Fluorescent Spectrofluorimetric Method for the Quantification of Harmine in Human Plasma Using Tinopal CBS-X

Harmine, a β-carboline alkaloid derived from plants like Banisteriopsis caapi and Peganum harmala, possesses significant pharmacological properties, including anti-inflammatory and neuroprotective effects, which make it a potential candidate for therapeutic applications. However, the precise determination of harmine in biological matrices, particularly human plasma, poses analytical challenges due to the complexity of the matrix. This study introduces a sensitive spectrofluorimetric method utilizing Tinopal CBS-X, a fluorescent dye, to enhance harmine determination through the formation of a stable ion-pair complex. The interaction between harmine and Tinopal CBS-X under acidic conditions led to a notable increase in fluorescence intensity (excitation at 345 nm, emission at 431 nm), enabling determination over a concentration range of 1–200 ng/mL, with limits of detection and quantification at 0.181 and 0.543 ng/mL, respectively. The method was validated in accordance with ICH guidelines, demonstrating excellent linearity (r² = 0.9997), accuracy (99.25% recovery), and precision (RSD < 1.3%). Additionally, the method demonstrated high selectivity, as no interference from the plasma matrix was observed, confirming its reliability. Its successful application to spiked human plasma samples resulted in a mean percent recovery of 98.99%, highlighting its suitability for harmine determination in plasma matrices.