Description: <b>Found</b> in roots, leaves, nut-hulls, bark and wood of walnut trees.<br>
Juglone (5-hydroxy-1,4-naphthoquinone) <br>
Juglans nigra refers to the black walnut tree, which is one of the most well-known sources of juglone<br>
-Research has focused on the hulls (the green outer covering of the walnut) because they have the highest concentrations.<br>
-Fresh hulls can contain juglone levels in the range of approximately 1–5% of the dry weight<br>
<br>
-Juglone can redox cycle to generate reactive oxygen species (ROS). <br>
-Increasing Bax, decreasing Bcl‑2, caspase activation, and MMP depolarization.<br>
-Modulation of MAPK pathways (including ERK, JNK, and p38) <br>
-May inhibit NF‑κB signaling<br>
-Cause DNA damage or stress that, in turn, leads to p53 pathway activation—
Pin1 Inhibition<br>
–Pin1, a peptidyl-prolyl cis/trans isomerase, is frequently overexpressed in cancer.<br>
<br>
-ic50 maybe 5-10uM<br>
-For matching 5uM, crude estimate is 5mg consumption of juglone required which might be 1.5 g of black walnut hull material<br>
<br>
<p><b>Juglone</b> — Juglone (5-hydroxy-1,4-naphthoquinone; JG) is a naturally occurring redox-active naphthoquinone found in plants of the <i>Juglans</i> genus, including black walnut (<i>Juglans nigra</i>), with particularly high concentrations reported in green walnut hulls. It is best classified as a natural small-molecule quinone and experimental anticancer agent rather than an established therapeutic drug. Its anticancer activity is strongly concentration-dependent and reflects electrophilic thiol reactivity, redox cycling, oxidative stress, mitochondrial injury, ferroptosis, apoptosis, and modulation of several oncogenic signaling pathways. Juglone is also widely used experimentally as a Pin1 inhibitor, although this designation should not imply high target selectivity because juglone can covalently modify protein sulfhydryl groups and affect transcription and other cellular proteins.</p>
<p><b>Primary mechanisms (ranked):</b></p>
<ol>
<li>Quinone redox cycling and electrophilic thiol reactivity causing ↑ ROS, ↓ glutathione-dependent antioxidant capacity, oxidative macromolecular injury, and oxidative-stress-driven cell death.</li>
<li>Ferroptosis induction through lipid peroxidation and disruption of antioxidant defenses, including ↓ GPX4 and, in some cancer models, ↓ NRF2 signaling or activation of the FOSL1-HMOX1 axis.</li>
<li>Mitochondrial apoptosis through ↓ mitochondrial membrane potential, ↑ Bax/Bcl-2 ratio, cytochrome-c release, and caspase activation.</li>
<li>Pin1 inhibition contributing to suppression of proliferation, cancer-cell stemness, EMT, migration, angiogenesis, and oncogenic signaling; however, juglone is not a highly selective Pin1 pharmacological probe.</li>
<li>Suppression of PI3K-AKT and related survival signaling, frequently downstream of or amplified by oxidative stress.</li>
<li>Cell-cycle arrest through modulation of cyclins, CDKs, p21, p27, p53, and related checkpoint pathways.</li>
<li>Stress-MAPK modulation, particularly ↑ p38 and ↑ JNK, contributing to apoptosis, ferroptosis, and autophagic responses.</li>
<li>Suppression of EMT, invasion, stem-like phenotype, Wnt/β-catenin signaling, HIF-1α, VEGF, and angiogenic/metastatic programs in selected cancer models.</li>
<li>Autophagy induction as a context-dependent stress response that can interact with apoptosis and oxidative injury.</li>
</ol>
<p><b>Bioavailability / PK relevance:</b> Free juglone has unfavorable drug-delivery characteristics, including hydrophobicity, high chemical reactivity, rapid disposition, and substantial renal exposure. In an animal intravenous PK study, free juglone had a plasma half-life of approximately 2 hours and showed prominent kidney localization; sterically stabilized liposomal delivery increased plasma half-life approximately 12-fold, improved tumor localization, and reduced renal toxicity. Robust human oral pharmacokinetic data are lacking. Consequently, dietary or walnut-hull intake cannot presently be converted reliably into a systemic micromolar juglone exposure.</p>
