Development and validation of a gas chromatographic method for the quantification of D-pinitol in decoctions of **Desmodium adscendens**
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences. Pharmacy
, p. 19-25
University of Antwerp
A decoction of the leaves and stems of Desmodium adscendens (Fabaceae), a herb occurring in Africa and South America, is used in traditional medicine. Previous phytochemical research revealed that flavonoids, soyasaponins, β-phenylethylamines, and an indol-3-alkylamine were present. Our investigations have led to the identification of D-pinitol, a carbohydrate with antihyperglycemic, hepatoprotective and anti-inflammatory effects, as a potentially active compound. In order to prepare a quantified extract to be used in in vivo experiments, an analytical method was developed and validated. A gas chromatographic method was developed. Two different derivatization methods, i.e. acetylation and trimethylsilylation, were evaluated. Trimethylsilylation yielded repeatable results and was selected. Five different sugar alcohols were evaluated in order to find a suitable internal standard. Xylitol was chosen since it did not co-elute and its structure closely resembled D-pinitol. Sonication and reflux extraction were investigated in order to obtain a quantitative extraction. This was achieved through reflux extraction during 0.5 h. The method was validated according to the ICH guidelines. The calibration model appeared to be linear, ranging from 5.13 μL/mL to 25.65 μL/mL. The method was precise with an inter-day precision lower than 1.3%. The accuracy ranged from 103.38% to 105.84%. The validated method was used for quantification of D-pinitol in lyophilized decoctions from D. adscendens administered in in vivo experiments. Typically, a D-pinitol level about 5% was measured. Additionally, different food supplements available on the market were screened. The amount D-pinitol found in these supplements ranged from 1.8 mg/capsule to 30 mg/capsule and was 2.0 mg/mL solution.