Federico Zappaterra

Poor aqueous solubility limits roughly 40% of marketed oral drugs and up to ~90% of development candidates. One established remedy is the prodrug strategy: the covalent attachment of a bioreversible promoiety that regenerates the parent drug in vivo. The same conjugation can move a molecule in either direction along the hydrophilic–lipophilic axis: lipophilization raises membrane and oil solubility for permeation-limited or topical uses, whereas hydrophilization raises aqueous solubility. This review addresses hydrophilization and asks whether enzymatic (biocatalytic) synthesis can replace conventional chemistry in building water-soluble prodrugs. We examine, class by class of hydrophilic promoiety (polyol and sugar esters, glycosides, amino acid esters, poly(ethylene glycol), and ionizable phosphates), the biocatalytic toolbox (lipases, acyltransferases, glycosidases, and glycosyltransferases), the molecular determinants of its selectivity, the pharmacokinetic consequences of hydrophilization, and the translation of these reactions to process, benchmarking each against the corresponding chemical route. A three-part test emerges: enzymes suffice, and frequently surpass chemistry, wherever an accessible hydroxyl or carboxyl must be functionalized regioselectively on a promoiety bearing no competing group and a moderate solubility gain is required. This is the regime of polyols, most sugars, and glycosides, with drug-conjugate aqueous-solubility increases of roughly 4-fold to 5500-fold; chemistry remains necessary for ionizable phosphates, amino acid esters, and PEG carriers. Two gaps limit translation: the field’s central ‘green’ claim is asserted far more often than it is measured (E-factor, PMI, life-cycle assessment), and in vivo pharmacokinetic data for enzymatically synthesized hydrophilizing prodrugs remain almost absent. We provide a decision flowchart that assigns each bond of a synthesis to biocatalysis or to chemistry, and reporting guidelines for the seven quantities that make a published E-factor recoverable.

Poor aqueous solubility limits roughly 40% of marketed oral drugs and up to ~90% of development candidates. One established remedy is the prodrug strategy: the covalent attachment of a bioreversible promoiety that regenerates the parent drug in vivo. The same conjugation can move a molecule in either of two opposite directions along the hydrophilic–lipophilic axis: hydrophilization raises aqueous solubility, whereas lipophilization instead raises membrane and oil solubility for permeation-limited or topical uses. This review addresses the hydrophilizing route and asks a single question: can enzymatic (biocatalytic) synthesis replace conventional chemistry in building water-soluble prodrugs? We examine, class by class of hydrophilic promoiety (polyol and sugar esters, glycosides, amino-acid esters, poly(ethylene glycol) and ionizable phosphates), the biocatalytic toolbox (lipases, acyltransferases, glycosidases and glycosyltransferases), the molecular determinants of its selectivity, the pharmacokinetic consequences of hydrophilization, and the translation of these reactions to process, benchmarking each against the corresponding chemical route. A consistent three-part test emerges: enzymes suffice, and frequently surpass chemistry, wherever an accessible hydroxyl or carboxyl must be functionalized regioselectively on a promoiety bearing no competing group and a moderate solubility gain is required. This is the regime of polyols, sugars and glycosides, with reported aqueous-solubility increases spanning roughly 4-fold to 5500-fold; chemistry remains necessary for ionizable phosphates, amino-acid esters and PEG carriers. Enzymatic routes are sufficient and advantageous for polyol and sugar prodrugs, yet the field’s central ‘green’ claim is asserted far more often than it is measured (E-factor, PMI, life-cycle assessment), and in-vivo pharmacokinetic data for enzymatically synthesized hydrophilizing prodrugs remain almost absent, the two gaps that most limit translation and set the agenda for the field.

