Excessive production of reactive oxygen species (ROS) causes oxidative stress and is involved in the development and progression of a wide variety of diseases. Therefore, techniques for measuring oxidative stress are indispensable for analysis of the mechanisms of various diseases. The method involving ESR and the durable nitroxyl radical (ESR/spin probe method) is useful for this purpose, because the ESR signal intensity of the spin probe changes on reacting with ROS and other unstable radicals. In this review, the author’s research applying the ESR/spin probe method to clarify disease mechanisms in vivo and in vitro is presented. The ESR signal of the probe injected into animals may decay through a few mechanisms besides reaction with ROS; thus, interpretation of the results is complicated. As the first approach to solving this problem, a probe resistant to enzymatic reduction by introducing a bulky group adjacent to the nitroxy group was created. The second approach was the use of a hydroxylamine probe which dominantly oxidized to nitroxyl radicals by reacting with superoxide anion radicals and oxidants. Using acyl-protected hydroxyl amine, it was demonstrated that sepsis model mice are under oxidative stress due to ROS production by activated phagocytes. On the other hand, it was shown in vitro that the UV-induced radical reaction of ketoprofen also occurs in lipid membranes, and that the reaction is related to ROS generation and membrane disruption. We believe that use of the ESR/spin probe method with ingenuity will clarify the mechanisms of various diseases.

Quantitative NMR (qNMR) is employed to determine the purity of reagents used as standards for HPLC quantification in the Japanese Pharmacopoeia (JP) and has become recognized as a new absolute quantification method in various fields such as pharmaceuticals, foods, and food additives. This report outlines how and why qNMR has been adopted as an official method in the JP and introduces its progression from JP16 to JP18. The results of a survey of companies in the Japan Pharmaceutical Manufacturers’ Association regarding how and when to use qNMR from development to manufacturing stages are introduced. The issues involved in the expansion of the use of qNMR in the field of chemical pharmaceuticals in 2017 are discussed and how these were resolved.

In Japan, quantitative NMR (qNMR) has already been recognized as a standard method for determining the purity of quantitative samples not only in the Japanese Pharmacopoeia and the Japanese Standards and Specifications for Food Additives but also in the Japanese Industrial Standard (JIS K 0138: 2018). However, since there was no consensus on the establishment of a standard method, the international standardization of qNMR was initiated based on a proposal from Japan. After three years of discussion among experts, International Organization for Standardization/Technical Committee on Food (ISO/TC34) published ISO 24583: 2022 “Quantitative nuclear magnetic resonance spectroscopy—Purity determination of organic compounds used for foods and food products—General requirements for ¹H-NMR internal standard method.” Publication of this standard has resulted in an internationally agreed upon set of requirements for purity determination using qNMR. New technologies emerge from the cycle of basic research, practical use, and standardization, and qNMR is no exception. A novel chromatographic quantification method based on relative molar sensitivity (RMS) is now being put into practical use. The RMS of an analyte with respect to a different reference substance can be determined by using qNMR to accurately determine the molar ratio and then introducing it into the chromatographic system. This method uses the RMS determined by combining qNMR and chromatography instead of the analyte’s reference material to determine its content in sample. This method has been adopted in the Japanese Pharmacopoeia, and the development of a general rule in the Japanese Agricultural Standards (JAS) is also under consideration.

Quantitative NMR (qNMR), particularly ¹H-qNMR, is useful for determining the absolute purity of organic molecules. However, identifying the target signal(s) for quantification is difficult, because of the overlap and complexity of organic molecules. Therefore, we focused on the ³¹P nucleus, owing to the simplicity of its signals, and investigated the ³¹P-qNMR absolute determination method by using organophosphorus drugs, water-soluble cyclophosphamide hydrate (CP), and water-insoluble sofosbuvir (SOF). The optimized and reproducible ³¹P-qNMR conditions, such as qNMR sample preparation [i.e., selecting suitable deuterated solvents and a reference standard (RS) for ³¹P-qNMR], hygroscopicity and solution stability of the analyte and RS, and qNMR measurements—such as acquisition time, relaxation delay time, and spectral width—were examined. The CP purities determined using ³¹P-qNMR agreed well with those for the established ¹H-qNMR method in D₂O. In contrast, the SOF purity determined using ³¹P-qNMR was 1.6% higher than that for ¹H-qNMR in the protic solvent CD₃OD. Therefore, using a protic solvent, such as CD₃OD, was not suitable for ³¹P-qNMR; the deuterium exchange with the RS for ³¹P-qNMR (i.e., phosphonoacetic acid) resulted in a small integrated intensity. Consequently, the aprotic solvent DMSO-d₆ was employed to determine the SOF purity. The data revealed that the SOF purities determined using ³¹P-qNMR agreed well with the established ¹H-qNMR values, indicating that the absolute quantification of SOF using both ³¹P-qNMR and ¹H-qNMR is possible in DMSO-d₆. Thus, we established an optimized and reproducible ³¹P-qNMR method in validation study across multiple laboratories.

