01 — Evidence
Evidence Summary
Baicalein's oncology evidence is preclinical-dominant. There is no controlled human trial of tumor regression, biomarker response, or survival — the human record is pharmacokinetic and safety data in healthy volunteers. Underneath sits broad, repeatedly positive animal tumor-model work and a large in-vitro mechanistic literature, read against a pharmacokinetic gap between the concentrations active in the laboratory and the free-compound levels reached in people.
Human
Clinical Record
Pharmacokinetic & safety trials only
Baicalein has no clinical oncology evidence. The controlled human trials that exist measured pharmacokinetics and tolerability in healthy volunteers, not tumor outcomes.
- No controlled trial has tested tumor regression, biomarker response, or survival
- Phase I single- and multiple-ascending-dose studies reported good tolerability
- Human development includes Phase I PK studies and a registered Phase IIa influenza program; no isolated-baicalein oncology trial exists
Animal
Preclinical Signal
Broad xenograft outcomes
Baicalein suppressed tumor growth across many cancer types — by oral, intragastric, and injected routes — often enhancing radiotherapy or chemotherapy rather than acting on its own.
- Shrank colorectal, breast, gastric, hepatocellular and other xenografts
- Reduced spontaneous lung metastasis in a transgenic breast model
- Radiosensitized and restored chemotherapy sensitivity in several models
In Vitro
Cell Model Data
Mechanistic; concentration-limited
Across diverse cancer lines baicalein suppresses proliferation, migration and survival signaling and triggers mitochondrial apoptosis — but the effective concentrations sit above the free-compound levels reached orally in people.
- Suppressed STAT3, PI3K–AKT–mTOR, ERK and NF-κB survival signaling
- Induced mitochondrial apoptosis and reversed EMT markers
- Showed selectivity — lower cytotoxicity to matched normal cells
Human
Clinical Record
Baicalein has no clinical oncology evidence: no controlled trial has tested tumor regression, biomarker response, or survival. The human data are pharmacokinetic and safety trials in healthy volunteers — a single-ascending-dose Phase I study and two independent multiple-ascending-dose studies — all reporting good tolerability with only mild, self-limiting adverse events.[46,47,48]
Continue reading — full research detail+
The single-ascending-dose study spanned 100–2800 mg[47], and the two multiple-ascending-dose studies covered 200–600 mg and 200–800 mg[46,48], all in healthy volunteers. Adverse events were mild and self-limiting, with no serious events and no signal of liver or kidney toxicity on laboratory testing.[46,47,48,49]
ClinicalTrials.gov lists only non-oncology baicalein registrations — a Phase 2a influenza-fever trial (registry status Unknown as of 2026, no results posted) and early work describing baicalein as a candidate neuroprotective agent for Parkinson's disease — so no human efficacy readout for any cancer currently exists, and the non-oncology programs are themselves early-stage. Human oral baicalein has been characterized only for its pharmacokinetics and tolerability, not for any anti-tumor endpoint.
Signal maturity: preclinical-dominant. The human evidence establishes tolerability and measurable exposure, not anti-tumor activity; every oncology-relevant claim on this page rests on animal or cell-model data, read against the pharmacokinetic gap below.
Animal
Preclinical Signal
Tumor-model outcomes are broad and repeatedly positive across colorectal, breast, hepatocellular, gastric, ovarian, nasopharyngeal, pancreatic, osteosarcoma and cervical systems — delivered by varied routes and schedules, from intragastric ~10–20 mg/kg in colorectal models to intraperitoneal 30 mg/kg in a spontaneous-metastasis breast model.[1,17]
Continue reading — full research detail+
Intragastric baicalein (10 and 20 mg/kg) dose-dependently shrank colorectal xenografts while inducing ferroptosis markers via the JAK2/STAT3/GPX4 axis[17]; as a direct TLR4 antagonist it suppressed a colorectal xenograft's growth and angiogenesis — Ki-67, CD31, VEGF and MMP-2[5]; and in the transgenic MMTV-PyMT breast model it reduced tumor onset, growth and pulmonary metastasis by blocking fibronectin/calpain-2-driven EMT.[1]
It also suppressed gastric[20], hepatocellular[24,26,33], nasopharyngeal[30], pancreatic-neuroendocrine[31] and osteosarcoma[27] tumor growth, and re-sensitized tamoxifen-resistant breast tumors by shutting down HIF-1α-driven glycolysis.[10] A recurring pattern is enhanced tumor suppression when baicalein is combined with radiotherapy or chemotherapy — radiosensitization of colorectal[19] and esophageal[11] tumors, and restored cisplatin[15] and 5-FU[12] sensitivity — rather than a standalone effect.
Signal maturity: the animal work is the credible translational signal, reproduced across many tumor types — though by different routes, doses, and schedules that cannot be directly converted into a human tumor exposure. What it does establish is that whole-organism metabolism does not abolish baicalein's activity. Several studies pair baicalein with standard therapy rather than testing it on its own.
In Vitro
Cell Model Data
Across diverse cancer lines baicalein suppresses proliferation, migration and invasion, arrests the cell cycle, and reduces survival signaling through STAT3, PI3K–AKT–mTOR, ERK and NF-κB; it induces mitochondrial apoptosis and reverses EMT markers. The load-bearing caveat is concentration.
