Separation And Analysis Of Carotenoids In Watermelon

There are many varieties and strains of watermelon which exhibit a wide range of fruit colors, such as red, pink, orange, yellow, and white due to the different carotenoid kinds and concentration. Analysis and detection of carotenoids in watermelon not only can make preparation for the production of watermelon carotenoids, but also can provide a foundation for the nutritional breeding of watermelon.Such four varieties of watermelon as "Zaohua" ( red in flesh color ), "Orange Flesh Watermelon"(orange), "307 Chaofeng" (yellow ), and "Sanbai" (white ) were used as experimental materials. Ultrasonic extraction method was chosen for the extraction of carotenoids from the watermelon fleshes by comparing the advantages of both solvent extraction and ultrasonic extraction methods.Carotenoids were extracted from the fruit fleshes of four watermelon varieties with petroleum ether and then were separated by open-column chromatography respectively. Magnesium oxide and silica (1:1, w/w) were used as the adsorbent in a column. The open-column was developed with gradient acetone-petroleum ether mixture of increasing concentration of acetone from 0% to 30%. The fruit pigments of "Zaohua", for example, were separated into five carotenoids by open-column chromatography. The identity of carotenoids separated was determined primarily after UV-vis absorption spectra of the colorful bands eluted from the column were measured on a spectrophotometer. After the separation and purification by column chromatography lycopene,β-carotene, andζ-carotene were further purified by recrystallization. The purity of the samples was verified to be 90%, used for HPLC analysis as standard.HPLC analysis was performed using a Vydac 201TP54 Cigcolum (250×4.6 mm, i.d.), fitted with a C₁₈ guard column, with the following gradient elution (A: methanol-methylene chloride-acetonitrile and B: methanol) : 100% A and 0% B initially, increased to 10% B in 2min, 20% B in 4min, 50% B in 8min, 80% B in 10min, and 100% B in 15min, 1 ml/min flow-rate, 25℃coulum temperature, and with detection at 400 nm and 450 run for watermelon carotenoid measurement.Lycopene andβ-carotene is the major pigment for the red-fleshed watermelon. In the yellow flesh watermelon the neoxanthin content are relatively high. Lycopene could not be detected in the white-fleshed wtaremelon.