Identification and quantification of anthocyanins in different coloured cultivars of ornamental kale (Brassica oleracea L. var. acephala DC)

ABSTRACT

Anthocyanins are responsible for the colour of many fruits, vegetables, flowers, and coloured-leaved trees. Ornamental kale (Brassica oleracea L. var. acephala DC) is widely cultivated for its colourful inner leaves. To investigate the relationship between the degree of colouration and anthocyanin distribution, content, and composition in ornamental kale, the authors studied the pigment characteristics of five cultivars with different coloured leaves (white, pink, red, purple, and purple-black). Microscopy observation, spectrophotometer, and high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis of fresh inner leaves revealed that pink, red, and purple colourations were associated with high levels of anthocyanin, while purple-black was the result of the combination of anthocyanins and chlorophyll. In the coloured cultivars, anthocyanins were abundant mainly in the first and second cell layers below the epidermis in both the hypocotyls and inner leaves. No anthocyanin was found in the white-leaved phenotype cultivar. Anthocyanin content increased as leaf colour deepened from pink, red, to purple cultivars, which had little chlorophyll and carotenoid. The authors identified eight anthocyanins in the four coloured cultivars, including one non-acylated, four monoacylated, and three diacylated cyanidin glycosides. Cyanidin-3-(sinapoyl)(feruloyl)-diglucoside-5-glucoside was the most abundant anthocyanin in the four coloured cultivars followed by cyanidin-3-(sinapoyl)-diglucoside-5-glucoside. The analysis of anthocyanin accumulation characterisation provides important information on evaluating colouration patterns in coloured plants, and will be helpful for breeding desired leaf colours in ornamental kale.

KEYWORDS:

• Anthocyanin
• Brassica oleracea var. acephala
• cyanidin
• HPLC-MS
• leaf colour

Disclosure statement

No potential conflict of interest was reported by the authors.

Author’s contributions

Pengfang Zhu analysed data and wrote the manuscript. Zhendong Tian, Zhichao Pan, and Xin Feng carried out hand-sectioning, HPLC-MS steps, plant matierial cultivation, and pigment extracting. All authors have read and approved the final manuscript.

Additional information

Funding

This study was funded by the National Natural Science Foundation of China (#31770739).