Chiang Mai Journal of Science

This study describes a validated reverse-phase paired-ion chromatography (RP-PIC) with diode array detector method to determine the intact glucosinolates in various Thai broccoli seed genotypes. It is a modified of the official AOCS method and followed the extraction glucosinolates step from broccoli seeds. The analyses were carried out on a Lichrospher RP-18 column (150 mm x 2.1 mm i.d., 5 mm), with a mobile phase gradient, which increases the acetonitrile level in a 50% acetonitrile plus 50% de-ionized water containing 5mM tetraoctylammonium bromide. The flow rate was 0.20 ml/min and detection set at 229 nm. These procedures were applied to samples of broccoli seeds cultivars grown in Thailand, in order to resolve and identify its major glucosinolates: 3-methylsulfinylpropyl-, 4- methylsulfinylbutyl-, 5-methylsulfinylpentyl-, 4-hydroxy-3-indolylmethyl-, 4-methylthiobutyl-, 4-methoxy-3-indolylmethyl- and 1-methoxy-3-indolylmethyl glucosinolate and the detection limits were 0.026 µg/ml, 0.031 µg/ml, 0.025 µg/ml, 0.022 µg/ml, 0.028 µg/ml, 0.021 µg/ml and 0.022 µg/ml, respectively. Thus, this analytical methodology provides a powerful technique for identifying and quantitating glucosinolates in broccoli seeds extracts without derivatization.