Tree Seed Compound Karanjin Pushes Cancer Cells Into Oxidative Overload and Self-Destruction

A furanoflavonoid extracted from the seeds of the karanja tree, Pongamia pinnata, has emerged as a strikingly selective killer of certain cancer cells, and researchers have now mapped in detail how it works. In a study published in Discover Chemistry, a team led by Ching-Yee Loo and Wing-Hin Lee of Universiti Kuala Lumpur combined laboratory experiments with computational modeling to trace the chain of events that unfolds when cancer cells are exposed to karanjin. The compound, already known for antioxidant and anti-inflammatory properties in other disease contexts, appears to flip its behavior inside malignant cells, acting as a pro-oxidant that floods them with reactive oxygen species and pushes their mitochondria past the point of no return.

The central finding is a tight quantitative link between oxidative stress, mitochondrial failure, and apoptosis. When the researchers pooled their measurements across four cancer cell lines, they found that reactive oxygen species levels correlated strongly with cell death, but that mitochondrial membrane depolarization was an even better predictor of apoptosis. Linear regression showed that roughly 88.5 percent of the variation in apoptotic response could be explained by the degree of mitochondrial depolarization alone. Once the researchers statistically adjusted for mitochondrial damage, the direct association between reactive oxygen species and apoptosis largely disappeared, suggesting that mitochondrial dysfunction sits downstream of oxidative stress and functions as the critical gatekeeper on the road to programmed cell death.

The experimental work covered an unusually broad panel of cell types: breast adenocarcinoma (MCF-7), lung adenocarcinoma (A549), colorectal carcinoma (HCT116), and cervical carcinoma (HeLa) cancer cells, alongside immortalized human keratinocytes (HaCaT) as a healthy control. The results were not uniform. Karanjin killed MCF-7, A549, and HCT116 cells in a dose- and time-dependent fashion, with the IC50 value for A549 cells falling from 65.4 micromolar at 24 hours to 39.5 micromolar at 72 hours, indicating growing potency with prolonged exposure. HeLa cells, by contrast, were remarkably resistant, showing little response even at the highest concentration of 100 micromolar after three days. Healthy HaCaT keratinocytes were essentially untouched, with viability remaining above 75 percent across all tested concentrations and durations.

The reactive oxygen species data told a consistent story. A549 cells treated with 100 micromolar karanjin produced intracellular ROS levels 1.97-fold higher than untreated controls at 24 hours, climbing to 2.45-fold by 72 hours. HCT116 cells showed increases ranging from 1.72- to 2.32-fold over the same period. HeLa and HaCaT cells generated far less oxidative stress, which the authors interpret as the key to their survival. Cancer cells typically live with elevated baseline ROS and compensate with robust antioxidant systems, including superoxide dismutase, glutathione, and thioredoxin reductase. The study found that karanjin depleted these defenses in the susceptible lines: after 50 micromolar treatment, A549 cells lost approximately 43.7 percent of their glutathione and 26.9 percent of their superoxide dismutase activity, while lipid peroxidation markers rose sharply, evidence that membranes, proteins, and DNA were being oxidatively damaged faster than the cells could repair them.

To prove that oxidative stress was genuinely driving the toxicity rather than merely accompanying it, the team pretreated cells with N-acetylcysteine, a well-established ROS scavenger. The results were decisive. In MCF-7 cells exposed to 50 micromolar karanjin, NAC pretreatment cut ROS levels from 178 percent to 122 percent of baseline and reduced lactate dehydrogenase release, a marker of membrane rupture and late-stage cell damage, from 23.4 percent to 8.2 percent, an approximately 65 percent reduction. Similar protective effects appeared in A549 and HCT116 cells, and brightfield microscopy showed that the cell-cell aggregation and morphological changes characteristic of apoptosis vanished when the antioxidant was present. HaCaT cells, which never accumulated significant ROS, retained their normal epithelial appearance under every condition tested.

Downstream of the oxidative assault, the mitochondria collapsed. Using the JC-10 fluorescent probe, the researchers measured membrane depolarization at 50 micromolar karanjin following a clear hierarchy: MCF-7 at 2.67-fold relative to control, A549 at 2.34-fold, HCT116 at 2.10-fold, and HeLa at only 1.45-fold. ATP production in the three sensitive lines fell to roughly 65 percent of control levels, consistent with damage to the electron transport chain. As the inner mitochondrial membrane lost its charge, cytochrome c escaped into the cytosol, caspase-3 activity surged, and DNA fragmentation followed. Annexin V flow cytometry confirmed the outcome: at 50 micromolar, apoptotic populations reached 36.8 percent in MCF-7, 35.0 percent in A549, and 34.5 percent in HCT116, while HeLa cells maxed out at 10.2 percent and HaCaT cells stayed between 3.2 and 5.5 percent regardless of dose.

