Molecular Hydrogen Research Articles

3He adsorbed on molecular hydrogen surfaces.

Using a diffusion Monte Carlo technique, we calculated the phase diagram of 3He adsorbed on a first solid layer of a molecular hydrogen isotope (H2, HD, and D2) on top of graphite. The results are qualitatively similar in all cases: a two-dimensional gas spanning from the infinite dilution limit to a second-layer helium density of 0.048 ± 0.004 Å-2. That gas is in equilibrium with a 7/12 commensurate structure, more stable than any incommensurate triangular solid of similar density. These findings are in reasonably good agreement with available experimental data.

Constraining dark matter-proton scattering from molecular cloud ionization

Optically dense clouds in the interstellar medium composed predominantly of molecular hydrogen, known as molecular clouds, are sensitive to energy injection in the form of photon absorption, cosmic-ray scattering, and dark matter (DM) scattering. The ionization rates in dense molecular clouds are heavily constrained by observations of abundances of various molecular tracers. Recent studies have set constraints on the DM-electron scattering cross section using measurements of ionization rates in dense molecular clouds. Here we calculate the analogous bounds on the DM-proton cross section using the molecular Migdal effect, recently adapted from the neutron scattering literature to the DM context. These bounds may be the strongest limits on a strongly coupled DM subfraction, and represent the first application of the Migdal effect to astrophysical systems. Published by the American Physical Society 2024

Effects of E-Cigarettes on the Lung and Systemic Metabolome in People with HIV

The popularity of e-cigarettes (vaping) has soared, creating a public health crisis among teens and young adults. Chronic vaping can induce gut inflammation and reduce intestinal barrier function through the production of the proinflammatory molecule hydrogen sulfide (H2S). This is particularly concerning for people with HIV (PWH) as they already face impaired immune function and are at a higher risk for metabolic dysregulation, diabetes, and chronic liver disease. Furthermore, PWH experience unhealthy behaviors, making it crucial to understand the systemic metabolic dysregulation and pathophysiological mechanisms associated with vaping in this population. Here, we employed liquid chromatography–mass spectrometry (LC-MS)-based metabolomics to investigate the upper respiratory, circulation, and gut metabolic profiles of PWH who vape (n = 7) and smoke combustible tobacco/marijuana (n = 6) compared to control participants who did not vape or smoke (n = 10). This hypothesis-generating exploratory study revealed systemic alterations in purine, neurotransmitter, and vitamin B metabolisms and tissue-specific changes in inflammatory pathways and cryptic sulfur cycling associated with vaping and combustible tobacco/marijuana smoking in PWH. In addition, this study provides the first link between microbial-derived metabolite 2,3-dihydroxypropane-1-sulfonate (DHPS) and vaping/smoking (tobacco and marijuana)-induced metabolic dyshomeostasis in the gut. These findings highlight the importance of identifying the full biological and clinical significance of the physiological changes and risks associated with vaping.

Full quantum eigensolvers based on variance

The advancement of quantum computation paves a novel way for addressing the issue of eigenstates. In this paper, two full quantum eigenvalue solvers based on quantum gradient descent are put forward. Compared to the existing classical-quantum hybrid approaches such as the variance-variational quantum eigenvalue solver, our method enables faster convergent computations on quantum computers without the participation of classical algorithms. As any eigenstate of a Hamiltonian has zero variance, this paper takes the variance as the objective function and utilizes the quantum gradient descent method to optimize it, demonstrating the optimization of the objective function on the quantum simulator. With the swift progress of quantum computing hardware, the two variance full quantum eigensolvers proposed in this paper are anticipated to be implemented on quantum computers, thereby offering an efficient and potent calculation approach for solving eigenstate problems. Employing this algorithm, we showcase 2 qubits of deuterium and hydrogen molecule. Furthermore, we numerically investigate the energy and variance of the Ising model in larger systems, including 3, 4, 5, 6, and 10 qubits.

Geometric Tuning of Coordinatively Unsaturated Copper(I) Sites in Metal-Organic Frameworks for Ambient-Temperature Hydrogen Storage.

