Cancer chemopreventive ingredients in Asian foods

Abstract

occurring or synthetic substances or their mixtures to intervene in the progress of carcinogenesis, before the malignancy manifests. Numerous chemical substances have been found to prevent or halt carcinogenesis, and it is noticeable that a substantial body of chemopreventive agents are derived from our ordinary foods, particularly vegetables and fruits. The National Cancer Institute(NCI) of United States has identified more than 40 plant-based foods that possess cancer-preventive properties. Examples are garlic, soya, ginger, onion, broccoli, cabbage, cauliflower, Brussels sprouts, and turmeric, many of which are widely used in Asian cuisine. The chemopreventive ingredients of some of edible plants used in Asian foods have been identified. Curcumin, a yellow colouring agent contained in turmeric( Curcuma longa L., Zingiberaceae), has been reported to possess strong antitumor promotional as well as anti-inflammatory and antioxidant activities. Recent studies from this laboratory have revealed that curcumin inhibits expression of cyclooxygenase-2(COX-2)in mouse skin treated with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA)through inactivation of the redox-sensitive eukaryotic transcription factor NF-κB. Inhibition of NF-κB by curcumin appears to be mediated by blocking ERK1/2 and p38 MAP kinases. Some diarylheptanoids structurally related to curcumin is widely present in the edible plants cultivated in South East Asian countries. These compounds have strong anti-inflammatory and antioxidative properties which may contribute to chemopreventive activities.[6]-Gingerol, a pungent ingredient present in ginger (Zingiber officinale Roscoe, Zingiberaceae), inhibited TPA-induced tumor necrosis facror-alpha production, ornithine decarboxylase activity, and skin tumor promotion in female ICR mice. Its anti-tumor promoting effects appears to be associated with inhibition of p38 MAP kinase and of subsequent NF-κB activation. Capsaicin, a major pungent priniciple of hot chili pepper (Capsicum annuum L., Solanaceae)with potential anti-inflammatory and anti-tumor promoting properties, also suppressed TPA-induced activation of NF-κB and AP-1, in mouse skin in vivo . It also exhibits strong antiangiogenic and antimetastatic activities. Wasabi (Eutrema wasabi Maxim) inhibited chemically-induced rat gastric carcinogenesis. Pretreatment of A/J mice with 6-methylthiohexyl isothiocyanate (6MHITC)isolated from Wasabia japonica (wasabi) by gavage inhibited O-methylguanine formation in lungs induced by 4(methylnitrosamino)-1(3-pyridyl)-1butanone. 6-MITC at nontoxic concentrations induced the cellular expression of phase-2 detoxification enzymes such as quinone reductase. Some volatile organosulfur compounds in garlic have strong antigenotoxic and anticarcinogenic effects. The soy isoflavone genisteine inhibits mammary carcinogenesis by several distinct mechanisms, such as modulation of estrogen metabolism, inhibition of cell signaling kinases, and induction of apoptosis. The chemopreventive effects of EGCG, a strong antioxidant in green tea, have been extensively investigated and its mechanisms of action are well-documented. Ginseng also has substantial chemopreventive potential, and identification of active ingredients merits further investigation.