10-Deacetylbaccatin III (10-DAB), CAS 32981-86-5, molecular formula C₂₉H₃₆O₁₀, relative molecular mass 544.59 g/mol, is a taxane diterpenoid obtained from Taxus species by extraction and chromatographic purification. Pharma grade API is supplied as a white to off-white crystalline powder under manufacturer-specific lot codes that indicate the intended dosage-form route, particle size grade, and compendial test package. No harmonized international model number exists; the product is defined by the certificate of analysis, the extraction or semi-synthetic route, and the end-use quality level for tablet, capsule, granule, or injectable processing. The C-13 hydroxyl is the primary site for downstream side-chain coupling, while the free C-10 hydroxyl differentiates the molecule from baccatin III and influences chromatographic retention, chemical stability, and solubility behavior. The product is used either as an unconjugated API in formulations that specifically identify 10-DAB as the active moiety or as a purified taxane starting material; its acceptance profile should not be assumed equivalent to paclitaxel or docetaxel.

How Is 10-Deacetylbaccatin III Characterized Against Impurity and Residual Solvent Monographs?

Release testing for pharma grade 10-DAB is performed with a validated reverse-phase HPLC method on a C₁₈ column using a water-acetonitrile gradient and UV detection in the range 227–230 nm. Identification includes infrared absorption concordance with a paired reference standard and HPLC retention time agreement. The acceptance criteria below are aligned with ICH Q3C, ICH Q3D, and relevant general chapters; manufacturer-specific specifications may be tighter for injectable use.

Residual solvent analysis is carried out by headspace gas chromatography with flame ionization detection; system suitability includes resolution between ethanol and methanol. Water content is determined by Karl Fischer titration with a precision of ±0.1%. Elemental impurities are assessed against ICH Q3D using inductively coupled plasma mass spectrometry after microwave digestion; limits depend on the intended daily dose and route of administration. For injectable-grade material, bacterial endotoxins and subvisible particulate matter are not optional tests; they are release specifications linked to the intended finished product claim.

For method validation under ICH Q2(R1), specificity is demonstrated by separating 10-DAB from baccatin III, 7-epi-10-deacetylbaccatin III, and other process impurities. System suitability requires resolution between 10-DAB and 7-epi-10-DAB ≥1.5, tailing factor ≤2.0, and injection precision RSD ≤1.0% for five replicate injections. Detection and quantitation limits are set so that unspecified impurities can be reported at ≤0.05% area. Forced degradation is used to confirm that the method is stability-indicating; taxane diterpenoids are sensitive to C-7 epimerization under alkaline conditions and to oxidation at the C-10 hydroxyl. Published data for 10-DAB under all compendial stress conditions is limited and should be verified by LC-MS for the specific process route.

Structurally, 10-DAB differs from baccatin III by the free C-10 hydroxyl; baccatin III carries a C-10 acetate ester and is therefore less polar. This difference reduces reversed-phase retention for 10-DAB and leaves the C-10 position available for subsequent acetylation or protection. 7-epi-10-deacetylbaccatin III is the C-7 epimer and is controlled as a related substance because incomplete resolution can inflate the 10-DAB assay. Paclitaxel and docetaxel contain the C-13 side chain that is absent in 10-DAB and are active anti-mitotic agents; 10-DAB cannot be substituted for these finished drug substances without validated side-chain coupling and purification. For operators purchasing 10-DAB as a tablet or capsule API, the specification should exclude baccatin III and 7-epi-10-DAB at the limits above and should confirm that particle size distribution, microbial quality, and residual solvents support oral dosage manufacture.

When 10-DAB Is Processed Into Tablet, Capsule, and Granule Dosage Forms

10-DAB is practically insoluble in water and exhibits cohesive powder flow; direct compression is therefore not recommended unless the active pharmaceutical ingredient is embedded in a coprocessed carrier. High-shear wet granulation in a 10 L bowl with aqueous binder solution is applied only after the API is pre-blended with a hydrophilic filler such as lactose monohydrate or microcrystalline cellulose. The granulation endpoint is monitored by impeller torque and product temperature; the wet mass is dried at 45–50°C to a loss on drying ≤2.0% before screening.

