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With increasing studies concerning the use of phytochemical compounds for drug screening, approaches to prepare phytochemical solutions to evaluate their optimal effects are worth giving attention to. Many aspects such as the dissolution methodology, dosage, and concentration are to be considered when preparing the compound1.
Solvent-based dissolution is widely used for organic compound preparation1. The commonly used solvents include water, oil, dimethyl sulfoxide (DMSO), methanol, ethanol, formic acid, Tween, glycerin, etc2. Although a suspension with undissolved substances is acceptable when the compound is administered by gastric gavage, a fully dissolved solute is critical for intravenous administration. Since oil solution, suspension, and emulsion can cause capillary embolisms, an aqueous solution for compound preparation is suggested, especially when administering intravenous, intramuscular, and intraperitoneal injections3.
The effective dose range varies among compounds and even among diseases treated with the same compound. Determinations of the effective and the safe dose and the concentration are dependant on literature and preliminary experiments4. Here, the preparation of the compound naringenin is demonstrated as an example.
Naringenin (4,5,7-trihydroxy-flavanone), a polyphenolic compound, has been studied in disease treatment for its hepatoprotective5, antidiabetic6, anti-inflammatory7, and anti-oxidant activities8. For in vivo applications, the oral administration of naringenin is commonly used. Previous studies reported preparing naringenin solution in 0.5%-1% carboxymethyl cellulose, 0.5% methylcellulose dose, 0.01% DMSO, and physiological saline (PS) at 50-100 mg/kg, administered by oral gavage9,10,11,12. Besides, other studies have reported supplementing naringenin with chow at 3% (wt/wt) for oral intake at a dose of 3.6 g/kg/d13,14. Studies have also reported using ethanol (0.5% v/v), PS, and DMSO to dissolve naringenin for intraperitoneal injection at 10-50 mg/kg15,16,17,18. In a study of temporal lobe epilepsy, mice received an injection of naringenin suspended in 0.25% carboxymethyl cellulose dissolved in PS19. Though these studies report the use of different solvents to prepare naringenin solutions, further details, such as dissolving status and animal response, have not been reported.
This protocol introduces a procedure for preparing naringenin solution for in vivo application in diabetic-induced osteoporosis. The preparation of the injection solution includes preparing solvents and compounds, dosage estimation, dissolution process, and filtration. The dosage was determined based on literature research and preliminary experiments by monitoring mice after administering injections every day for 3 days and modifying the dosage according to mouse behaviors. The final chosen concentration (20 mg/kg b.w.) was administered intraperitoneally 5 days per week for 8 weeks in a high-fat diet and streptozotocin (STZ)-induced diabetic mice20,21. The effects of naringenin in diabetic osteoporosis were evaluated by blood glucose testing, micro-CT, tartrate-resistant acid phosphatase (TRAP) staining, and enzyme-linked immunosorbent assay (ELISA).
Overall, it was observed that naringenin at a concentration range of 40-400 mg/mL did not completely dissolve in either ethanol or DMSO or 5% (ethanol or DMSO) plus 95% PS (v/v). However, naringenin dissolved completely in a mixture of 3.52% DMSO, 3.52% Tween 80, and 92.96% PS. The detailed procedure will help researchers to prepare the compound as an injection solution for in vivo application.