Improved recovery of galloyl metabolites from mango (Mangifera indica L.) in human plasma using protein precipitation with sodium dodecyl sulfate and methanol
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Extraction of polyphenolic metabolites from blood fractions can be challenging since compound recovery can be limited by chemical structure, polarity, and protein-binding affinity of analytes. Gallic acid and its metabolites exhibit particularly low recoveries from plasma and can lead to an underestimation of their bioavailability from foods. A modified method to extract free gallic acid and its metabolites from human plasma aided by sodium dodecyl sulfate and acidified methanol (SDS-MeOH) was applied to extract free gallic acid and its metabolites from human plasma after a single consumption of 400g of mango (cv. Ataulfo) pulp by 10 healthy male and female subjects. The use of SDS-MeOH facilitated extraction of significantly (p<0.05) more pyrogallol, free gallic acid, 4-O-methylgallic acid, and ethyl gallate with recovery rates exceeding 80% in standard recovery from human blood plasma when compared to conventional methods that rely on solvent extraction or solid phase extraction. The method was reproducible and precise for standards from 50 to 500g/L. In pharmacokinetic plasma samples five predominant metabolites of gallic acid were tentatively characterized by HPLC-MS and absorption kinetics evaluated over 8h for catechol-O-sulfate, 4-O-methylgallic acid-3-O-sulfate, and pyrogallol-O-sulfate, methylpyrogallol-O-sulfate, and 4-O-methylgallic acid with AUC0-8h of 95203370, 60301310, 59901690, 40201040, and 27901190g/Lh respectively. Plasma extraction was rapid and reproducible with superior recovery rates compared to conventional methods when evaluating polar phenolic metabolites.