SURFACE-ENHANCED RESONANCE RAMAN-SPECTROSCOPY OF HYPOCRELLIN-A - AN EFFECT OF EXCITATION WAVELENGTH AND PH

Surface-enhanced Raman (SERS) and surface-enhanced resonance Raman spe ctroscopy (SERRS) of hypocrellin A, a photoactive antiviral and antine oplastic agent, are reported for the first time on aqueous silver coll oid. An analysis of the excitation and pH dependent SERRS spectra of h ypocrellin leads to: (i) the interpretation of the main vibrational mo des of hypocrellin; (ii) the determination of hypocrellin SERRS marker bands for the carbonyl group protonation; and (iii) a conclusion abou t similar character of region where intramolecular hydrogen bond betwe en quinoid carbonyl group and adjacent hydroxyl group is formed in hyp ocrellin with that of the structurally related phenanthro-perylen mole cule, hypericin. (C) 1998 Elsevier Science B.V. All rights reserved.