Cholesterol (Plant-Derived) Pharma Grade API, CAS 57-88-5, molecular formula C₂₇H₄₆O, molar mass 386.65 g/mol, is supplied as a white to off-white crystalline powder for tablet, capsule, granule, oral liquid, and injectable formulation. The plant-derived route is based on phytosterol fermentation or enzymatic conversion of vegetable sterols rather than lanolin extraction; the resulting material is controlled to the cholesterol monographs of USP/NF and Ph.Eur. Compendial chemical release limits include assay by gas chromatography at 98.0%–102.0% on the dried basis, loss on drying not more than 0.30% per USP <731>, residue on ignition not more than 0.10% per USP <281>, and melting range 147–150°C. The model designation is manufacturer-specific and normally separates oral solid dosage grade, micronised injectable grade, and granulation grade by particle-size class and endotoxin load rather than by a single trade code.

Supplier dossiers for injectable material add bacterial endotoxin acceptance of ≤0.5 EU/mg by USP <85> or Ph.Eur. 2.6.14 and microbial enumeration limits of total aerobic microbial count ≤100 CFU/g and total yeast and mold count ≤10 CFU/g by USP <61>. Because the plant-derived route uses no animal-derived starting or processing materials, the product can be documented under EMA/410/01 Rev 3 as non-animal-origin. The vegan and Halal/Kosher certification status applies to the plant-derived grade and not to the lanolin-derived grade, but the pharmacopoeial chemical identity and assay are identical.

When Plant-Derived Cholesterol Replaces Wool Grease-Derived Material in Injectable Lipid Systems

Substitution of wool grease-derived cholesterol with plant-derived cholesterol in liposomal and lipid-nanoparticle operations alters the trace sterol profile but not the bilayer-stabilising function. The lanolin-derived product carries lanosterol, dihydrolanosterol, and wool-fat odor markers; the plant-derived product carries β-sitosterol, campesterol, and stigmasterol as potential process-related markers. Compendial identification and assay are sufficiently specific only when system suitability resolution between cholesterol and β-sitosterol is not less than 2.0 by gas chromatography. In liposome processing, cholesterol is incorporated at 20–45 mol% relative to phospholipid to reduce membrane permeability and broaden the gel-to-liquid-crystalline phase transition. Above 50 mol%, cholesterol can destabilise lamellar bilayer packing and increase vesicle size heterogeneity. High-shear rotor-stator premixing followed by high-pressure homogenisation at 800–1000 bar is used to achieve a homogeneous lipid dispersion; the plant-derived grade behaves similarly to lanolin-derived cholesterol in this unit operation, provided the material is protected from oxygen and iron/copper contact surfaces above 60°C to avoid free-radical autoxidation to 7-ketocholesterol and 7α/β-hydroperoxides.

In oral tablet and capsule manufacture, the low aqueous solubility of cholesterol confines dissolution-rate control to particle size and solid dispersion. A granulation-grade powder with D50 25–75 µm and D90 ≤150 µm by laser diffraction (ISO 13320:2020) is suitable for immediate-release capsules and non-aqueous wet granulation. Direct compression on high-speed rotary presses is generally avoided because cholesterol exhibits poor compactibility and low bulk density; roller compaction with microcrystalline cellulose and lactose monohydrate is preferred to reduce segregation. Ethanolic or isopropanolic wet granulation is acceptable, while aqueous granulation requires pre-mixing with a surfactant to overcome hydrophobic clumping. Drying is performed under vacuum at 40–50°C; temperatures above 60°C accelerate oxidative degradation and should be avoided unless an inert gas cover and antioxidant are present.

Dissolution testing for oral solid dosage forms containing cholesterol as the active or functional excipient is performed with USP <711> apparatus II at 50–75 rpm, using a medium containing 0.1–0.5% sodium dodecyl sulfate or polysorbate 80 because the compound is practically insoluble in water. The plant-derived grade does not alter sink conditions relative to lanolin-derived cholesterol, but trace β-sitosterol and campesterol impurities can crystallise with cholesterol in solid dispersion formulations and should be monitored during polymorph screening. A binary phase diagram with common lipids shows that plant sterol residues above 2.0% can lower the melting endotherm by 3–5°C; this effect is not clinically relevant but can shift differential scanning calorimetry identification acceptance if the sample is not equilibrated under the same drying protocol.

What Analytical Burden Distinguishes the Plant-Derived Grade from Mixed Phytosterol Products?

Mixed phytosterol dietary ingredients and wood sterol preparations should not be interchanged with this API because the sum of β-sitosterol, campesterol, and stigmasterol in those materials may exceed 90% of the sterol fraction, whereas this product maintains cholesterol assay at 98.0%–102.0% on the dried basis. The plant-derived grade is also distinct from synthetic cholest-5-en-3β-ol produced by total synthesis, which may contain process impurities from chiral auxiliaries or transition-metal catalysts; published data for commercial synthetic cholesterol at pharma scale is limited. Gas chromatographic release testing uses a non-polar capillary column with flame-ionisation detection; system suitability includes baseline resolution not less than 2.0 between cholesterol and β-sitosterol. Residual solvents are controlled under ICH Q3C; ethanol and isopropanol are Class 3 solvents with a general limit not more than 5000 ppm. Elemental impurities are assessed under ICH Q3D; because the plant-derived route does not use nickel, palladium, or platinum hydrogenation catalysts, those elements are not expected above their PDE-based limits.

