Anticancer Potential of Medicinal Plants of the Western Ghats of India: Phytochemistry, Molecular Mechanisms, Therapeutic Prospects and Conservation Challenges

Abstract

Cancer has been a constant battle globally with a lot of development in cures and preventative therapies. The disease is characterised by cells in the human body continually multiplying with the inability to be controlled or stopped. Consequently, forming tumours of malignant cells with the potential to be metastatic. Current treatments include chemotherapy, radiotherapy and chemically derived drugs. Treatments such as chemotherapy can put patients under a lot of strain and further damage their health. Therefore, there is a focus on using alternative treatments and therapies against cancer. The Western Ghats of India constitute one of the world's major biodiversity hotspots and harbour a remarkable diversity of medicinal and endemic plant species traditionally used by indigenous communities for the management of numerous ailments. Increasing interest in plant-derived anticancer agents has highlighted the Western Ghats as a valuable reservoir of structurally diverse secondary metabolites with potential chemo preventive and therapeutic applications. Alkaloids, flavonoids, phenolics, terpenoids, tannins, xanthones, lignans and other specialized metabolites derived from medicinal plants have demonstrated antiproliferative, pro-apoptotic, anti-inflammatory, antioxidant, anti-invasive and anti-angiogenic activities in experimental models. Among Western Ghats-associated medicinal plants, Nothapodytes nimmoniana is particularly significant because it is a natural source of camptothecin, a potent topoisomerase-I inhibitor from which clinically important anticancer derivatives such as irinotecan and topotecan have been developed. Population-level investigations of N. nimmoniana from the Western Ghats have demonstrated substantial variation in camptothecin accumulation, highlighting both pharmaceutical potential and conservation concerns. Recent research has also demonstrated anticancer activity of Tarenna alpestris collected from the Megamalai Hills of the Western Ghats against HT-29 colon cancer cells, providing evidence for continued exploration of less-studied regional taxa. This review critically summarizes the ethnomedicinal importance, major phytochemical classes, experimental anticancer activities and possible molecular mechanisms associated with medicinal plants of the Western Ghats. Particular attention is given to apoptosis, cell-cycle arrest, oxidative stress modulation, inhibition of PI3K/Akt, MAPK and NF-κB-associated pathways, suppression of angiogenesis and inhibition of DNA topoisomerases. The review also discusses limitations of current evidence, including extract variability, incomplete phytochemical characterization, inadequate pharmacokinetic studies, toxicity concerns and the predominance of in vitro investigations. Sustainable harvesting, plant tissue culture, metabolite production through biotechnology and conservation of threatened medicinal plants are considered essential for translating biodiversity into clinically relevant anticancer discoveries. The Western Ghats therefore represent an important natural resource for anticancer drug discovery, but systematic pharmacological validation and conservation-oriented research are required to bridge the gap between traditional knowledge and evidence-based oncology. This review also explains an overview of potential therapeutic plants, including a brief description of their pharmacological effect and mechanism of action.