Porous solids can accommodate and release molecular hydrogen readily, making them attractive for minimizing the energy requirements for hydrogen storage relative to physical storage systems. However, H2 adsorption enthalpies in such materials are generally weak (-3 to -7 kJ/mol), lowering capacities at ambient temperature. Metal-organic frameworks with well-defined structures and synthetic modularity could allow for tuning adsorbent-H2 interactions for ambient-temperature storage. Recently, Cu2.2Zn2.8Cl1.8(btdd)3 (H2btdd = bis(1H-1,2,3-triazolo-[4,5-b],[4',5'-i])dibenzo[1,4]dioxin; CuI-MFU-4l) was reported to show a large H2 adsorption enthalpy of -32 kJ/mol owing to π-backbonding from CuI to H2, exceeding the optimal binding strength for ambient-temperature storage (-15 to -25 kJ/mol). Toward realizing optimal H2 binding, we sought to modulate the π-backbonding interactions by tuning the pyramidal geometry of the trigonal CuI sites. A series of isostructural frameworks, Cu2.7M2.3X1.3(btdd)3 (M = Mn, Cd; X = Cl, I; CuIM-MFU-4l), was synthesized through postsynthetic modification of the corresponding materials M5X4(btdd)3 (M = Mn, Cd; X = CH3CO2, I). This strategy adjusts the H2 adsorption enthalpy at the CuI sites according to the ionic radius of the central metal ion of the pentanuclear cluster node, leading to -33 kJ/mol for M = ZnII (0.74 Å), -27 kJ/mol for M = MnII (0.83 Å), and -23 kJ/mol for M = CdII (0.95 Å). Thus, CuICd-MFU-4l provides a second, more stable example of optimal H2 binding energy for ambient-temperature storage among reported metal-organic frameworks. Structural, computational, and spectroscopic studies indicate that a larger central metal planarizes trigonal CuI sites, weakening the π-backbonding to H2.

Unveiling spectroscopic behaviour and molecular features (DFT studies) of Exemestane-maleic acid cocrystal as model multicomponent system

The present study aimed to investigate the Exemestane - maleic acid (Ex-Mal) cocrystal using Fourier-transform Raman (FT-Raman), Fourier-transform Infrared (FT-IR), Powder X-ray Diffraction (PXRD) and Differential Scanning Calorimeter (DSC) experimental techniques and quantum chemical calculations. Exemestane (Ex) is an irreversible aromatase inhibitor, clinically used for the treatment of postmenopausal women having primary or advanced breast cancer. Maleic acid (Mal), a dicarboxylic acid is found in many vegetables and fruits and is used as a food additive and sweetener. Solution crystallization of Ex and Mal was done in the generation of Ex-Mal cocrystal (1:1). PXRD and DSC analysis confirmed the successful generation of Ex-Mal Cocrystal. Intermolecular hydrogen bonding (O4-H12···O13 & C8-O3···H36) also suggested the formation of a multi-component system, Ex-Mal cocrystal (1:1), as the respective modes shifted in the vibrational (Raman & IR) spectra of cocrystal than the Ex. Further, the quantum theory of atoms in molecules (QTAIM) has been done to analyze the strength and nature of inter-/intra molecular hydrogen bonding. Natural bond orbital (NBO) analysis was performed to check the stabilization energy of the system. The frontier molecular orbital (FMO) analysis predicted that Ex-Mal cocrystal is more reactive and less stable than Ex. Molecular electrostatic potential (MEP) surface showed that electrophilic (C16-H36)/(O4-H12), and nucleophilic (C8=O3)/(C17=O13) reactive groups in Ex/Mal and Mal/Ex, respectively, neutralized after the formation of Ex-Mal cocrystal, confirming the presence of hydrogen bonding interactions (C16-H36∙∙∙O3=C8) and (C17=O13∙∙∙H12-O4). Molar Refractivity (MR) was calculated to check the drug-likeness behaviours of Ex-mal cocrystal. This study provided a comparison of experimental and theoretical results to understand the hydrogen bonding interactions and structural activity of the system.

Light-Induced Electron Transfer in a [NiFe] Hydrogenase Opens a Photochemical Shortcut for Catalytic Dihydrogen Cleavage.

[NiFe] hydrogenases catalyze the reversible cleavage of molecular hydrogen into protons and electrons. Here, we have studied the impact of temperature and illumination on an oxygen-tolerant and thermostable [NiFe] hydrogenase by IR and EPR spectroscopy. Equilibrium mixtures of two catalytic [NiFe] states, Nia-C and Nia-SR'', were found to drastically change with temperature, indicating a thermal exchange of electrons between the [NiFe] active site and iron-sulfur clusters of the enzyme. In addition, IR and EPR experiments performed under illumination revealed an unusual photochemical response of the enzyme. Nia-SR'', a fully reduced hydride intermediate of the catalytic cycle, was found to be reversibly photoconverted into another catalytic state, Nia-L. In contrast to the well-known photolysis of the more oxidized hydride intermediate Nia-C, photoconversion of Nia-SR'' into Nia-L is an active-site redox reaction that involves light-driven electron transfer towards the enzyme's iron-sulfur clusters. Omitting the ground-state intermediate Nia-C, this direct interconversion of these two states represents a potential photochemical shortcut of the catalytic cycle that integrates multiple redox sites of the enzyme. In total, our findings reveal the non-local redistribution of electrons via thermal and photochemical reaction channels and the potential of accelerating or controlling [NiFe] hydrogenases by light.