Quantitative NMR (qNMR) has been adopted by documentary standards, including the Japanese Pharmacopoeia (JP), United States Pharmacopoeia (USP), and International Organization for Standardization (ISO), owing to its reliability and efficiency. Note that qNMR can be used for quantifying target components using the signal integration ratio of an analyte to a reference. In qNMR, a modern NMR instrument with high resolution and sensitivity is used to record reliable spectra. This instrument can detect small signals from impurities in a solvent, which may result in inaccurate signal integration in the spectrum. In this study, we investigated the influence of solvent quality on qNMR accuracy focusing on organic impurities, water content, and deuteration ratio. If signals from organic impurities and signals from the analyte overlap, the duplication of signal integration will directly affect the qNMR analytical result. To examine overlapping, we performed blank solvent tests. Additionally, a high water content and low deuteration ratio affect the detection sensitivity, thus reducing the signal-to-noise (S/N) ratio of the target. Thus, these factors must be considered to obtain accurate qNMR results.

Crude drugs and Kampo formulations derived from natural materials such as plants, animals, and minerals are multicomponent medicines that contain numerous chemical constituents. Quantitative determination of characteristic constituents for quality control is crucial for the standardization and quality assurance of natural medicines. Quantitative assays to determine marker compound contents are commonly performed using HPLC systems. In order to achieve accurate quantitative determination, it is essential to use standard materials with well-defined purities corresponding to the target analytes. Many marker compounds used as standard materials must be purified and isolated from natural products while ensuring sufficient purity. However, the composition of impurities in the standard material differs among different batches due to differences in the raw materials and their extraction, separation, and purification processes. Therefore, controlling the purity of standard materials derived from natural products is more complex than that of synthetic substances. Quantitative NMR (qNMR), which has become widely used as an absolute quantitative method for low-molecule organic compounds, makes it possible to solve these issues. qNMR has been introduced into the crude drug section of the Japanese Pharmacopoeia (JP) for evaluating the purity of standard materials used for the assay. This review outlines an example of quantitative determination using relative molar sensitivity (RMS) based on qNMR adopted in the JP and introduces the latest efforts toward the application of qNMR to standard materials used for crude drugs in this context.

NMR is well known as one of the most important methods for elucidating the structure of organic compounds. Furthermore, it has recently been recognized as a powerful tool for quantitative analysis. The quantitative NMR (qNMR) has become an official analytical method described in detail in the Japanese Pharmacopoeia. And today, it is widely applied in drug development. The qNMR method offers many new advantages over traditional and conventional quantitative analysis methods. For example, this method requires only a few milligrams of the analyte and allows absolute quantitation of the analyte without using a qualified reference standard as a control sample. Then, it can be easily applied to most chemicals without expending significant time and resources on method development. In addition, residual solvent can be determined using qNMR methods. The peak area of an NMR spectrum is directly proportional to the number of protons contributing to the resonance. Based on this principle, the residual solvent can be determined by counting the signal corresponding to the residual solvent in the sample solution. We have applied qNMR as an alternative to GC. Thus, qNMR is an innovative and promising analytical technique that is expected to make significant progress in the future. Recently, the analytical research and quality control departments have been working together to expand this technology to a wide range of areas in the pharmaceutical industry.

Various organisms with different lifespans such as yeast, nematodes, fruit fly, mice, and rats are used for basic research on mechanisms of aging and anti-aging. These organisms are often genetically engineered and used to elucidate the contribution of certain genes to aging. For example, genetic recombination techniques revealed that the lifespan of superoxide dismutase (SOD) transgenic flies extended up to approximately 30%. This result suggests that increasing antioxidant capacity extends lifespan possibly by reducing oxidative damage. However, a similar experiment conducted in mice did not shown any positive effect of prolonging lifespan. Likewise, differences between animal species have also been observed in administration experiments of antioxidants such as resveratrol and curcumin. Further complicating the understanding of aging processes are differences among substrain and sex differences. For instance, the activity of catalase (CAT) in rat liver decreases with age in males, but increases in females. In this review, we describe the diversity of age-related changes, focusing on species, strain/substrain, and sex differences and introduce some efforts to address these issues in aging research.

