Changes in the Proanthocyanidin Composition and Related Gene Expression in Bilberry (Vaccinium myrtillus L.) Tissues.

Jussi Suvanto,Kaisu Riihinen,Katja Karppinen,Juha-Pekka Salminen,Laura Jaakola

doi:10.1021/acs.jafc.0c02158

Abstract

Berries of genus Vaccinium are rich in flavonoids and proanthocyanidins (PAs). We studied the PA composition and biosynthesis in bilberry (Vaccinium myrtillus L.) tissues and during fruit development. Soluble PAs, analyzed by UHPLC–MS/MS, were most abundant in stem and rhizome with the mean PA polymerization level varying between 4 and 6 in all tissues. Both A- and B-type PAs were present in all tissues. Procyanidin subunits were more common than prodelphinidin subunits in PAs. During fruit ripening, the amount of procyanidin subunits decreased while prodelphinidin subunits and F3′5′H expression increased, indicating a shift in biosynthesis toward the delphinidin branch of the flavonoid pathway. Epicatechin was the most abundant flavan-3-ol in all tissues. Expression of ANR and three isolated LAR genes, analyzed by qRT-PCR, showed connection to accumulation of PAs and flavan-3-ols biosynthesized from different flavonoid branches. Insoluble PAs accumulated during berry development, suggesting that PAs are not recycled after biosynthesis.

Highlights

Genus Vaccinium contains economically important cultivated berry species, including blueberries (e.g. V. corymbosum and V.angustifolium), American cranberry (V. macrocarpon), and wild berry species, such as bilberry (V. myrtillus) and lingonberry ( V. vitis-idaea).[1]
The selected reaction monitoring (SRM) PA methods utilize the electrospray ionization chamber of the mass spectrometer to cleave monomer-linking bonds of the PAs using three different optimized cone voltages, resulting in quinone methide cleavage depolymerization products, which are further fragmented in the collision cell and filtered using the final quadrupole to eliminate false positives
PC subunits were prevalent in all bilberry tissues indicating higher biosynthetic activity of the cyanidin branch of the flavonoid pathway

Summary

Introduction

Genus Vaccinium contains economically important cultivated berry species, including blueberries (e.g. V. corymbosum and V.angustifolium), American cranberry (V. macrocarpon), and wild berry species, such as bilberry (V. myrtillus) and lingonberry ( V. vitis-idaea).[1]. PAs, known as condensed tannins, are oligomers (2−10 subunits) and polymers (>10 subunits) of flavan-3-ols. PAs are linked to many bioactivities, such as anti-inflammatory and antioxidant properties, and have been associated with the reduced risks of cardiovascular disease, cancer, and type 2 diabetes.[3] PAs show a high degree of structural diversity deriving from the myriad of flavan-3-ol monomers, types of linkage between the monomers (A- and B-type linkages and multiple possible linkage positions), and the degree of polymerization (DP). PA oligomers and polymers consist of one terminal flavan-3-ol unit linked with one or more extension flavan-3-ol units by B-type (most commonly 4ß → 8 or 4ß → 6) and/or A-type (typically with an additional 2ß → O → 7) bonds. PAs containing A-type linkages are more rare, both A- and B-type PAs have earlier been detected in Vaccinium berries.[4,5]

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Results

Conclusion