We have recenlty studied some properties of an angular furoquinolinone, 1,4,6,8,-tetramethyl-2H-furo[2,3-h] quinolin-2-one (FQ) which can be regarded as an angelicin isoster, in comparison with an isomer, 4,6,8,9,-tetramethyl-2H-furo[2,3-h] quinolin-2-one

Do furocoumarins induce different kinds of DNA-protein cross-links?

F.Bordin, C.Marzano, F.Carlassare, M.Simonato, A.Guiotto and F.Baccichetti

Dep. Pharmaceutical Sciences of Padova University; Centro di Studio sulla Chimica del Farmaco e dei Prodotti Biologicamente Attivi del C.N.R. (associated to the National Institute for the Chemistry of Biological Systems) - C.N.R.; Padova, Italy.

INTRODUCTION

We have recently studied some properties of two angular furoquinolinones, which can be regarded as angelicin isosters, 1,4,6,8-tetramethyl-2H-furo[2,3-h]quinolin-2-one (FQ) and 4,6,8,9-tetramethyl-2H-furo[2,3-h]-quinolin-2-one (HFQ).

The main difference in the structure is at N₁, which carries a methyl group in FQ and a hydrogen atom in HFQ. Both compounds are characterised by a strong capacity of damaging DNA and a high photosensitizing activity. Table 1 shows the damage induced in DNA in comparison with 8-MOP.

Table 1 - Activity relative to 8-MOP
Compound	SSB	ISC	DNA binding	DPC
HFQ	0.18	0.01	5.70	2.40
FQ	0.20	0.01	9.56	8.50
8-MOP	1.0	1.0	1.0	1.0

SSB: single strand breaks; ISC: inter-strand cross-links; DPC: DNA-protein cross-links.

As shown, FQ and HFQ are completely unable of inducing inter-strand cross-links (ISC) [1], but form a lot of C₄-cycloadducts in DNA [2]. They induce another severe kind of lesion, that is a number of DNA-protein-cross-links (DPC) [1]. In this paper we are showing some data obtained studying the relationship between the formation of DPC and the biological activity of such compounds.