Chemical studies on the oriental plant drugs. 23. Peoniflorin, a glucoside of Chinese paeony root

New Monoterpene Glycoside Paeoniflorin Derivatives as NO and IL-1β Inhibitors: Synthesis and Biological Evaluation

Several monoterpene glycoside compounds were extracted from Paeonia lactiflora Pall. Among them, paeoniflorin, a water-soluble monoterpene glycoside found in the root of Paeonia lactiflora Pall, exhibits excellent antioxidant pharmacological functions. Initially, Sc(CF3SO3)3 was employed as the catalyst for paeoniflorin's dehydration and rearrangement reactions with alcohols. Subsequently, structural modifications were performed on paeoniflorin through a series of responses, including acetylation, deacetylation, and debenzoylation, ultimately yielding 46 monoterpene glycoside derivatives. The potential inhibitory effects on the pro-inflammatory mediators interleukin-1 beta (IL-1β) and nitric oxide (NO) were assessed in vitro. The results revealed that compounds 29 and 31 demonstrated notable inhibition of NO production, while eight derivatives (3, 8, 18, 20, 21, 29, 34, and 40) displayed substantial inhibitory effects on the secretion of IL-1β. Computational research was also undertaken to investigate the binding affinity of the ligands with the target proteins. Interactions between the proteins and substrates were elucidated, and corresponding binding energies were calculated accordingly. The findings of this study could provide valuable insights into the design and development of novel anti-inflammatory agents with enhanced pharmacological properties.

Paeoniflorin in Paeoniaceae: Distribution, influencing factors, and biosynthesis

Paeoniflorin, a monoterpene glucoside, is increasingly used in the clinical treatment of many diseases because it has a variety of pharmacological activities. Besides, paeoniflorin has been considered the characteristic chemical constituent of Paeoniaceae plants since it was first reported in 1963. Therefore, how to better develop and utilize paeoniflorin in Paeoniaceae has always been a research hotspot. We reviewed the current knowledge on paeoniflorin in Paeoniaceae, with particular emphasis on its distribution and influencing factors. Moreover, the limited understanding of the biosynthesis pathway has restricted the production of paeoniflorin by synthetic biology. This review provides insights into the post-modification pathway of paeoniflorin biosynthesis and proposes directions for further analysis in the future.

Genus Paeonia: A comprehensive review on traditional uses, phytochemistry, pharmacological activities, clinical application, and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Paeonia, which comprises approximately 52 shrubs or herbaceous perennials around the world, is the only genus of the Paeoniaceae and is pervasively distributed in Asia, southern Europe, and North America. Many species of the genus Paeonia have been used for centuries in ethnomedical medical systems.

AIM OF THE REVIEW

The present study aims to summarize the traditional uses, clinical applications, and toxicology of the genus Paeonia, to critically evaluate the state-of-the-art phytochemical and pharmacological studies of this genus published between 2011 and 2020, and to suggest directions for further in-depth research on Paeonia medicinal resources.

MATERIALS AND METHODS

Popular and widely used databases such as PubMed, Scopus, Science Direct, and Google Scholar were searched using the various search strings; from these searches, a number of citations related to the traditional uses, phytochemistry, biological activities, clinical application, and toxicology of the genus Paeonia were retrieved.

RESULTS

The use of 21 species, 2 subspecies, and 7 varieties of the genus Paeonia as traditional herbal remedies has been reported, and many ethnomedicinal uses, such as the treatment of hematemesis, blood stasis, dysmenorrhea, amenorrhea, epilepsy, spasms, and gastritis, have been recorded. The roots and root bark are the most frequently reported parts of the plants used in medicinal applications. In phytochemical investigations, 451 compounds have been isolated from Paeonia plants to date, which contains monoterpenoid glucosides, flavonoids, tannins, stilbenes, triterpenoids and steroids, and phenols. Studies of their pharmacological activities have revealed the antioxidant, anti-inflammatory, antitumour, antibacterial, antiviral, cardiovascular protective, and neuroprotective properties of the genus Paeonia. In particular, some bioactive extracts and compounds (total glucosides of peony (TGP), paeonol, and paeoniflorin) have been used as therapeutic drugs or tested in clinical trials. In addition to the "incompatibility" of the combined use of "shaoyao" and Veratrum nigrum L. roots in traditional Chinese medicine theory, Paeonia was considered to have no obvious toxicity based on the available toxicological tests.

CONCLUSION

A large number of phytochemical and pharmacological reports have indicated that Paeonia is an important medicinal herb resource, and some of its traditional uses including the treatment of inflammation and cardiovascular diseases and its use as a neuroprotective agent, have been partially confirmed through modern pharmacological studies. Monoterpenoid glucosides are the main active constituents. Although many compounds have been isolated from Paeonia plants, the biological activities of only a few of these compounds (paeoniflorin, paeonol, and TGP) have been extensively investigated. Some paeoniflorin structural analogues and resveratrol oligomers have been preliminarily studied. With the exception of several species (P. suffruticosa, P. ostii, P. lactiflora, and P. emodi) that are commonly used in folk medicine, many medicinal species within the genus do not receive adequate attention. Conducting phytochemical and pharmacological experiments on these species can provide new clues that may lead to the discovery of medicinal resources. It is necessary to identify the effective phytoconstituents of crude extracts of Paeonia that displayed pharmacological activities by bioactivity-guided isolation. In addition, comprehensive plant quality control, and toxicology and pharmacokinetic studies are needed in the future studies.

