Hypoglycemic triterpenoid glycosides from Cyclocarya paliurus (Sweet Tea Tree)

Natural products with potential hypoglycemic activity in T2DM: 2019-2023

As currently the most common metabolic disease, type 2 diabetes mellitus (T2DM) has shown a continuous increase in the number of patients in recent decades. Most anti-T2DM drugs tend to cause some side effects. Given the pathogenesis of T2DM, natural products have emerged as an important source of anti-T2DM drugs. This article reviews natural products with potential hypoglycemic activity from 2019 to 2023. A total of 200 previously natural products were discovered on SciFinder, PubMed and Web of Science. These products were categorized based on their structural frameworks and their biological activities were summarized. Although the mechanisms of action of most compounds are unclear, these compounds could still serve as candidates for the development of lead compounds. Therefore, further structure and activity research of natural products will significantly contribute to the development of potential anti-T2DM drugs.

Antitumor effects of Cypaliuruside F from Cyclocarya paliurus on HepG2 cells

An undescribed dammarane triterpenoid saponin Cypaliuruside F was isolated from the leaves of Cyclocarya paliurus in our preliminary study. The MTT assay, flow cytometry, cell scratch, and DAPI staining were used to detect the antitumor effects of Cypaliuruside F on HepG2 cells. Subsequently, network pharmacology and molecular docking analysis were used to analyse the key targets of Cypaliuruside F against HCC. In addition, a Western blot was performed to determine the effects of Cypaliuruside F on the expression of key proteins in HepG2 cells. The experimental results indicated that the damarane triterpenoid saponin Cypaliuruside F from Cyclocarya paliurus inhibits the proliferation of HepG2 cells by inducing apoptosis and cell cycle arrest. These changes may promote the apoptosis of HepG2 cells by inhibiting the expression of mTOR, STAT3, and Bcl-2 while activating Bax.

Triterpenoid Compounds from Cyclocarya paliurus: A Review of Their Phytochemistry, Quality Control, Pharmacology, and Structure-Activity Relationship

Cyclocarya paliurus (Batalin) Iljinskaja (C. paliurus) is a single species of Cyclocarya paliurus in Juglandaceae. It is a unique rare medicinal plant resource in China that is mainly distributed in the south of China. The leaves of C. paliurus, as a new food ingredient, are processed into tea products in daily life. Triterpenoids are the main active ingredient in C. paliurus. So far, 164 triterpenoid compounds have been isolated and identified from C. paliurus, which are included 3,4-seco-dammaranes, dammaranes, oleanane, ursane, lupinanes, taraxeranes, and norceanothanes. Modern pharmacological studies manifested that these ingredients have a wide range of pharmacological activities both in vitro and in vivo, such as reducing blood sugar, lowering blood lipids, and anti-tumor, anti-inflammatory, anti-oxidant, and other activities. In addition, current results indicate that the pharmacological mechanisms of triterpenoids were closely related to their chemical structure, molecular signaling pathways, and the expression of related proteins. In order to further study C. paliurus based on the current research situation, this review summarizes the prospect and systematic summary of the triterpenes of C. paliurus from the aspects of structural characteristics, quality control, biological activity, and the structure-activity relationship, which provide a reference for further research and application of the triterpenoids from C. paliurus in the field of functional food and medicine.

Two new dammarane triterpenoid saponins from the leaves of Cyclocarya paliurus

Two undescribed dammarane triterpenoid saponins, cypaliurusides O and P (1 and 2), were isolated from the ethanol extracts of the leaves of Cyclocarya paliurus. Bioactivity assay results showed that compound 1 has potential cytotoxic activities against selected human cancer cell lines in vitro, with IC₅₀ values ranging from 14.55 ± 0.55 to 22.75 ± 1.54 µM. Compound 1 showed better antitumor activity against HepG2 cells with IC₅₀ of 14.55 ± 0.55 µM. In addition, compound 2 showed no obvious antitumor activity.

