Availability of Food-based Antioxidants

Broccoli (B. oleracea L., Italica group) is a rich source of glucoraphanin, an aliphatic glucosinolate which degrades to 4-methylsulphinylbutyl isothiocyanate, which induces production of phase II enzymes, some of which are antioxidants.

Swedes (B. napobrassica L.) contain glucobrassicanapin, an aliphatic glucosinolate which produces pent-4-enyl isothiocyanate. It is not known whether this isothiocyanate induces therapeutic enzyme activity.

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Antioxidants from glucosinolate degradation

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Glucosinolate derivatives as antioxidants In a review of glucosinolate research in 1997, Fenwick and co-workers 1 identified four stages in the investigative activity :- 1. Structural studies (late 19th century) 2. Natural product chemistry (1950-1970) 3. Antinutritional effects in commercial oilseeds (1970s) 4. Biological effects as antifungal, antimicrobial and anticarcinogenic agents (1980 - 1997) Since then, the interest in the glucosinolate degradation products, nitriles, isothiocyanates etc. has intensified as links to the induction of phase II enzymes was substantiated, and one compound, 4-methylsulphinylbutyl isothiocyanate (commonly called sulforaphane), from glucoraphanin, prominent in broccoli, has received much attention, justified by the fact that endogenous antioxidant enzymes exert a longer lasting effect than vitamin and flavanoid antioxidants. From studies with rats, there is growing evidence that other glucosinolate degradation products will have therapeutic effects on humans. Further analytical work will recognise other food sources of sulforaphane. Reference 1. E.A.S. Rosa et al., in Hort. Rev., 19, p 99, ed. J. Janick, pub. John Wiley and sons, inc. New York, 1997

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