Mechanistic Investigation of Visible-Light-Induced Intermolecular [2 + 2] Photocycloaddition Catalyzed with Chiral Thioxanthone

The recent thioxanthone-sensitizer-catalyzed intermolecular [2 + 2] cycloaddition induced by visible-light irradiation set the stage for the future development of feasible photocycloadditions. Nonetheless, the mechanism of this reaction still remains under debate, especially on the activation mode of the thioxanthone photosensitizer (energy transfer, bielectron exchange, and hydrogen transfer are all possible mechanisms). To settle this issue, systematic density functional theory calculations have been carried out. The results indicate that the energy-transfer pathway is more favorable than the bielectron-exchange and the hydrogen-transfer pathways. Meanwhile, the overall transformations involve the complexation and excitation of photosensitizer, the first C-C bond formation, the dissociation of the sensitizer, the triplet-to-singlet electronic state crossing, and the second C-C bond formation. The first C-C bond formation is the rate- and selectivity-determining step, and synergistic energy and electron transfer from photosensitizer to substrate moieties takes place along this process. On this basis, the effect of olefin substrates (ethyl vinyl ketone vs vinyl acetate) on the stereoselectivity was finally analyzed.

Cyclobutane and cyclobutene synthesis: catalytic enantioselective [2+2] cycloadditions

Cyclobutanes and cyclobutenes are important structural motifs found in numerous biologically significant molecules, and they are useful intermediates for chemical synthesis. Consequently, [2+2] cycloadditions to access cyclobutanes and cyclobutenes have been established to be particularly useful transformations. Within the last 10 years, an increase in the frequency of publications for catalytic enantioselective [2+2] cycloadditions has occurred. These reactions provide access to a wide array of enantiomerically enriched chemical diversity that was not previously attainable. Described in this review are the advances made in catalytic enantioselective [2+2] cycloadditions to access cyclobutanes and cyclobutenes.

Choosing chemical markers for quality assurance of complex herbal medicines: Development and application of the herb MaRS criteria

With increasing use of herbal medicines for chronic or serious illness, relevant quality assurance methods are essential for making claims of therapeutic benefit. Adequate demonstration of safety and efficacy based on chemical composition and ensuring consistency between manufactured batches is critical. To date, there has been no uniform standard approach or detailed framework provided to industry for selecting relevant chemical markers used to standardize herbal products. We developed the Herbal Marker Ranking System (Herb MaRS) providing guidance on prioritizing the selection of chemical markers for quality control of complex multi-herb mixtures, while also taking into account the bioactivity in relation to the symptoms of the disease and its concentration in the formula. We apply the Herb MaRS evaluation criteria to a seven-herb formulation for the treatment of irritable bowel syndrome with constipation. Our ranking scale accommodates the clinical and pharmacological use of the formulation and its claimed indications.

Paeonia japonica, Houttuynia cordata, and Aster scaber water extracts induce nitric oxide and cytokine production by lipopolysaccharide-activated macrophages

Natural products are increasingly recognized as potential targets for drug discovery and development. We previously reported that Paeonia japonica, Houttuynia cordata, and Aster scaber enhanced macrophage activation both in vitro and in vivo. In the present study we investigated the immunomodulating effects of these plants on lipopolysacharide (LPS)-stimulated macrophages. An aqueous extract of each plant was administered to female BALB/c mice every other day for 4 weeks. Peritoneal macrophages were then collected and incubated to examine the immunoreactivity of macrophages against LPS at different time points. The expression levels of inducible nitric oxide (NO) synthetase (iNOS), cyclooxygenase (COX)-2, and inhibitory factor kappaB alpha (IkappaBalpha) proteins and the production of NO metabolite (nitrite), prostaglandin (PG) E(2), and the pro-inflammatory cytokines interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha were determined in the activated macrophages treated with extracts from each plant individually or combined. High levels of pro-inflammatory cytokines were produced by A. scaber-, P. japonica-, and H. cordata-treated macrophages following 24 hours of LPS stimulation. P. japonica, H. cordata, and A. scaber treatment also induced the production of nitrate by LPS-treated macrophages. Induction of iNOS mRNA and protein was also different in each group. PGE(2) secretion was up-regulated by all extract-treated macrophages at early time points; however, no significant differences were observed between the groups by 8 hours post-LPS stimulation. Treatment with A. scaber extract resulted in the highest levels of IkappaBalpha degradation. Our findings illustrate that the natural plant products P. japonica, H. cordata, and A. scaber may enhance immune function by modulating ex vivo pro-inflammatory cytokine and NO production as well as the expression of iNOS and COX-2.

