Doxorubicin (DOX) is a prevalent anticancer agent; however, it is unfortunately characterized by high cardiotoxicity, myelosuppression, and multiple other side effects. To overcome DOX limitations, two novel pyridoxine-derived doxorubicin derivatives were synthesized (DOX-1 and DOX-2). In the present study, their antitumor activity and mechanism of action were investigated. Of these two compounds, DOX-2, in which the pyridoxine fragment is attached to the doxorubicin molecule via a C3 linker, revealed higher selectivity against specific cancer cell types compared to doxorubicin and a promising safety profile for conditionally normal cells. However, the compound with a C1 linker (DOX-1) was not characterized by selectivity of antitumor action. It was revealed that DOX-2 obstructs cell cycle progression, induces apoptosis via the mitochondrial pathway without the development of necrosis, and showcases antioxidant capabilities, underlining its cell-regulatory roles. In contrast to doxorubicin’s DNA-centric mechanism, DOX-2 does not interact with nuclear DNA. Given these findings, DOX-2 presents a new promising direction in cancer therapeutics, which is deserving of further in vivo exploration.

Beetle luciferases catalyze bioluminescent reactions using identical substrates—luciferin, ATP, and oxygen—yet emit colors ranging from green to red. As the luciferase fold is highly conserved, the structural basis of this spectral diversity remains elusive. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) was used to systematically probe the conformational dynamics of green-emitting Amydetes vivianii luciferase (GB _Av ) and red-emitting Phrixothrix hirtus luciferase (RE _Ph ), along with their color-shifting mutants, R337L and L334R, respectively. HDX-MS profiling in the apo and ligand-bound states mapped dynamic changes associated with substrate binding and color modulation. RE _Ph and the red-shifted R337L GB _Av mutant exhibited globally higher dynamics, particularly in N-terminal domain peptides surrounding the active site, than their blue-green-emitting counterparts. Substrate binding reduced deuterium uptake in all enzymes; however, red-emitting forms retained greater flexibility. These findings establish a direct link between structural dynamics and bioluminescence color tuning in beetle luciferases, providing mechanistic insight into spectral control.

Molecular targets for a promising antitumor agent based on trans-stilbene containing a pyridoxine fragment were identified. The lead compound, (E)-6-(3,4-dimethoxystyryl)-2,2,5,8-tetramethyl-4H-[1,3] dioxino[4,5-c]pyridine, was found to selectively induce apoptosis in MCF-7 breast adenocarcinoma cells overexpressing estrogen receptor, but not in MDA-MB-231 cells negative for estrogen receptor. The mechanism by which the novel trans-stilbene derivative acts as a selective estrogen receptor modulator was analyzed, and the affinity for human estrogen receptor α (ERα) was assessed by fluorescence polarization. Unlike its structural analogs—tamoxifen and raloxifene, the lead compound showed no affinity for ERα and did not form complexes with it. Therefore, it was concluded that the selective action of the pyridoxine-containing derivative of trans-stilbene on estrogen-positive breast cancer cells occurs through an alternative mechanism. The EC 50 values for the displacement of the fluorescent ligand from the ERα active site were 22, 120, and 595 nM for estradiol, raloxifene, and tamoxifen, respectively.