Insights into the transformation of VO2+ motif to VO3+, V2O34+ and VO2+ motifs and their interconversion along with a detailed mechanistic study of their anti-cancer activity in SiHa cervical cancer cells

The basic criteria for the formation of complexes with VO³⁺, V₂O₃⁴⁺ and VO₂⁺ motifs from the VO²⁺ motif and their interconversion were explored utilizing two multidentate O,N-donor hydrazone ligands namely, E-2-Hydroxy-N'-(4-oxopentan-2-ylidine)benzohydrazide (H₃L¹) and E-2-Hydroxy-N'-(4-oxo-4-phenylbutan-2-ylidine)benzohydrazide (H₃L²), derived from the condensation of 2-hydroxybenzoylhydrazide with acetylacetone and benzoylacetone respectively. Under aerobic condition, the possibility of forming complexes with different motifs in different solvents with varying pH was examined theoretically by computational methods with results that were verified experimentally. This study reveals that under aerobic condition, complexes with VO³⁺ (1,2) and V₂O₃⁴⁺ (3, 4) motifs were formed in protic CH₃OH and neutral CHCl₃ solvent respectively while the formation of complexes (5-14) with VO₂⁺ motif required protic CH₃OH solvent and higher pH (≥ 7). Interconversion of VO³⁺, V₂O₃⁴⁺ and VO₂⁺ motifs are associated with specific acid-base equilibria, substantiated by ⁵¹V NMR titrations. Complexes containing these three motifs exhibited promising in vitro anticancer activity in SiHa cervical cancer cells without affecting healthy cells; among them complexes (5-14) with VO₂⁺ motif are more potent. A detailed systematic mechanistic study was carried out, utilizing the two most potent complexes 5 and 6 (IC₅₀ = 13, 6 μM respectively), which indicates that cytotoxicity and anti-proliferative activity of these complexes are manifested through oxidative stress induced apoptotic pathways (caspase mediated).

Taking Advantage of the Renewable Forest Bioresource Turpentine to Prepare α,β-Unsaturated Compounds as Highly Efficient Fungicidal Candidates

In a continuous study on the high-value-added exploration of a renewable forest bioresource turpentine in modern organic agriculture, two series of α-pinene derivatives containing amide and α,β-unsaturated ketone pharmacophores were prepared. Through an in-depth fungicidal activity study, the title compounds presented excellent inhibitory activity against common crop fungi, especially Sclerotinia sclerotiorum, and the notable EC₅₀ values of α,β-unsaturated compounds 3u (funan containing) and 3v (thiophene containing) were 1.657 and 1.749 μg/mL, respectively. Further physiological and biochemical studies on S. sclerotiorum revealed that compounds 3u and 3v reduced the ergosterol content in the cell membrane and increased the permeability of the cell membrane. In combination with their effect on mycelial morphology, the title compounds might have inhibitory effects on the biosynthesis of ergosterol, which is a paramount component of the target cell membrane. Moreover, quantitative structure-activity relationship (QSAR) and SAR studies revealed that the charge distribution of α,β-unsaturated carbonyl ketone derivatives played an important role in the observed fungicidal activity. In summary, this study highlights the design and development of novel high-efficacy turpentine-based antifungal agents.

Synthesis, characterization, and cytotoxic and antimicrobial activities of mixed-ligand hydrazone complexes of variable valence VOz+ (z = 2, 3)

Mixed-ligand complexes of VO²⁺ and VO³⁺ motifs incorporating a family of hydrazone ligands were reported, which exhibited promising cytotoxic activity against lung cancer cell line and antimicrobial activity against four pathogenic bacterial stains.

Exploring the effect of substituent in the hydrazone ligand of a family of μ-oxidodivanadium(v) hydrazone complexes on structure, DNA binding and anticancer activity

