Siegesbeckiae Herba Veterinary Grade API, model SHV-API-201, is a dry hydroalcoholic extract of the aerial parts of Siegesbeckia orientalis (L.) Moench, Siegesbeckia pubescens Makino, and Siegesbeckia glabrescens Makino. The extract is standardized by reversed-phase high-performance liquid chromatography to ≥2.0% w/w kirenol and ≥4.5% w/w total diterpenoids calculated as kirenol on the dried basis. It is supplied as a brownish-yellow to olive fine powder with a D90 particle diameter of ≤75 µm, loss on drying ≤5.0%, and water activity ≤0.60. The product is released for further manufacture of registered veterinary tablets, injections, capsules, powders, granules, premix, and solutions; it is not dispensed as a finished dose. Injection-grade sub-lot SHV-API-201I is additionally controlled for bacterial endotoxin at ≤0.5 EU/mg and visible particulate matter. Solution-grade SHV-API-201S is sieved through 80 mesh and subjected to a cold-water dispersibility test. All grades are packaged in double polyethylene bags inside foil-aluminum laminate sacks at 25 kg net weight under nitrogen.

Release Specifications and Analytical Testing Matrix

The release panel follows compendial botanical identity, purity, and elemental impurity frameworks. Identification is confirmed by thin-layer chromatography and HPLC retention profile against a kirenol reference standard. Assay is by reversed-phase HPLC with a C18 column, detection at 210 nm, gradient elution, and quantification of kirenol. Results are normalized to anhydrous basis using loss on drying determined by USP <731>. Total diterpenoids are estimated by ultraviolet spectroscopy and calculated as kirenol; this value is not a single-compound assay and is used for batch-to-batch consistency.

Extraction of the botanical charge uses 70% v/v ethanol-water at 60–70°C for two cycles of 2 h each. The combined extract is clarified through 10 µm bag filters, concentrated under vacuum at product temperature ≤50°C to a relative density of 1.08–1.12, and spray dried through a rotary atomizer at inlet temperature 180–200°C and outlet temperature 85–95°C. The resulting powder is passed through an 80 mesh screen and blended in a 2000 L double-cone blender for 30 min. Temperature excursions above 60°C during concentration darken the extract and reduce kirenol recovery; published data for this specific configuration is limited, so each batch is monitored by high-performance thin-layer chromatography before spray drying.

Microbial control is applied through validated dry heat treatment of the finished powder at 80°C ± 5°C for 120 min or equivalent, except for injection grade, where aseptic processing after final filtration is used. Bioburden is tested according to USP <61> and USP <62>; absence of Salmonella and Escherichia coli in 25 g is mandatory for oral and premix grades. Residual solvent limits follow USP <467> and VICH GL18; ethanol is the only expected solvent and is controlled at ≤5000 ppm.

Elemental impurities are controlled under ICH Q3D and USP <233>. For veterinary products, the relevant route-specific permitted daily exposures are applied based on the finished dosage form and species. Lead and arsenic are controlled at ≤5 ppm and ≤2 ppm, respectively, because siegesbeckiae herba sourced from mineralized soils may accumulate these elements.

Stability of the unopened API is monitored under long-term storage at 25°C ± 2°C and 60% ± 5% RH for 24 months, with accelerated testing at 40°C ± 2°C and 75% ± 5% RH for 6 months. Kirenol content, water activity, and microbial limits are repeated at each station. The API is not sterilized by ethylene oxide because residual gas may react with unsaturated diterpenes; dry heat or aseptic processing is used instead.

When Injection-Grade Solubility and Endotoxin Load Dictate Process Design

Injection-grade processing is constrained by the limited aqueous solubility of the diterpenoid fraction, the endotoxin background of plant-derived material, and the sensitivity of kirenol to terminal moist-heat sterilization. Kirenol is poorly soluble in purified water at neutral pH; published solubility data for this specific extract configuration is limited. Injection solutions are therefore prepared by pre-dissolving the API in a co-solvent vehicle of 20–40% v/v propylene glycol, 10–20% v/v glycerol, and water for injection, adjusted to pH 5.5–6.5 with citrate-phosphate buffer. The bulk solution is filtered through a 0.45 µm prefilter and a 0.22 µm sterilizing-grade polyethersulfone membrane under nitrogen pressure. Terminal steam sterilization at 121°C for 15 min is avoided unless the formulation demonstrates kirenol loss ≤2.0%; aseptic filtration is the default for thermolabile veterinary parenterals.

Aseptic filling occurs in ISO 14644-1 Class 7 or better cleanrooms with Grade B/C background and Grade A filling zone. Depyrogenated glass vials and siliconized chlorobutyl closures are used. The injection-grade sub-lot SHV-API-201I is tested for bacterial endotoxin by limulus amebocyte lysate kinetic chromogenic method according to USP <85>; the release limit of ≤0.5 EU/mg is set to allow finished-product endotoxin compliance after formula dilution.