<p><b>In-vitro vs systemic exposure relevance:</b> Most direct anticancer studies use approximately low-to-tens-of-micromolar juglone, commonly around 5–20 µM. Whether these free-drug concentrations can be maintained safely in human tumors is not established. Recent quantitative work also demonstrates limited intracellular accumulation despite extracellular juglone exposure. Thus, common in-vitro concentrations should not be assumed to be achievable through oral walnut or black-walnut-hull consumption.</p>
<p><b>Clinical evidence status:</b> Preclinical. Juglone has substantial cell-culture evidence and multiple mouse/xenograft studies showing antitumor activity, including apoptosis, ferroptosis, anti-metastatic, and anti-angiogenic effects. There is no established anticancer dose, regulatory approval, or convincing human clinical efficacy evidence for juglone itself. Translation is limited by nonspecific electrophilic/redox chemistry, systemic toxicity risk, formulation and pharmacokinetic limitations, and the uncertain therapeutic window between cancer and normal tissues.</p>
<h3>Juglone Mechanistic Profile</h3>
<table>
<thead>
<tr>
<th>Rank</th>
<th>Pathway / Axis</th>
<th>Cancer Cells</th>
<th>Normal Cells</th>
<th>TSF</th>
<th>Primary Effect</th>
<th>Notes / Interpretation</th>
</tr>
</thead>
<tbody>
<tr>
<td>1</td>
<td>Quinone redox cycling and thiol reactivity</td>
<td>↑ ROS; ↑ oxidative stress; ↓ cellular thiol buffering</td>
<td>↑ oxidative injury possible</td>
<td>P/R</td>
<td>Oxidative-stress overload</td>
<td>Central upstream mechanism. Juglone participates in redox cycling and can react with protein and glutathione sulfhydryl groups; this contributes to efficacy but also limits selectivity.</td>
</tr>
<tr>
<td>2</td>
<td>Glutathione and antioxidant defense</td>
<td>↓ GSH; ↓ GPX4; ↓ SOD (model-dependent)</td>
<td>↓ antioxidant reserve possible (dose-dependent)</td>
<td>R</td>
<td>Loss of redox buffering</td>
<td>Creates a permissive environment for ROS accumulation, lipid oxidation, apoptosis, and ferroptosis.</td>
</tr>
<tr>
<td>3</td>
<td>Ferroptosis and lipid peroxidation</td>
<td>↑ ferroptosis; ↑ lipid peroxidation; ↑ MDA; ↑ labile iron</td>
<td>Potential ferroptotic toxicity at sufficient exposure</td>
<td>R/G</td>
<td>Iron-dependent oxidative cell death</td>
<td>Strong recent evidence in hepatocellular carcinoma and glioblastoma; pathway execution is cancer-type dependent.</td>
</tr>
<tr>
<td>4</td>
<td>NRF2 GPX4 antioxidant axis</td>
<td>↓ NRF2; ↓ GPX4 (model-dependent)</td>
<td>Not established</td>
<td>R/G</td>
<td>Ferroptosis sensitization</td>
<td>Demonstrated particularly in glioblastoma. NRF2 modulation should not be generalized to every tumor model.</td>
</tr>
<tr>
<td>5</td>
<td>FOSL1 HMOX1 ferroptosis axis</td>
<td>↑ FOSL1; ↑ HMOX1</td>
<td>Not established</td>
<td>G</td>
<td>Ferroptosis amplification</td>
<td>Recent HCC and pan-cancer evidence identifies this transcriptional axis as an important juglone-responsive ferroptotic mechanism.</td>
</tr>
<tr>
<td>6</td>
<td>Mitochondrial membrane integrity</td>
<td>↓ membrane potential; ↑ cytochrome-c release</td>
<td>Mitochondrial toxicity possible</td>
<td>R</td>
<td>Intrinsic apoptosis initiation</td>
<td>Observed across breast, gastric, prostate, and other cancer models.</td>
</tr>
<tr>
<td>7</td>
<td>BAX BCL2 caspase apoptosis</td>
<td>↑ BAX; ↓ BCL2; ↑ caspase-3/7; ↑ caspase-8/9</td>
<td>Apoptosis possible at cytotoxic exposure</td>
<td>R/G</td>
<td>Programmed cell death</td>
<td>Both intrinsic and extrinsic apoptotic pathways can participate. Recent colorectal cancer data support activation of caspase-8 as well as mitochondrial caspase-9 signaling.</td>
</tr>
<tr>
<td>8</td>
<td>Pin1 prolyl isomerase</td>
<td>↓ Pin1 activity/function</td>
<td>↓ Pin1 and other thiol-sensitive proteins possible</td>
<td>P/R</td>
<td>Reduced oncogenic signaling and stemness</td>
<td>Important experimental target associated with ↓ proliferation, ↓ EMT, ↓ stemness, and ↓ angiogenesis. Juglone is not Pin1-selective and can directly modify sulfhydryl-containing proteins.</td>
</tr>
<tr>
