Simultaneous spectrophotometric determination of trigonelline, diosgenin and nicotinic acid in dosage forms prepared from fenugreek seed extract

Mathematical algorithms offer a useful method for quantitative analysis of compounds in multi-component mixtures to overcome the overlapping problems occurred in UV spectrophotometry. The aim of this study is to develop a method to determine the bioactive compounds in herbal dosage forms produced from fenugreek extract. A UV- spectrophotometric method based on mathematical algorithm was used to simultaneous determination of trigonelline (TRG), diosgenin (DI) and nicotinic acid (NA). The maximum absorbance (λmax) was determined to be 232.65 nm, 296.23 nm, and 262.60 nm for TRG, DI and NA respectively. The calibration curves showed good linearity for all analytes in the concentration range of 1–20 μg/mL (R2=0.9995, 0.9997, 0.9994 for TRG, DI and NA respectively). The Intra- and inter-day precisions were in the range of 1.1-10.7% and 1.2-8.2% respectively. The accuracy of the method was 96.0% for TRG, 92.9% for DI, and 104.2% for NA. The limits of detection (LOD) and quantification (LOQ) were found to be 0.91 and 3.06 µg/mL for TRG, 0.99 and 3.30 µg/mL for DI and 0.33 and 1.10 µg/mL for NA. The validated method was applied for determination of the analytes in tablet, capsule and biofilm dosage forms prepared by fenugreek seed extract. The mean recovery percentages of the analytes were in the range of 90.0-97.4%, 85.6-105.4%, and 90.0-99.0% for tablet, capsule, and film dosage forms respectively. Generally,the validated method could be a good candidate for routine spectrophotometry determination of the analytes without any necessity for pre-analysis extraction.