Notably, phosphorylated NF-κB, a transcription factor often implicated in cancer cell survival and drug resistance, was not significantly altered by karanjin in any of the cell lines, ruling out one popular mechanistic hypothesis. Instead, the computational arm of the study pointed elsewhere. Network pharmacology, drawing on target prediction databases and protein-protein interaction analysis, identified nine core targets for lung cancer, including EGFR, SRC, STAT1, GRB2, and the chaperone proteins HSP90AA1 and HSP90AB1. KEGG pathway enrichment highlighted the PI3K-Akt signaling cascade, EGFR tyrosine kinase inhibitor resistance, chemical carcinogenesis via reactive oxygen species, and other cancer-related pathways. Comparative analyses across breast, colon, and cervical cancer datasets showed substantial overlap in these core targets, suggesting a common mechanism of action, with cervical cancer sharing only six of the nine hub proteins, a difference that may partly explain HeLa’s resistance.

Molecular docking with AutoDock Vina lent further support. Karanjin bound favorably to all ten cancer-related protein targets tested, with binding free energies between -6.0 and -8.3 kilocalories per mole, a range associated with stable ligand-protein interactions. The strongest predicted binding was to MEK at -8.3 kilocalories per mole, followed by mTOR at -7.9, RAF at -7.6, and RAS and PI3K at -7.4 each. These interactions, mediated through hydrogen bonds with residues such as Met 146 of MEK and Arg 348 of PI3K, suggest that karanjin could suppress the RAS/RAF/MEK/ERK and PI3K/AKT/mTOR survival cascades that cancer cells rely on for proliferation and metabolic regulation. The authors are careful to note that direct protein-level validation was beyond the scope of this work, so the docking results remain hypothesis-generating rather than conclusive.

The selectivity story comes with honest caveats. Because the IC50 for healthy HaCaT cells was never reached within the tested range, the team conservatively estimated selectivity indices using 100 micromolar as the ceiling, yielding values above 1.53 for A549, 1.36 for MCF-7, and 1.23 for HCT116 at 24 hours, all of which grew with longer exposure. Even so, these indices remain below the threshold conventionally associated with highly selective anticancer compounds, and the authors explicitly frame their findings as evidence of moderate cancer-selective activity rather than definitive tumor specificity. Karanjin’s drug-like profile, including compliance with Lipinski’s rule of five, high gastrointestinal absorption, and a predicted ability to inhibit the P-glycoprotein efflux pump implicated in multidrug resistance, keeps it interesting as a lead compound.

What makes the study methodologically notable is its integration of correlation and regression modeling with classical mechanistic assays, an approach that transforms a pile of individual measurements into a causal narrative. The data support a coherent sequence: karanjin overwhelms the antioxidant buffering capacity of susceptible cancer cells, ROS accumulates, the mitochondrial electron transport chain falters and leaks more electrons, the membrane potential collapses, and apoptosis executes in near-proportional response to the degree of depolarization. Healthy keratinocytes, with their redox systems intact, simply absorb the insult. The authors call for in-depth mechanistic evaluation and in vivo therapeutic efficacy studies to determine whether karanjin’s mitochondrial tipping point can be exploited in living tumors, a question that will determine whether this karanja tree flavonoid graduates from laboratory curiosity to genuine drug candidate.

Subject of Research: Mechanism of karanjin-induced oxidative stress, mitochondrial depolarization, and apoptosis in cancer cells

Article Title: Oxidative stress-associated mitochondrial depolarization correlates with apoptotic response in karanjin-treated cancer cells

Article References: Loo, C.-Y., Gnanaraj, C., Musa, S. H., Sivapragasam, G., Sandanamsamy, S., Siew, E. L., Yeung, S., & Lee, W.-H. (2026). Oxidative stress-associated mitochondrial depolarization correlates with apoptotic response in karanjin-treated cancer cells. Discover Chemistry, 3(1), Article 492. https://doi.org/10.1007/s44371-026-00945-6

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00945-6

Keywords: karanjin, Pongamia pinnata, reactive oxygen species, mitochondrial depolarization, apoptosis, oxidative stress, cancer cells, PI3K-Akt pathway, molecular docking, network pharmacology, flavonoids, cytotoxicity