**Author details**

**6.** Isosilybin A (ISBN) (extracted from *Silybum marianum*) activates apoptotic machinery in

**Plant Mode of action References**

14

33 37

54

Significantly induced caspase-3 mRNA and suppressed expression of the pro survival kinase Akt-1. Apoptosis was induced by activation of caspase-3 and

Significant block of G1 to S phase transition manifested by the increase of cell

Up-regulates DNA-protein kinase-dependent p53 activation to enhance UVB-

Activates apoptotic machinery in human prostate cancer cells via targeting Akt–

Inhibition of microtubule assembly 70

The topoisomerase-mediated DNA damage seems to be a candidate mechanism, by which some flavonoids may exert their cytotoxic potential

Inhibits active Stat3 phosphorylation, and causes caspase activation

**Table 4.** Mode of action of anticancer activity of phytochemicals present in selected North American medicinal plants

Currently, natural products, especially plant secondary metabolites such as isoprenoids, phenolics and alkaloids, have been demonstrated to be the leading providers of novel anticancer agents. Thiese important groups of phytochemicals represent a vast majority of chemical groups, including alkaloids, flavonoids, flavonols, flavanols, terpenes and terpe‐ noids, phenols, flavonolignans and steroids. Potential anticancer properties of these phyto‐ chemicals have been shown by both cell culture (*in vitro* methods) and animal (*in vivo* methods) studies. However, *in vitro* and *in vivo* findings should be strengthened by valid human clinical

trial data before introducing to the medicine cabinet as natural therapeutics or drugs.

**CEM**, Human drug-sensitive leukemia cells; **CEM/VLB**, Human multidrug-resistant-derived leukemia cells; **Jurkat clone E6-1**, Acute T-cell leukemia cells; **WiDr** and **HT29**, Human colon

human prostate cancer cells via targeting Akt–NF-kB–AR axis.

174 Using Old Solutions to New Problems - Natural Drug Discovery in the 21st Century

inhibiting Akt phosphorylation.

number in G0/G1 phase

induced apoptosis

Increases total p53 levels

NF-kB–AR axis

Activation of the mitochondrial apoptotic pathway

Induces G1 arrest in cell cycle progression

**7.** ISBN increases p53 protein levels.

Achyranthes aspera (Devil's Horsewhip)

Olea europaea (Olive)

Plantago lanceolata (Ribwort plantain)

Silybum marianum (Milkthistle)

Podophyllum peltatum

**6. Conclusion**

**Abbreviations**

(Mayapple)

Wasundara Fernando and H. P. Vasantha Rupasinghe\*

\*Address all correspondence to: vrupasinghe@dal.ca

Faculty of Agriculture, Dalhousie University, Truro, Nova Scotia, Canada

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