Cysts are abnormal fluid-filled sacs found in various human organs, including the liver. Liver cysts can be associated with known causes such as parasite infections and gene mutations, or simply aging. Among these causes, simple liver cysts are often found in elderly people. While they are generally benign, they may occasionally grow but rarely shrink with age, indicating their clear association with aging. However, the mechanism behind the formation of simple liver cysts has not been thoroughly investigated. Recently, we have generated transgenic mice that specifically overexpress fibroblast growth factor (FGF)18 in hepatocytes. These mice exhibit severe liver fibrosis without inflammation and spontaneously develop liver cysts that grow with age. Our findings suggest that simple liver cysts can be induced by fibrosis accompanied by sterile inflammation or injury, whereas fibrosis accompanied by severe inflammation or injury may lead to cirrhosis. We also discuss the detrimental effects of disease- and aging-associated fibrosis in various organs, such as the heart, lungs, and kidneys. Additionally, we provide a brief summary of the two currently approved anti-fibrotic drugs for idiopathic pulmonary fibrosis, nintedanib and pirfenidone, as well as their possibility of future expansion of application toward other fibrotic diseases.

The moderate restriction of dietary energy intake (dietary restriction: DR) extends the lifespan and health span of various laboratory animals, suggesting that it delays the aging process inherent in many animal species. Attenuated growth hormone and insulin-like growth factor-1 (IGF-1) signaling caused by mutations also increases the lifespan of mice, even those allowed to feed freely. In nematodes, the Daf16, mammalian Forkhead box O (FoxO) transcription factor, was shown to be required for lifespan extension in response to reduced IGF-1 signaling. Because DR also decreases the plasma concentration of IGF-1 in mammals, the IGF-1–FoxO axis may play a central role in the lifespan extension effect of DR and, thus, retardation of aging. Studies using knockout mice under DR conditions revealed the importance of FoxO1 and nuclear factor erythroid-derived 2-like 2 (Nrf2) in tumor suppression, and FoxO3 in lifespan extension. Human genomic studies also identified a strong association between a FOXO3 single nucleotide polymorphism and longevity. The aging mechanism is the most important risk factor for disease and frailty in aging humans. Therefore, further research on the application of DR to humans, the development of compounds and drugs that mimic the effects of DR, and mechanisms underlying FOXO3 polymorphisms for longevity is highly relevant to extending the human health span.

Long-term caloric restriction (CR) is an effective intervention that improves whole-body metabolism, suppresses age-related pathophysiology, and extends lifespan. Although the beneficial effects of caloric restriction mediated by growth hormone/insulin-like growth factor-1 (GH/IGF-1) have been extensively studied, the mechanisms independent of GH/IGF-1 remain largely unknown. In this review, we focus on these GH/IGF-1-independent mechanisms, with a particular emphasis on the role of sterol regulatory element-binding protein 1c (SREBP-1c). CR increases the expression of SREBP-1c through the suppression of leptin signaling and enhances downstream factors involved in fatty acid synthesis in white adipose tissue (WAT). SREBP-1c also directly and indirectly increases the expression of peroxisome proliferator-activated receptor gamma coactivator-1 alpha, a master regulator of mitochondrial biogenesis, leading to an increase in the number of mitochondria. Furthermore, SREBP-1c elevates expression of mitochondrial intermediate peptidase, which contributes to improving mitochondrial quality through the processing of sirtuin 3 into its mature form. Thus, it appears that CR exerts beneficial effects by modulating mitochondrial quantity and quality in WAT in a GH/IGF-1 signal-independent manner.

In view of the current claim by many researchers that biological aging is a treatable disease, the possibility is discussed whether the claim is realistic, based on several proposed mechanisms of aging. The definition of biological aging is stated referring to physiological aging and pathological aging, since biological aging must be defined for the discussion of whether it can be cured. Aging in animal model is compared with that in humans in terms of common age-associated phenotypes. Major proposed mechanisms of aging are next examined including Genome Instability Theory of aging, Free Radical or Oxidative Stress Theory of Aging, Mitochondrial Theory of Aging, Error Catastrophe Theory of Aging/Translational Error Theory of Aging, Altered Protein Theory of Aging/Proteostasis Theory of Aging, and Epigenetic Theory of Aging. Finally, we discuss whether treatment of aging as a disease is realistic in comparison with possible lifespan extension by retardation of biological aging.

