Identification and reactivity of pigments in prominent vegetable leaves of Basella alba L. var. 'Rubra' (Malabar spinach)

[Display omitted] •Basella alba L. var. 'Rubra' - promising food-plant in daily diet with bioactive gomphrenins.•Unique pigment profiles in leaves of Basella alba L. var. 'Rubra'.•Novel methoxy-E-cinnamoylated betacyanins identified in leaves of B. 'Rubra'.•Protecting activity of B. 'Rubra' leaf extract against metal cation-assisted pigment degradation.•Protection by B. 'Rubra' leaf extract against pigment degradation under UV/Vis irradiation. The unique profiles of betacyanins as well as their stability and antioxidant activity in purple leaf extracts of the fast-growing, soft-stemmed vine Basella alba L. var. 'Rubra', known as Malabar spinach, are partly characterized for the first time. The distribution of gomphrenin and its acylated derivatives in the leaves is completely different from the profiles of the pigments in the fruits. The most abundant acylated pigment in leaves (24%) turned out 6′-O-E-sinapoyl-gomphrenin (gandolin), however, the most significant difference in the pigment profiles is a presence of two novel pigments tentatively identified as highly abundant 6′-O-(3,4-dimethoxy-E-cinnamoyl)-gomphrenin and 6′-O-(3,4,5-trimethoxy-E-cinnamoyl)-gomphrenin as well as their isoforms. Significant degradation of the pigments in the fruit extracts under the impact of selected metal cations and UV–Vis irradiation as well as high protective activity of the leaf extract matrix were observed. Partial chromatographic purification of the leaf extract resulted in an increase of the pigment concentration which was correlated positively with the increased antioxidant activity of obtained fractions.