Role of Antioxidant Phytochemicals in Prevention, Formation and Treatment of Cancer

Abstract

Reactive oxygen species (ROS) played an important role in cancer. Although low levels of ROS can be beneficial in normal physiological functions, chronic exposure to ROS is associated with increased risk of cancers. Increased ROS levels can also induce apoptosis and cell death in various types of cancer. Taken together, the role of ROS in cancer prevention, formation and therapy is extremely complex and very challenging to study. Although the antioxidant activity of phytochemicals is well recognized and generally used to prevent cancer, they can have pro-oxidant and ROS generating activities under certain conditions, especially at high doses or in the presence of metal ions. The basal redox levels of cancer cells are also different from those of normal cells. Therefore, higher levels of free form of metal ions and higher levels of endogenous ROS production in cancer cells sensitizes them to phytochemicals mediated pro-oxidant cytotoxicity. In conclusion, people tend to intake of antioxidant phytochemicals for the detrimental effects of ROS. However, excessive intake of phytochemicals could have cancer development or therapeutic potential by generating ROS. In this section, the role of phytochemicals in the prevention, development and removal of cancer has been discussed.

Dendrimer Nanodevices and Gallic Acid as Novel Strategies to Fight Chemoresistance in Neuroblastoma Cells

“…The results herein obtained in GA-treated cells at concentrations sub-active of GA confirm those obtained in the time-course and dose-dependent experiments, which show that, as reported previously [23,24], GA cytotoxic action is dose dependent and is performed only at high dosage, similar to many natural antioxidant-pro-oxidant compounds [97].…”

“…In addition, as reported for many other kinds of tumors [98], these findings confirmed that, also on NB cells, GA exerts a ROS-mediated cytotoxic anticancer activity at high doses, while it loses its pro-oxidant properties at low doses [97].…”

“…In fact, this correlation, extensively reported for phytochemicals such as GA [97], was further confirmed by the exact overlap of the active concentrations of GA able to cause both a significant increase in ROS and a significant decrease in cell viability at 48 and 72 h.…”

Optimization of Ultrasound-Assisted Extraction Conditions Followed by Solid Phase Extraction Fractionation from Orthosiphon stamineus Benth (Lamiace) Leaves for Antiproliferative Effect on Prostate Cancer Cells

“…However, natural chemotherapy drugs from herbal plants, which may induce apoptosis in cancer cells, can serve as chemotherapeutic agents [3]. Besides that, natural compounds that have high antioxidants have been demonstrated to have a protective effect against cancer development [4].…”

ROS-Mediated Cancer Cell Killing through Dietary Phytochemicals

“…As dietary phytochemicals lack mechanistic selectivity, these natural compounds display a variety of effects in different cancer cell types and thus the discrepancies in results among separate studies. Other possible reasons for divergent findings in different studies include changes or differences in (i) stability of the bioactive compounds in cell culture medium, for example, stability of Qu decreases at pH 7 or 8 [175]; (ii) release of bioactive compounds under different conditions, for example, the maximum release of curcumin occurs in phosphate buffered saline at pH 6.4 [176]; (iii) sensitivity of different cell types to bioactive compounds; (iv) cellular permeability of bioactive compounds; (v) presence or contamination by metal ions [177]; (vi) number of hydroxyl groups present in a molecule [177]; and (vii) in vivo biodistribution.…”