The neural cell death in cerebral infarction is suggested to be ferroptosis-like cell death, involving the participation of 15-lipoxygenase (15-LOx). Ferroptosis is induced by lipid radical species generated through the one-electron reduction of lipid hydroperoxides, and it has been shown to propagate intracellularly and intercellularly. At lower oxygen concentration, it appeared that both regiospecificity and stereospecificity of conjugated diene moiety in lipoxygenase-catalysed lipid hydroperoxidation are drastically lost. As a result, in the reaction with linoleic acid, the linoleate 9-peroxyl radical-ferrous lipoxygenase complex dissolves into the linoleate 9-peroxyl radical and ferrous 15-lipoxygenase. Subsequently, the ferrous 15-lipoxygenase then undergoes one-electron reduction of 13-hydroperoxy octadecadienoic acid, generating an alkoxyl radical (pseudoperoxidase reaction). A part of the produced lipid alkoxyl radicals undergoes cleavage of C–C bonds, liberating small molecular hydrocarbon radicals. Particularly, in ω-3 polyunsaturated fatty acids, which are abundant in the vascular and nervous systems, the liberation of small molecular hydrocarbon radicals was more pronounced compared to ω-6 polyunsaturated fatty acids. The involvement of these small molecular hydrocarbon radicals in the propagation of membrane lipid damage is suggested.

The simple suspension method (SSM) involves administering tablets or capsules using a tube after disintegration and suspension in hot water without crushing or opening the capsule. Particularly, for anticancer drugs, it is an excellent method of administration that reduces the risk of exposure during dispensing. In contrast, information on SSM for individual drugs is insufficient. Anticancer drugs present a therapeutic challenge because their information is limited. We investigated whether SSM is possible with 36 anticancer drugs. Furthermore, we examined the pH of the suspension of these drugs, for which no information on SSM is available. We found that suspension was possible for 24 of the 36 drugs. Furthermore, the pH of the suspension was measured, which provided important information when considering dissolution solutions other than hot water. Little changes in the pH were observed before or after passing through the tube. The results of this study may improve medication adherence in patients with cancer experiencing dysphagia.

Drug-induced acute kidney injury (AKI) is a serious adverse drug reaction, which results in a significant decline in renal function and is known to progress to chronic kidney disease (CKD). Therefore, appropriate drug therapy is important to avoid the risk of drug-induced AKI and CKD, which are serious concerns in clinical practice. In this study, using the medical information database of Hamamatsu University Hospital, we investigated the risk factors that accelerate the onset of drug-induced AKI or its progression to CKD in patients who received aminoglycoside antibiotics (AGs) or glycopeptide antibiotics (GPs), which are strongly associated with drug-induced AKI and CKD. We performed logistic regression analysis using patients’ background, laboratory test results, and concomitant drug use, among other such factors as explanatory variables and drug-induced AKI or CKD onset as objective variables to explore the risk factors for drug-induced AKI and CKD. Our results showed that co-administration of amphotericin B, piperacillin-tazobactam and other AGs and GPs, increased serum creatinine (Scr) and chloride concentrations, serum lactate dehydrogenase activity, and decreased serum albumin concentration were risk factors for drug-induced AKI onset. Moreover, a reduced blood urea nitrogen : Scr ratio at drug-induced AKI onset served as a risk factor for CKD. These results suggest that careful monitoring of the aforementioned factors is important to ensure appropriate usage of these drugs in patients treated with AGs and GPs.

In Japan, the use of frame retardants [tris(2,3-dibromopropyl)phosphate: TDBPP and bis(2,3-dibromopropyl)phosphate: BDBPP] in several household textile products is banned under the “Act on the Control of Household Products Containing Harmful Substances.” As the official analytical methods for testing these substances have not been revised for over 42 years, several issues such as the using of harmful reagents, have been pointed out. Therefore, we developed a new method to revise the official method in our previous study. In this study, the validity of the developed test method is evaluated at six laboratories using two types of textile samples spiked with TDBPP and BDBPP at three concentrations (4, 8, and 20 µg/g). TDBPP and BDBPP are extracted under reflux using methanol containing hydrochloric acid. TDBPP is analyzed using GC-MS, and BDBPP is also analyzed using GC-MS after methylation with trimethylsilyl diazomethane. Although the accuracy (70–120%), repeatability (<10%), and reproducibility (<15%) of a few samples, mainly low concentration samples, are out of range, overall, the concentration level of detection limits of TDBPP and BDBPP (8 and 10 µg/g) in official analytical methods are quantifiable with sufficient precision using the proposed method. Furthermore, harmful reagents are not used in this method. Thus, the method validated in this study is effective as a revised method for the testing of TDBPP and BDBPP in household textile products.