Hesperidine Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable is supplied as a flavanone glycoside with the chemical identity hesperetin-7-O-rutinoside and CAS registry number 520-26-3. The molecule has a relative molecular mass of 610.56 g/mol, with the formula C₂₈H₃₄O₁₅, and is released as a crystalline or microcrystalline powder. No harmonised model nomenclature exists across manufacturers; certificates of analysis instead carry grade codes linked to assay, particle-size distribution, residual solvent class, and endotoxin claim. Oral grades are commonly designated by a D90 value in the range 50–100 µm, while injectable grades are released as micronized material with a D90 typically ≤ 10 µm. The designations “micronized” and “sterile-filterable” on supplier documentation therefore describe performance attributes rather than a universal model number.

Why Does Particle Size Control Define Tablet and Capsule Performance?

Because hesperidine is practically insoluble in water, dissolution rate rather than solubility equilibrium governs release from solid oral dosage forms. Particle-size reduction to a D90 of ≤ 50 µm is specified for tablets and capsules where immediate release is intended; for granules, retention of some larger agglomerates is acceptable if the granule disintegrates rapidly. Direct compression of unmilled API is not recommended; low bulk density and poor flow create weight variation and capping. In production-scale trials, tablets containing greater than 30% w/w unmilled hesperidine have exhibited capping at compression forces above 15 kN; roller compaction or high-shear wet granulation mitigates this. Dissolution testing per USP <711> typically requires a surfactant-containing medium; 0.5% w/v sodium lauryl sulfate in phosphate buffer at pH 6.8 is used to discriminate batches with inadequate particle-size control. Air-jet milling and pin milling are preferred over hammer milling because they reduce the formation of amorphous surface domains that recrystallise during storage.

Pharmacopoeial Release Criteria and Analytical Markers

Release control relies on orthogonally selective methods. Where a pharmacopoeial monograph for hesperidin is applied, assay and related substances are determined by reversed-phase HPLC; where no monograph is available in a given jurisdiction, supplier methods aligned with Ph. Eur. 2.2.29 and USP <621> are accepted provided they are shown to be stability-indicating. The representative release criteria in Table 1 apply to oral and injectable grades, with the injectable grade subject to additional endotoxin and sterility controls.

For assay and related substances, a stability-indicating reversed-phase HPLC method is used with an octadecylsilane column of 150 mm × 4.6 mm, 5 µm particle size, operated at 30°C. Detection at 280–284 nm and gradient elution using acidified aqueous methanol are typical. The method must resolve hesperidine from the isomeric flavanone neohesperidin, if present, with a resolution of ≥ 2.0, tailing factor ≤ 1.5, and injection precision ≤ 2.0% RSD. Residual solvents in commercial hesperidine are primarily methanol and ethanol from citrus peel extraction and subsequent purification. Methanol is controlled to ≤ 3000 ppm and ethanol to ≤ 5000 ppm unless a supplier-specific limit is justified under ICH Q3C.

Regulatory submissions for oral tablets and capsules typically reference the same API release data, but granule formulations may require additional sieve-distribution data after blending. For injectable products, the drug substance section of the dossier must include endotoxin method validation and compatibility data with the chosen solubilising excipient. Where a CEP or US DMF is used, the applicant is responsible for demonstrating that the dosage-form manufacturing process does not introduce new impurities above qualification thresholds under ICH Q3B; storage below 25°C and protected from light is required within the re-test period.

When the Oral Grade Is Transferred to High-Shear Granulation Lines

When the oral grade is processed on high-shear granulation equipment, the low aqueous solubility and hygroscopic character of hesperidine create a narrow processing window. In a bowl of 300–600 L working capacity, representative processing conditions for this class of flavanone glycoside include a wet-massing time of 4–6 min at an impeller tip speed of 10 m/s; longer massing produces denser granules that later fail dissolution specifications. The granules exhibit a bimodal particle-size distribution and hard agglomerates when the water/binder ratio exceeds 18–22% w/w. Subsequent drying in a fluid-bed dryer with product temperature above 65°C accelerates oxidative discolouration, so exhaust air temperature is controlled at 55–60°C. In production batches, end-of-drying LOD is set at ≤ 2.5% w/w for tablet compression and ≤ 3.5% w/w for capsule filling to avoid picking and caking. The dried granulate is milled through a 1.0 mm conical screen and blended with external disintegrant to restore disintegration time below 15 min in pH 6.8 phosphate buffer with 0.5% w/v sodium lauryl sulfate as per USP <711>. If dry granulation is selected, roller compaction with a gap of 2.0 mm and a roll pressure of 80–120 bar is used; ribbons are milled at 500 rpm to produce granules with a bulk density suitable for encapsulation.

