Synthesis, crystal and solution structures of platinacyclic complexes containing eugenol, the main bioactive constituent of Ocimum sanctum L. oil

Crystal structures of three platinacyclic complexes bearing isopropyl eugenoxyacetate and pyridine derivatives

Three new platinum(II) complexes bearing a eugenol and a pyridine derivative, namely (η2-2-allyl-4-meth-oxy-5-{[(propan-2-yl-oxy)carbon-yl]meth-oxy}phenyl-κC 1)chlorido-(pyridine-κN)platinum(II), [Pt(C15H19O4)Cl(C5H5N)], (I), (η2-2-allyl-4-meth-oxy-5-{[(propan-2-yl-oxy)carbon-yl]meth-oxy}phenyl-κC 1)chlorido-(4-methyl-pyridine-κN)platinum(II), [Pt(C15H19O4)Cl(C6H7N)], (II), and (η2-2-allyl-4-meth-oxy-5-{[(propan-2-yl-oxy)carbon-yl]meth-oxy}phenyl-κC 1)chlorido(pyridine-4-carb-oxy-lic acid-κN)platinum(II), [Pt(C15H19O4)Cl(C6H5NO2)], (III), have been synthesized and further characterized by single-crystal X-ray diffraction. The PtII atoms exhibit the usual distorted square-planar coordination and are surrounded by one Cl atom, one N atom, and a C atom and C=C double bond of the eugenol ligand. The donor N atom of the pyridine ligand occupies a cis position with respect to the double bond. Complexes (I) and (II) crystallize isomorphously in space group P and display a similar crystal packing characterized by C-H⋯O hydrogen bonding, C-H⋯π and π-π inter-actions. However, the presence of the additional methyl group in the 4-methyl-pyridine ligand in (II) disturbs the π-π inter-actions. The crystal packing of (III) is characterized by O-H⋯O hydrogen bonding, resulting in the formation of chains of mol-ecules connected in a head-to-tail fashion and running in the [101] direction. The IC50 values for the HepG2 and KB cell lines are 150.9, 122.3 µM for (I) and 138.9, 93.2 µM for (II), respectively.

Mixed natural arylolefin-quinoline platinum(II) complexes: synthesis, structural characterization and in vitro cytotoxicity studies

Five new platinum(II) complexes bearing a eugenol and a quinoline derivative, namely [η²-4-allyl-2-methoxy-1-(propoxycarbonylmethoxy)benzene]-trans-dichlorido(quinoline-κN)platinum(II), [PtCl₂(C₁₅H₂₀O₄)(C₉H₇N)], (2), {η²-4-allyl-2-methoxy-1-[(propan-2-yloxy)carbonylmethoxy]benzene}-trans-dichlorido(quinoline-κN)platinum(II), [PtCl₂(C₁₅H₁₉O₄)(C₉H₇N)], (3), [η²-4-allyl-2-methoxy-1-(propoxycarbonylmethoxy)benzene]chlorido(quinolin-8-olato-κ²N,O)platinum(II), [Pt(C₉H₆NO)Cl(C₁₅H₂₀O₄)], (4), {η²-4-allyl-2-methoxy-1-[(propan-2-yloxy)carbonylmethoxy]benzene}chlorido(quinolin-8-olato-κ²N,O)platinum(II), [Pt(C₉H₆NO)Cl(C₁₅H₂₀O₄)], (5), and [η²-4-allyl-2-methoxy-1-(propoxycarbonylmethoxy)benzene]chlorido(quinolin-2-carboxylato-κ²N,O)platinum(II), [Pt(C₁₀H₆NO₂)Cl(C₁₅H₂₀O₄)], (6), have been synthesized and fully characterized spectroscopically. A single-crystal X-ray diffraction study was carried out for complexes (2) and (4)-(6). PrEug [or 4-allyl-2-methoxy-1-(propoxycarbonylmethoxy)benzene] in (2), (4) and (6), and ⁱPrEug (the propan-2-yloxy analogue of PrEug) in (3) and (5) coordinate with Pt^II at the ethylenic double bond of the allyl group. In (2)-(6), the donor N atom of the amine group occupies a trans position with respect to the double bond. A comparison of the IC₅₀ values of 0.38-29.23 µM for (2)-(6) with cisplatin, as well as other platinum(II) complexes, indicates an excellent in vitro cytotoxicity against the KB, LU, Hep-G2 and MCF-7 cancer cell lines, with the highest cytotoxic effect (IC₅₀ = 0.38-1.99 µM) being for complexes (4) and (5) bearing a quinolin-8-olate ligand.