Extraction and Stability of Anthocyanins Present in the Skin of the Dragon Fruit ( Hylocereus undatus)

Abstract

The extraction of anthocyanins present in the skin of the dragon fruit was performed using trifluoroacetic acid (TFA) plus a mixture of methanol, acetic acid and water; the anthocyanins were then purified with a LC-18 cartridge, using methanol acidified with TFA as eluent, reaching concentrations of 44.3865 ± 1.3125 mg/100g of sample. The extracts were put through stability tests under different storage conditions, modifying the pH of the extracts (pH of 1, 4 and 6), the temperature (4˚C, 25˚C and 68˚C) and the absence and presence of light for a time period of 4 days; the tests indi-cated that anthocyanins remain more stable at a temperature of 4˚C with a pH of 4 in the absence of light, retaining up to 80% of the pigment. Three anthocyanins were partially identified in the extracts by high performance liquid chroma-tography (HPLC); they were: cyanidin 3-O-glucoside, cyanidin 3,5 O-glucoside and pelargonidin 3,5 O-glucoside.