Molecular Hydrogen for Outpatients with COVID-19 (Hydro-COVID): A Phase 3 Randomised, Triple-Blinded, Pragmatic, Placebo-Controlled, Multicentre Trial

Background. Due to its antioxidant, anti-inflammatory, anti-apoptosis, and anti-fatigue properties, molecular hydrogen (H2) is potentially a novel therapeutic nutrient for patients with coronavirus acute disease 2019 (COVID-19). We determined the efficacy and safety profile of hydrogen-rich water (HRW) to reduce the risk of COVID-19 progression. Methods: We also conducted a phase 3, triple-blind, randomised, placebo-controlled trial to evaluate treatment with HRW initiated within 5 days after the onset of signs or symptoms in primary care patients with mild-to-moderate, laboratory-confirmed COVID-19. Participants were randomised to receive HRW or placebo twice daily for 21 days. The incidence of clinical worsening and adverse events were the primary endpoints. Results: A total of 675 participants were followed up to day 30. HRW was not superior to placebo in preventing clinical worsening at day 14: in H2 group, 46.1% in the H2 group, 43.5% in the placebo group, hazard ratio 1.09, 90% confidence interval [0.90–1.31]. One death was reported at day 30 in the H2 group and two in the placebo group at day 30. Adverse events were reported in 91 (27%) and 89 (26.2%) participants, respectively. Conclusions: HRW taken twice daily from the onset of COVID-19 symptoms for 21 days did not reduce clinical worsening.

Fe II] 1.644 μm imaging survey of planetary nebulae with low-ionisation structures

Low-ionisation structures (LISs) are commonly found in planetary nebulae (PNe), but they are still poorly understood. The recent discovery of unforeseen molecular hydrogen gas (H$_2$) has impacted what we think we know about these microstructures and PNe. To obtain an overall understanding of LISs, we carried out an 1.644 mu m imagery survey in PNe with LISs, with the aim to detect the 1.644mu m emission line, a common tracer of shocks. We present the first detection of 1.644 mu m line directly associated with the LISs in four out of five PNe. The theoretical H I 12-4 recombination line was also computed either from the Brgamma or the Hbeta line and subtracted from the observed narrow-band line fluxes. The 1.644 mu m flux ranges from 1 to 40 times $ ergs cm$^ $ s$^ $ and the intensity from 2 to 90 times 10$^ $ erg s$^ $ cm$^ $ sr$^ $. The R( 1.644 mu m/Brgamma line ratio was also computed and found to range between 0.5 and 7. In particular, the 1.644 mu m line was detected in NGC 6543 (R( along with the outer pairs of LISs in NGC 7009 (R( and the jet-like LISs in IC 4634 (R( 1), and in several LISs in NGC 6571 (2$<$R( The low R( result for NGC 6543 is attributed to the UV radiation from the central star. In contrast, the higher values in NGC 6571 and IC 4634 are indicative of shocks. The moderate R( in NGC 7009 likely indicates the contribution of both mechanisms.

Hydrogen as an innovative nootropic in health and disease.

Molecular hydrogen (H2, dihydrogen) is an antioxidant and signaling molecule with potent antioxidative, antiapoptotic, and anti-inflammatory properties. Despite the growing interest in H2 as a potential therapeutic agent, the evidence regarding its potential as a nootropic remains limited. Only a handful of studies on the human population have evaluated its effects, although there are suggestive indications of its efficacy. The present paper overviews H2's potential as a novel agent for improving cognitive functions in health and disease contexts, highlighting its mechanisms of action and areas for further investigation. Current evidence suggests that H2 improves executive function, alertness and memory in several clinical trials, from healthy young and elderly individuals to individuals with altered circadian rhythms, neurodegenerative disorders, and cancer. Further investigations are needed to confirm the potential positive effects of dihydrogen as a nootropic agent in both health and disease.