<td>9</td>
<td>PI3K AKT survival signaling</td>
<td>↓ PI3K; ↓ AKT; ↓ p-AKT</td>
<td>Context-dependent</td>
<td>R/G</td>
<td>Survival pathway suppression</td>
<td>ROS scavenging can partially reverse this effect in NSCLC, indicating substantial coupling between oxidative stress and PI3K-AKT inhibition.</td>
</tr>
<tr>
<td>10</td>
<td>p38 JNK stress signaling</td>
<td>↑ p38; ↑ JNK</td>
<td>Context-dependent</td>
<td>R</td>
<td>Stress-mediated apoptosis and ferroptosis</td>
<td>Activation is frequently associated with ROS production and can contribute to NRF2-GPX4 suppression and programmed cell death.</td>
</tr>
<tr>
<td>11</td>
<td>Cell cycle checkpoints</td>
<td>↑ arrest; ↓ CDK2; ↓ CDK4; ↓ cyclins; ↑ p21; ↑ p27</td>
<td>Growth inhibition possible</td>
<td>G</td>
<td>Proliferation blockade</td>
<td>Cell-cycle phase varies by model. Recent colorectal cancer data support G0/G1 arrest with suppression of CCND1, CCNB1, CDK2, and CDK4.</td>
</tr>
<tr>
<td>12</td>
<td>p53 DNA damage response</td>
<td>↑ DNA damage; ↑ γH2AX; ↑ p53 (model-dependent)</td>
<td>Genotoxicity possible</td>
<td>R/G</td>
<td>Checkpoint activation and apoptosis</td>
<td>May arise partly from quinone-driven ROS and electrophilic stress rather than a specific DNA-targeting interaction.</td>
</tr>
<tr>
<td>13</td>
<td>Intracellular calcium and mitochondrial stress</td>
<td>↑ Ca²⁺ (model-dependent)</td>
<td>Not established</td>
<td>P/R</td>
<td>Apoptotic signaling</td>
<td>Increased intracellular Ca²⁺ has been demonstrated in MCF-7 cells together with ROS elevation and mitochondrial depolarization.</td>
</tr>
<tr>
<td>14</td>
<td>EMT migration and invasion</td>
<td>↓ EMT; ↑ E-cadherin; ↓ N-cadherin; ↓ Snail; ↓ migration; ↓ invasion</td>
<td>Not established</td>
<td>G</td>
<td>Reduced metastatic phenotype</td>
<td>Pin1, AKT-GSK3β-Snail, TGF-β-related, and other signaling systems have been implicated depending on tumor model.</td>
</tr>
<tr>
<td>15</td>
<td>Cancer stemness</td>
<td>↓ sphere formation; ↓ tumor-initiating phenotype</td>
<td>Not established</td>
<td>G</td>
<td>Reduced self-renewal and metastatic potential</td>
<td>Pin1 inhibition appears to contribute. Effects have been demonstrated in colorectal and other tumor-initiating cell models.</td>
</tr>
<tr>
<td>16</td>
<td>Wnt beta-catenin signaling</td>
<td>↓ Wnt/β-catenin (model-dependent)</td>
<td>Not established</td>
<td>G</td>
<td>Reduced invasion and angiogenesis</td>
<td>Most clearly demonstrated in pancreatic cancer models; not necessarily a universal primary mechanism.</td>
</tr>
<tr>
<td>17</td>
<td>HIF-1α VEGF angiogenic signaling</td>
<td>↓ HIF-1α; ↓ VEGF; ↓ angiogenesis</td>
<td>Potential vascular effects not well characterized</td>
<td>G</td>
<td>Reduced tumor vascular support</td>
<td>Secondary/contextual anticancer mechanism reported in pancreatic cancer and Pin1-related models.</td>
</tr>
<tr>
<td>18</td>
<td>Autophagy stress response</td>
<td>↑ LC3-II; ↑ Beclin-1; ↓ p62 (model-dependent)</td>
<td>Context-dependent</td>
<td>G</td>
<td>Autophagic stress and death crosstalk</td>
<td>Autophagy can accompany ROS/MAPK signaling but its contribution to net cytotoxicity varies by cell type and experimental conditions.</td>
</tr>
<tr>
<td>19</td>
<td>Chemosensitization</td>
<td>↑ drug cytotoxicity in selected combinations</td>
<td>Potential ↑ combination toxicity</td>
<td>G</td>
<td>Combination-treatment sensitization</td>
<td>Juglone can enhance etoposide cytotoxicity through Pin1-related mechanisms, but sequence of administration can substantially alter the interaction.</td>
</tr>
<tr>
<td>20</td>
<td>Clinical Translation Constraint</td>
<td>Effective concentrations commonly ~5–20 µM in vitro</td>
<td>Systemic electrophilic and oxidative toxicity limits selectivity</td>
<td>G</td>
<td>Uncertain therapeutic window</td>
<td>Human bioavailability and therapeutic exposure are not established. Free juglone has short animal plasma persistence, renal accumulation, and nephrotoxicity; formulations such as liposomes materially alter PK and distribution.</td>
</tr>
</tbody>
</table>
<p>P: 0–30 min R: 30 min–3 hr G: >3 hr</p>
>