Benzyl Glucosinolate Hydrolysis Products in Papaya (Carica papaya)

Gayathri Nagappan, and Noumie Surugau, (2011) Benzyl Glucosinolate Hydrolysis Products in Papaya (Carica papaya). In: UNSPECIFIED.

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Abstract

Glucosinolates are sulphur-containing secondary metabolites found largely in Brassicaceae family. Glucosinolates undergo hydrolysis readily upon cell rupture, such as cutting and cooking, by the naturally-occurring enzyme myrosinase to formmainly isothiocyanates and/or simple nitriles. Isothiocyanates are known to possess anticarcinogenic properties while nitriles are largely inactive. Benzyl , a hydrolysis product of benzyl glucosinolate, is one of the most potent anticancer agents for breast, lung liver and colon cancers. However, formation of benzyl isothiocyanate is depending upon reaction conditions where benzyl nitrile is formed at the expense of benzyl isothiocyanate. Thus, the potential health benefits of benzyl isothiocyanate may be surpassed by the ineffective benzyl nitrile. In this study, the factors influencing the formation of benzyl isothiocyanate were investigated to understand further the benzyl glucosinolate hydrolysis pathway. Based on the sole presence of benzyl isothicyanate/nitrile, the results show that its precursor, benzyl glucosinolate, is the major (if not sole) glucosinolate in papaya. The concentration of benzyl isothiocyanate was found greater in leaf with 52.2 mg/kg (dry weight), followed by 18.0 mg/kg in unripe fruit and 3.6 mg/kg in flower. The highest amount of benzyl isothiocyanate produced was observed at room temperature (25°C) where it decreases gradually as the temperature increases up to 80°C. Comparing three common domestic methods of cooking vegetable i.e. blanching, boiling and slow heating, the results show that the high temperature treatment produced mainly benzyl nitrile; while slow heating up to 40°C produced more benzyl isothiocyanate. In these cooking experiments, both hydrolysis products were found largely leached into the cooking liquid (soup}. As for the effects of pH, production of benzyl isothiocyanate was optimum at pH 6-7. The addition of both ferrous and ferric ions (0 -10 mM) favours the formation of benzyl nitrile. Conveniently, adding an iron-chelating agent, EDTA, has shown an increasing trend in the formation of benzyl isothiocyanate. Small amount of ascorbic acid enhanced the formation of benzyl isothiocyanate, however, higher concentration inhibits the benzyl isothiocyanate production. Overall, this work has shown that to ensure an optimum uptake of this beneficial compound from papaya consumption, food preparation practices have to be favouring the formation of benzyl isothiocyanate. Beside, the presence of reductant agents such as iron and ascorbic acid has to be at low concentration.

Item Type:Conference Paper (UNSPECIFIED)
Uncontrolled Keywords:Penampang, Sabah , Glucosinolates hydrolysis products extraction , GC/MS Perkin Elmer , benzyl isothiocyanate
Subjects:T Technology > TP Chemical technology
ID Code:8615
Deposited By:IR Admin
Deposited On:27 Mar 2014 16:03
Last Modified:08 Sep 2014 16:21

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