Previous work has shown that food contains a large number of minor dietary constituents that can inhibit the occurrence of
cancer. Additional inhibitors from four different natural sources will be the subject of this presentation. 1. Citrus fruit
oils. Orange, tangerine, lemon, and grapefruit
oils given p.o. induce increased
glutathione (GSH) S-
transferase activity in tissues of the mouse. When fed in the diet prior to and during the course of administration of
benzo(a)pyrene (BP), the four citrus fruit
oils inhibit formation of
tumors of both the forestomach and lungs of mice. When fed either before or after the administration of
7,12-dimethylbenz(a)anthracene (DMBA)
orange oil inhibits mammary
tumor formation. 2.
Garlic oil.
Allyl methyl trisulfide (AMT), a constituent of
garlic oil, has been synthesized recently. When given p.o. 96 and 48 hr prior to BP, AMT inhibits the occurrence of forestomach
tumors in mice. 3. Green
coffee beans. Two
diterpene esters,
kahweol palmitate and
cafestol palmitate, which are potent inducers of GSH S-
transferase activity have been isolated from
coffee beans. When administered p.o. prior to DMBA the two
diterpene esters inhibit mammary
tumor formation. 4. Cruciferous vegetables. Several
glucosinolates occur in cruciferous vegetables. Efficient procedures for the isolation of these compounds have been developed recently. The inhibitory effects of three of these i.e.
glucobrassicin,
glucotropaeolin, and glucosinalbin were studied in several animal models.
Glucobrassicin caused substantial inhibition of BP-induced
neoplasia of the lung and forestomach of the mouse and DMBA-induced
neoplasia of the breast in rats. Glucosinalbin and
glucotropaeolin are less active in these systems. In addition to protective effects,
indoles derived from the hydrolysis of
glucobrassicin have potential harmful properties. The implications of multiple properties and factors which may determine their consequence will be discussed.