New metal complexes of derivatives of natural porphyrins with gallium: Synthesis and spectral characteristics

Objectives. Porphyrins are known to selectively accumulate in tumor cells and exhibit photosensitizing properties. However, the use of free-base porphyrins is accompanied by side effects due to the slow elimination of such drugs from the body and long-term skin phototoxicity. One approach to solving this problem is to obtain metal complexes of porphyrins offering reduced phototoxicity. Gallium metal complexes of porphyrins are additionally known for their antimicrobial activity, which expands the range of their applications. In this connection, the work set out to synthesize gallium metal complexes of porphyrins as potential photosensitizers for use in antitumor and antimicrobial photodynamic therapy (PTD) applications.

Methods. Strategies for the synthesis of metal complexes of derivatives of natural porphyrins with gallium were implemented. The structures of the obtained compounds were obtained by mass spectrometry, ultraviolet spectroscopy, and X-ray photoelectron spectroscopy. The resulting compounds were isolated and purified by thin-layer chromatography, column chromatography, dialysis, and recrystallization.

Results. Strategies were developed for the synthesis of gallium metal complexes of etioporphyrin II, protoporphyrin IX dimethyl ether, and Dimegin for potential use in PTD. Based on the structural analysis of the obtained compounds using a combination of physicochemical methods, the elemental composition and chemical state of the atoms were identified to confirm the formation of metal complexes with gallium. Natural porphyrins and their derivatives, in particular etioporphyrin II, protoporphyrin IX, and Dimegin, were confirmed to have been successfully metalated with gallium at high yields. The high chelating ability of derivatives of natural porphyrins was demonstrated.

Conclusions. The resulting compounds are potential photosensitizers for antimicrobial and antitumor photodynamic therapy.

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