Raffaele Saladino

Covalent grafting of porphyrins on kraft and enzymatic hydrolytic lignin by Mitsunobu reaction afforded a panel of novel heterogeneous photocatalysts useful for the blue‐LED synthesis of dialkylimines by oxidative coupling of aromatic amines. The catalytic performance of photocatalysts was improved by nanostructuration via sustainable solvent‐shift procedure. Compared to previously reported encapsulated systems, covalent grafting limited porphyrin leaching and enhanced electronic transfer processes. Optical band gap and singlet oxygen quantum yield revealed that the acetylation of lignin modulated the excited‐state dynamics reducing non‐radiative deactivation pathways. The synthesis of dialkylimines from aromatic amines occurred in high yield, kraft lignin being the best support. The possibility to reuse photocatalysts for more runs further improved the sustainability of the system. Overall, covalent grafting was an effective strategy to control stability, excited‐state behavior, and catalytic efficiency of porphyrins in lignin‐based photocatalytic systems.

The phosphorylation of nucleosides and their subsequent polymerization are key issues in the study of the Origins of Life. How these chemical processes took place on primitive Earth remains a puzzle. In this study, we examine the thermal phosphorylation of guanosine in water under wet‐dry conditions and in the presence of sodium pyrophosphate, without the use of condensing agents or chemical catalysts. Phosphorylation occurs selectively, yielding cyclic guanosine monophosphates and cyclic guanosine polyphosphates bearing polyphosphate side chains of different lengths. Interestingly, this reaction mimics the phosphorylation of nucleosides by purine nucleotide pyrophosphotransferase enzymes in present‐day organisms. The fact that the phosphorylation reaction is not thermodynamically spontaneous in aqueous solutions, even at moderate water activities, highlights the efficacy of the reported procedure. These observations outline a plausible prebiotic scenario for the formation of building‐blocks of the pre‐genetic apparatus involving a simple phosphorylating reagent and wet‐dry cycles.

Enzymatic cascades, defined here as multi-enzymatic sequences operating on a shared reaction pathway and inspired by the spatial and temporal organization of metabolism, have emerged as powerful and versatile tools for sustainable organic synthesis. They minimize intermediate isolation, enhance atom economy and ensure outstanding chemo-, regio- and stereoselectivity, providing efficient alternatives to conventional multistep routes. Here, we highlight the conceptual role of substrate channeling, minimal cells, artificial metabolism and enzyme promiscuity in the translation of enzymatic cascades into synthetic strategies. Special attention is focused on advanced immobilization on functional and renewable supports, which enhance stability and recyclability and introduce new ways for thermodynamic and kinetic control. Hybrid systems integrating enzymes with photocatalysis, electrochemistry and chemical modules expand the catalytic repertoire far beyond biology. Complementary tools in bioinformatics, structural modeling and artificial intelligence may also enable pathway balancing, predictive design and dynamic optimization. Applications span from the valorization of renewable feedstocks to the synthesis of privileged scaffolds and fine chemicals.

The mammalian target of rapamycin pathway, mTOR, is a crucial signaling pathway that regulates cell growth, proliferation, metabolism, and survival. Due to its dysregulation it is involved in several ailments such as cancer or age-related diseases. The discovery of mTOR and the understanding of its biological functions were greatly facilitated by the use of rapamycin, an antibiotic of natural origin, which allosterically inhibits mTORC1, effectively blocking its function. In this entirely computational study, we investigated mTOR’s interaction with seven ligands: two clinically established inhibitors (everolimus and rapamycin) and five lignin-derived oligomers, a renewable natural polyphenol recently used for the drug delivery of everolimus. The seven complexes were analyzed through all-atom molecular dynamics simulations in explicit solvent using a high-performance computing platform. Trajectory analyses revealed stable interactions between mTOR and all ligands, with lignin-derived compounds showing comparable or enhanced binding stability relative to reference drugs. To evaluate the stability of the molecular complex and the behavior of the ligand over time, we analyzed key parameters including root mean square deviation, root mean square fluctuation, number of hydrogen bonds, binding free energy, and conformational dynamics assessed through principal component analysis. Our results suggest that lignin fragments are a promising, sustainable scaffold for developing novel mTOR inhibitors.