Low-energy atomic and molecular hydrogen ion interaction with low-work function electride 12CaO · 7Al2O3

To efficiently generate H− ions from positive atomic or molecular hydrogen beams injected onto a solid surface, it has been suggested to use a material with a low-work function as the target material. However, it is not clear under what conditions the most efficient H− production is realized for incident beam parameters or reflection angles. Therefore, we studied the interaction between low-energy atomic and molecular hydrogen beams (less than 1 keV/nucleon) with a low-work function electride 12CaO⋅7Al2O3 (C12A7). The production ratio of H− to H+ ions from the C12A7 electride was much higher than Mo targets with higher work functions, especially at smaller incident and smaller reflection angles. The H− to H+ production ratio slightly increased as the incident energies were decreased, but there was no significant difference between the electride and Mo targets. These results indicate that smaller incident angles and lower beam energies of the incident hydrogen beam are favorable for the enhancement of the production ratio of H− to H+ ions in C12A7. The higher production ratio appeared at the vertical beam energies less than on the order of 100 eV, where quantum mechanical processes may become important.

Nonadiabatic Molecular Dynamics with Fermionic Subspace-Expansion Algorithms on Quantum Computers.

We introduce a novel computational framework for excited-state molecular quantum dynamics simulations driven by quantum-computing-based electronic-structure calculations. This framework leverages the fewest-switches surface-hopping method for simulating the nuclear dynamics and calculates the required excited-state transition properties with different flavors of the quantum subspace expansion and quantum equation-of-motion algorithms. We apply our method to simulate the collision reaction between a hydrogen atom and a hydrogen molecule. For this system, we critically compare the accuracy and efficiency of different quantum subspace expansion and equation-of-motion algorithms and show that only methods that can capture both weak and strong electron correlation effects can properly describe the nonadiabatic effects that tune the reactive event.

Synthesis of new pyrazine-pyrazole-thiazolidin-4-one and pyrazine-triazole-thiazolidin-4-one conjugates, molecular modelling and docking as antimicrobial agents

The ever-increasing incidence of microbial resistance provide a significant peril to the scientific community. Thus, the need for the discovery and development of new antimicrobial agents is becoming critical. An effective approach to address this challenging problem is to generate hybrid molecules by combining two or more pharmacophores covalently linked to a single-molecule platform. Antimicrobial hybrids have been proposed as promising solution to overcome drug resistance and/or presumably having a broader spectrum of activity. This guided us to synthesize a new series of eight final target pyrazine-pyrazole-thiazolidin-4-one and pyrazine-triazole-thiazolidin-4-one hybrids 7, 8a-c, 12, and 13a-c and investigate their biological activities. Characterization of the designed hybrids were performed using IR, 1H NMR, 13C NMR, and mass analyses. The DFT/B3LYP approach revealed that the synthesized hybrids had a non-planar configuration. The nitrobenzylidene derivatives 8c and 13c exhibited the highest polarizability and hyperpolarizability. We examined the antimicrobial activity, DNA gyrase inhibition, molecular docking, and Swiss ADME analysis of different pyrazine-pyrazole-thiazolidin-4-one and pyrazine-triazole-thiazolidin-4-one conjugates. These compounds are effective against a number of bacterial and fungal strains, suggesting possible treatments for certain infections. DNA gyrase inhibition experiments demonstrated that conjugate 13b was more effective than novobiocin. A molecular docking study sheds light on the binding affinities and interactions of these conjugates with target proteins, revealing strong and specific bindings for numerous conjugates. Swiss ADME studies examine important pharmacokinetic parameters and show issues with bioavailability and membrane permeability in the mouth because of variations in molecular weight, lipophilicity, and hydrogen bond interactions. Swiss ADME studies have studied the drug-like qualities of these conjugates, revealing their potential in antibacterial applications.

Pd-substitution impact in nickel–cobalt spinel oxide grown on Ni foam as very effectual electrocatalyst for green hydrogen production supported by DFT study

