A comparative metabolomics investigation of flavonoid variation in faba bean flowers

Abstract

Introduction Faba bean (Vicia faba L.) flowers are edible and used as garnishes because of their aroma, sweet flavor and attractive colors. Anthocyanins are the common plant pigments that give flowers their vivid colors, whereas non-anthocyanin flavonoids can serve as co-pigments that can modify the color intensity of flowers. Objectives To explore the polyphenol diversity and differences in standard and wing petals of faba bean flowers; and identify glycosylated flavonoids that contribute to flower color. Methods Flower standard and wing petals from 30 faba bean genotypes (eight color groups with a total of 60 samples) were used for polyphenol extraction. Samples were analyzed using a targeted method and a semi-untargeted analysis using liquid chromatography–high resolution mass spectrometry (LC–HRMS) combined with photodiode array (PDA) detection. Compound Discoverer software was used for polyphenol identification and multivariate analysis. Results The semi-untargeted analysis guided by the PDA detected 90 flavonoid metabolites present in faba bean flower petals. Ten anthocyanins largely influenced the flower colors, but other flavonoids (63 flavonols and 12 flavones) found with variable levels in different flower color groups appeared to also influence color, especially in mixed colors. Conclusion Analysis of the different colored faba bean flowers confirmed that the color variation between the flowers was mainly controlled by anthocyanins in brown, red and purple-red flowers. Of the other flavonoids, multiglycosylated kaempferols were abundant in white and brown flowers, monoglycosylated kaempferols were common in red and purple-red flowers, and quercetin and apigenin glycosides were abundant co-pigments in purple-red flowers.

Nitric oxide delays the postharvest nutritional quality decline of “Golden Hook” beans

“…Among them, 6-C-methylquercetin-3-O-rutinoside, licoflavone C, licoflavone A, kushenol A, and uralenol were the five flavonoids with the largest difference in abundance between CK-12d and SNP-12d, and their content is higher in the purple red pods of the SNP-12d group. The accumulation of 6-C-methylquercetin-3-O-rutinoside and other kaempferol glycosides is high in the purplish red faba bean flowers (Elessawy et al, 2023). The structural genes CHS, F3′H, and FLS involved in flavonoid biosynthesis are also the precursor genes of anthocyanin synthesis, and the high expression of these genes is conducive to the accumulation of purplish red in "Golden Hook" beans (Guo et al, 2019).…”