For tablet and capsule manufacture, the hygroscopicity of the dried extract requires blending under relative humidity ≤45%. Direct compression is generally not recommended unless the API is pre-dispersed with anhydrous dibasic calcium phosphate and microcrystalline cellulose in a 1:1:1 ratio. Dry granulation with 0.25–0.50% w/w colloidal silicon dioxide and 0.5–1.5% w/w magnesium stearate is preferred for tablets. A rotary tablet press with 16–24 stations is operated at precompression 6–10 kN and main compression 12–20 kN for a 600 mg target tablet. Hardness is adjusted to 8–12 kp, and friability is maintained below 1.0% according to USP <1216>. Tablets typically require a disintegrant system of croscarmellose sodium 2.0–4.0% w/w and crospovidone 2.0–5.0% w/w; disintegration time is tested according to USP <701> and should be ≤15 min in water at 37°C ± 2°C. Film-coated tablets may require a moisture barrier coating of polyvinyl alcohol-polyethylene glycol copolymer at 3.0% weight gain to reduce moisture uptake.

Hard gelatin capsules are filled on an intermittent-motion capsule filler at 20,000–40,000 capsules/h; the final blend bulk density is controlled at 0.55–0.65 g/cm³. Dissolution testing uses USP <711> Apparatus 2 at 50 rpm in 900 mL of pH 6.8 phosphate buffer; release limits are established by the marketing authorization holder because no public veterinary monograph for siegesbeckiae extract exists.

For powders, granules, and feed premix, the API is diluted by geometric mixing with lactose monohydrate or precipitated silica to a final concentration of 0.5–5.0% w/w. Mixing is validated by sampling 10 positions and testing kirenol uniformity; the coefficient of variation should not exceed 5.0%. Fluid-bed granulation with 5% povidone K30 aqueous binder at inlet air temperature 65–75°C is used to improve flow and reduce dust; product temperature is maintained at ≤50°C to limit diterpenoid degradation. The granules are dried to water activity ≤0.60 and sized through a 20 mesh screen before packaging. Feed premix stability is improved by using calcium carbonate or wheat middlings as carrier; oil-based carriers are avoided because unsaturated diterpenoids may oxidize.

Oral solutions require a preservative system. Potassium sorbate 0.1% w/w and sodium benzoate 0.1% w/w are compatible at pH 5.5–6.5. Disodium edetate 0.05% w/w may be added to chelate trace metal ions that catalyze oxidation of phenolic diterpenoids. The solution is sparged with nitrogen and packed in amber glass. Oral solution viscosity at 20°C is typically below 50 mPa·s when the API is dissolved at 1.0% w/w; this allows metering pumps and standard bottle-filling lines. Suspensions require wetting agents if API content exceeds 2.0% w/w. The pH should not exceed 9.0; alkaline hydrolysis of ester-linked diterpenoids reduces kirenol recovery and may produce precipitates. Light exposure during processing is minimized because ultraviolet radiation accelerates discoloration.

Why Does Standardized Siegesbeckiae Extract Differ from Raw Herb Powders?

Unprocessed Siegesbeckiae herba powder varies in kirenol content as a function of harvest year, drying temperature, plant-part ratio, and soil conditions. A raw milled powder may contain kirenol from 0.05% to 0.8% w/w and total ash above 10%; that variability prevents reproducible tablet compression and parenteral manufacture. The standardized veterinary API is produced from authenticated plant material, extracted under controlled temperature, vacuum-concentrated, and spray dried. The process removes fibrous polysaccharides and poorly compressible plant-matrix components, producing a powder with compressibility and flow characteristics suitable for dry granulation and capsule filling.

Compared with simple water decoction powders, the hydroalcoholic extract contains a higher diterpene aglycone fraction and lower polysaccharide load. This difference is relevant to injection filtration because water-extracted polysaccharides can foul 0.22 µm membranes and increase viscosity. The standardized extract is not intended for extemporaneous decoction use, as it has been processed for direct incorporation into modern veterinary dosage forms. In addition, the raw herb may contain agrochemical residues and soil-derived heavy metals; the API applies batch-specific pesticide residue screens under USP <561> and elemental impurity limits under ICH Q3D.

Formulators should note that the API is hygroscopic. When relative humidity exceeds 60% during handling, the opened container should be pre-dried at 45°C ± 5°C for 4 h before weighing. The powder should not be combined with strong oxidizing agents, strong acids, or strongly basic excipients that raise the microenvironmental pH above 9.0; such conditions accelerate kirenol degradation. For food-producing species, the absence of established residue depletion data for kirenol means that a finished product registration must include a target-species depletion study and a defined withdrawal period under applicable regional guidance. Batch-to-batch consistency is controlled by the release tests in the first table; any vendor lot not meeting ≥2.0% w/w kirenol is not suitable for registered veterinary dosage forms.