The demand for sustainable and natural alternatives in the flavor and fragrance industries has driven interest toward enzymatic synthetic routes. This study reports the enzymatic production of geranyl benzoate, a monoterpenoid ester with potential bioactivity and commercial applications, catalyzed by immobilized lipases using a solvent‐free system. A central composite design was employed to optimize the key process variables: molar ratio, temperature, and enzyme loading using Lipozyme 435 as the biocatalyst. Under optimal conditions (1:7 molar ratio, 80°C, 30% enzyme), a high geraniol conversion (72%) was achieved within 6 hr, as validated by a predictive model. The study also investigated the inhibitory effects of coproduced methanol, demonstrating that open‐reactor systems (enabling methanol evaporation) enhanced conversion (>99% in 48 h) compared to closed systems. Additionally, substrate‐exposure experiments highlighted methyl benzoate's inhibitory effect on Lipozyme 435, reducing its activity by 54%, whereas Lipura Flex showed greater resilience. Reusability tests indicated a decline in enzyme performance, with Lipozyme 435 retaining 22% activity after five cycles. Cell tests demonstrated no cytotoxicity and proliferative effect at high concentrations. These findings highlight the potential of solvent‐free enzymatic processes for sustainable production of geranyl benzoate and provide insights into operational challenges, including methanol management and biocatalyst stability.

A chemical platform for post-polymerization methods was developed, starting from the ecodesign and enzymatic synthesis of safe and sustainable bio-based polyesters containing discrete units of itaconic acid. This unsaturated bio-based monomer enables the covalent linkage of molecules that can impart desired properties such as hydrophilicity, flexibility, permeability, or affinity for biological targets. Molecular descriptor-based computational methods, which are generally used for modeling the pharmacokinetic properties of drugs (ADME), were employed to predict in silico the hydrophobicity (LogP), permeability, and flexibility of virtual terpolymers composed of different polyols (1,4-butanediol, glycerol, 1,3-propanediol, and 1,2-ethanediol) with adipic acid and itaconic acid. Itaconic acid, with its reactive vinyl group, acts as a chemical platform for various post-polymerization functionalizations. Poly(glycerol adipate itaconate) was selected because of its higher hydrophilicity and synthetized via solvent-free enzymatic polycondensation at 50 °C to prevent the isomerization or crosslinking of itaconic acid. The ecotoxicity and marine biodegradability of the resulting oligoester were assessed experimentally in order to verify its compliance with safety and sustainability criteria. Finally, the viability of the covalent linkage of biomolecules via Michael addition to the vinyl pendant of the oligoesters was verified using four molecules bearing thiol and amine nucleophilic groups: N-acetylcysteine, N-Ac-Phe-ε-Lys-OtBu, Lys-Lys-Lys, and glucosamine.

A chemical platform for post-polymerisation methods was developed, starting from the ecodesign and enzymatic synthesis of safe and sustainable bio-based polyesters containing discrete units of itaconic acid. This unsaturated bio-based monomer enables the covalent linkage of molecules that can impart desired properties such as hydrophilicity, flexibility, permeability or affinity for biological targets. Molecular descriptor-based computational methods, which are generally used for modelling the pharmacokinetic properties of drugs (ADME), were employed to predict in silico the hydrophobicity (LogP), permeability and flexibility of virtual terpolymers composed of different polyols (1,4-butanediol, glycerol, 1,3-propanediol and 1,2-ethanediol) with adipic acid and itaconic acid. Itaconic acid, with its reactive vinyl group, acts as a chemical platform for various post-polymerisation functionalisations. Poly(glycerol adipate itaconate) was selected because of its higher hydrophilicity and synthetized via solvent-free enzymatic polycondensation at 50°C to prevent the isomerization or crosslinking of itaconic acid. The ecotoxicity and marine biodegradability of the resulting oligoester were assessed experimentally in order to verify its compliance with safety and sustainability criteria. Finally, the viability of the covalent linkage of biomolecules via Michael addition to the vinyl pendant of the oligoesters was verified using four molecules bearing thiol and amine nucleophilic groups: N-acetylcysteine, N-Ac-Phe-ε-Lys-OtBu, Lys-Lys-Lys and glucosamine.

