant , medicine , alternative medicine , pathology
The muscadine grape is a natural source of phenolic compounds that exhibit anti‐oxidant properties. Muscadine grape supplements (MGS) are considered a potential therapeutic approach to combat oxidative stress; however, it's unclear as to the precise identity and content of individual phenolics in various MGS. Thus, we compared the major phenolic compounds among several MGS preparations by targeted ultra‐high pressure liquid chromatography and mass spectroscopy (UHPLC‐MS). The four MGS preparations were derived from either the MG seed, skin or both seed and skin. Samples were extracted in 70% methanol/1% formic acid (1:100), homogenized in a Qiagen Tissue Lyser [5 mins at 30 Hz] and centrifuged at 100,000 xg for 60 min. The extracts from the supplements were initially assessed for total phenolic content (TPC) expressed as mg/gm of the initial material. MGS extracts were spiked with isotopically‐labeled catechin as an internal standard and applied directly for UHPLC‐MS analysis using gradient conditions that resolve 17 phenolic standards with a limit of detection of 200 pg/μl. TPC (mg/gm) was highest in the Piedmont Research & Development Corporation proprietary MGS seed [PRDC; 257.7±5.4] as compared to three other commercial supplements ‐ Nature's Pearl MGS seed [36.2±2.4]; Muscadine Naturals Premier Gold MGS skin [13.5±0.7] and Muscadinex MX1 MGS skin/seed [11.7±0.7]. UHPLC‐MS analysis of the individual phenolic components revealed that PRDC MGS primarily contained epitcatechin, gallic acid, procyanidin, catechin and catechin‐gallate. Nature's Pearl seed contained primarily epitcatechin and gallic acid, while the Premier Gold skin and Muscadinex skin/seed contained primarily ellagic and gallic acid. The individual phenolic content expressed as mg/gm material is graphically shown below. PRDC MGS contained significantly higher levels of epitcatechin [22.0±0.7], gallic acid [13.5±0.6], procyanidin B [7.1±0.3], ellagic acid [4.7±0.4], catechin [2.7±0.1] and catechin gallate [1.8±0.1] as compared to the other supplements. For all four supplements, other phenolics including resveratrol, quercetin and myricetin were below the assay detection limit. Among the MGS preparations tested, the PRDC MGS proprietary exhibited the greatest TPC that reflects higher levels of epitcatechin, gallic acid, ellagic acid, catechin and procyanidin. Support or Funding Information Chronic Disease Research Fund