Continue reading — full research detail+
Several studies note selectivity — lower cytotoxicity to matched normal cells, for example an ovarian LD50 of 25–40 µM versus 68 µM for normal ovarian epithelium.[7] The mechanistic readouts are consistent: mitochondrial-membrane depolarization, cytochrome-c release and caspase-9/-3 activation on the death side, and reversal of EMT markers on the invasion side.
As with most flavonoids, the effective in-vitro concentrations — typically tens of micromolar (ovarian LD50 25–40 µM[7]; osteosarcoma and several apoptosis studies ~35–100 µM) — substantially exceed the free-compound plasma levels achievable orally, where human steady-state free-baicalein Cmax is roughly 2.3 µM at a 600 mg three-times-daily dose.[46]
Signal maturity: the in-vitro mechanistic case is deep and consistent, but most targets require concentrations at or above the free-compound plasma level reached orally — which is why the animal work, not these numbers, carries the translational read. Dominant evidence tier: preclinical.
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02 — Pathways
Pathway Interaction Profile
In laboratory and animal research, baicalein has been reported to engage several distinct biological pathways relevant to tumor behavior, grouped below by the functional role each one supports. These include direct anti-tumor mechanisms and, further down, a separate set of pathways reported to support the body's own resilience. All five roles are read as partial: the mechanisms are reproduced in laboratory and animal systems, but human oral pharmacokinetics sit below the concentrations active in the laboratory, and no human oncology outcome has been measured.
Baicalein's Contain classification rests on anti-metastatic and anti-angiogenic activity reproduced across several animal models — EMT reversal that lowered spontaneous lung metastasis in a transgenic breast model, and a TLR4→HIF-1α→VEGF anti-angiogenic mechanism confirmed in a colorectal xenograft. It is read as partial because the effective exposures were reached in animal and in-vitro systems, and human oral pharmacokinetics sit below the in-vitro effective range.
Prevent Tumor Cell Shedding
Research concerning pathways related to invasion and escape from existing lesions, including EMT and ECM-breach mechanisms.
EMT & metastatic invasion
Baicalein's strongest Contain node. In the transgenic MMTV-PyMT breast model — a spontaneous metastasis system, not injected cells — baicalein blocked fibronectin-induced EMT by lowering calpain-2 activation (via reduced intracellular Ca²⁺ and ERK), restoring E-cadherin/ZO-1 and lowering N-cadherin/vimentin/Snail, and reduced tumor onset, growth and pulmonary metastasis in vivo.[1] In colorectal cells it reversed Snail-induced EMT, lowering vimentin/Twist1/Snail and raising E-cadherin/p53/p21[3]; in breast cancer it repolarized tumor-associated macrophages and cut TGF-β1 secretion, reducing tumor size and lung-metastasis lesions in vivo[2]; and it suppressed TGF-β1-induced EMT through NF-κB/Slug in breast epithelial and cancer cells.[4]
Block Seeding & Niche Formation
Research concerning pathways related to the formation of supportive pre-metastatic niches at distant sites.
Angiogenesis / VEGF / HIF-1α
Baicalein's best-established anti-angiogenic node. In colorectal cancer it acts as a direct TLR4 antagonist, interrupting the LPS·MD-2·TLR4 complex to lower p-NF-κB/p-AKT, HIF-1α and VEGF; TLR4 overexpression abolished the effect. In a xenograft it reduced tumor growth, Ki-67, VEGF, CD31 and MMP-2 and suppressed vessel formation in chick-yolk-sac, rat-aortic-ring and HUVEC tube-formation assays, comparable to the TLR4 inhibitor TAK-242 and without weight, liver or renal toxicity.[5] Baicalein's measured TLR4 binding is weak, however — dissociation constants well above its ~5 µM human plasma peak — so whether oral dosing occupies TLR4 enough to drive this mechanism in people is unestablished. The same node is fed by baicalein's canonical lipid-pathway target: as a selective platelet-type 12-lipoxygenase inhibitor it lowered VEGF in prostate cancer cells, while 12-LOX overexpression conversely tripled VEGF and drove endothelial-cell migration.[8] Independently, baicalein arrested VEGF-stimulated endothelial cells at G1/S through the p53/Rb axis[6], and in ovarian cancer it lowered VEGF, HIF-1α, cMyc and NF-κB.[7]
NF-κB / TNF-α / IL-6 inflammatory axis
In hepatocellular carcinoma baicalein upregulated miR-3663-3p to target SH3GL1 and inactivate the EGFR/ERK/NF-κB axis, inducing apoptosis and S-phase arrest and reducing xenograft tumor volume and weight.[9]
Baicalein applies genuinely tumor-directed metabolic pressure, but the evidence is in-vitro and animal. The story is glycolytic (HIF-1α-mediated), not respiratory — baicalein actually restores mitochondrial function in at least one model, so an electron-transport-chain-inhibition mechanism is not supported.
Glucose Axis Pressure
Research concerning pathways related to glycolytic ATP production and the generation of intermediates used by cancer cells.
