Experimental and theoretical investigation of the apomorphine Raman spectrum

Apomorphine (aporphine-10,11-diol, CA Registry Number 58004) is a non-narcotic derivative of morphine discovered in 1869 by Mattheisen and it is a well-known potent short-acting dopamine agonist at D1 and D2 dopamine receptors, typically used in the treatment of patients with advanced Parkinson’s disease (PD). To identify the unknown vibrational spectrum of this compound, apomorphine bare salt and its commercial drug formulation (Apofin) were examined by means of Raman spectroscopy. In the Raman spectrum of apomorphine (both bare salt and commercial drug), two strong characteristic signals were found, whichwere assigned with the help of first-principles calculations: the band at 1589 cm−1 (assigned to the stretching mode of the B aromatic ring coupled with C–H in-plane bending) and the band at 1302 cm−1 (assigned to O-H in-plane bending and CH2 twisting and wagging vibrations).