Scale-up of oral granulation from a 10 L high-shear mixer to a 300 L production granulator requires monitoring impeller tip speed, not merely time, because cholesterol agglomerates are hydrophobic and respond to wet mass density changes. An impeller tip speed of 4–6 m/s and a chopper speed of 1500–3000 rpm are typical starting sets for ethanolic granulation; the endpoint is determined by power consumption curve inflection rather than fixed granulation time. Over-granulation produces coarse granules with poor tablet content uniformity; under-granulation leaves free cholesterol crystals that segregate during bin transfer. The granule fraction between 150 µm and 850 µm is retained for tableting, while fines below 150 µm are recycled into dry mixing. These process conditions assume a non-aqueous solvent system; aqueous high-shear granulation requires more surfactant and a longer wet massing phase.

Direct compression of cholesterol is feasible only with coprocessing because the pure crystal has low bulk density and poor flow. A co-spray-dried or roller-compacted grade with D50 50–100 µm, Hausner ratio below 1.25, and Carr index below 20 is required for rotary tablet presses operating above 60,000 tablets/h. If the formulation contains high-dose cholesterol above 30% w/w, compression force at 8–15 kN may lead to capping due to elastic recovery; addition of a plastic binder such as copovidone or a dry binder such as silicified microcrystalline cellulose reduces capping tendency. Lubrication with magnesium stearate should be limited to 0.5–1.0% w/w and mixed for 3–5 min because cholesterol is hydrophobic and extended lubrication can delay dissolution.

Injectable-Grade Lyophilisation and Terminal Sterilisation Boundaries

Injectable formulations containing cholesterol are commonly lyophilised liposomal or lipid-complex powders because cholesterol-containing bilayers are sensitive to hydrolysis and aggregation during terminal steam sterilisation at 121°C. Aseptic filtration through a 0.22 µm membrane is the preferred sterilisation route after high-pressure homogenisation; a 0.45 µm pre-filter may be required to reduce membrane loading by large vesicles. Lyophilisation with sucrose or trehalose as lyoprotectant at a cryoprotectant-to-lipid mole ratio of 5:1 to 10:1 preserves bilayer integrity; the primary drying shelf temperature is kept below the collapse temperature determined by freeze-drying microscopy. Published data for this specific plant-derived grade in lyophilised injectable products is limited, but the general liposome-processing boundaries apply. The plant-derived injectable grade is typically micronised to D90 ≤10 µm before lipid dissolution; the terminal sterile liposomal dispersion must still pass USP <788> particulate matter and USP <85> endotoxin criteria. The manufacturing environment should maintain residual moisture below 2.0% after lyophilisation to minimise oxidation and cake shrinkage.

For liposomal injections, the lipid phase containing cholesterol, hydrogenated soy phosphatidylcholine, and distearoylphosphatidylglycerol is dissolved in ethanol or tert-butanol at 55–65°C before injection into an aqueous phase at 40–50°C. The resulting crude emulsion is processed through a high-pressure homogeniser with a fixed geometry interaction chamber at 800–1000 bar for 5–10 passes; particle size is monitored by dynamic light scattering (ISO 22412:2017) with a polydispersity index target below 0.15. Filtration through a 0.22 µm membrane follows after buffer exchange. Plant-derived cholesterol with D90 ≤10 µm dissolves rapidly in the lipid phase; larger crystals from oral-grade material can persist as undissolved cores and increase the risk of filter blockage.

The Plant-Derived Route Removes TSE Documentation but Not Oxidation Control

Cholesterol autoxidation proceeds via hydrogen abstraction at C-7, followed by oxygen addition and hydroperoxide formation; the primary markers are 7α-hydroxycholesterol, 7β-hydroxycholesterol, and 7-ketocholesterol. The reaction is accelerated by light above 300 nm, by peroxides in excipients, and by residual water. For dry powder, a nitrogen-flushed container with an oxygen headspace below 1.0% maintains 7-ketocholesterol below 0.10% for 24 months at 25°C/60% RH. At 40°C/75% RH in open storage, the same marker can increase within weeks. These limits are not compendial but are common stability-indicating controls in supplier dossiers and lipid-excipient qualifications. Stability-indicating HPLC with UV detection at 205–210 nm can separate cholesterol from 7-ketocholesterol and epoxide degradation products; method validation follows ICH Q2(R2) for specificity, linearity, and precision.

Regulatory documentation for the plant-derived grade should include the manufacturer’s TSE/BSE statement, allergen statement, residual solvent declaration under ICH Q3C, elemental impurity risk assessment under ICH Q3D, and stability data under ICH Q1A(R2). Because the plant-derived grade is not an animal-derived product, it may simplify the viral safety section of a marketing authorisation; however, the removal of lanolin-derived impurities does not remove the general obligation to validate the manufacturing process under ICH Q7 and qualify the supply chain under ISO 9001 or equivalent. The active substance master file should clearly distinguish the plant-derived route from the lanolin-derived route through starting material specification and trace sterol profiling.

For tablet and capsule applications, the oral grade is not released by the same endotoxin limit as the injectable grade; the oral route does not require USP <85> compliance unless the product is also used for sterile oral liquids. The injectable grade is co-milled under nitrogen to avoid particle surface oxidation and is packaged in double polyethylene bags inside aluminium foil to maintain water content at ≤0.30%. The oral grade may be delivered in fibre drums with low-density polyethylene liners, whereas the injectable grade is shipped in sealed, nitrogen-flushed containers. These packaging differences are part of the model designation and are not interchangeable without requalification of the downstream process.