Aerobic glycolysis (Warburg effect)
Baicalein's strongest Starve node, acting through HIF-1α. In tamoxifen-resistant breast cancer it promoted HIF-1α interaction with PHD2/pVHL, driving its proteasomal degradation to shut down aerobic glycolysis (glucose uptake, lactate, ATP) while restoring mitochondrial biogenesis and ROS to re-enable tamoxifen-induced mitochondrial apoptosis, and it re-sensitized the tumors in vivo (the HIF-1α stabilizer DMOG reversed the effect).[10] In esophageal squamous carcinoma it targeted HIF-1A, lowered glycolytic rate and Cyclin D1/CDK4 and radiosensitized the cells[11]; in gastric cancer under hypoxia it suppressed the glycolytic enzymes HK2, LDH-A and PDK1 via PTEN/AKT/HIF-1α, reversing 5-FU resistance.[12] A cell-free flavonoid screen places baicalein as a moderate direct LDH-A inhibitor (IC50 ≈ 33–87 µM)[16], but at concentrations far above achievable plasma — the in-vivo effect is HIF-1α-mediated, not direct enzyme blockade.
Metabolic Flexibility Suppression
Research concerning pathways involved in metabolic adaptation and switching between fuel sources under pressure.
Autophagy & lysosomal system
Baicalein modulates autophagy in opposite directions by tumor type, so it is carried as context-dependent. In colorectal cancer the autophagy it induces is cytoprotective — co-treatment with the autophagy inhibitor chloroquine amplified baicalein-induced caspase-3 apoptosis[13]; whereas in breast cancer it drove apoptosis and autophagic death through PI3K/AKT/mTOR suppression, confirmed in vivo[14], and in cisplatin-resistant gastric cancer it induced apoptosis plus autophagy via Akt/mTOR and Nrf2/Keap1 and re-sensitized the cells to cisplatin.[15]
Baicalein's broadest and best-corroborated role — suppression of survival- and proliferation-signaling consistent across cancer types, several nodes carrying xenograft confirmation, subject to the same systemic-pharmacokinetic caveat.
Expansion Suppression
Research concerning pathways related to proliferation, cell-cycle progression, and the capacity of lesions to add durable mass.
JAK/STAT (STAT3)
A well-corroborated node. In colorectal cancer baicalein bound JAK2 directly, lowered p-STAT3 and GPX4, and dose-dependently shrank xenografts with ferroptosis induction[17]; in breast cancer it inhibited STAT3 transcriptional activity and Tyr-phosphorylation, cut IL-6 secretion and reduced metastasis in vivo[18]; and in radioresistant colorectal cancer it restored radiosensitivity through JAK2/STAT3 inhibition in a syngeneic model, an effect reversed by forced JAK2.[19]
PI3K–AKT–mTOR (signaling)
In gastric cancer baicalein suppressed FAK and p-PI3K/AKT/mTOR dose-dependently and inhibited xenograft growth[20]; in cervical cancer it induced G0/G1 arrest and apoptosis by up-regulating a circHIAT1/miR-19a-3p axis to block AKT/mTOR, confirmed in a xenograft[21]; and in androgen-independent prostate cancer it lowered caveolin-1 and p-AKT/p-mTOR to suppress growth and invasion.[22]
RAS–RAF–MEK–ERK (MAPK)
In colorectal cancer baicalein lowered p-ERK and MMP-2/9 and inhibited xenograft metastasis, with MEK1 overexpression partially rescuing the effect[23]; in hepatocellular carcinoma it down-regulated p-MEK1/ERK, MMP-2/9 and u-PA and raised TIMP-1/2 to block invasion and metastasis in vivo[24]; and in colon cancer it drove apoptosis through ERK/p38 in a humanized-mouse xenograft.[25] Direction caveat: in anaplastic thyroid models baicalein raises ERK/p38 phosphorylation while still driving apoptosis, so its MAPK effect is context-specific rather than a uniform ERK block.
Wnt / β-catenin
In hepatocellular carcinoma baicalein promoted β-catenin and cyclin-D1 degradation with G0/G1 arrest and inhibited xenograft growth[26]; in osteosarcoma it up-regulated lncRNA-NEF to inactivate Wnt/β-catenin and suppressed growth and metastasis in vivo (lncRNA-NEF knockdown reversed it)[27]; and in cervical cancer it blocked β-catenin nuclear translocation to target cyclin-D1/CCND1.[28]
Cell cycle checkpoints (CDK4/6–RB–E2F, G1/S, G2/M)
Baicalein produces cell-cycle arrest by degrading cyclin D1: in oral cancer it forced G1 arrest, decreasing CDK4, cyclin D1 and phospho-Rb through GSK-3β-dependent cyclin-D1 loss and AhR activation[29]; on tumor endothelium it arrested G1/S by up-regulating p16/p21/p27/p53 and lowering cyclin D/E–CDK4/6.[6] Cyclin-D1 degradation also underlies the Wnt and STAT3 nodes above.
Baicalein drives direct tumor-cell death by several routes — reproducible across many tumor types in vitro and in animal models, with the same systemic-exposure caveat.
Direct Tumor-Directed Killing
Research concerning pathways related to regulated tumour-cell death pathways, including apoptosis, ferroptosis, and necroptosis.
