Mechanisms of citral phototoxicity.
Citral, a monoterpene aldehyde synthesized by several plant genera, has been reported to exhibit antimicrobial activity. For the first time, we report that critral exhibits UV-A (315-400 nm) light enhanced oxygen-dependent toxicity against a series of Escherichia coli strains differing in DNA repair and catalase proficiency. Those E. coli strains carrying a gene leading to catalase deficiency (katF) are particularly sensitized to inactivation by citral and UV-A treatment when compared to catalase proficient strains (katF+). Consistent with these in vivo observations, citral when treated with UV-A in vitro produces H2O2. When tested against Fusarium oxysporum and F. solani, fungal root pathogens of Citrus, enhanced toxicity by citral in the presence of UV-A was demonstrated, while dark toxicity was negligible. When the plasmid pBR322 was treated with citral in the presence of UV-A, a change in conformation from the covalently closed circular to the open circular and, ultimately, the linear form was observed. The change in plasmid conformation corresponded to a reduction in transforming activity. Holding plasmid DNA which had been treated with UV-A light in the presence of citral at 4 degrees C for 22 h in the dark resulted in continued degradation of the DNA and loss of transforming activity. Holding plasmid DNA treated with UV-A or citral alone under identical conditions had no detectable effect on either plasmid conformation or transforming activity.
Asthana
A
A
Department of Plant Biology, University of Illinois, Urbana 61801.
Larson
R A
RA
Marley
K A
KA
Tuveson
R W
RW
D000080462:Acyclic Monoterpenes; D004269:DNA, Bacterial / Q000187:drug effects / Q000528:radiation effects; D004926:Escherichia coli / Q000187:drug effects; D005658:Fungi / Q000187:drug effects; D039821:Monoterpenes; D010777:Photochemistry; D013729:Terpenes / Q000494:pharmacology* / Q000528:radiation effects; D014466:Ultraviolet Rays
D000080462:Acyclic Monoterpenes; D004269:DNA, Bacterial; D039821:Monoterpenes; D013729:Terpenes; C007076:citral