Effects of luteolin-rich chrysanthemum flower extract on purine base absorption and blood uric acid in Japanese subjects

Background and objective: Chrysanthemum flowers are consumed as fresh condiments, herbal teas, and processed foods in Japan and Taiwan. They contain luteolin as a major polyphenol and are traditionally used for eye care. We previously demonstrated that the ingestion of Chrysanthemum flower extract (CFE) for 1 month reduced serum uric acid levels. However, the findings obtained were considered to be biased because the study was performed by a CFE manufacturer. Therefore, we herein conducted a clinical trial on CFE on a larger scale and examined its effects on purine base absorption from the intestines, which represents an effective approach for reducing serum uric acid levels. Methods: Both studies were performed as randomized, double-blind, placebo-controlled trials and CFE (100 mg) containing 1 mg of luteolin was used as the active sample. We enrolled 44 healthy Japanese men and women with 6.0 to 7.9 mg/dL serum uric acid. All subjects were randomly allocated to an active group (n=22) or placebo group (n=22) using a computerized random number generator. In the purine base absorption study, CFE was ingested with a purine base-rich diet and serum uric acid levels were measured chronologically. In the 12-week consecutive ingestion study, CFE or placebo was administered between January and April 2021. Serum uric acid levels after 12 weeks were assessed as the primary outcome, and uric acid were measured before and after 4 weeks of the intervention as secondary outcomes. Blood, urine and body parameters were examined to evaluate the safety of CFE. Results: Thirty-nine subjects completed the trial, and the per protocol set comprised 18 and 21 subjects in the active and placebo groups, respectively. In the single dosing study of CFE on subjects loaded by the purine base-rich diet, no significant changes were observed between the CFE and placebo groups. On the other hand, in the 12-week ingestion study, serum uric acid levels were significantly lower in the CFE group than in the placebo group. Laboratory tests revealed no abnormalities to suggest any side effects of CFE.Conclusions: CFE (100 mg/day) containing 1 mg of luteolin reduced serum uric acid levels. CFE may be beneficial for improving hyperurichemia. Trial Registration: UMIN-CTR: UMIN000042327Foundation: The present study was funded by Oryza Oil & Fat Chemical Co., Ltd. Keywords: Chrysanthemum, luteolin, uric acid, purine base

Thienopyrimidine: A Promising Scaffold to Access Anti-Infective Agents

Thienopyrimidines are widely represented in the literature, mainly due to their structural relationship with purine base such as adenine and guanine. This current review presents three isomers—thieno[2,3-d]pyrimidines, thieno[3,2-d]pyrimidines and thieno[3,4-d]pyrimidines—and their anti-infective properties. Broad-spectrum thienopyrimidines with biological properties such as antibacterial, antifungal, antiparasitic and antiviral inspired us to analyze and compile their structure–activity relationship (SAR) and classify their synthetic pathways. This review explains the main access route to synthesize thienopyrimidines from thiophene derivatives or from pyrimidine analogs. In addition, SAR study and promising anti-infective activity of these scaffolds are summarized in figures and explanatory diagrams. Ligand–receptor interactions were modeled when the biological target was identified and the crystal structure was solved.

Insight into the mechanism of H+-coupled nucleobase transport

Members of the nucleobase/ascorbic acid transporter (NAT) gene family are found in all kingdoms of life. In mammals, the concentrative uptake of ascorbic acid (vitamin C) by members of the NAT family is driven by the Na+ gradient, while the uptake of nucleobases in bacteria is powered by the H+ gradient. Here we report the structure and function PurTCp, a NAT family member from Colwellia psychrerythraea. The structure of PurTCp was determined to 2.80 Å resolution by X-ray crystallography. PurTCp forms a homodimer and each protomer has 14 transmembrane segments folded into a substrate-binding domain (core domain) and an interface domain (gate domain) A purine base is present in the structure and defines the location of the substrate binding site. Functional studies reveal that PurTCp transports purines but not pyrimidines, and that purine binding and transport is dependent on the pH. Mutation of a conserved aspartate residue close to the substrate binding site reveals the critical role of this residue in H+-dependent transport of purines. Comparison of the PurTCp structure with transporters of the same structural fold suggests that rigid-body motions of the substrate-binding domain are central for substrate translocation across the membrane.

