Understanding the molecular mechanisms of cancer prevention by dietary phytochemicals: From experimental models to clinical trials

Table 4 Properties and biological effects of dietary phytochemicals and approved chemopreventive agents

Dietary phytochemicals	Approved chemopreventive agents
Occurrence
Natural compounds of plant origin	Majority are synthetic compounds while some are biological and/or natural agents
Long History of exposure to humans through food	Human exposure as prescribed drug/vaccine
Easily available and relatively cheaper	Available on prescription and relatively expensive
Properties
Anti-oxidant/polyphenolic in nature, sparingly soluble in water	Widely differing properties and characteristics
Chemopreventive efficacy
Established in experimental models, yet to prove efficacy in clinical trials	Established both in experimental models and clinical trials
Effects-weak to moderate	Effects-moderate to strong
Successful against different classes of carcinogens and at multiple organ sites	May not be successful against different classes of carcinogens and at multiple organ sites
Mechanism(s)
Modulators of redox status and kinase functions, inducer of phase II enzymes	Mechanisms are diverse and may not be related to redox status and/or kinase functions, may not be modulating phase II enzymes
Modulate multiple pathways/targets	Modulation of specific targets/pathways
Specificity
Relatively less specific/non-specific (Pleotropic effects)	Relatively specific to defined agent/exposure and/or molecular pathways
Toxicity
Depends on dose and duration of exposure. Non-toxic at the doses present in food	Depends on dose and duration of exposure