Triterpenoids from the Leaves of Cyclocarya paliurus and Their Glucose Uptake Activity in 3T3-L1 Adipocytes

Four new dammarane triterpenoid saponins cypaliurusides Z₁-Z₄ (1-4) and eight known analogs (5-12) were isolated from the leaves of Cyclocarya paliurus. The structures of the isolated compounds were determined using a comprehensive analysis of 1D and 2D NMR and HRESIMS data. The docking study demonstrated that compound 10 strongly bonded with PTP1B (a potential drug target for the treatment of type-II diabetes and obesity), hydrogen bonds, and hydrophobic interactions, verifying the importance of sugar unit. The effects of the isolates on insulin-stimulated glucose uptake in 3T3-L1 adipocytes were evaluated and three dammarane triterpenoid saponins (6, 7 and 10) were found to enhance insulin-stimulated glucose uptake in 3T3-L1 adipocytes. Furthermore, compounds 6, 7, and 10 exhibited potent abilities to promote insulin-stimulated glucose uptake in 3T3-L1 adipocytes in a dose-dependent manner. Thus, the abundant dammarane triterpenoid saponins from C. paliurus leaves exhibited stimulatory effects on glucose uptake with application potential as a antidiabetic treatment.

Triterpene constituents from the fruits of Cyclocarya paliurus and their anti-HIV-1IIIB activity

Four new norceanothane-type triterpenes, cyclopalin A-D (1-4), and sixteen known compounds (5-20) were obtained from the fruits of Cyclocarya paliurus. Their structures were determined by spectroscopic data, experimental electronic circular dichroism (ECD) and X-ray single crystal analyses. All isolated compounds were assayed for their anti-HIV-1_IIIB activity. Compound 18 exhibited potent anti-HIV-1_IIIB activity with an EC₅₀ value of 1.32 μM (SI = 151.52).

Progress in Research on the Alleviation of Glucose Metabolism Disorders in Type 2 Diabetes Using Cyclocarya paliurus

Globally, the incidence of diabetes is increasing annually, and China has the largest number of patients with diabetes. Patients with type 2 diabetes need lifelong medication, with severe cases requiring surgery. Diabetes treatment may cause complications, side-effects, and postoperative sequelae that could lead to adverse health problems and significant social and economic burdens; thus, more efficient hypoglycemic drugs have become a research hotspot. Glucose metabolism disorders can promote diabetes, a systemic metabolic disease that impairs the function of other organs, including the heart, liver, and kidneys. Cyclocarya paliurus leaves have gathered increasing interest among researchers because of their effectiveness in ameliorating glucose metabolism disorders. At present, various compounds have been isolated from C. paliurus, and the main active components include polysaccharides, triterpenes, flavonoids, and phenolic acids. C. paliurus mainly ameliorates glucose metabolism disorders by reducing glucose uptake, regulating blood lipid levels, regulating the insulin signaling pathway, reducing β-cell apoptosis, increasing insulin synthesis and secretion, regulating abundances of intestinal microorganisms, and exhibiting α-glucosidase inhibitor activity. In this paper, the mechanism of glucose metabolism regulation by C. paliurus was reviewed to provide a reference to prevent and treat diabetes, hyperlipidaemia, obesity, and other metabolic diseases.

Cyclocarya paliurus (Batalin) Iljinskaja: Botany, Ethnopharmacology, phytochemistry and pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Cyclocarya paliurus (Batalin) Iljinskaja (C. paliurus) also known as Sweet tea tree, Money tree, Money willow, green money plum, mountain willow and shanhua tree, is a native rare monocotyledonous plant in Southern China. It possesses numerous traditional benefits, including clearing heat, detoxification, producing saliva, slake thirst, anti-inflammatory, insecticidal, dispelling wind and relieving itching. It is also effective in preventing and treating diabetes, hypertension, hyperlipidemia, dizziness and swelling and pain, as well as reducing cholesterol, and modulating the functions of the immune system. The stem, leaves and bark of this plant are all medicinal parts, but the leaves have the highest research value.

AIM OF THE STUDY

This article summarized the plant's botanical description, distribution, ethnopharmacology, phytochemical profiles and pharmacological for the first time, to provide possible directions for future development and research in brief.