Designing of specialized fish food products with a reduced content of nitrogen extractives

The authors consider the possibility of using low-value pelagic fish species in the diet of people with restrictions on the consumption of nitrogenous extractive substances including nucleic acids which are sources of purine base metabolism. The objects of the study were chopped mackerel fillets from boiled fish and chopped boiled fillets from raw fish, quick-frozen minced horse mackerel of industrial processing in a boiled form. The studies were carried out in accordance with the experimental plan in which the duration of the heat treatment and the temperature of the cooking medium were the variable factors. The technology of combined fish masses with the addition of functional plant components has been proposed. It has been established that the dynamics of dry matter losses and heat losses of fish fillets is determined by the duration of cooking. In terms of organoleptic characteristics boiled minced meat from raw mackerel fillets is significantly inferior to the organoleptic characteristics of minced meat from pre-boiled fillets. When comparing the data for frozen and freshly prepared mince from horse mackerel, it has been found that the loss of nucleic acids in industrially prepared minced meat is 4.6-13.1 % higher ( T = 82 ± 2 and 98 ± 2 °C), the loss of nucleic acids by absolutely dry matter is higher by 11.3-5.8 %, mass - by 8.4-14.6 %. The content of the total amount of nucleic acids in industrial minced meat is 11.1 % lower than in freshly prepared minced meat. Obviously, in the process of preparing products for specialized purposes, including for preventive nutrition, it is preferable to use minced meat from boiled fish fillets.

The Reactivity of Human and Equine Estrogen Quinones towards Purine Nucleosides

Conjugated estrogen medicines, which are produced from the urine of pregnant mares for the purpose of menopausal hormone replacement therapy (HRT), contain the sulfate conjugates of estrone, equilin, and equilenin in varying proportions. The latter three steroid sex hormones are highly similar in molecular structure as they only differ in the degree of unsaturation of the sterane ring “B”: the cyclohexene ring in estrone (which is naturally present in both humans and horses) is replaced by more symmetrical cyclohexadiene and benzene rings in the horse-specific (“equine”) hormones equilin and equilenin, respectively. Though the structure of ring “B” has only moderate influence on the estrogenic activity desired in HRT, it might still significantly affect the reactivity in potential carcinogenic pathways. In the present theoretical study, we focus on the interaction of estrogen orthoquinones, formed upon metabolic oxidation of estrogens in breast cells with purine nucleosides. This multistep process results in a purine base loss in the DNA chain (depurination) and the formation of a “depurinating adduct” from the quinone and the base. The point mutations induced in this manner are suggested to manifest in breast cancer development in the long run. We examine six reactions between deoxyadenosine and deoxyguanosine as nucleosides and estrone-3,4-quinone, equilin-3,4-quinone, and equilenin-3,4-quinone as mutagens. We performed DFT calculations to determine the reaction mechanisms and establish a structure–reactivity relationship between the degree of unsaturation of ring “B” and the expected rate of DNA depurination. As quinones might be present in the cytosol in various protonated forms, we introduce the concept of “effective barriers” to account for the different reactivity and different concentrations of quinone derivatives. According to our results, both equine estrogens have the potential to facilitate depurination as the activation barrier of one of the elementary steps (the initial Michael addition in the case of equilenin and the rearomatization step in the case of equilin) significantly decreases compared to that of estrone. We conclude that the appearance of exogenous equine estrogen quinones due to HRT might increase the risk of depurination-induced breast cancer development compared to the exposure to endogenous estrone metabolites. Still, further studies are required to identify the rate-limiting step of depurination under intracellular conditions to reveal whether the decrease in the barriers affects the overall rate of carcinogenesis.

Sequence dependence of transient Hoogsteen base-pairing in DNA

Hoogsteen (HG) base-pairing is characterized by a 180° rotation of the purine base with respect to the Watson-Crick-Franklin (WCF) motif. Recently, it has been found that both conformations coexist in a dynamical equilibrium and that several biological functions require HG pairs. This relevance has motivated experimental and computational investigations of the base-pairing transition. However, a systematic simulation of sequence variations has remained out of reach. Here, we employ advanced path-based methods to perform unprecedented free-energy calculations. Our methodology enables us to study the different mechanisms of purine rotation, either remaining inside or after flipping outside of the double helix. We study seven different sequences, which are neighbor variations of a well-studied A·T pair in A6-DNA. We observe the known effect of A·T steps favoring HG stability, and find evidence of triple-hydrogen-bonded neighbors hindering the inside transition. More importantly, we identify a dominant factor: the direction of the A rotation, with the 6-ring pointing either towards the longer or shorter segment of the chain, respectively relating to a lower or higher barrier. This highlights the role of DNA's relative flexibility as a modulator of the WCF/HG dynamic equilibrium. Additionally, we provide a robust methodology for future HG proclivity studies.

