Investigation of riboflavin sensitized degradation of purine and pyrimidine derivatives of DNA and RNA under UVA and UVB

DNA and RNA undergo photodegradation in UVC (200–290 nm) due to direct absorption by the purine and pyrimidine bases. Limited effects are observed under UVB (290–320 nm) or UVA (320–400 nm). We have observed that an endogenous photosensitizer, riboflavin (RF), upon exposure to UVB or UVA can extensively damage the DNA and RNA bases. Guanine, uracil, thymine, adenine and cytosine were degraded by 100%, 82%, 60.4%, 46.3% and 10.3% under UVA (12 J) and by 100%, 54.1%, 38.9%, 42.2% and <1.0% under UVB (6 J), respectively. Guanosine and deoxyguanosine were degraded by 98 ± 1.0% and 80 ± 1.0% under UVA (4 J) and UVB (12 J), respectively. With an exception of GMP (53–82%), dGMP (51–88%) and to some extent TMP (3–4%) the remaining nucleosides and nucleotides were resistant to RF-induced photodecomposition. The photodegradation of G derivatives by RF was 2-fold higher than a well known photodynamic agent rose bengal. A comparison of the intensities of UVA and UVB sources used in this study with natural sunlight suggests that exposure with the latter along with an endogenous photosensitizer can have similar effects on DNA and RNA depending upon the duration of exposure.

Research highlights
► Synergistic action of riboflavin and UVA or UVB caused extensive degradation of all the five bases of DNA and RNA.
► The guanine derivatives were equally sensitive to photosensitization.
► The extent of degradation by riboflavin was more than the recognized photodynamic agent rose bengal.
► Reactive oxygen species are likely intermediates involved in the photodegradation.