The hydrothermal preparation of catalytic NiPdxCo2-xO4 (x ≦ 0.08) nano-electrocatalysts on Ni foam (NF) was successfully accomplished. The morphology and chemical composition of the catalysts are confirmed by advanced analytical techniques XRD, SEM, EDX, TEM, HR-TEM, and XPS. The NiPdxCo2-xO4 (x = 0.06) NF nano-electrocatalyst demonstrated remarkable performance in the HER, with an overpotential of 191.6 mV, a Tafel slope of 84.7 mV/dec, and extraordinary stability over 24 h using chronopotentiometry methods. The surface and electrochemical analyses demonstrated that the sample, doping with a 6.0% Pd2+ concentration, had appreciably enhanced performance in the HER. The improvement may be attributed to a much larger electrochemical surface area and fast charge transfer kinetics at the semiconductor and electrolyte interface. The influence of Pd dopants on the HER performance of CNs is studied with the help of density functional theory. It elucidates the way in which hydrogen and water molecules bind to the surface of PCN slabs. The theoretical results suggest that the incorporation of Pd dopants enhances the electrocatalytic process and boosts the HER activity as the concentration of Pd increases. The density of state spectra reveals their effect on spin-dependent electronic structure characteristics. Our findings point to a practical path for creating distinctive electrocatalysts that will serve as better electrodes for a variety of forthcoming hydrogen fuel cell applications.

Recent Advances in Heterogeneously Catalyzed Acceptorless Dehydrogenation of Alcohols to Carbonyl Derivatives and N-heterocyclic Compounds

Oxidation of alcohols in an oxidant-free condition, commonly known as the acceptorless dehydrogenation (AD) reaction, has recently emerged as one of the widely used processes in synthetic organic chemistry. Alcohol acts as an excellent chemical precursor that produces a variety of dehydrogenated value-added products such as carbonyls, acids, acetals, and several coupling products, followed by the concomitant evolution of molecular hydrogen gas. AD reaction of alcohol, therefore, can be considered as a vital reaction for the hydrogen economy using alcohols as a liquid hydrogen carrier. Over the past decade, the growing importance of AD reactions has set the way for the continuous development of various homogeneous and heterogeneous catalytic systems. With the advantage of reusability and recyclability, heterogeneous catalysts have now become more promising and significant in the catalytic domain. This review aims to make an overview of the transition metal-based heterogeneous catalytic system of acceptorless alcohol dehydrogenation reaction reported till December, 2023.

S-Equol Ameliorates Menopausal Osteoarthritis in Rats through Reducing Oxidative Stress and Cartilage Degradation.

Osteoarthritis (OA) is a chronic degenerative disease leading to articular cartilage destruction. Menopausal and postmenopausal women are susceptible to both OA and osteoporosis. S-equol, a soy isoflavone-derived molecule, is known to reduce osteoporosis in estrogen-deficient mice, but its role in OA remains unknown. This study aimed to explore the effect of S-equol on different degrees of menopausal OA in female Sprague-Dawley (SD) rats induced by estrogen deficiency caused by bilateral ovariectomy (OVX) combined with intra-articular injection of mono-iodoacetate (MIA). Knee joint histopathological change; serum biomarkers of bone turnover, including N-terminal propeptide of type I procollagen (PINP), C-terminal telopeptide of type I collagen (CTX-I) and N-terminal telopeptide of type I collagen (NTX-I); the cartilage degradation biomarkers hyaluronic acid (HA) and N-terminal propeptide of type II procollagen (PIINP); and the matrix-degrading enzymes matrix metalloproteinases (MMP)-1, MMP-3 and MMP-13, as well as the oxidative stress-inducing molecules nitric oxide (NO) and hydrogen peroxide (H2O2), were assessed for evaluation of OA progression after S-equol supplementation for 8 weeks. The results showed that OVX without or with MIA injection induced various severity levels of menopausal OA by increasing pathological damage, oxidative stress, and cartilage matrix degradation to various degrees. Moreover, S-equol supplementation could significantly reduce these increased biomarkers in different severity levels of OA. This indicates that S-equol can lessen menopausal OA progression by reducing oxidative stress and the matrix-degrading enzymes involved in cartilage degradation.

Effect of Support Functionalization on Catalytic Direct Hydrogenation and Catalytic Transfer Hydrogenation of Muconic Acid to Adipic Acid

The liquid-phase hydrogenation of muconic acid (MA) to produce bio-adipic acid (AdA) is a prominent environmentally friendly chemical process, that can be achieved through two distinct methodologies: catalytic direct hydrogenation using molecular hydrogen (H2), or catalytic transfer hydrogenation utilizing a hydrogen donor. In this study, both approaches were explored, with formic acid (FA) selected as the hydrogen source for the latter method. Palladium-based catalysts were chosen for these processes. Metal’s nanoparticles (NPs) were supported on high-temperature heat-treated carbon nanofibers (HHT-CNFs) due to their known ability to enhance the stability of this metal catalyst. To assess the impact of support functionalization on catalyst stability, the HHT-CNFs were further functionalized with phosphorus and oxygen to obtain HHT-P and HHT-O, respectively. In the hydrogenation reaction, catalysts supported on functionalized supports exhibited higher catalytic activity and stability compared to Pd/HHT, reaching an AdA yield of about 80% in less than 2 h in batch reactor. The hydrogen-transfer process also yielded promising results, particularly with the 1%Pd/HHT-P catalyst. This work highlights the efficacy of support functionalization in improving catalyst performance, particularly when formic acid is used as a safer and more cost-effective hydrogen donor in the hydrogen-transfer process.

