Anthocyanins are the red, purple, and blue pigments responsible for the beautiful color of many fruits and vegetables. Previous research suggests a high correlation between diets rich in brightly colored fruits and vegetables and a lower incidence of certain types of cancers. Acylated anthocyanins have been found to exhibit increased stability in food matrices as compared to non-acylated anthocyanins. With the addition of acylation comes added protection from environmental conditions, but do these acylated anthocyanins also offer important chemoprotection? The objective of this study was to evaluate the role of acylation on anthocyanin chemoprevention properties. To determine this objective four predominately acylated anthocyanin sources containing the cyanidin aglycone were evaluated: red onion, purple corn, red cabbage, and black carrot. The red onion and purple corn were acylated with aliphatic acids and the red cabbage and black carrot were acylated with cinnamic acids.
Anthocyanins were extracted and purified using acetone, chloroform, methanol and water. The extracts were used to treat human adenocarcinoma cells (HT29 colon cancer cells). Growth inhibition was measured using the sulfurhodamine B assay. Chemopreventative properties of the four anthocyanin extracts were measured before and after removal of acylating groups (saponification).
Saponification of anthocyanins decreased or slightly (but not significantly, p>0.05) increased the inhibitory effect of the starting anthocyanin material. Purple corn anthocyanin extract’s percent inhibition values, with and without aliphatic acid acylation for concentrations of 100µg cyanidin-3-glucoside equivalent/ml, were 67.7 percent and 79.7 percent respectively. Red cabbage anthocyanin extract, acylated with cinnamic acids, showed a growth inhibition of 20.4 percent as compared to 24.7 percent (not significantly increased) for the saponified red cabbage at a treatment dose of 100µg cyanidin-3-glucoside equivalent/ml. However, cinnamic acid acylated black carrot showed a growth inhibition of 50.8 percent, significantly higher that the 24.1 percent inhibition obtained with non-acylated black carrot anthocyanins at a treatment dose of 50µg cyanidin-3-glucoside equivalent/ml. These results suggest that glycosylation pattern also plays an important role in anthocyanin chemopreventative activity. The differences in the anthocyanins composition accounted for the differences in chemopreventative properties.
Both the acylated and the non-acylated anthocyanin extracts displayed inhibition properties during the treatment of human adenocarcinoma cells (HT29). However, due to their increased stability, the acylated anthocyanin extracts may be able to impart a higher level of chemoprevention than the non-acylated anthocyanin extracts and also may be more widely used by the food industry in the production of functional foods.