Tannins from different parts of the chestnut (Castanea sativa Mill.) trunk: a green and efficient extraction method and their profile by HPLC-DAD-MS

Chestnutwoodisarichsourceofhydrolyzabletannins,whichincludegallotanninsandellagitannins,suchascastalin, vescalin, castalagin, andvescalagin.The studywas aimed to improveknowledgeonhydrolyzable tannins fromchestnutwood, evaluating theextractionprocess, thecuring timeofwood, andthecompositionof thedry tanninextracts.Different extraction conditions(e.g.,wood-chips/solvent ratioandtemperature)wereevaluated, andmorethan50ellagitanninsandgallotanninswere tentatively identifiedbyHPLC-MS.Thehighestyields intanninsondriedmatterwereobtainedfor thesampleswiththehigher curingtimebytheextractioncarriedout at100°C(maximumappliedtemperature).Theextractsofdifferent chestnut samples extractedat100°Cshowedahighcontentoftotaltannins,withvaluesdeterminedbyHPLC-DADrangingbetween19.6and25.6% ofthedryextract.ThevaluesoftotaltannincontentdeterminedusingboththeHPLC-DADandtheFolin-Ciocalteumethods,both expressedasgallicacid,werecomparedandcorrelated,andamultiplicationfactorof3.25wasproposed.Theuseof thisfactor isa simpleway to convert nonhomogeneous quantitative results on tanninconcentration inchestnutwoodpresent so far in the literature.