ANALYSIS OF PURINIC ALKALOIDS BY XRD AND MOLECULAR MODELING METHODS

Theophylline, theobromine and caffeine, are purine-based alkaloids in which the main differentiation in the molecular structure is the presence of methyls, one, two and three, respectively in these substances. This study presents an analysis by XRD and molecular modeling methods of the alkaloid’s caffeine and theobromine. The crystalline structure of caffeine was characterized as a monoclinic system, and the diffractogram of the caffeine crystals showed peaks with regions of greater intensity at 2θ = 11.7616 ° (d = 7.51 Å; I% = 80.13) and 2θ = 11.9416 ° (d = 7.40 Å; I% = 98.14). In the diffractogram of the theobromine crystal sample, peaks of greater intensity occurred in the regions 2θ = 13.4616 ° (d = 6.57 Å; I% = 98.92) and 2θ = 27.0816 ° (d = 3, 28 Å; I% = 67.23). Results obtained by XRD for caffeine and theobromine were compatible with standard cards of the X’Pert High Score Plus® program. The presence of an extra methyl in the structure of the caffeine purine base, suggests, a shift in the values ​​of the angle 2 θ for the main peaks of theobromine, as well as an increase in intensity, mainly in 27.016, theobromine also presents a peak in the region 10.6 which does not occur in caffeine. Statistical results reveal that the linear models for data of peaks of specific angles in 2θ of the samples, presented good linear correlation (R2> 98%) and satisfactory results after the procedure of cross validation. caffeine and theobromine also showed important differences in interactions with adenosine A2AR, particularly in hydrophobic and hydrogen interactions.

Safety assessment of purine nucleosidase from Aspergillus luchuensis

Purine nucleosidase (EC 3.2.2.1) catalyzes the N-riboside hydrolysis of purine nucleosides to D-ribose and a purine base. This enzyme may be used in the production of beer and other alcoholic beverages to reduce the purine content of these products. Purine nucleosidase was obtained from Aspergillus luchuensis naturally occurring in grain sources. The safety profile of purine nucleosidase is not well documented in the scientific literature, and a series of toxicological studies were undertaken to investigate the safety of its use in food production. Purine nucleosidase from A. luchuensis was non-mutagenic and non-clastogenic in a standard Ames test and in vitro mammalian chromosome aberration assay. Administration of purine nucleosidase in a 90-day subchronic toxicity study in Sprague-Dawley rats did not elicit adverse findings on any hematology, clinical chemistry, urinalysis, organ weight, or histopathological parameter at doses up to 1700 mg total organic solids (TOS)/kg body weight/day, the highest dose tested. The results suggest purine nucleosidase to lack systemic toxic effect. The no-observed-adverse-effect level was concluded to be 1700 mg TOS/kg body weight/day. The results of the toxicology studies support the safety of purine nucleosidase from a non-genetically modified strain of A. luchuensis when used in food production.

Unique Role of Caffeine Compared to Other Methylxanthines (Theobromine, Theophylline, Pentoxifylline, Propentofylline) in Regulation of AD Relevant Genes in Neuroblastoma SH-SY5Y Wild Type Cells

Methylxanthines are a group of substances derived from the purine base xanthine with a methyl group at the nitrogen on position 3 and different residues at the nitrogen on position 1 and 7. They are widely consumed in nutrition and used as pharmaceuticals. Here we investigate the transcriptional regulation of 83 genes linked to Alzheimer’s disease in the presence of five methylxanthines, including the most prominent naturally occurring methylxanthines—caffeine, theophylline and theobromine—and the synthetic methylxanthines pentoxifylline and propentofylline. Methylxanthine-regulated genes were found in pathways involved in processes including oxidative stress, lipid homeostasis, signal transduction, transcriptional regulation, as well as pathways involved in neuronal function. Interestingly, multivariate analysis revealed different or inverse effects on gene regulation for caffeine compared to the other methylxanthines, which was further substantiated by multiple comparison analysis, pointing out a distinct role for caffeine in gene regulation. Our results not only underline the beneficial effects of methylxanthines in the regulation of genes in neuroblastoma wild-type cells linked to neurodegenerative diseases in general, but also demonstrate that individual methylxanthines like caffeine mediate unique or inverse expression patterns. This suggests that the replacement of single methylxanthines by others could result in unexpected effects, which could not be anticipated by the comparison to other substances in this substance class.