MATERIAL AND METHODS

The literature for this current manuscript was obtained from reports published from 1992 to May 2021 in diverse databases such as the China Knowledge Resource Integrated databases (CNKI), SciFinder, Google Scholar, Baidu Scholar, Elsevier and Pub-Med. The domestic and foreign references published about C. paliurus over recent years were collected, analyzed and summarized.

RESULTS

The botanical characteristics of the fruits of C. paliurus are unique in having a central nutlet surrounded by a circular wing to distinguish the living genera of Juglandaceae. In traditional medicine, C. paliurus leaves are used by the local people of Southern China to make tea to prevent diabetes. More than 210 compounds have been isolated from C. paliurus. Among them, the characteristic 3,4-seco-dammaranes accounted for the most. Other compounds include dammarane tetracyclic triterpenoids, various pentacyclic triterpenoids, flavonoids, isosclerones, phenolic derivatives and polysaccharides. The plant extracts and compounds have been reported to exert various pharmacological activities, such as anti-hyperglycemic, anti-hyperlipidemic, anti-cancer, cytotoxic, anti-oxidative, anti-inflammatory, hepatoprotective, and anti-microbial activities.

CONCLUSIONS

Comprehensive literature analysis shows that C. paliurus extract and its compounds have a variety of biological activities for the treatment of various diseases. The current modern pharmacology research is mostly related to the records of ethnic pharmacology, mainly in vitro research, relatively few in vivo research. Therefore, future studies should focus on this aspect. In addition, we also would like to recommend further research should concentrate on toxicity studies and quality control of C. paliurus to fill the study gap, as well as to provide theoretical support for the further development of the potential functions and clinical applications of the plant.

Synthesis and biological evaluation of (20S,24R)-epoxy-dammarane-3β,12β,25-triol derivatives as α-glucosidase and PTP1B inhibitors

The dammarane triterpenoid (20S,24R)-epoxy-dammarane-3β,12β,25-triol obtained from Cyclocarya paliurus in our previous study showed inhibitory activity on α-glucosidase in vitro with an inhibitory ratio of 32.2% at the concentration of 200 μM. In order to reveal the structure-activity relationships (SARs) and get more active compounds, 42 derivatives of (20S,24R)-epoxy-dammarane-3β,12β,25-triol were synthesized by chemical modification on the hydroxyls (C-3 and C-12), rings A and E, and assayed for their α-glucosidase and PTP1B inhibitory activities. Two compounds (8, 26) increased activity against α-glucosidase, and four compounds (8, 15, 26, 42) significantly inhibited PTP1B. It was noted that compounds 8 and 26 could inhibit both α-glucosidase and PTP1B as dual-target inhibitors with IC₅₀ values of 489.8, 467.7 μM (α-glucosidase) and 319.7, 269.1 μM (PTP1B). Compound 26 was revealed to be a mix-type inhibitor on α-glucosidase and a noncompetitive-type inhibitor on PTP1B based on enzyme kinetic study. Furthermore, compound 42 could selectively inhibited PTP1B as a mix-type inhibitor with IC₅₀ value of 134.9 μM, which was 2.5-fold higher than the positive control, suramin sodium (IC₅₀ 339.0 μM), but not inhibit α-glucosidase.

-Glucosidase inhibitors screening from Cyclocarya paliurus based on spectrum-effect relationship and UPLC-MS/MS

Cyclocarya paliurus is an edible and medicinal plant exhibiting significant hypoglycemic effect. However, its active components are still unclear and need further elucidation. In this research, the active components of the leaves of C. paliurus responsible for α-glucosidase inhibitory activity were screened and identified based on spectrum-effect relationship study in combination with ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) analysis. The 70% ethanol eluate fraction of the leaves of C. paliurus with the strongest α-glucosidase inhibitory activity was obtained after extraction and purification with macroporous resin. Their chromatographic fingerprints (15 batches) were established by UPLC analysis and 32 common peaks were specified by similarity analysis. Their IC₅₀ values for α-glucosidase inhibition were measured by an enzymatic reaction. Several multivariate statistical analysis methods including hierarchical cluster analysis, principal component analysis, partial least square analysis and grey relational analysis were applied to explore the spectrum-effect relationship between common peaks and IC₅₀ values, and the chromatographic peaks making great contribution to efficacy were screened out. To further elucidate the active components of leaves of C. paliurus, the 70% ethanol eluate fraction was characterized by UPLC-MS/MS analysis, and 10 compounds were identified. This study provided a valuable reference for further research and development of hypoglycemic active components of C. paliurus.

