Simple, sensitive, selective and validated spectrophotometric methods for the estimation of a biomarker trigonelline from polyherbal gels

Simple, accurate, reproducible, selective, sensitive and cost effective UV-spectrophotometric methods were developed and validated for the estimation of trigonelline in bulk and pharmaceutical formulations. Trigonelline was estimated at 265 nm in deionised water and at 264 nm in phosphate buffer (pH 4.5). Beer's law was obeyed in the concentration ranges of 1–20 μg mL−1 (r2 = 0.9999) in deionised water and 1–24 μg mL−1 (r2 = 0.9999) in the phosphate buffer medium. The apparent molar absorptivity and Sandell's sensitivity coefficient were found to be 4.04 × 103 L mol−1 cm−1 and 0.0422 μg cm−2/0.001A in deionised water; and 3.05 × 103 L mol−1 cm−1 and 0.0567 μg cm−2/0.001A in phosphate buffer media, respectively. These methods were tested and validated for various parameters according to ICH guidelines. The detection and quantitation limits were found to be 0.12 and 0.37 μg mL−1 in deionised water and 0.13 and 0.40 μg mL−1 in phosphate buffer medium, respectively. The proposed methods were successfully applied for the determination of trigonelline in pharmaceutical formulations (vaginal tablets and bioadhesive vaginal gels). The results demonstrated that the procedure is accurate, precise, specific and reproducible (percent relative standard deviation <2%), while being simple and less time consuming and hence can be suitably applied for the estimation of trigonelline in different dosage forms and dissolution studies.