Inhibitors of aldose reductase and formation of advanced glycation end-products in moutan cortex (Paeonia suffruticosa)

The methanol extract of Moutan cortex (Paeonia suffruticosa) afforded two new compounds, 8-O-benzoylpaeonidanin (1) and 5-hydroxy-3S-hydroxymethyl-6-methyl-2,3-dihydrobenzofuran (2), in addition to 4-O-butylpaeoniflorin (3) as an artifact of the separation, seven monoterpene glycosides (4-10), two monoterpenes (11, 12), four acetophenones (13-16), and two triterpenes (17, 18). The structures of the compounds were determined by spectroscopic methods, and the compounds were evaluated for inhibitory effects against rat lens aldose reductase (RLAR) and advanced glycation end-product (AGEs) formation. Compounds 17 and 18 showed the most potent inhibitory activity against RLAR, with IC(50) values of 11.4 and 28.8 microM, respectively. Compounds 3 and 6 also inhibited RLAR with IC(50) values of 36.2 and 44.6 microM, respectively. The positive control, 3,3-tetramethyleneglutamic acid, had an IC(50) value of 31.8 microM. Compounds 3 and 6 inhibited AGE formation with IC(50) values of 10.8 and 11.3 microM, respectively. Compound 2 had an IC(50) value of 177.0 microM, whereas the positive control, aminoguanidine, had an IC(50) value of 1026.8 microM.

Four new compounds from Paeonia albiflora

Studies on the chemical constituents of the roots of Paeonia albiflora Pall. led to the isolation of four new compounds named (3R,4S)-3-methyl-3,4-dihydro-5,6,7-trihydroxy-4-(3'-methoxy-4'-hydroxyphenyl)-1H-[2]-benzopyran-1-one (1), 5-hydroxy-6-methyl-1H-indole-3-carbaldehyde (2), trans-5-hydroxy-2-methoxy-6-methyl-2,3-dihydrobenzofuran-3-yl methyl benzoate (3) and cis-5-hydroxy-2-methoxy-6-methyl-2,3-dihydrobenzofuran-3-yl methyl benzoate (4), and two known ones, (7S,8S)-3-methoxy-3',7-epoxy-8,4'-oxyneligna-4,9,9'-triol (5) and (7S,8R)-dihydrodehydrodiconifery alcohol (6). Their structures were determined mainly by spectroscopic techniques including 2D-NMR (HSQC, HMBC, NOESY), MS, and CD experiments.

A new phenolic glycoside from Paeonia lactiflora

A new phenolic glycoside , 2-methoxy-5-(E)-propenyl-phenol-beta-vicianoside, was isolated from the root of Paeonia lactiflora. The structure of the new glycoside was elucidated by chemical and spectroscopic methods.

A new phenolic glycoside from the roots of Paeonia veitchii

From the roots of Paeonia veitchii Lynch., a new phenolic glycoside, 2-O-[alpha-L-arabinopyranosyl-(1 --> 6)-beta-D-glucopyranoside]-benzaldehyde (1) was isolated together with seven known phenolic compounds. Their structures were elucidated by spectroscopic method.

Capillary electrophoretic determination of the constituents of paeoniae radix

A method combining the techniques of capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) has been developed to separate a total of eight peony constituents. The CZE method was used to determine the content of paeonol, oxypaeoniflorin, benzoic acid, pentagalloylglucose and gallic acid, and MEKC technique based on sodium cholate was applied to analyze albiflorin, paeoniflorin, benzoyla biflorin, paeonol and oxypaeoniflorin. Linearity around two orders of magnitude of concentration was generally obtained and limits of detection for these compounds were in the range of 2.6-23.7 micrograms/ml. The relative standard deviations of migration times were less than 1.43% (n = 6). Contents of peony constituents in an ethanol-water extract of Paeonia lactiflora Pall. sample could easily be determined by this method.

Blocking effects of a new component, paeoniflorigenone, in paeony root on neuromuscular junctions of frogs and mice

A new monoterpene, paeoniflorigenone (PFG) (100-900 micrograms/ml), which was isolated from paeony roots and identified chemically, suppressed both indirectly and directly stimulated muscle twitchings of frog sciatic nerve-sartorius muscle preparation, and it indirectly stimulated muscle twitchings of phrenic nerve-diaphragm muscle preparations. The suppression effect by PFG (300 micrograms/ml) on twitching was not reversed by neostigmine (60 micrograms/ml) and was restored by washing out of PFG. PFG (150 micrograms/ml) depolarized the diaphragm muscle membranes by 10 mV and did not change the electrotonic potentials. PFG (100 micrograms/ml) inhibited weakly acetylcholine (5 micrograms/ml)-induced slow contractions. These results demonstrated that PFG is a depolarizing neuromuscular blocking agent, being similar to succinylcholine, except that PFG did not produce any contraction, but succinylcholine did.