Study on Aggregation of Carotenoids in Hydrated Organic Solution System

Carotenoids have numerous biological activities which are beneficial for human health, and can be spontaneously aggregated to different aggregates in certain conditions. In this paper, the effects of different proportions of hydrated organic solutions and different adding sequences on the types of carotenoids aggregates (H aggregates, M monomer and J aggregates), formation conditions and stability of three carotenoids (astaxanthin, lutein and β-carotene) were investigated. The astaxanthin acetone solution, lutein ethanol solution and β-carotene acetone solution were mixed in two different dropping sequences: Water into organic and organic into water, according to the proportion of organic solvents in the total volume from 10% to 90%, and the resulting sample was observed and analyzed by the UV-vis absorption spectrum. These results showed that when the astaxanthin, lutein and β-carotene formed H aggregates the volume ratios of organic solvents were 10%~20%, 10%~50% and 10%~40%, respectively. Astaxanthin formed J aggregates at 30% and β-carotene formed J aggregates at 50%~70%, respectively. Lutein was a lutein monomer when organic solvent takes up 60%~90% of the total volume. The conditions for the formation of aggregates were similar to those of organic water in addition sequence. However, it was found that the movement of absorption peak in UV-vis spectrum was more obvious under the sequence of organic water addition. After the samples were placed at room temperature (25 ℃) for 24 h and 48 h, the stability of aggregates was investigated. The H aggregates of lutein remains unchanged, however the H aggregates of astaxanthin and β-carotene gradually transformed into J aggregates. This study provides data support for the formation conditions and stability of carotenoid aggregates, thus offering theoretical basis for the application of carotenoids and their aggregates in food, medicine, cosmetics and other fields.