Ag(I) complexes with natural products and triphenylphosphine: activity against tumor cell lines and mycobacterium tuberculosis

Cancer and tuberculosis remain among the leading causes of morbidity and mortality worldwide, and the emergence of drug resistance in both diseases highlights the urgent need for new therapeutic strategies. In this context, metal-based compounds combined with bioactive natural products have emerged as promising alternatives to conventional drugs. In the present study, a series of silver (I) complexes containing natural products (curcumin, lawsone, lapachol or alizarin) and triphenylphosphine (PPh3) (complexes 1–4) were synthesized and structurally characterized by IR spectroscopy, elemental analysis, molar conductivity, NMR (1H, 13C, 31P{1H}) spectroscopy and single crystal X-ray diffraction. The results of single crystal diffraction show that the two silver complexes are four-coordinated with two PPh3 and two O atoms of natural product, forming a distorted tetrahedral geometry. The in vitro cytotoxicity of silver(I) complexes was evaluated by MTT assay against four cancer cells and two normal cells, the result shows that the complexes presented a low IC50 value in general, including in normal cell lines. The complexes show better cytotoxic activity for A2780cis (cisplatin-resistant ovarian tumor cell line), being nearly 30 times higher than cisplatin. Silver complexes were tested against Mycobacterium tuberculosis (Mtb) reaching the threshold for effective antimicrobial activity. Furthermore, complex 4 showed good activity against clinical isolates of Mtb resistant to multiple first-line anti-TB drugs.