Granule sachet formulations are distinct from tablets because they are reconstituted in water before administration. Hesperidine remains suspended rather than dissolved; particle size after reconstitution must remain below 500 µm to avoid mouthfeel defects and dosing variability. Wet granulation with mannitol or sorbitol provides dispersibility, but hygroscopic exposure above 60% RH causes the granules to agglomerate in aluminium-foil sachets. A desiccant is therefore included when the sachet barrier is not fully aluminium-laminated.

Terminal Sterilisation Is Not the Default Route for Hesperidine Injectables

Injectable-grade hesperidine is released only after additional purification to reduce endotoxin and bioburden. The API itself is practically insoluble in water; aqueous formulations require a co-solvent system, cyclodextrin complexation, or phospholipid/surfactant micellar solubilisation. Sterile filtration through a 0.22 µm PVDF or PES membrane is feasible only when the drug is fully solubilised and the solution has low viscosity. A 0.45 µm prefilter is placed upstream to prevent premature fouling. Terminal sterilisation at 121°C for 15 min may be used only after forced-degradation studies demonstrate a shelf-life-acceptable loss of assay; if the aqueous formulation shows degradation above 2% or colour shift, aseptic filtration is required. The injectable-grade API must meet Ph. Eur. 2.6.14 / USP <85> for bacterial endotoxins and Ph. Eur. 2.6.1 / USP <71> for sterility. Avoid combination with strong bases and strong oxidising agents because the phenolic hydroxyls at positions 5 and 3’ undergo oxidative coupling and ring scission. Published data for this specific configuration is limited.

The oral grade is not interchangeable with the injectable grade. Oral-grade material may display endotoxin levels and viable counts that are acceptable for solid-dose manufacture but fail parenteral limits. Injectable-grade material is typically further processed by solvent recrystallisation, activated-carbon treatment, or ultrafiltration to reduce high-molecular-mass polyphenolic aggregates; these operations narrow the impurity profile but can increase cost and reduce yield. In lyophilised injectable formulations, mannitol or trehalose is used as a bulking agent at 4–6% w/v; the hesperidine concentration is limited by the solubility of the selected cyclodextrin or co-solvent system rather than by the dry powder itself.

Comparing Hesperidine with Diosmin, Hesperetin, and Rutin

Hesperidine, diosmin, hesperetin, and rutin are related polyphenolic substances with divergent formulation behaviour. Hesperidine is a flavanone 7-O-rutinoside; diosmin is the corresponding flavone 7-O-rutinoside and differs by oxidation at the C2–C3 bond. Hesperetin is the aglycone with a relative molecular mass of 302.28 g/mol and crosses biological membranes more readily, but its lower glycosidic mass reduces the hydrophilicity advantage of the parent glycoside. Rutin, a flavonol 3-O-rutinoside, has a relative molecular mass of 610.52 g/mol and a different oxidation profile. In solid-dose processing, diosmin is frequently more electrostatic and requires wet granulation; hesperetin has higher log P and may require lipid excipients; rutin is more hydrophilic but degrades rapidly at pH above 8. Table 2 summarises the comparative formulation constraints.

Selection of an oral or injectable grade of hesperidine is therefore governed by the downstream unit operations and microbiological requirements. The oral grade is accepted for tablets, capsules, and granules where particle size, LOD, and residual solvent limits are controlled; the injectable grade is used only after endotoxin, sterility, and sub-visible particulate testing. In both cases, the API must be protected from light in amber glass or opaque polyethylene-lined drums, stored below 25°C, and quarantined until HPLC assay, moisture, and impurity results conform to the release specification. Avoid contact with strong oxidising agents, and avoid processing in high-humidity environments exceeding 60% RH without pre-drying.