Intrinsic apoptosis (mitochondrial / Bcl-2)
Baicalein's most reproduced Attack mechanism, with a consistent Bax↑/Bcl-2↓/cytochrome-c/caspase-9→-3 signature: nasopharyngeal carcinoma, with CNE1/CNE2 xenograft suppression[30]; pancreatic neuroendocrine tumor (caspase-3/Bax↑, survivin/Bcl-2↓, xenograft shrinkage)[31]; colorectal cancer, where baicalein is the active enteric-microbiome metabolite of baicalin (S-phase arrest, caspase-3/9, xenograft)[32]; and hepatocellular carcinoma, where mitochondrial-membrane collapse and caspase-9/3 activation accompanied MEK-ERK/Bad blockade and xenograft suppression.[33] In breast MCF-7 cells baicalein acts as a pro-oxidant, mobilizing intracellular copper to generate hydroxyl radicals, blocked by a Cu(I) chelator and ROS scavengers.[34]
Extrinsic apoptosis (death receptors)
Baicalein overcomes TRAIL resistance by up-regulating the death receptor DR5 through two cell-specific routes — CHOP-dependent DR5-promoter activation in colon cancer and ROS-dependent DR5 induction in prostate cancer — with DR5 knockdown abolishing the sensitization and normal cells spared.[35] A single but mechanistically rigorous study, and the only death-receptor node in the baicalein corpus.
Ferroptosis (execution / cell death)
Direction is context-dependent, and its default is protective — so this node does not positively support Attack. As a 12/15-lipoxygenase inhibitor and lipid-radical scavenger, baicalein is in most models a ferroptosis inhibitor: a natural-product screen identified it as a potent blocker of erastin-induced ferroptosis, limiting iron accumulation, glutathione depletion and lipid peroxidation and preventing GPX4 degradation.[37] It flips to a pro-ferroptotic inducer only where it lowers GPX4 upstream — in colorectal cancer, JAK2/STAT3 blockade lowered GPX4 and produced liproxstatin-rescuable ferroptosis with dose-dependent xenograft suppression[17]; in acute myeloid leukemia, high-dose baicalein engaged SLC7A11/GSH/GPX4 ferroptosis in vitro.[36] The clinical implication runs the other way: if a cancer therapy depends materially on ferroptotic/lipid-peroxidation death, baicalein could in principle antagonize it — a theoretical combination concern with no human data (see Co-Dosing). It carries no Summary card.
DNA damage & repair — mismatch-repair-selective killing
One of baicalein's most distinctive findings: it selectively killed tumor cells deficient in DNA mismatch repair (MutSα). Baicalein bound preferentially to mismatched DNA; in repair-proficient cells it triggered a protective CHK2-linked S-phase arrest, but in MutSα-deficient cells replication continued in its presence, generating double-strand breaks and apoptosis. It selectively shrank MutSα-deficient xenografts and suppressed colon tumors in colon-specific MSH2-knockout mice.[59] A genotype-selective preclinical mechanism relevant to mismatch-repair-deficient tumors — not evidence that baicalein treats those cancers in people.
Baicalein's host benefits are real but entirely preclinical — no human host-outcome evidence exists — so the role is partial. Oncology Host-Status carries the (preclinical) chemoprevention evidence; the Disease-Resilience blocks below carry the organ-protection findings and a recurring redox direction-selectivity proposed as a dual-benefit (Synergy) pattern, though not demonstrated as a selective switch in a tumor-bearing host.
Oncology Host-Status
Chemoprevention — oral baicalein suppressed benzo(a)pyrene-induced pulmonary carcinogenesis in mice while inhibiting A549 growth, notably raising ROS/Nrf2/HO-1 in the host-antioxidant direction while driving caspase-dependent apoptosis (p53/Bax/caspase-3) in tumor cells.[38] This is a carcinogenesis-prevention finding in mice, not evidence for treating established cancer.
Hepatic Resilience & Clearance
Human and preclinical research concerning hepatic enzyme systems, bile-acid handling, xenobiotic metabolism, and liver-related clinical markers.
Hepatoprotection
In acetaminophen-induced acute liver injury in mice, baicalein pretreatment dose-dependently lowered serum IL-6/IL-1β/TNF-α and hepatic malondialdehyde and restored SOD/GSH/CAT, reducing histological damage.[39] Preclinical (mouse); baicalein's own liver-safety signal is reassuring — see Safety.
Other Organ-System Reserve
Research concerning renal, cardiac, pulmonary, and other non-hepatic organ-system reserve under systemic or treatment-related stress.
Cardio-, nephro- and radio-protection
Baicalein's most cancer-relevant organ-protection signal is anthracycline cardioprotection. In doxorubicin-treated mice, oral baicalein lowered CK-MB/LDH/AST/ALT, restored myocardial antioxidants, up-regulated Nrf2/HO-1 and reversed the Bax/Bcl-2 ratio and p53/caspase-3 signaling[40]; in a cardiomyocyte model baicalein plus doxorubicin cut ROS and cell death and preserved mitochondrial potential, and a separate MCF-7 breast-cancer assay found concurrent baicalein did not abolish doxorubicin's antiproliferative effect.[41] That check was a cell assay, not the same tumor-bearing animal — preserved anti-tumor efficacy in a cardioprotection model has not been shown. Separately, oral baicalein reduced BUN/creatinine and malondialdehyde and raised GSH/SOD while suppressing IL-6/NF-κB/TLR-2/TLR-4 in cisplatin nephrotoxicity[42], and it mitigated whole-body-radiation hematopoietic injury and improved survival via MAPK-phosphatase/ERK/Nrf-2 signaling and expanded hematopoietic stem cells.[44] The radioprotection study used non-tumor-bearing mice, so whether normal-tissue radioprotection would spare the tumor during radiotherapy is untested and could cut either way. All preclinical.
