Light intensity plays the key role in the regulation of leaf color, anthocyanin and polyphenol profiles, as well as antioxidant activity of Photinia × fraseri leaves

Photinia × fraseri is an important ornamental plant species widely cultivated in China with vibrant leaf color. However, there is limited information about the difference of phenolic constituents and bioactivity among P. fraseri leaves (PFL) with varied color, and the key factor which determines its color formation. Therefore, the aim of the present study was devoted to establishing the correlation among leaf color, anthocyanins and polyphenols profiles, together with antioxidant activity of PFL under varied light intensity. Results of color and pigment analysis on the four PFL groups indicated that total anthocyanins content was positively correlated with red color formation. Meanwhile, red leaves further exhibited a higher level of total anthocyanins (0.66 ± 0.02 mg/g), phenols (24.86 ± 1.33 mg/g), tannins (6.98 ± 0.23 mg/g), phenolic acids (73.60 ± 3.56 mg/g), condensed tannins (131.24 ± 5.51 mg/g), flavanols (3.42 ± 0.03 mg/g), flavonols (57.58 ± 0.19 mg/g), and antioxidant activities (0.17 ± 0.00 mmol/g for DPPH, 0.99 ± 0.06 mmol/g for ABTS, 1.73 ± 0.03 mmol/g for FRAP). Furthermore, a total of 11 phenolic compounds were identified from PFL, while caffeoylquinic acid derivatives and cyanidin-3-O-glucoside were the key phenolic compounds rich in red leaves. Principal component, hierarchical cluster, and correlation analysis indicated that high light intensity was the key factor responsible for the red color formation, as well as the high levels of total anthocyanins, phenolic acids and flavanols and antioxidant activities in the red leaves. Overall, the present study shall contribute to the exploration of the medicinal potential of the important horticultural plant P. fraseri and provide theoretical guidance for its further industrial development and application.