Recently, oligoribonucleotide (ORN)-based preparations have become increasingly popular. ORNs have a wide range of biological properties. They are used as antiviral drugs and have antitumor and anti-inflammatory action. They act on both RNA and DNA-containing viruses and stimulate the innate antiviral immunity system. The biological activity of such drugs can partly be correlated with their spectral properties
As samples, we took the "Nuclex" pharmaceutical drugs based on an ORN and alcohol sugar D-mannitol (D-M), and the main components of these drugs (active substance - ORN and excipient - D-M). We measured the UV-Vis absorption (Specord 210 Plus two-beam spectrophotometer; Analytik Jena), fluorescence (Fluoromax-Plus spectrofluorimeter; HORIBA Instruments Inc.), and fluorescence excitation spectra for solutions in degassed bi-distillated water at room temperature.
Control of the ORN concentration was performed by measuring the absorption spectra and monitoring the maximum at 260 nm. The shape of the spectrum and the position of the absorption peak of ORN and Nuclex coincided and corresponded to the absorption spectrum of adenosine. During the study, a possible complexation between the active substance and the excipient (ORN-D-M) was identified. By excitation of ORN and Nuclex at a wavelength of 260 nm, we obtained a wide range of fluorescence in the region of 280-550 nm with a maximum at 380 nm. Measuring the fluorescence spectrum and the fluorescence excitation of the Nucleus and ORN, two large emission centers were detected with a maximum luminescence at 380 nm for an excitation wavelength of 290 nm (emission at 310-550 nm) and a maximum at 440 nm, with excitation at 360 nm (emission at 350-610 nm). In the absorption spectrum, those maxima did not appear, but we observed a strong emission compared to the excitation at a wavelength of 260 nm. In Nuclex, the excitation peak at 290 nm is significantly dominated by the intensity of the excitation peak at 360 nm, and in the ORN, the ratio between similar centers is reversed. When D-M is added, the ratio between the emission peaks at 380 and 440 nm changed, what might indicate the complexation of ORN and D-M. When D-M wa added to the ORN, the position of the emission peaks and the shape of the peaks did not change.
In the course of our research, we found fluorescence centers of Nuclex, and identified the possibility of complexes between ORN and D-M.