Neuroendocrine / Sleep / Stress Axis
Human and preclinical research concerning neuroendocrine, sleep, and stress-axis regulation.
Chemotherapy-neuropathy protection
Baicalein reversed oxaliplatin-induced behavioral deficits and sensory nerve-conduction loss in rats (↑MnSOD/HO-1/GSH, ↓TNF-α/IL-6/NF-κB, ↓Wnt/β-catenin); a separate HCT-116 colorectal-cell assay found it did not alter oxaliplatin cytotoxicity.[43] Preclinical (rat + separate cell assay) — the host-protection and the cancer-cell check were different systems, not a single tumor-bearing animal showing neuroprotection with preserved tumor control.
GI Integrity & Microbiome
Research concerning gut-barrier integrity and inflammatory tone in the host.
Colitis & barrier protection
Baicalein ameliorated DSS colitis by restoring ZO-1/occludin tight junctions through an AhR/IL-22 axis in innate lymphoid cells.[45] Preclinical (mouse). This is a chemically-induced colitis model — it supports intestinal-barrier and anti-inflammatory activity, not specifically radiation enteritis, chemotherapy mucositis, or improved treatment tolerance, which have not been tested.
Host-Selective Redox Buffering
Studies evaluating whether redox buffering can be supported in normal host tissues selectively, separately from tumor-cell redox vulnerability.
Direction-selective redox — a proposed dual-benefit pattern
This is baicalein's proposed dual-benefit pattern — a hypothesis worth testing, not a demonstrated therapeutic switch. In some tumor cells baicalein acts pro-oxidant, mobilizing copper and raising ROS to drive mitochondrial apoptosis (the Attack pro-oxidant card, e.g. breast MCF-7)[34], while in stressed normal tissue it activates Nrf2/HO-1 and antioxidant enzymes to limit oxidant injury in heart, kidney, nerve and irradiated tissue.[40,42,43,44]
But these tumor and host findings come from different cancers, tissues, doses, and experimental systems, and baicalein's ferroptosis biology shows it can also protect cells from oxidative death — so a clinically selective tumor-versus-host redox window has not been shown. The chemotherapy-toxicity studies with separate cancer-cell controls suggest the host benefit need not abolish tumor kill, which is a reason to investigate the combination rather than proof of a selective mechanism.[41,43]
Prevent Tumor Cell Shedding
Research concerning pathways related to invasion and escape from existing lesions, including EMT and ECM-breach mechanisms.
In a transgenic breast model baicalein reversed EMT and reduced spontaneous lung metastasis, restoring E-cadherin while lowering N-cadherin, vimentin and Snail — reproduced in colorectal cells.
Glucose Axis Pressure
Research concerning pathways related to glycolytic ATP production and the generation of intermediates used by cancer cells.
Aerobic glycolysis (Warburg effect)
Baicalein drives HIF-1α degradation to shut down aerobic glycolysis — glucose uptake, lactate and ATP — while restoring mitochondrial function, re-sensitizing tamoxifen-resistant breast tumors in animal studies.
Expansion Suppression
Research concerning pathways related to proliferation, cell-cycle progression, and the capacity of lesions to add durable mass.
Across colorectal and breast cancer baicalein binds JAK2 and lowers STAT3 signaling, cutting IL-6 secretion and reducing metastasis in animal models, with radiosensitization in a resistant colorectal model.
Direct Tumor-Directed Killing
Research concerning pathways related to regulated tumour-cell death pathways, including apoptosis, ferroptosis, and necroptosis.
Intrinsic apoptosis (mitochondrial / Bcl-2)
Baicalein's most reproduced killing mechanism: a Bax-up, Bcl-2-down, cytochrome-c, caspase-9/3 signature across nasopharyngeal, pancreatic, colorectal and hepatocellular tumors, several with xenograft support.
Host-Selective Redox Buffering
Studies evaluating whether redox buffering can be supported in normal host tissues selectively, separately from tumor-cell redox vulnerability.
Direction-selective redox (proposed)
Baicalein can act pro-oxidant in tumor cells yet activate Nrf2/HO-1 to shield heart, kidney and nerve in animal studies — a proposed dual-benefit pattern, but a clinically selective tumor-versus-host switch has not been demonstrated.
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03 — Pharmacokinetics
Pharmacokinetics and Administration
How baicalein moves through the body is the governing limit on this whole profile. Oral baicalein is absorbed quickly but heavily converted to conjugated metabolites, so the free-compound levels reached in people fall well below the concentrations active in the laboratory — a gap that formulation can narrow but not erase.
Absorption
Oral baicalein is absorbed rapidly (peak within ~2 h) but its systemic signal is dominated by conjugated metabolites. At steady state, circulating conjugates such as baicalein-7-O-sulfate run roughly elevenfold higher (by mass) than the free compound.