RNA in situ hybridization and expression of related genes regulating the accumulation of triterpenoids in Cyclocarya paliurus

Cyclocarya paliurus (Batal.) Iljinskaja, a woody medicinal species in the Juglandaceae, grows extensively in subtropical areas of China. Triterpenoids in the leaves have health-promoting effects, including hypoglycemic and hypolipidemic activities. To understand triterpenoid biosynthesis, transport and accumulation in C. paliurus during the growing season, gene cloning, gene expression and RNA in situ hybridization of related genes were used, and accumulation was examined in various organs. The complete coding sequences (CDSs) of three genes, CpHMGR, CpDXR and CpSQS, were obtained from GenBank and RACE. RNA in situ hybridization signals of the three genes mainly occurred in the epidermis, palisade tissue, phloem and xylem of leaf, shoot and root, with the signals generally consistent with the accumulation of metabolites in tissues, except in the xylem. Both gene expression and triterpenoid accumulations showed seasonal variations in all organs. However, total triterpenoid content in the leaves was significantly higher than that in the shoots, with the maximum in shoots in August and in leaves in October. According to Pearson correlation analysis, triterpenoid accumulation in the leaves was significantly positively related with the relative expression of CpSQS. However, the relation between gene expression and accumulation was dependent on the role of the gene in the pathway as well as on the plant organ. The results suggested that most of the intermediates catalyzed by CpHMGR and CpDXR in young shoots and roots were used in growth and flowering in the spring, whereas subsequent triterpenoid biosynthesis in the downstream catalyzed by CpSQS mainly occurred in the leaves by using transferred and in situ intermediates as substrates. Thus, this study provides a reference to improve triterpenoid accumulation in future C. paliurus plantations.

A critical review on the use of DP4+ in the structural elucidation of natural products: the good, the bad and the ugly. A practical guide

Covering: 2015 up to the end of 2020Even in the golden age of NMR, the number of natural products being incorrectly assigned is becoming larger every day. The use of quantum NMR calculations coupled with sophisticated data analysis provides ideal complementary tools to facilitate the elucidation process in challenging cases. Among the current computational methodologies to perform this task, the DP4+ probability is a popular and widely used method. This updated version of Goodman's DP4 synergistically combines NMR calculations at higher levels of theory with the Bayesian analysis of both scaled and unscaled data. Since its publication in late 2015, the use of DP4+ to solve controversial natural products has substantially grown, with several predictions being confirmed by total synthesis. To date, the structures of more than 200 natural products were determined with the aid of DP4+. However, all that glitters is not gold. Besides its intrinsic limitations, on many occasions it has been improperly used with potentially important consequences on the quality of the assignment. Herein we present a critical revision on how the scientific community has been using DP4+, exploring the strengths of the method and how to obtain optimal results from it. We also analyze the weaknesses of DP4+, and the paths to by-pass them to maximize the confidence in the structural elucidation.

