Localized surface plasmon resonances supported on metal nanoparticles cause an enhancement of the Raman and fluorescence spectra. While SERS is principally due to the first layer of molecules deposited on the metal surface, SEF experiments need to be successful to establish a distance between fluorophore and nanoparticles. This distance can be fixed by placement of a new molecule named spacer or by aggregation of the fluorescent molecule. The anti tumoral drugs emodin and hypericin belong to the group of natural anthraquinones dyes and both present and acid-base equilibrium. At several pHs molecules aggregate making possible some molecules to be situated at a certain distance of the nanoparticles surface and so to obtain fluorescence enhancement. SEF and SERS experiments recorded simultaneously permit to obtain vibrational and electronic information at the same time. Thus the aggregation, ionization and molecular structure of emodin and hypericin can be investigated. The binding of the dyes to biomolecules can also be studied through these spectroscopic techniques enhanced by metal nanoparticles.