Radical Scavenging and Anti-Inflammatory Activities of Representative Anthocyanin Groupings from Pigment-Rich Fruits and Vegetables

Abstract

Anthocyanins, the naturally occurring pigments responsible for most red to blue colours of flowers, fruits and vegetables, have also attracted interest because of their potential health effects. With the aim of contributing to major insights into their structure-activity relationship (SAR), we have evaluated the radical scavenging and biological activities of selected purified anthocyanin samples (PASs) from various anthocyanin-rich plant materials: two fruits (mahaleb cherry and blackcurrant) and two vegetables (black carrot and "Sun Black" tomato), differing in anthocyanin content (ranging from 4.9 to 38.5 mg/g DW) and molecular structure of the predominant anthocyanins. PASs from the abovementioned plant materials have been evaluated for their antioxidant capacity using Trolox Equivalent Antioxidant Capacity (TEAC) and Oxygen Radical Absorbance Capacity (ORAC) assays. In human endothelial cells, we analysed the anti-inflammatory activity of different PASs by measuring their effects on the expression of endothelial adhesion molecules VCAM-1 and ICAM-1. We demonstrated that all the different PASs showed biological activity. They exhibited antioxidant capacity of different magnitude, higher for samples containing non-acylated anthocyanins (typical for fruits) compared to samples containing more complex anthocyanins acylated with cinnamic acid derivatives (typical for vegetables), even though this order was slightly reversed when ORAC assay values were expressed on a molar basis. Concordantly, PASs containing non-acylated anthocyanins reduced the expression of endothelial inflammatory antigens more than samples with aromatic acylated anthocyanins, suggesting the potential beneficial effect of structurally diverse anthocyanins in cardiovascular protection.

Keywords: ICAM-1; VCAM-1; anthocyanins with aromatic acylation; black carrot; blackcurrant; endothelial adhesion molecules.; mahaleb cherry; non-acylated anthocyanins; structure–activity relationship (SAR); “Sun Black” tomato.

Figure 1

Anthocyanins in purified extracts of mahaleb cherry (1–4), blackcurrant (2, 4–6), black carrot (7–11) and “Sun Black” tomato (12, 13).

Figure 2

Inhibitory effects of PASs from the mahaleb cherry, blackcurrant, black carrot and “Sun Black” tomato on the expression of endothelial adhesion molecules. Endothelial cells were pre-treated with PASs at different concentrations (1, 10, 25 and 50 μg/mL) or vehicle (control) for 24 h and then stimulated with TNF-α (10 ng/mL) for 16 h. Cell surface expression of VCAM-1 (A) and ICAM-1 (B) was analysed by cell-surface enzyme immunoassay (EIA). Each experiment was performed in triplicate. Data are expressed as the percentage of TNF-α induced expression (mean ± S.D.). ^# p < 0.01 vs. control; * p < 0.05, ** p < 0.01 vs. TNF-α alone.

Figure 3

HPLC chromatograms of crude extracts (CE) and purified anthocyanin samples (PASs) of mahaleb cherry, blackcurrant and black carrot, detected at λ = 520 nm (red line) and 280 nm (blue line). See Table 1 for identities.