Date of Award

8-12-2014

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

First Advisor

Dr. Ritu Aneja

Abstract

Chemotherapy, employing single-molecule or multidrug concoctions inspired by the diverse repository of plant chemicals, has been the mainstay of cancer treatment for years. However, isolating single molecules has proven to be expensive along with limited therapeutic window and toxicity. On the other hand, whole foods, while preserving the natural complex balance between their constituent phytochemicals and being non-toxic, have proven to impart better disease-fighting efficacies, thus leading to an increased focus on dietary interventions to both treat and prevent cancer. Owing to the complex interactions between their constituent phytochemicals, several dietary agents have been investigated for their therapeutic and preventive efficacies. However, due to lack of emphasis on confounding factors like bioavailability, absorption, metabolism, and excretion, essentially driven by phytocomplexity, incorporation of whole foods in therapeutic regimen has not been successful. This thesis exemplifies the need to investigate factors associated with the limitations in the current approach with respect to dietary agents. Bioactivity-guided fractionation of sweet potato greens extract (SPGE) led to the identification of ~100-fold more potent fraction in vitro. However, this efficacy could not be translated in vivo. We also studied whole ginger extract (GE) for its in vitro and in vivo prostate tumor growth-inhibitory and apoptosis-inducing effects. In addition, GE proved to be more efficacious as compared to its individual most-active constituents owing to the differences in their pharmacokinetic (PK) and bioavailability measurements. Hence, these studies emphasize the crucial role of synergistic/additive interactions among the constituents of whole foods in successful translation of their therapeutic benefits. Another factor that seeks further attention is the unique cellular mechanisms engaged by these phytochemicals to confer their remarkable effects. Phenolic compounds, the most-abundant of all phytochemicals, are well known for their antioxidant properties and act via reactive oxygen species (ROS)-mediated mechanisms. We however assert the underappreciated xenohormetic prooxidant role of phenolics, where cancer cell death is caused by induction of intolerable levels of ROS. We demonstrated that a Piper betel constituent, hydroxychavicol (HC), mediates cytotoxicity via ROS-induced DNA-damage. This thesis thus provides compelling grounds for future preclinical studies to validate their potential usefulness for cancer management.

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