Structural characterization of native and oxidized procyanidins (condensed tannins) from coffee pulp (Coffea arabica) using phloroglucinolysis and thioglycolysis-HPLC-ESI-MS

• Published in: Food chemistry 2021-03, Vol.340, p.127830-127830, Article 127830
• Main Authors: Wong-Paz, Jorge E., Guyot, Sylvain, Aguilar-Zárate, Pedro, Muñiz-Márquez, Diana B., Contreras-Esquivel, Juan C., Aguilar, Cristóbal N.
• Format: Article
• Language: English
• Subjects: Biflavonoids - analysis; Biflavonoids - chemistry; Catechin - analysis; Catechin - chemistry; Chemical engineering; Chemical Sciences; Chromatography, High Pressure Liquid - methods; Coffea - chemistry; Coffee; Coffee - chemistry; Flavonoids; Food and Nutrition; Food engineering; Glycolysis; Life Sciences; Oxidation markers; Oxidation-Reduction; Proanthocyanidins - analysis; Proanthocyanidins - chemistry; Procyanidins-A type; Spectrometry, Mass, Electrospray Ionization - methods; Tannins; Thioglycolysis
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2020.127830

•The (+)-catechin molecule was absent in the structure of the procyanidins from coffee pulp.•A water long elution helps to increase the purity of procyanidins when Sephadex LH-20 is used to purification.•Thioglycolysis can be improved by increasing the amount of sample in the reaction. Procyanidins from coffee pulp are responsible from the limited valorization of this by-product. Information about procyanidin structure is still scarce and imprecise. The aim of this work was to study the native and oxidized procyanidins from coffee pulp with respect to composition and structure. An aqueous acetone extract from coffee pulp was purified using Sephadex LH-20. Butanolysis, phloroglucinolysis and thioglycolysis coupled to HLPC-ESI-MS were applied for the characterization of the native and oxidized procyanidins. The purification allowed to recovery three fractions (aqueous, ethanolic and acetonic) and only acetone fraction showed a high concentration of procyanidins (98%, w/w). HPLC-ESI-MS of procyanidins-rich fraction without any reaction resulted in a UV–Vis chromatogram unresolved typical of the presence of procyanidins. The extracted ion chromatogram and MS2 analysis revealed the presence from dimers to pentamers of native procyanidins. Interestingly, by first time an A-type trimeric procyanidin (m/z of 863) was observed in coffee pulp. In our study, (−)-epicatechin was the constitutive unit of procyanidins with an aDP of 6.8 (oligomeric native procyanidins) according to the phloroglucinolysis assay. Two oxidation markers useful to characterization of oxidized procyanidins were observed in the procyanidins-rich fraction after thioglycolysis, a dimer A2-ext and a molecule that corresponds to a linkage between an extension and a terminal unit. Coffee pulp procyanidins were presented with only a minor class of oxidized procyanidins. As far as we know, this is the first study about characterization of the oxidized procyanidins from coffee pulp.