Identification and Characterization of Major Constituents in Different-Colored Rapeseed Petals by UPLC–HESI-MS/MS

Oilseed
rape (Brassica napus L.)
is the second highest yielding oil crop worldwide. In addition to
being used as an edible oil and a feed for livestock, rapeseed has
high ornamental value. In this study, we identified and characterized
the main floral major constituents, including phenolic acids and flavonoids
components, in rapeseed accessions with different-colored petals.
A total of 144 constituents were identified using ultrahigh-performance
liquid chromatography–HESI-mass spectrometry (UPLC–HESI-MS/MS),
57 of which were confirmed and quantified using known standards and
mainly contained phenolic acids, flavonoids, and glucosinolates compounds.
Most of the epicatechin, quercetin, and isorhamnetin derivates were
found in red and pink petals of B. napus, while kaempferol derivates were in yellow and pale white petals.
Moreover, petal-specific compounds, including a putative hydroxycinnamic
acid derivative, sinapoyl malate, 1-O-sinapoyl-β-d-glucose, feruloyl glucose, naringenin-7-O-glucoside, cyanidin-3-glucoside, cyanidin-3,5-di-O-glucoside, petunidin-3-O-β-glucopyranoside,
isorhamnetin-3-O-glucoside, kaempferol-3-O-glucoside-7-O-glucoside, quercetin-3,4′-O-di-β-glucopyranoside, quercetin-3-O-glucoside, and delphinidin-3-O-glucoside, might
contribute to a variety of petal colors in B. napus. In addition, bound phenolics were tentatively identified and contained
three abundant compounds (p-coumaric acid, ferulic
acid, and 8-O-4′-diferulic acid). These results
provide insight into the molecular mechanisms underlying petal color
and suggest strategies for breeding rapeseed with a specific petal
color in the future.