Improved Method for the Stabilization of Anthocyanidins

Anthocyanidins, prepared by the acid hydrolysis of black bean and blackberry anthocyanins, were deposited in C18 solid-phase extraction (SPE) cartridges from four different manufacturers. The amount of the black bean anthocyanidins, delphinidin, petunidin, and malvidin (monitored at 520 nm) was unchanged for the first 7 days of storage in SPE cartridges under nitrogen atmosphere at 2 °C. After 45 days of storage the level of delphinidin, petunidin, and malvidin was reduced to 82, 63, and 49% of the original content, respectively. In contrast, the level of delphinidin, petunidin, and malvidin decreased to 17, 10, and 3%, respectively, of the original amount when these anthocyanidins were stored for 3 days in acidic methanol (0.01% HCl) at 2 °C. Similarly, after 46 days of storage in SPE cartridges under nitrogen atmosphere at 2 °C the amount of cyanidin (obtained from evergreen blackberry puree) decreased to 75% of the original content. Cyanidin almost completely disappeared (only 0.2% remained) when it was stored for 4 days in acidic methanol (0.01% HCl) at 2 °C. Anthocyanidin stability was markedly different depending on the brand of the SPE cartridge on which it was stored. Keywords: Solid-phase extraction; anthocyanidin stabilization; delphinidin; petunidin; malvidin; cyanidin