TUDCA vs UDCA
Research Comparison

Research Overview

TUDCA and UDCA share one steroid core. UDCA (ursodeoxycholic acid) is a hydrophilic bile acid and a minor fraction of human bile acids, per its FDA label. In people it is a secondary bile acid: colonic bacteria form it from chenodeoxycholic acid, mainly through 7-ketolithocholic acid (Fromm et al., 1983). TUDCA (tauroursodeoxycholic acid) is UDCA joined to taurine by an amide bond, and a primary constituent of bear bile (Boatright et al., 2006).

What is the difference between TUDCA and UDCA? Taurine adds a sulfonic acid group, and gut enzymes can split the taurine off again. TUDCA leads in ER stress, retinal and neuronal models; UDCA is the FDA-approved drug ursodiol. Disguised Alpha lists TUDCA in one product, a capsule blend with S-acetyl glutathione (250MG TUDCA and 100MG S-acetyl glutathione per capsule, 60 capsules per bottle) for laboratory research use only, and does not list UDCA.

Structure and Class

UDCA is 3α,7β-dihydroxy-5β-cholan-24-oic acid: C24H40O4, 392.6 g/mol (PubChem CID 31401), the 7β-hydroxy epimer of chenodeoxycholic acid (Carey et al., 1981). TUDCA joins that C-24 carboxyl group to the amino group of taurine by an amide bond: C26H45NO6S, 499.7 g/mol (PubChem CID 9848818).

Taurine changes charge behavior more than shape. On a reversed-phase HPLC hydrophobicity index set at 0 for taurocholate and 1 for taurolithocholate, TUDCA scored -0.47 and its 7α epimer, taurochenodeoxycholate, +0.46. Taurine conjugates held constant values from pH 2.8 to 9.0, while protonated unconjugated bile acids scored about 0.76 above their ionized salts (Heuman, 1989).

Micelles follow the conjugate. Both epimers and their conjugates had critical micellar concentrations of about 1 to 5 mM, but taurine conjugates formed micelles of 15 to 17 monomers and free species about 5. Free UDCA bound cholesterol about 23 times less strongly than free chenodeoxycholate (Carey et al., 1981).

In living systems the forms cycle. Per the ursodiol tablet label, the liver conjugates UDCA with glycine or taurine, ileal enzymes can deconjugate the conjugates for reabsorption and reconjugation, and unabsorbed UDCA becomes mostly lithocholic acid in the colon (FDA label). In a randomized crossover in 12 women with primary biliary cirrhosis (now primary biliary cholangitis), TUDCA was better absorbed and, though partly deconjugated and reconjugated with glycine, underwent less biotransformation to more hydrophobic metabolites; lithocholic acid was higher in every fluid measured during UDCA (Invernizzi et al., 1999).

Side by Side

Research Context: TUDCA

TUDCA's research identity is the chemical chaperone. TUDCA and 4-phenylbutyric acid reduced ER stress in cultured cells and in mouse models of type 2 diabetes, where they normalized hyperglycemia and restored insulin sensitivity (Ozcan et al., 2006). In Mode-K intestinal epithelial cells, TUDCA inhibited tunicamycin-induced GRP78 expression and upstream signaling in all three branches of the unfolded protein response (Berger and Haller, 2011). Models: cells and mice.

In perfused rat livers made cholestatic with taurolithocholic acid (10 µM), TUDCA (25 µM) reversed the fall in bile flow and raised the canalicular density of the export pump Mrp2 four fold, through protein kinase C dependent mechanisms (Beuers et al., 2001). Model: rat liver.

In rd10 and light-damaged mice, systemic TUDCA preserved photoreceptors and ERG amplitudes and suppressed apoptosis (Boatright et al., 2006). In R6/2 Huntington's disease mice, it reduced striatal atrophy, apoptosis and huntingtin inclusions (Keene et al., 2002). Models: mice only.

In a 54-week pilot, 34 people with amyotrophic lateral sclerosis (ALS) on riluzole were randomized to TUDCA or placebo after a 3-month lead-in. Responders, with at least 15% slower decline on the ALS functional rating scale than in the lead-in, were 87% with TUDCA and 43% with placebo; adverse events did not differ (Elia et al., 2016).

