Absorption and fluorescence spectral characteristics of norepinephrine, epinephrine, isoprenaline, methyl dopa, terbutaline and orciprenaline drugs

Abstract

The absorption and fluorescence spectral characteristics of norepinephrine, epinephrine, isoprenaline, methyl dopa, orciprenaline and terbutaline have been investigated for levels of different pH and β-cyclodextrin (β-CD). The inclusion processes are discussed based on absorption, emission and semiempirical quantum mechanical calculations (CAChe – DFT). The pH study reveals that, deprotonation takes place in the CHOH group and the longer wavelength emission at 450 nm is due to intramolecular proton transfer. The β-CD study shows that the above-mentioned drugs form 1:1 inclusion complexes. Single-emission maximum in water (∼316 nm) and dual emission (316 nm, 450 nm) in β-CD is noticed for drugs. In the β-CD solutions, the shorter wavelength fluorescence intensity is regularly decreased and longer wavelength fluorescence intensity is increased. The alkyl chain and the hydroxyl group are present in the interior and hydrophilic parts of the β-CD cavity, respectively.