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

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.

Basella alba L. (Malabar Spinach) as an Abundant Source of Betacyanins: Identification, Stability, and Bioactivity Studies on Natural and Processed Fruit Pigments.

The antioxidant and anti-inflammatory activities of acylated and decarboxylated gomphrenins, as well as Basella alba L. fruit extract, were investigated in relation to gomphrenin, known for its high biological potential. The most abundant natural acylated gomphrenins, namely, 6'-O-E-caffeoyl-gomphrenin (malabarin) and 6'-O-E-4-coumaroyl-gomphrenin (globosin), were isolated from B. alba extract for the studies. In addition, controlled thermal decarboxylation of gomphrenin in the purified B. alba extract at 65-75 °C resulted in the formation of the most prevalent decarboxylated products, including 17-decarboxy-gomphrenin and 2,17-bidecarboxy-gomphrenin, along with their isoforms. The structures of the decarboxylated pigments were confirmed by NMR analyses. Exploring the matrix effect on pigment reactivity revealed a tremendous increase in the stability of all betacyanins after the initial stage of extract purification using a cation exchanger under various conditions. This indicates the removal of a substantial portion of the unfavorable matrix from the extract, which presumably contains reactive species that could otherwise degrade the pigments. Furthermore, the high concentration of citrates played a significant role in favoring the formation of 2-decarboxy-gomphrenin to a considerable extent. In vitro screening experiments revealed that the tested compounds demonstrated strong anti-inflammatory properties in lipopolysaccharide (LPS)-activated human macrophages. This effect encompassed the selective inhibition of cytokine and chemokine release from activated macrophages, modulation of the chemotactic activity of immune cells, and the regulation of tissue remodeling mediators' release.