Investigation of facile spectroscopic approaches for rapid calycosin determination in invitro biological samples and pharmaceuticals; application to the content uniformity of capsules

[Display omitted] •Five spectroscopic methods were adopted for calycosin determination.•For the first time; highly sensitive spectrofluoremetric methods were carried out relying on measuring the native fluorescence of calycosin.•The fluorescence intensity was measured at 340 nm after excitation at 282 nm.•The sensitivity of the method allows its use in assay of calycosin in spiked human plasma with acceptable recoveries.•The proposed methods are sensitive, rapid and cost-effective without addition of any reagents. Calycosin, the major bioactive isoflavonoid inAstragali Radix and an important anti-viral drug with a variety of pharmacological actions, is being determined by five different spectroscopic methods. Two spectrophotometric methods have been investigated including measuring the absorption spectra at λmax = 270 nm and the first derivative spectra at λ = 288 nm for methods I and II, respectively. For the first time; the native fluorescence of calycosin is measured without adding any reagents. The fluorescence intensity was measured at 340 nm after excitation at 282 nm in method III. The fourth method involves the direct measuring of a first derivative spectrofluorimetric emission peak at 292 nm. In method V synchronous fluorescence spectra were recorded in methanol at Δλ = 70 nm. The linear range for the fluorescence-based methods was 0.05–1.0 µg/mL and for the UV-based methods was 0.5–10.0 µg/mL. The methods were validated per International Council of Harmonization (ICHQ2R1) guidelines. The limits of detection were found to be down to 0.11 and 0.12 µg/mL for the spectrophotometric methods, and 15.0, 18.0,16.0 ng/ mL, for the spectrofluorimetric approaches respectively, representing the high sensitivity. Accordingly, this permitted the quantitation of calycosin in spiked human plasma samples with satisfactory percentage recoveries (94.50.–102.50 %). The methods were utilized for calycosin analysis in different matrices including plasma and capsules with high precision and accuracy.