Furanochromone radical cations: generation, characterization and interaction with DNA.
The radical cations of naturally occurring furanochromones visnagin (VI) and khellin (KH) have been generated and identified for the first time by use of laser flash photolysis and pulse radiolysis techniques. The lifetimes of VI(.+) and KH(.+) are determined as approximately 6 and approximately 35 micros under these conditions, respectively. Direct 308-nm excitation of VI in aqueous buffer at physiological pH results in monophotonic photoionization to generate VI(.+), with a quantum yield of 0.075, which is much higher than that of 8-methoxypsoralen and KH under identical conditions. Though VI(.+) is a more powerful oxidant than KH(.+), both of them react with guanosine mononucleotide (k=1.2x10(9) and 3.8x10(7) dm(3) mol(-1) s(-1), respectively) via electron transfer to give the guanine radical cation. Furthermore, selective oxidation of guanine in single and double strand DNA by VI(.+) was also observed. These novel findings suggest that electron transfer reactions involving furanochromone radical cations may be of considerable importance in furanochromone photochemotherapy.
Pan
J X
JX
Laboratory of Radiation Chemistry, Shanghai Institute of Nuclear Research, Academia Sinica, P.O. Box 800-204, Shanghai 201800, PR China.
Han
Z H
ZH
Miao
J L
JL
Yao
S D
SD
Lin
N Y
NY
Zhu
D Y
DY
D002412:Cations; D004247:DNA / Q000737:chemistry*; D005609:Free Radicals; D007666:Khellin / Q000031:analogs & derivatives* / Q000737:chemistry*
D002412:Cations; D005609:Free Radicals; D007666:Khellin; D004247:DNA; C044999:visnagin