The Protective Role of Molecular Hydrogen in Ischemia/Reperfusion Injury.

Ischemia/reperfusion injury (IRI) represents a significant contributor to morbidity and mortality associated with various clinical conditions, including acute coronary syndrome, stroke, and organ transplantation. During ischemia, a profound hypoxic insult develops, resulting in cellular dysfunction and tissue damage. Paradoxically, reperfusion can exacerbate this injury through the generation of reactive oxygen species and the induction of inflammatory cascades. The extensive clinical sequelae of IRI necessitate the development of therapeutic strategies to mitigate its deleterious effects. This has become a cornerstone of ongoing research efforts in both basic and translational science. This review examines the use of molecular hydrogen for IRI in different organs and explores the underlying mechanisms of its action. Molecular hydrogen is a selective antioxidant with anti-inflammatory, cytoprotective, and signal-modulatory properties. It has been shown to be effective at mitigating IRI in different models, including heart failure, cerebral stroke, transplantation, and surgical interventions. Hydrogen reduces IRI via different mechanisms, like the suppression of oxidative stress and inflammation, the enhancement of ATP production, decreasing calcium overload, regulating cell death, etc. Further research is still needed to integrate the use of molecular hydrogen into clinical practice.

Investigation of hydrogen uptake capacity for FAU, MOR, MTW, MWW

In this study, the hydrogen storage properties of various synthetic zeolites, including Zeolite Y (FAU), Mordenite (MOR), ZSM-12 (MTW), and MCM-22 (MWW) are determined at 77 K and atmospheric pressure. The structures of the zeolites are characterized by XRD, ICP-OES, FE-SEM, TGA and N2 adsorption-desorption isotherms. The results show that H-MCM-22 zeolite has the highest hydrogen storage capacity at 1.0 bar with 1.19 wt%, followed by H-MOR zeolite with 1.05 wt%, H–Y zeolite with 0.75 wt% and H-ZSM-12 zeolite with 0.60 wt%. The hydrogen adsorption data on FAU, MOR, MTW, and MWW at 77 K obey the Sips isotherm model. The experimental data show that the ultra-micropore volume of the zeolite is effective in hydrogen adsorption at low-pressure ranges. In addition, increasing the aluminum content of the zeolite increases the hydrogen adsorption capacity of the zeolite at atmospheric pressure. Therefore, zeolites with channel sizes close to the kinetic diameter of a hydrogen molecule, large cage volumes, and high aluminum content are potential candidates for energy storage applications.

Molecular Hydrogen Protects against Various Tissue Injuries from Side Effects of Anticancer Drugs by Reducing Oxidative Stress and Inflammation.

While drug therapy plays a crucial role in cancer treatment, many anticancer drugs, particularly cytotoxic and molecular-targeted drugs, cause severe side effects, which often limit the dosage of these drugs. Efforts have been made to alleviate these side effects by developing derivatives, analogues, and liposome formulations of existing anticancer drugs and by combining anticancer drugs with substances that reduce side effects. However, these approaches have not been sufficiently effective in reducing side effects. Molecular hydrogen (H2) has shown promise in this regard. It directly reduces reactive oxygen species, which have very strong oxidative capacity, and indirectly exerts antioxidant, anti-inflammatory, and anti-apoptotic effects by regulating gene expression. Its clinical application in various diseases has been expanded worldwide. Although H2 has been reported to reduce the side effects of anticancer drugs in animal studies and clinical trials, the underlying molecular mechanisms remain unclear. Our comprehensive literature review revealed that H2 protects against tissue injuries induced by cisplatin, oxaliplatin, doxorubicin, bleomycin, and gefitinib. The underlying mechanisms involve reductions in oxidative stress and inflammation. H2 itself exhibits anticancer activity. Therefore, the combination of H2 and anticancer drugs has the potential to reduce the side effects of anticancer drugs and enhance their anticancer activities. This is an exciting prospect for future cancer treatments.