Several herbs and herbal compounds are believed to suppress the transformative, hyperproliferative and inflammatory process that initiates carcinogenesis and dramatically inhibit the vascular endothelial growth factor (VEGF), whose production is considered essential for the migration of cancer cell and for angiogenesis.

Polyphenols are receiving considerable attention for the potential implications in cancer therapy, particularly resveratrol, (grapes), quercetin (broccoli, onions and tea), curcumin (turmeric), genistein (soy), epigallocatechin (green tea) and their sources. In particular, quercetin strongly inhibited in a time and dose-dependent the expression of themutated p53 protein in breast cancer, while the anti-tumour activity of resveratrol occurs through p53-mediated apoptosis. Another mechanism for anticancer activity of resveratrol is the inhibition of a wide range of angiogenic growth factors including VEGF expression.

Curcumin, found in turmeric and its derivatives, has demonstrated a significant inhibition of VEGF and directly inhibits angiogenesis in vivo and in vitro. Moreover, curcumin is also known for interfering with the endothelial cell function by inhibiting the specific integrin engagement. However, it does not interfere with normal cell function; this being the beauty of these safe compounds. Moreover, Aggarwal et al. reported that the ability of curcumin stems of suppressing the proliferation of a wide variety of tumour cells entails the anticancer effect of downregulating the Nf-kB, AP-1 and Egr-1 transcription factors and the expression of COX2, LOX, NOS, MMP-9, uPA, and TNF.

Regarding green tea and its extracts, findings have shown that they suppress chromosomal abnormalities induced by carcinogens. For this reason, interest in these compounds has grown as they also play a role in delaying the cumulative genetic damage necessary for a cell to evolve from normality to one with aggressive metastatic capabilities [34]. An appropriate dose of VEGF blockade would be 2 to 4 g of standardized green tea extract. Each gram of this extract provides 400 to 500 mg of EGCG.

The seed cones from magnolia trees inhibited the growth of new blood vessels in mice. Silybin, a silymarin compound in milk thistle, bound to phosphatidylcholine, was shown to inhibit VEGF when used as a single agent against human ovarian cancer.

Aloe-emodina, a hydroxyanthraquinone from Aloe vera and other plants, has been indicated as a new antiangiogenic compound with a remarkable photocytotoxic effect on tumour cells. Emodin has been reported to be non-toxic for normal cells while possessing specific toxicity for neuroectodermal tumour cells. Edible berries (bilberry, cranberry, elderberry, raspberry seed) may have potent chemopreventive properties by inhibiting both H2O2 and TNF-a, which induced VEGF expression. Ginkgo has multiple actions including antiedemic, antihypoxic, antioxidant, antiplatelet, free-radical scavenging and microcirculatory properties.

Terpenes, and especially triterpenes, due to their broad spectrum of biological activity, are studied by many researchers since there is growing interest in the evaluation of triterpenoid extracts for cancer treatment. Several triterpene compounds that have recently appeared in the literature in preclinical studies suggest potential therapeutic opportunities. Betullinic acid, boswellic acid, squalene, ursolic acid, oleanolic acid and triterpenoid saponins are among the growing number of compounds evaluated in preclinical and some clinical studies.

Alfa-bisabolol is a sesquiterpene alcohol present in the essential oil of chamomile and other plants which exerts, according to Cavalieri et al. [44], a strong timeand dose-dependent cytotoxic action against human pancreatic cell line. However, it failed to affect the viability of human fibroblasts. Based on these results, alfabisabolol should be considered a novel promising compound for inhibiting the growth and survival of transformed cells with high malignancy.

The efficacy of Ginseng in the treatment of physical performance, psychomotor performance, cognitive function and immune modulation has been investigated. The conclusion of this analysis is that the efficacy of ginseng is not established beyond reasonable doubt for any of these indications. However, a retrospective trial involving 4634 patients suggested a dose-response relationship between ginseng consumption and a decrease in the risk of cancer, with a 40% relative risk reduction.

Iscador, a derivative of mistletoe, is an example of an immunostimulant causing either an increase in cytotoxic T lymphocytes or natural killer cells or endogenous production of interferon and interleukins. Iscador is available in many mainstream European cancer clinics. European governments have approved studies on the efficacy of iscador against cancer. The results are mixed, since some 212 G. Benoni and L. Cuzzolin studies suffer methodological shortcomings. According to another systematic review, none of the methodologically well-made trials showed efficacy in survival.

Several mushroom-derived compounds have been approved for use as cancer treatment in Japan. Trials on polysaccharide Kureha (PSK), an extract of the mushroom Coriolus versicolor, showed superior survival with PSK in both gastrectomy and esophagectomy. Two randomized trials of PSK given after curative resection for colorectal cancer showed that both disease-free and overall survival rates were significantly higher in the PSK group. Results were less encouraging in breast cancer and leukaemia. The proposed mechanism was immune modulation of a beta glucan, a natural carbohydrate, present in great quantities in mushroom, bound to specific receptors on neutrophils. An interesting association between the response to PSK treatment and HLA type was reported.

Several studies have been published on the chemistry, pharmacology and clinical applications of Echinacea, in particular E. purpurea. Among these, many have described the use of Echinacea for immune system stimulation. Astragalus has been proved to have immunologic benefits by stimulating macrophage and natural killer cell activity and inhibiting T-helper cell type2 cytokines. Mc. Culloch et al, found evidence that Astragalus-based Chinese herbal medicine may increase the effectiveness (by improving survival, tumour response and performance status) and reduce the toxicity of standard platinum-based chemotherapy for advanced nonsmall- cell lung cancer. Garlic has been used in a variety of conditions as a chemopreventive agent for gastrointestinal tumours.