As of October 2026, PubMed holds no peer-reviewed outcome from a phase 3 trial of TUDCA alone; see the TUDCA research guide. The FDA approved a sodium phenylbutyrate-taurursodiol combination for ALS in adults on September 29, 2022. Its phase 3 trial, PHOENIX, did not meet its prespecified primary and secondary endpoints, and approval was withdrawn as of August 29, 2025 (Federal Register). Models: human trials and the FDA record.

Research Context: UDCA

UDCA has the longer drug record. Drugs@FDA lists ursodiol capsules approved December 31, 1987, now labeled for certain gallbladder stones (NDA 019594), and tablets approved December 10, 1997, labeled for primary biliary cholangitis (NDA 020675).

In mice fed UDCA as 0.5% of their diet, common bile duct ligation led to higher biliary pressure, ruptured cholangioles, more hepatocyte necrosis and higher mortality; in Mdr2 knockout mice with biliary strictures, UDCA induced bile infarcts. The authors traced both to its choleretic action against an obstruction (Fickert et al., 2002). Model: mice.

One double-blind trial compared the two directly in 199 adults with primary biliary cholangitis over 24 weeks. A fall in alkaline phosphatase of more than 25% was reached by 76% with TUDCA and 81% with UDCA (P = 0.453). Pruritus rose from 1.43% to 10.00% with UDCA and did not change with TUDCA, and adverse event rates were comparable (Ma et al., 2016). Model: a randomized human trial.

Choosing Between Them for a Research Question

The TUDCA vs UDCA choice follows from the question. ER stress work in cells can use either, though not interchangeably at equal concentrations (Berger and Haller, 2011); TUDCA suits media where pH may drop (Heuman, 1989). Gut metabolism and transport questions need both forms plus a measure of what the system made of them (Invernizzi et al., 1999). Cholestasis findings depend on the model, as the perfused liver and bile duct ligation studies above show.

Compare on moles: about 2.00 µmol per milligram of TUDCA free acid against 2.55 µmol for UDCA, so 1 mg of TUDCA carries as many moles of steroid as about 0.79 mg of UDCA. A salt form shifts these values; use the form on the lot certificate when stated. Every capsule of the blend listed here also carries S-acetyl glutathione, so a design built on it needs a control for that second compound.

Handling and Storage

As listed on the product page, the capsules are stored at 15 to 25°C in the original sealed container, away from moisture and direct light. The container is a sealed plastic or glass bottle or a resealable pouch, depending on the batch; close it fully after each opening and record the lot number. The certificate summary on the product page lists appearance and HPLC identity, lot certificates are also in the COA portal, and the glutathione research guide covers the second ingredient.

Mass alone cannot separate the urso forms from their 7α epimers: TUDCA and taurochenodeoxycholic acid share C26H45NO6S, and UDCA and chenodeoxycholic acid share C24H40O4 (PubChem CIDs 387316 and 10133). Reversed-phase HPLC tells the taurine pair apart, at -0.47 and +0.46 on the index above (Heuman, 1989). The ursodiol capsule label lists the free acid as insoluble in water and freely soluble in ethanol, methanol and glacial acetic acid (FDA label); acidic aqueous buffers favor its protonated form.

Questions Researchers Ask

What is the difference between TUDCA and UDCA?

One taurine group. TUDCA is UDCA with taurine bound at C-24, adding about 107 g/mol and a sulfonic acid group; taurine conjugates held constant hydrophobicity indices from pH 2.8 to 9.0 (Heuman, 1989). UDCA is the free bile acid, the 7β epimer of chenodeoxycholic acid (Carey et al., 1981).

Ursodiol vs TUDCA: are they the same compound?

No. Ursodiol is UDCA's drug name, first approved by the FDA in 1987 (Drugs@FDA). Taurursodiol, TUDCA's drug name, had FDA approval only within a combination withdrawn as of August 29, 2025 (Federal Register).

Does TUDCA turn into UDCA?

Partly. In a 12-person crossover, TUDCA was partly deconjugated and reconjugated with glycine, yet formed fewer hydrophobic metabolites than UDCA (Invernizzi et al., 1999).

UDCA vs TUDCA: which one acts on ER stress?

Both, in cell models. In Mode-K cells, the UDCA part carried TUDCA's GRP78 effect, taurine alone was inactive, and UDCA was 10 times more effective than TUDCA; both limited protein aggregation in a cell-free assay (Berger and Haller, 2011). The mouse chaperone work used TUDCA (Ozcan et al., 2006).