Natural compounds with significant bioactive properties can be found in abundance within biomasses. Especially prominent for their anti-inflammatory, neuroprotective, antibacterial, and antioxidant activities are cinnamic acid derivatives (CAs). Ferulic acid (FA), a widely studied phenylpropanoid, exhibits a broad range of therapeutic and nutraceutical applications, demonstrating antidiabetic, anticancer, antimicrobial, and hepato- and neuroprotective activities. This research investigates the green enzymatic synthesis of innovative and potentially bifunctional prodrug derivatives of FA, designed to enhance solubility and stability profiles. Selective esterification was employed to conjugate FA with xylitol, a biobased polyol recognized for its bioactive antioxidant properties and safety profile. Furthermore, by exploiting t-amyl alcohol as a green solvent, the enzymatic synthesis of the derivative was optimized for reaction parameters including temperature, reaction time, enzyme concentration, and molar ratio. The synthesized derivative, xylitol monoferulate (XMF), represents a novel contribution to the literature. The comprehensive characterization of this compound was achieved using advanced spectroscopic methods, including ¹H-NMR, ¹³C-NMR, COSY, HSQC, and HMBC. This study represents a significant advancement in the enzymatic synthesis of high-value biobased derivatives, demonstrating increased biological activities and setting the stage for future applications in green chemistry and the sustainable production of bioactive compounds.

Given the natural origins of flavylium derivatives, their chemical modifications, and their large potential uses in food, medicine, or green chemistry, the present review is a comprehensive study of flavylium-derived compounds. Several topics such as the green extraction and isolation techniques of flavylium derivatives including their chemical modifications and various characterization tools such as NMR, HPLC, and mass spectrometry are discussed in the review. Furthermore, the use of these derivatives in medicine, food, and materials science is presented, highlighting their relevance and the need for further investigation. Therefore, by examining the advantages and disadvantages of natural and synthetic sources, the review asserts the increased relevance of flavylium-based compounds in active molecules.

Ferulic acid (Fer) and geraniol (Ger) are natural compounds whose antioxidant and anti-inflammatory activity confer beneficial properties, such as antibacterial, anticancer, and neuroprotective effects. However, the short half-lives of these compounds impair their therapeutic activities after conventional administration. We propose, therefore, a new prodrug (Fer-Ger) obtained by a bio-catalyzed ester conjugation of Fer and Ger to enhance the loading of solid lipid microparticles (SLMs) designed as Fer-Ger delivery and targeting systems. SLMs were obtained by hot emulsion techniques without organic solvents. HPLC-UV analysis evidenced that Fer-Ger is hydrolyzed in human or rat whole blood and rat liver homogenates, with half-lives of 193.64 ± 20.93, 20.15 ± 0.75, and 3.94 ± 0.33 min, respectively, but not in rat brain homogenates. Studies on neuronal-differentiated mouse neuroblastoma N2a cells incubated with the reactive oxygen species (ROS) inductor H₂O₂ evidenced the Fer-Ger ability to prevent oxidative injury, despite the fact that it appears ROS-promoting. The amounts of Fer-Ger encapsulated in tristearin SLMs, obtained in the absence or presence of glucose, were 1.5 ± 0.1%, allowing the control of the prodrug release (glucose absence) or to sensibly enhance its water dissolution rate (glucose presence). These new “green” carriers can potentially prolong the beneficial effects of Fer and Ger or induce neuroprotection as nasal formulations.

Ursodeoxycholic acid (UDCA) and acetoacetate are natural compounds present in the human intestine and blood, respectively. A number of studies highlighted that besides their well-known primary biological roles, both compounds possess the ability to influence a variety of cellular processes involved in the etiology of various diseases. These reasons suggested the potential of acetoacetate–UDCA hybrids as possible therapeutic agents and prompted us to develop a synthetic strategy to selectively derivatize the hydroxyl groups of the bile acid with acetoacetyl moieties. 3α-acetoacetoxy UDCA was obtained (60% isolated yield) via the regioselective transesterification of methyl acetoacetate with UDCA promoted by the Candida antarctica lipase B (CAL-B). 3α,7β-bis-acetoacetoxy UDCA was obtained instead by thermal condensation of methyl acetoacetate and UDCA (80% isolated yield). This bis-adduct was finally converted to the 7β-acetoacetoxy UDCA (82% isolated yield) via CAL-B catalyzed regioselective alcoholysis of the ester group on the 3α position. In order to demonstrate the value of the above new hybrids as UDCA-based scaffolds, 3α-acetoacetoxy UDCA was subjected to multicomponent Biginelli reaction with benzaldehyde and urea to obtain the corresponding 4-phenyl-3,4-dihydropyrimidin-2-(1H)-one derivative in 65% isolated yield.