The Concentration Gap
Laboratory cell-death work sits at tens of micromolar, above the ~5 µM parent-compound plasma peak — though several molecular and platelet effects occur nearer that peak. Human tumor, intracellular, and unbound exposure remain unknown.
Clinical Dose Context
Human oral baicalein has been characterized only in Phase I studies — single doses of 100–2800 mg and repeated dosing up to 600 mg three times daily (1800 mg/day) — in healthy volunteers. Exposure is less than dose-proportional, and no oncology dose-finding data exist.
Metabolism
Baicalein is cleared mainly by glucuronidation in intestine and liver, with sulfation secondary; the dominant metabolite is baicalin. Gut bacteria hydrolyze baicalin back to baicalein, feeding enterohepatic recycling.
Co-Dosing
Baicalein inhibits CYP3A4 and P-glycoprotein, is antiplatelet, and raised oral cyclosporine exposure in rats — a documented interaction signal detailed in the full table in Research view.
Formulation
Formulation is the dominant exposure lever but a partial one. A lab-prepared phospholipid-complex system raised relative oral bioavailability to ~449% of free baicalein in rats — an experimental comparator, not a property of oral base baicalein or of any retail product.
Absorption
Oral baicalein is absorbed rapidly but its systemic signal is dominated by conjugated metabolites. In healthy subjects at steady state (600 mg three times daily on days 4–9, i.e. 1800 mg/day), free baicalein reached a peak concentration (Cmax) of ~1323 ng/mL (≈4.9 µM) — the average steady-state concentration was lower at ~634 ng/mL (≈2.3 µM) — with a terminal half-life of ~11–15 h and moderate accumulation (ratio ≈2.9), while the conjugate metabolites circulated far higher: baicalein-7-O-sulfate Cmax reached ~15,080 ng/mL, roughly elevenfold the parent Cmax by mass concentration (the two species have different molecular weights, so this is not a molar ratio).[46] Peak plasma is reached within ~2 h. Single-dose human exposure is nonlinear and less than dose-proportional — parent Cmax rose 280 → 629 → 845 ng/mL from 200 to 600 mg but fell to ~490 ng/mL at 800 mg — so a higher oral dose does not guarantee proportionally higher parent exposure, and food had little effect on exposure of the tested tablet.[49]
A characteristic multi-peak plasma and urinary profile (a second peak at ~12–24 h) reflects biliary excretion and enterohepatic recycling; total urinary recovery of baicalein plus metabolites over 72 h was only ~25%, with unchanged baicalein under 3% and roughly a quarter of the dose eliminated unchanged in feces.[46,47] Baicalein is Rule-of-5-compliant on paper (MW 270.2, ALogP ~2.6, zero violations), so the limiter is not intrinsic permeability but poor aqueous solubility plus extensive first-pass conjugation.
The Concentration Gap
Many of the cell-death experiments work at tens of micromolar — ovarian LD50 25–40 µM[7], osteosarcoma and several apoptosis studies ~35–100 µM, and a moderate direct LDH-A IC50 of 33–87 µM[16] — several-fold above the ~4.9 µM steady-state parent Cmax measured in people (1800 mg/day)[46], and the free unbound level is lower still because circulating compound is overwhelmingly conjugate. But the gap is not uniform: several molecular and cellular effects occur in the high-single-digit micromolar range, close to that measured peak — the colorectal ferroptosis work was active from ~7.5 µM[17], the CYP3A4 and platelet-aggregation effects near 6–9 µM[54,56] — so some mechanisms are more plausibly reachable than the cell-death numbers suggest. Human tumor, intracellular, and unbound exposure remain unmeasured. The animal efficacy is valuable because it shows first-pass metabolism does not abolish activity, but the doses were given by varied routes and schedules (intragastric ~10–20 mg/kg in colorectal cancer[17], intraperitoneal 30 mg/kg in the breast model[1]) and an animal mg/kg dose cannot be equated with a human tumor concentration without species-specific pharmacokinetics.
| Benchmark | Concentration | Note |
|---|---|---|
| Typical in-vitro mechanistic range | ~25–100 µM | ovarian LD50 25–40 µM[7]; apoptosis studies ~35–100 µM |
| Direct LDH-A inhibition (cell-free) | IC50 33–87 µM | far above plasma; not the in-vivo mechanism[16] |
| Human steady-state parent Cmax | ~1323 ng/mL (≈4.9 µM) | 600 mg TID = 1800 mg/day, healthy subjects (Cavg ~634 ng/mL)[46] |
| Circulating conjugate (sulfate) Cmax | ~15,080 ng/mL | ~11× the parent Cmax by mass — the plasma signal is conjugate[46] |
| In-vivo animal doses (route varies) | ~10–30 mg/kg | i.g. 10–20 mg/kg (colorectal)[17]; i.p. 30 mg/kg (breast)[1] — mg/kg ≠ human exposure |
Clinical Dose Context
Human oral baicalein has been characterized only in Phase I pharmacokinetic and safety studies: single doses of 100–2800 mg[47] and repeated dosing of 200–800 mg twice daily and up to 600 mg three times daily (1800 mg/day)[46,48], all in healthy volunteers, confirming tolerability and measurable exposure. The steady-state exposure figures on this page come from the 1800 mg/day regimen, not a 600 mg daily dose. Human exposure is nonlinear and less than dose-proportional, so a larger oral dose does not guarantee proportionally more parent compound. No oncology dose-finding data exist, and because circulating drug is largely conjugate, laboratory findings should not be assumed to reflect tumor exposure without formulation-specific pharmacokinetic confirmation.
