Title

Total glucosinolate content of selected local vegetables and effects of processing and storage on broccoli (Brassica oleracea L. var Italica) glucosinolates

College

College of Science

Department/Unit

Chemistry

Document Type

Conference Proceeding

Source Title

Proceedings of the Osaka University - De La Salle University Academic Research Workshops

Volume

11

Publication Date

9-2008

Abstract

The chemopreventive properties of Brassica vegetables have been attributed to glucosinolates and their corresponding hydrolytic products. In this study, the total glucosinolate levels of stored and processed broccoli florets, as well as those of other locally grown vegetables were determined. Methanol extracts were prepared from fresh, frozen and processed (microwave-heated, blanched, steamed, boiled and stir-fried) broccoli (Brassica oleracea L. var italica) and their total glucosinolate contents were subsequently determined by HPLC analysis of the desulfated derivatives. Raw samples of other vegetables were similarly analyzed. The levels of the most predominant glucosinolates in broccoli, were observed to decrease after frozen storage for up to 14 days and individual glucosinolate concentrations were variably affected by processing. ln comparison with the raw sample, glucosinolate concentrations were higher after boiling, decreased after blanching. stir -frying and steaming but were only slightly affected by microwave heating. The changes in glucosinolate levels during processing and storage were attributed to enzymatic and/or thermal degradation.

Glucosinolates differ quantitatively and qualitatively among vegetables. Of all the samples tested, the highest total glucosinolate content (85.30 µmole/gram) was found in leaves of Busella rubra L. (alugbati or Malabar Night Shade). Four major glucosinolates were detected in the extracts. To our knowledge, this is the first report on the occurrence of significant glucosinolate levels in alugbati.

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Disciplines

Chemistry

Keywords

Glycosides; Broccoli—Analysis; Vegetables—Effect of temperature on

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