Marica T. Engström

Rapid qualitative and quantitative analyses of proanthocyanidin oligomers and polymers by UPLC-MS/MS.

This paper presents the development of a rapid method with ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for the qualitative and quantitative analyses of plant proanthocyanidins directly from crude plant extracts. The method utilizes a range of cone voltages to achieve the depolymerization step in the ion source of both smaller oligomers and larger polymers. The formed depolymerization products are further fragmented in the collision cell to enable their selective detection. This UPLC-MS/MS method is able to separately quantitate the terminal and extension units of the most common proanthocyanidin subclasses, that is, procyanidins and prodelphinidins. The resulting data enable (1) quantitation of the total proanthocyanidin content, (2) quantitation of total procyanidins and prodelphinidins including the procyanidin/prodelphinidin ratio, (3) estimation of the mean degree of polymerization for the oligomers and polymers, and (4) estimation of how the different procyanidin and prodelphinidin types are distributed along the chromatographic hump typically produced by large proanthocyanidins. All of this is achieved within the 10 min period of analysis, which makes the presented method a significant addition to the chemistry tools currently available for the qualitative and quantitative analyses of complex proanthocyanidin mixtures from plant extracts.

Rapid Fingerprint Analysis of Plant Extracts for Ellagitannins, Gallic Acid, and Quinic Acid Derivatives and Quercetin-, Kaempferol- and Myricetin-Based Flavonol Glycosides by UPLC-QqQ-MS/MS.

This paper describes the development of a rapid method with ultraperformance liquid chromatography-triple-quadrupole mass spectrometry that can specifically measure group-specific fingerprints from plant extracts for the following polyphenol groups: (1) ellagitannins, (2) gallic acid derivatives, (3) quinic acid derivatives, (4) quercetin-based flavonol glycosides, (5) kaempferol-based flavonol glycosides, and (6) myricetin-based flavonol glycosides. In addition, the method records simultaneously diode array and full scan mass spectrometry data that can be used to later characterize and quantify the main individual polyphenols if necessary. All of this is achieved within the 10 min period of analysis, which makes the presented method a significant addition to the chemistry tools currently available for the rapid analysis of complex polyphenol mixtures from plant extracts.

Large Variability of Proanthocyanidin Content and Composition in Sainfoin (Onobrychis viciifolia).

Proanthocyanidins (PAs) in sainfoin (Onobrychis viciifolia Scop.) are of interest to ameliorate the sustainability of livestock production. However, sainfoin forage yield and PA concentrations, as well as their composition, require optimization. Individual plants of 27 sainfoin accessions from four continents were analyzed with LC-ESI-QqQ-MS/MS for PA concentrations and simple phenolic compounds. Large variability existed in PA concentrations (23.0–47.5 mg g–1 leaf dry matter (DM)), share of prodelphinidins (79–96%), and mean degree of polymerization (11–14) among, but also within, accessions. PAs were mainly located in leaves (26.8 mg g–1 DM), whereas stems had less PAs (7.8 mg g–1 DM). Overall, high-yielding plants had lower PA leaf concentrations (R2 = 0.16, P < 0.001) and fewer leaves (R2 = 0.66, P < 0.001). However, the results show that these two trade-offs between yield and bioactive PAs can be overcome.

Chemical Structures of Plant Hydrolyzable Tannins Reveal Their in Vitro Activity against Egg Hatching and Motility of Haemonchus contortus Nematodes

The use of synthetic drugs against gastrointestinal nematodes of ruminants has led to a situation where resistance to anthelmintics is widespread, and there is an urgent need for alternative solutions for parasite control. One promising approach is to use polyphenol-rich bioactive plants in animal feeds as natural anthelmintics. In the present work, the in vitro activity of a series of 33 hydrolyzable tannins (HTs) and their hydrolysis product, gallic acid, against egg hatching and motility of L1 and L2 stage Haemonchus contortus larvae was studied. The effect of the selected compounds on egg and larval structure was further studied by scanning electron microscopy. The results indicated clear relationships between HT structure and anthelmintic activity. While HT size, overall flexibility, the types and numbers of functional groups, together with the linkage types between monomeric HTs affected the activity differently, the optimal structure was found with pentagalloylglucose.

Isolation of chemically well-defined semipreparative liquid chromatography fractions from complex mixtures of proanthocyanidin oligomers and polymers

In this study, a semipreparative liquid chromatography method was developed for the isolation of chemically well-defined proanthocyanidin (PA) oligomer and polymer fractions. The aim was to achieve better separation than traditionally achieved for the PAs with other chromatographic methods. The method was tested with eleven PA rich Sephadex LH-20 fractions, which originated from eleven different plant species. The resulting semipreparative fractions were analyzed by both triple quadrupole and high-resolution mass spectrometry assisted by ultrahigh-performance liquid chromatography (UPLC) separation. The results showed remarkable differences in the procyanidin to prodelphinidin ratio, mean degree of polymerization, and specific oligomeric and polymeric content. However, some of these features indicated consistent patterns between species as the function of UPLC retention time. The developed method enables the production of tens of well-defined fractions of PA oligomers and polymers from the unresolved chromatographic PA hump. Accordingly, this allows researchers to explore the most bioactive parts of the complex PA humps of any plant species, which have not been possible earlier.