The ongoing exploration of planets such as Mars is producing a wealth of data to define habitable environments beyond the Earth. The inferred presence of neutral to alkaline aqueous fluids on Mars in its early history suggests that many potentially habitable environments existed on the planet. Terrestrial analogues with similar chemical and physical properties are being explored and characterized in order to assess their suitability for triggering the Origin of Life on Mars. Recently, a novel Mars analogue site has been identified in the Bagno dell’Acqua Lake, which is located in the island of Pantelleria in Sicily (Italy). We report here that microbialite from the Bagno dell’Acqua Lake acts as an efficient catalyst for prebiotic processes, starting from a ternary mixture of well-recognized chemical precursors, including ammonium formate, diaminomalonitrile, and alpha-amino acids. Under thermal conditions, significant amounts of building blocks of both RNA and PNA were obtained. Furthermore, samples of the water from the Bagno dell’Acqua Lake have been found to promote the polymerization of the H-form of 3′,5′-cyclic GMP, resulting in the generation of RNA oligomers of up to 15 units in length.

The photochemistry of resveratrol with singlet oxygen (¹O₂) under blue‐LED irradiation is explored in the presence of three metal‐free porphyrins as photosensitizers. Irradiation at 450 nm yields products of CC bond scission, 6‐electron electrocyclic ring closure, and [4 + 2] cycloaddition, including benzaldehydes, 2,4,6‐trihydroxyphenanthrene, and resveratrol cyclic endoperoxide. The selectivity of the process is controlled by the structure of the metal‐free porphyrin and by the nominal capacity of the blue‐LED photon. The scope of the reaction is extended to sustainable heterogeneous photosensitizers produced by immobilization of metal‐free porphyrins on lignin, the most abundant polyphenol in nature characterized by beneficial photochemical properties.

Benzoxazine and benzoxazepine derivatives with tricyclic five-, six-, and seven-membered lactone and lactam rings were synthesized in one-pot conditions by using biochemo multienzyme cascade of lipase M and tyrosinase. The reaction involves tyrosinase-mediated ortho-hydroxylation of the phenolic moiety, followed by 1,6-Michael addition and tandem intramolecular ring closure. The method achieves high atom economy, minimizes purification steps, and provides a sustainable alternative to conventional multistep syntheses. Enzymes showed excellent reusability, further enhancing the green approach.

UVB radiation induces DNA damage generating several thymine photo-adducts (TDPs), which can lead to mutations and cellular transformation. The DNA repair pathways preserve genomic stability by recognizing and removing photodamage. These DNA repair side products may affect cellular processes. We previously synthesized novel thymine biomimetic thymine dimers (BTDs) bearing different alkane spacers between nucleobases. Thus, the present study investigates whether novel BTDs and their TDPs can modulate DNA damage safeguard pathways of primary keratinocytes and fibroblasts using 2D and 3D models. We found that the p53/p21^waf1 pathway is activated by BTDs and TDPs in primary cells similar to UVB exposure. Compound 1b can also induce the p53/p21^waf1 pathway in a 3D skin model. However, BTDs and TDPs exhibit distinct effects on cell survival. They have a protective action in keratinocytes, which maintain their clonogenic ability following treatments. Conversely, compounds induce pro-apoptotic pathways in fibroblasts that exhibit reduced clonogenicity. Moreover, compounds induce inflammatory cytokines mainly in keratinocytes rather than fibroblasts. Matrix metalloproteinase 1 is up-regulated in both cell types after treatments. Therefore, BTDs and TDPs can act in the short term as safeguard mechanisms helping DNA damage response. Furthermore, they have distinct biological effects depending on photodamage form and cell type.

Vicinal halohydrins are key building blocks to produce bioactive molecules and drugs, especially if they can be obtained in enantiomerically pure form. In this study, we present a bi‐enzymatic sequence that allows to obtain vic‐halohydrins through a photochemoenzymatic olefin hydroxy halogenation followed by a lipase catalysed kinetic resolution. The absolute configuration of the resulting products was determined using Mosher's method

Molecular hybridization is a widely used strategy in drug discovery and development processes that consists of the combination of two bioactive compounds toward a novel entity. In the current study, two libraries of hybrid derivatives coming from the linkage of sesquiterpene counterparts dihydroartemisinin and artesunic acid, with a series of monoterpenes, were synthesized and evaluated by cell viability assay on primary and metastatic melanoma cell lines. Almost all the obtained compounds showed micromolar antimelanoma activity and selectivity toward the metastatic form of this cancer. Four hybrid derivatives containing perillyl alcohol, citronellol, and nerol as monoterpene counterpart emerged as the best compounds of the series, with nerol being active in combination with both sesquiterpenes, dihydroartemisinin and artesunic acid. Preliminary studies on the mechanism of action have shown the dependence of the pharmacological activity of newly synthesized hybrids on the formation of carbon- and oxygen-centered radical species. This study demonstrated the positive modulation of the pharmacodynamic effect of artemisinin semisynthetic derivatives dihydroartemisinin and artesunic acid due to the hybridization with monoterpene counterparts.