α-Glucosidase inhibitory and anti-inflammatory activities of dammarane triterpenoids from the leaves of Cyclocarya paliurus

Diabetes mellitus is caused by chronic inflammation and affects millions of people worldwide. Cyclocarya paliurus leaves have been widely used in traditional folk tea as a remedy for diabetes, but the antidiabetic constituents remain to be further studied. The α-glucosidase inhibitory and anti-inflammatory activities were examined to evaluate their effects on diabetes mellitus, and bioassay-guided separation of C. paliurus leaves led to the identification of twenty dammarane saponins, including eleven new dammarane saponins (1-11). The structures of the isolates were elucidated by spectroscopic methods. Bioactivity assay results showed that compounds 1 and 2 strongly inhibited α-glucosidase activity, with IC50 values ranging from 257.74 μM, 282.23 μM, and strongly inhibited the release of NO, with IC50 values of 9.10 μM, 9.02 μM. Moreover, compound 2 significantly downregulated the mRNA expression of iNOS, COX-2, IL-1β, NF-κB, IL-6 and TNF-α in LPS-mediated RAW 264.7 cells and markedly suppressed the protein expression of iNOS, NF-κB/p65, and COX-2. Dammarane glucoside 2 exhibited the strongest α-glucosidase inhibitory and anti-inflammatory activities. In addition, the structure-activity relationships (SARs) of the dammarane saponins were investigated. In summary, C. paliurus leaves showed marked α-glucosidase inhibitory and anti-inflammatory activities, and dammarane saponins are responsible for regulating α-glucosidase, inflammatory mediators, and mRNA and the protein expression of proinflammatory cytokines, which could be meaningful for discovering new antidiabetic agents.

Two new triterpenoid glycosides from leaves of Cyclocarya paliurus

Two dammarane glycosides (1-2) were isolated from the leaves of Cyclocarya paliurus. The structures of new compounds were established by application of spectroscopic methods, including one-dimensional and two-dimensional NMR, HRESIMS, and chemical hydrolysis. When evaluated against seven human cancer cell lines, the two compounds exhibited selective cytotoxicity to MCF-7 cells.

Bioactive dammarane triterpenoid saponins from the leaves of Cyclocarya paliurus

Thirteen undescribed dammarane triterpenoid saponins (cypaliurusides A-M), including eleven seco-dammarane type triterpenoids, were isolated from Cyclocarya paliurus. Each of these compounds has the unique feature of having a monosaccharide attached to C-11, rather than C-12, compared to the same type of saponins found in this plant. The structures of them were determined by comprehensive analysis of 1D, 2D NMR and HRESIMS data. Cypaliuruside J showed significant α-glucosidase inhibitory effect with IC50 value of 2.22 ± 0.13 μM. In addition, Cypaliurusides F and K exhibited modest cytotoxic activities against selected human cancer cell lines in vitro, with IC50 values ranging from 4.61 ± 0.13 to 15.23 ± 3.88 μM.

Four new prenylflavonol glycosides from the leaves of Cyclocarya paliurus

Four new prenylflavonol glycosides (1-4) along with two known analogues (5-6) were isolated from the leaves of Cyclocarya paliurus for the first time. The structures of these compounds were characterized by comprehensive analysis of 1 D, 2 D NMR, HRESIMS, UV data and enzymatic hydrolysis. In bioassays, compounds 1-4 were evaluated for inhibitory effects on xanthine oxidase (XOD) and effects on the inhibition of nitric oxide (NO) production in lipopolysaccharide (LPS) induced RAW264.7 cells. Moreover, compounds 1 and 2 showed outstanding XOD inhibitions with IC₅₀ values of 18.16 ± 3.91 and 37.65 ± 5.67 µM, and exhibited inhibitions against LPS-induced NO production with IC₅₀ values of 80.50 ± 3.09 and 82.28 ± 2.87 µM.

New prenylflavonol glycosides with xanthine oxidase inhibitory activity from the leaves of Cyclocarya paliurus

Eight new prenylflavonol glycosides (1-8), along with five known analogues (9-13) were isolated from the n-butanol extract of the dried leaves of Cyclocarya paliurus (family Juglandaceae) for the first time. The structures of these compounds were characterized by comprehensive analysis of 1D, 2D NMR, HRESIMS, UV data and acid hydrolysis. In bioassay, all these thirteen prenylflavonol glycosides exhibited inhibitory effects on xanthine oxidase (XOD) activity. Especially compounds 2 and 7, showed outstanding IC₅₀ values of 31.81 ± 2.20 and 29.71 ± 3.69 μM, respectively.