For moisture-sensitive formulations, dry granulation by roller compaction is preferred. A roller compactor with side seals and a roll gap of 1.5–2.5 mm compacts the pre-blend; the ribbons are milled through a 1.0 mm screen. The resulting granules are blended in a bin blender with a fill volume of 50–70% and sampled at 10 locations to demonstrate blend uniformity with RSD ≤5.0%. Lubrication with magnesium stearate at 0.25–0.5% w/w is performed for 3–5 min to avoid over-lubrication.

Tablet compression is conducted on a rotary tablet press to a hardness of 40–80 N and disintegration time ≤15 min according to USP <701>. Capsule filling using the same roller-compacted granulate follows mass uniformity and content uniformity testing under USP <905>. For granule-filled sachets, the granulate is sieved to 180–850 µm, and fines below 180 µm are limited to ≤20% to reduce segregation. Dissolution testing uses USP Apparatus II at 50–75 rpm with a surfactant-containing medium; published data for this specific configuration is limited and should be generated during formulation development.

Particle size distribution is controlled by laser diffraction according to ISO 13320:2020. Oral-grade D₉₀ is typically ≤50 µm, while micronized injectable-grade material is set at ≤10 µm when reduced aggregation and improved uniformity are required. Handling areas should be maintained below 60% RH because the free C-10 hydroxyl increases moisture interaction and can affect flowability. Pre-drying of excipients may be necessary when the relative humidity exceeds 60% for extended periods.

Compared with baccatin III, 10-DAB may require additional protection against C-10 oxidation during wet granulation. The lower lipophilicity of 10-DAB relative to baccatin III changes the dissolution profile in surfactant media; in vitro testing should use a discriminating medium that meets USP <1092> solubility criteria rather than assuming the same surfactant concentration used for baccatin III. Gelatin capsule shells should be pre-conditioned below 45% RH because the API can retain moisture; hydroxypropyl methylcellulose capsules may be used when moisture sensitivity is observed.

Injectable-Grade 10-DAB: Endotoxin, Particulate, and Solubility Constraints

Injectable-grade lots are released with reduced bioburden, endotoxin control, and particulate matter testing. The API is dissolved in a non-aqueous or co-solvent system because of its practically insoluble aqueous solubility; ethanol, dimethyl sulfoxide, or a non-ionic surfactant-containing vehicle is selected only after compatibility screening with the free C-10 hydroxyl and the C-13 hydroxyl. The bulk solution is filtered through a 0.22 µm membrane and filled aseptically. Terminal steam sterilization is avoided unless thermal stability data for the specific solvent system are available; the taxane core is sensitive to hydrolytic degradation and C-7 epimerization in aqueous media above pH 6.0.

Subvisible particulate matter is controlled according to USP <788>; visible particulates are inspected under Ph. Eur. 2.9.20. Bacterial endotoxins are tested with Ph. Eur. 2.6.14 or USP <85>; a limit of ≤0.5 EU/mg is commonly applied when the finished dosage form requires a pyrogen-free claim. Residual solvent levels for injectable use must satisfy ICH Q3C options based on daily exposure; methanol ≤3000 ppm and dichloromethane ≤600 ppm are baseline controls, but lower limits may be required for high daily doses. Closure compatibility is assessed by extraction studies under USP <381>, and vial headspace oxygen is controlled under nitrogen purging with a dissolved oxygen specification of ≤1.0 mg/L for oxidation-sensitive taxane formulations.

For lyophilized injectable presentations, the fill solution is prepared under nitrogen and freeze-dried after aseptic filtration. The collapse temperature of the frozen formulation is determined by differential scanning calorimetry or freeze-drying microscopy; primary drying is set below the collapse temperature, and secondary drying is continued until cake moisture reaches ≤2.0% by Karl Fischer titration. The free C-10 hydroxyl in 10-DAB can alter the glass transition of the maximally freeze-concentrated solution relative to baccatin III; published data for this specific configuration is limited and should be established with formulation-specific thermophysical characterization. Any reprocessing from oral-grade to injectable-grade material is not recommended without validated purification, sterile filtration, and compliance with FDA 21 CFR 211.67 and 21 CFR 211.94.