Synthesis, characterization, and evaluation of the antimicrobial, cytotoxic properties of alkaline earth metal complexes containing the nucleobase guanine

Alkaline earth metal (Mg2+, Ca2+, Sr2+, Ba2+) complexes of guanine (Gu), a purine-based nucleobase were synthesized. The characterization of these complexes involved elemental analysis (CHN), determination of metal and chloride contents, FTIR, UV-Visible, 1H-NMR spectroscopy, thermal analysis (TGA, DSC), molar conductance, and PXRD measurements. Based on the elemental analysis, the molecular formulae of the complexes were proposed as [Mg(Gu)2Cl2]<middle dot>4H2O, [Ca(Gu)2Cl2]<middle dot>3H2O, [Sr(Gu)3Cl2]<middle dot>5H2O and [Ba(Gu)3Cl2](Gu)<middle dot>5H2O. The molar conductance measurement showed that the complexes were non-electrolytic. The mode of chelation of guanine through N(7) and O(6) sites was explained using FTIR and 1H-NMR spectral analysis. Thermal analysis in a nitrogen atmosphere showed that the complexes were fairly stable up to 100 degrees C, with decomposition starting above this temperature and indicating the presence of hydrated water. The crystallite size, microstrain, and dislocation density of the complexes were determined using XRD data. The antibacterial and antifungal activities of guanine and its complexes were screened against five gram-positive, eight gram-negative bacteria, and three fungi. Guanine did not exhibit any antibacterial activity, while the metal complexes showed significant antibacterial and antifungal activities. In vitro cytotoxicity testing revealed that the alkaline earth metal complexes exhibited potential cytotoxic activity, with LC50 values ranging from 18.55 to 40.61 mu g mL-1. HeLa cervical cancer cell lines were used to investigate the anticancer activity of metal complexes, and each complex demonstrated cytotoxicity toward HeLa cell lines.