Emerging classes of antioxidant to cancer therapy: a review of clinical and experimental studies

This review mainly focuses on the relation between antioxidants with cancer therapy. Antioxidants have been reported to play an essential role to reduce free radical species. Free radicals commonly cause oxidative damage which is a common factor in the aging process, and also the vital factor of formation, and development of major disease specially cancer. Although, since last many decades several antioxidants belong to natural and synthetic origin have been tested in clinical trials against oxidative stress, however these clinical trials end up with undesirable effects. This review also complied with the most recent findings of oxidative stress, highlighting of free racial production, and its related oxidative damage at cellular and molecular level, with the new and existing natural and synthetic classes of free radical scavenger and their related clinical trials.

💡 Research Summary

The review article provides a comprehensive overview of the relationship between oxidative stress and cancer therapy, emphasizing both the biochemical mechanisms of free‑radical generation and the therapeutic potential of emerging antioxidant classes. It begins by describing the fundamental imbalance between reactive oxygen/nitrogen/sulfur species (ROS/RNS/RSS) and the cellular antioxidant defense system, highlighting mitochondria‑derived superoxide, NADPH oxidases, xanthine oxidase, and enzymatic scavengers such as super‑oxide dismutase (SOD) and catalase. The authors explain how these reactive species cause damage to DNA, proteins, and lipids, leading to mutations, altered signaling pathways (e.g., NF‑κB, AP‑1, MAPKs) and ultimately tumor initiation or progression.

The manuscript then surveys natural and synthetic antioxidants that have been evaluated in pre‑clinical and clinical settings. Natural compounds include polyphenols, flavonoids, carotenoids, glutathione, ubiquinol, and lipoic acid, many of which are derived from plant extracts and have shown free‑radical scavenging activity in vitro. Synthetic derivatives are discussed in three main families:

1. Pyrimidine‑based agents – nucleobase analogues such as zidovudine (AZT) and 5‑fluorouracil (5‑FU) are described as having dual antiviral/anticancer activity through incorporation into DNA/RNA and inhibition of nucleotide synthesis, thereby reducing oxidative DNA damage and slowing tumor cell proliferation.

2. Bis‑coumarin derivatives – coumarin scaffolds (e.g., 7‑hydroxycoumarin) are presented as inhibitors of farnesylation and modulators of the arachidonic‑acid inflammatory pathway, with activity demonstrated in several cancer cell lines (HL‑60, MCF‑7, A549) and phase‑II trials for prostate, melanoma, and renal cell carcinoma.

3. Thiazole derivatives – heterocyclic thiazoles are highlighted for their broad pharmacological profile (antioxidant, anti‑inflammatory, antihypertensive, antitumor) and recent development as potent anticancer agents.

The authors critically assess clinical trial outcomes, noting that many antioxidant interventions have produced undesirable side effects or failed to improve survival, possibly due to the dual role of ROS in cancer cell signaling and host defense. They argue that timing, dosage, and patient selection are crucial variables that have been inadequately addressed in past studies.

Finally, the review outlines future directions: the need for rational design of antioxidants that selectively target tumor‑specific redox vulnerabilities, integration of redox biomarkers to stratify patients, and combination strategies that pair antioxidants with conventional chemotherapy, radiotherapy, or immunotherapy to mitigate treatment‑induced oxidative damage while preserving anticancer efficacy. The authors conclude that emerging classes of antioxidants, especially those derived from rationally engineered pyrimidine, coumarin, and thiazole scaffolds, hold promise for augmenting cancer therapy, provided that rigorous mechanistic and clinical validation is performed.