Metabolism
Baicalein is cleared predominantly by glucuronidation in both intestine and liver, with sulfation secondary. The dominant metabolite is baicalein-7-O-glucuronide (baicalin), formed mainly by UGT1A9 with contributions from UGT1A1/1A3/1A7/1A8/2B15[50]; glucuronidation and sulfation both display substrate-inhibition kinetics, with sulfation dominant at low concentrations — the basis of baicalein's nonlinear, saturable first-pass behavior.[51] Gut-microbiota β-glucuronidase hydrolyzes baicalin back to baicalein, feeding the enterohepatic recycling and the baicalein↔baicalin interconversion behind the multi-peak profile.[46]
Co-Dosing Considerations
Baicalein carries a mechanistically documented interaction signal on three fronts — enzyme and transporter inhibition, an absorption-site drug interaction, and antiplatelet activity. Each row below is flagged by the most cautious guidance the evidence supports.
Discuss whether to combine, separate, or avoid Baicalein and a medication with your treating oncology team or physician.
| Flag | Interaction |
|---|---|
| Avoid | Immunosuppressants dependent on gut absorption — cyclosporine. Purified baicalein (112 µmol/kg) raised oral cyclosporine Cmax by ~88% and AUC by ~150% in rats, an interaction attributed to the absorption site — a large change in a narrow-therapeutic-index drug, flagged Avoid pending human data (no human interaction study exists). Notably, in the same work a whole Scutellaria root decoction did the opposite, lowering cyclosporine exposure — so isolated baicalein, baicalin, and whole-herb preparations are not interchangeable.[55] |
| Caution | CYP3A4 / P-glycoprotein substrates. Baicalein inhibits CYP3A4 (IC50 ~9 µM) and P-gp experimentally, and in rats raised the oral bioavailability of the CYP3A4/P-gp substrate nimodipine from ~22% to ~31–35%; no controlled human interaction study has quantified the effect.[54] |
| Caution | Anticoagulant / antiplatelet drugs. Baicalein inhibits agonist- and tumor-cell-induced platelet aggregation (suppressing P-selectin, integrin αIIbβ3 and intracellular Ca²⁺, raising cAMP/VASP, and directly inhibiting PI3K), an additive-bleeding concern consistent with its platelet-12-LOX inhibition.[56] |
| Monitor | Ferroptosis-dependent therapies. Because baicalein is in most models a ferroptosis inhibitor (12/15-LOX inhibition, GPX4 stabilization), it could in principle blunt treatments whose tumor kill relies on lipid-peroxidation/ferroptotic death — a theoretical, mechanism-level concern with no human combination data.[37] |
| Monitor | Co-ingested UGT/SULT inhibitors. Baicalein's glucuronidation and sulfation are inhibited by curcumin, piperine, (–)-epicatechin and acetaminophen, which can raise its own exposure — so pairing it with those can change how much baicalein reaches circulation.[57] |
Formulation
Formulation is the dominant exposure lever but a partial one, because the bottleneck is both poor solubility and first-pass conjugation. An author-prepared, laboratory-compounded baicalein-phospholipid-complex self-microemulsifying system (BAPC-SMEDDS) raised relative oral bioavailability to ~449% of free baicalein (a conventional SMEDDS, also lab-made, ~343%) and shifted absorption toward the lymphatic route (18.8%→70.2%) in rats[52]; a baicalein nanocrystal raised oral relative bioavailability ~1.67-fold, with pulmonary delivery approaching intravenous exposure.[53] These are experimental formulation-versus-free comparators in animals — properties of specific research preparations, not of oral base baicalein and not transferable to any commercial "phospholipid" or "liposomal" product without its own pharmacokinetic data.
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04 — Onset & Washout
Onset and Washout
Baicalein's plasma clock and its studied effect timeline are two different things: free baicalein peaks within about two hours and declines over the following day (half-life ~11–15 h), but the preclinical tumor and host effects emerged only over repeated dosing across weeks.
Immediate Onset
Oral baicalein is absorbed within about two hours but is rapidly conjugated, so free-compound exposure is brief and the circulating signal shifts quickly to metabolites.
Steady State
Human dosing reached steady state after roughly six to eight days, with moderate accumulation and a second plasma peak from enterohepatic recycling. A consistently bioavailable preparation, not any single dose, governs useful exposure.
Accumulated Effect
The preclinical tumor and host effects emerged over repeated daily dosing across multi-week animal studies — not from single doses.
Dosing Pattern in Studies
Human Phase I trials used once- to three-times-daily oral dosing over up to ten days; preclinical anti-tumor studies used steady daily or intragastric dosing over weeks. This is how baicalein was studied, not a recommended regimen.
Washout
How long baicalein stays a relevant factor for co-administered medications before it clears.