The reaction of 2-hydroxybenzoylhydrazine (H₂bh) separately with equimolar amounts of [V^IVO(aa)₂] and [V^IVO(ba)₂] in CHCl₃ afforded the complexes [VO₃(HL¹)₂] (1) and [VO₃(HL²)₂] (2) respectively in good to excellent yield ((HL¹)^2- and (HL²)^2- represent respectively the dianionic form of 2-hydroxybenzoylhydrazones of acetylacetone (H₃L¹) and benzoylacetone (H₃L²) (general abbreviation H₃L)). From X-ray structure analysis, the V^V-O-V^V angle was found to be ∼115° and 180° in 1 and 2 respectively. Upon one-electron reduction selectively at one V centre at an appropriate potential, each of 1 and 2 generated mixed-valence [(HL)V^VO-(μ-O)-OV^IV(HL)]^- species 1A and 2A respectively, which showed valence delocalization at room temperature and localization at 77 K, and the V^IV-O-V^V bond angles were calculated to be 177.5° and 180° respectively. The intercalative mode of binding of the two complexes 1 and 2 with CT DNA has been suggested by UV-visible spectroscopy (K_b = 7.31 × 10⁵ M^-1 and 8.71 × 10⁵ M^-1 respectively for 1 and 2), fluorescence spectroscopy (K_sv = 6.85 × 10⁵ M^-1 and 8.53 × 10⁵ M^-1 respectively for 1 and 2) and circular dichroism spectroscopy. Such intercalative mode of binding of these two complexes with CT DNA and HPV DNA has also been confirmed by molecular docking study. Both complexes 1 and 2 exhibited promising anti-cancer activity against SiHa cervical cancer cells with IC₅₀ values of 28 ± 0.5 μM and 25 ± 0.5 μM respectively for 24 h which is significantly better than that of widely used cisplatin (with IC₅₀ value of 63.5 μM). Nuclear staining experiments reveal that these complexes kill the SiHa cells through apoptotic mode. It is interesting to note that these two complexes are non-toxic to normal T293 cell line. Complex 2 showed higher DNA binding ability with CT DNA and HPV DNA as well as better anti-cancer properties towards SiHa cervical cancer cells in comparison to complex 1, a fact which can be explained by considering the lower energy of LUMO (which favours electron transition from DNA to the metal complex) and also the higher surface area of complex 2 in comparison to complex 1 due to the presence of one extra electron-withdrawing phenyl group in the former.

Exploring the effect of hydroxylic and non-hydroxylic solvents on the reaction of [VIVO(β-diketonate)2] with 2-aminobenzoylhydrazide in aerobic and anaerobic conditions

Refluxing [V^IVO(β-diketonate)₂], namely [V^IVO(acetylacetonate)₂] and [V^IVO(benzoylacetonate)₂], separately with an equivalent or excess amount of 2-aminobenzoylhydrazide (ah) in laboratory grade (LG) CH₃OH in aerobic conditions afforded non-oxidovanadium(iv) and oxidovanadium(v) complexes of the type [V^IV(L¹)₂] (1), [V^VO(L¹)(OCH₃)]₂ (3) and [V^IV(L²)₂] (2), and [V^VO(L²)(OCH₃)] (4), respectively. (L¹)^2- and (L²)^2- represent the dianionic forms of 2-aminobenzoylhydrazone of acetylacetone (H₂L¹) and benzoylacetone (H₂L²), respectively, (general abbreviation, H₂L), which was formed by the in situ condensation of ah with the respective coordinated [β-diketonate] in medium-to-good yield. The yield of different resulting products was dependent upon the ratio of ah to [V^IVO(β-diketonate)₂]. For example, the yield of 1 and 2 complexes increased significantly associated with a decrease in the amount of 3 and 4 with an increase in the molar ratio of ah. Upon replacing CH₃OH by a non-hydroxylic solvent, LG CHCl₃, the above reaction yielded only oxidovanadium(v) complexes of the type [V^VO(L¹)(OH)]₂ (5), [V^VO(L²)(OH)] (6) and [VO₃(L)₂] (7, 8) whereas, upon replacing CHCl₃ by another non-hydroxylic solvent, namely LG CH₃CN, only the respective [VO₃(L)₂] (7, 8) complex was isolated in 72-78% yield. However, upon performing the above reactions in the absence of air using dry CH₃OH or dry CHCl₃, only the respective [V^IV(L)₂] complex was obtained, suggesting that aerial oxygen was the oxidising agent and the type of pentavalent product formed was dependent upon the nature of solvent used. Complexes 3 and 4 were converted, respectively, to 7 and 8 on refluxing in LG CHCl₃via the respective unstable complex 5 and 6. The DFT calculated change in internal energy (ΔE) for the reactions 2[V^VO(L²)(OCH₃)] + 2H₂O → 2[V^VO(L²)(OH)] + 2CH₃OH and 2[V^VO(L²)(OH)] → [VO₃(L²)₂] + H₂O was, respectively, +3.61 and -7.42 kcal mol^-1, suggesting that the [V^VO(L²)(OH)] species was unstable and readily transformed to the stable [VO₃(L²)₂] complex. Upon one-electron reduction at an appropriate potential, each of 7 and 8 generated mixed-valence [(L)V^VO-(μ-O)-OV^IV(L)]^- species, which showed valence-delocalisation at room temperature and localisation at 77 K. Some of the complexes showed a wide range of toxicity in a dose-dependent manner against lung cancer cells comparable with that observed with cis-platin.

A family of mixed-ligand oxidovanadium(v) complexes with aroylhydrazone ligands: a combined experimental and computational study on the electronic effects of para substituents of hydrazone ligands on the electronic properties, DNA binding and nuclease activities

Substituents at 5-position in the acetophenone ring of the hydrazone ligands in a family of mixed-ligand oxidovanadium(v) complexes show marked influence on the electronic properties, DNA binding ability and nuclease activity.