No compound-specific washout interval has been established. Free baicalein peaks within ~2 h and declines over the following day (half-life ~11–15 h, so several days are needed for near-complete elimination on repeated dosing), but because baicalein is antiplatelet and a CYP3A4/P-glycoprotein inhibitor and raises the absorption of a narrow-therapeutic-index immunosuppressant, interaction timing should be raised with the care team as soon as use begins rather than managed by a fixed window.
Two Distinct Clocks
Baicalein's timeline splits into two layers. The direct-pharmacology clock (Immediate Effect) is fast: baicalein is absorbed within about two hours but is rapidly conjugated, so free-compound exposure is brief and the circulating signal shifts quickly to metabolites.[46]
The downstream clock (Accumulated Effect) is where the preclinical tumor and host effects emerged — over repeated daily dosing across multi-week animal studies.[5,17,40] No measurement here connects the fast plasma clock to the slow phenotypic clock; sustained, repeated dosing is simply what every study used to reach an effect.
Steady State
In human dosing, steady state was reached after about six to eight days of repeated administration, with moderate accumulation (ratio ≈2.9) and a characteristic second plasma and urinary peak from enterohepatic recycling.[46,48] Because free baicalein is heavily conjugated, consistency of a bioavailable preparation — not any single dose — governs whether useful exposure is reached; carrier formulations raise and sustain exposure.[52,53]
Dosing Pattern in Studies
Human Phase I trials used once- to three-times-daily oral dosing (200–800 mg per dose, up to 1800 mg/day) over up to ten days[46,47,48]; preclinical anti-tumor studies used steady daily or intragastric dosing over weeks.[5,17] This describes how baicalein was studied, not a recommended regimen.
Washout
No compound-specific washout interval has been established. Plasma clearance of free baicalein is relatively rapid (half-life ~11–15 h), but because baicalein is an antiplatelet compound and a CYP3A4/P-glycoprotein inhibitor[54,56], and raises the absorption of a narrow-therapeutic-index immunosuppressant[55], any interaction consideration should be raised with the care team as soon as baicalein use begins rather than managed by a fixed window, and any decision before surgery or a new medication defers to the treating team.
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05 — Safety
Safety Profile
Oral baicalein has been generally well tolerated across four Phase I studies in healthy volunteers, with mild, reversible adverse events and no serious or persistent organ toxicity — though transient proteinuria was common in one repeated-dose study. Its most consequential safety-adjacent properties are the interaction and off-target ones — detailed under Co-Dosing, not repeated here.
Mild, reversible adverse events — across four Phase I studies (single doses 100–2800 mg; repeated dosing up to 1800 mg/day), adverse events were mild to moderate and reversible, with no serious events; frequency was not dose-related.
Transient proteinuria was the most common finding — in one repeated-dose study proteinuria was the most frequently reported drug-related event; mildly elevated high-sensitivity CRP and triglycerides and isolated transient transaminase elevation also occurred. All were mild and resolved.
Skullcap-the-herb liver reports are not baicalein — the rare liver-injury reports linked to skullcap mostly involve American skullcap in polyherbal products and repeated germander adulteration; the concern attaches to the herb, not to purified baicalein.
Adverse Effects in Human Trials
Oral baicalein has been generally well tolerated in four Phase I studies in healthy volunteers spanning single doses of 100–2800 mg and repeated dosing up to 1800 mg/day.[46,47,48,49] Adverse events were mild to moderate and reversible, with no serious events. In one repeated-dose study, however, adverse events occurred in roughly half of baicalein recipients, the most frequent being transient proteinuria, alongside mildly elevated high-sensitivity CRP and triglycerides and isolated transient transaminase elevation — so "well tolerated" is not the same as event-free.[46,49] Adverse-event frequency was not dose-related, and long-term oncology-specific safety at higher or sustained exposures has not been characterized.
Liver Safety and the Skullcap Distinction
On the compound's own liver safety, no consistent or clinically significant hepatotoxicity signal emerged in the short Phase I studies, though isolated transient transaminase abnormalities were reported. Baicalein's preclinical hepatoprotection (carried under Protect) does not establish human hepatic safety — a compound can protect against one injury model at one exposure and still cause direct, idiosyncratic, or interaction-mediated injury at another — and the long-term hepatic safety of isolated high-dose baicalein remains inadequately characterized.
Separately, the NCBI LiverTox liver-injury reports concern Scutellaria/skullcap the herb and cannot be attributed specifically to purified baicalein: LiverTox rates skullcap a likelihood-score "B" cause of rare clinically apparent liver injury, but notes the mechanism is unknown, most reports involve American skullcap (S. lateriflora) taken in polyherbal products, and phytochemical analyses have repeatedly found germander (Teucrium) adulteration in implicated skullcap material.[58] The most consequential safety-adjacent properties are the interaction and off-target ones — antiplatelet activity, CYP3A4/P-gp inhibition, and an absorption-site interaction with cyclosporine — detailed under Co-Dosing above.
06 — Sourcing
Sourcing Guide
Formulation is the biggest factor in whether a baicalein product delivers meaningful exposure, because oral baicalein is limited by both poor aqueous solubility and heavy first-pass conjugation. Our Sourcing Guide lists products we have assessed on formulation, characterization, and brand quality.
Baicalein Sourcing Guide07 — Literature
References
Last reviewed: 2026-08-08