Polyprenylated Tetraoxygenated Xanthones from the Roots of Hypericum monogynum and Their Neuroprotective Activities

Hyperguanyes A and B, two new PPAPs from the branches and leaves of Hypericum perforatum L. with anti-cholinesterase activities

Two new polycyclic polyprenylated acylphloroglucinols, hyperguanyes A and B (1-2) together with eight known compounds (3-10), were isolated from Hypericum perforatum L. Their structures were determined by using comprehensive spectroscopic techniques and quantum chemical calculation. The in vitro anti-cholinesterase activity of all compounds were studied. Among them, compounds 1-4, 8 and 9 exhibited anti-AchE and anti-BchE effects with IC50 ranging from 0.34 ± 0.04 to 15.68 ± 0.54 μM.

The discovery of an anti-Candida xanthone with selective inhibition of Candida albicans GAPDH

OBJECTIVES

This study aimed to discover novel antifungals targeting Candida albicans glyceraldehyde-3-phosphate dehydrogenase (CaGAPDH), have an insight into inhibitory mode, and provide evidence supporting CaGAPDH as a target for new antifungals.

METHODS

Virtual screening was utilized to discover inhibitors of CaGAPDH. The inhibitory effect on cellular GAPDH was evaluated by determining the levels of ATP, NAD, NADH, etc., as well as examining GAPDH mRNA and protein expression. The role of GAPDH inhibition in C. albicans was supported by drug affinity responsive target stability and overexpression experiments. The mechanism of CaGAPDH inhibition was elucidated by Michaelis-Menten enzyme kinetics and site-specific mutagenesis based on docking. Chemical synthesis was used to produce an improved candidate. Different sources of GAPDH were used to evaluate inhibitory selectivity across species. In vitro and in vivo antifungal tests, along with anti-biofilm activity, were carried out to evaluate antifungal potential of GAPDH inhibitors.

RESULTS

A natural xanthone was identified as the first competitive inhibitor of CaGAPDH. It demonstrated in vitro anti-C. albicans potential but also caused hemolysis. XP-W, a synthetic side-chain-optimized xanthone, demonstrated a better safety profile, exhibiting a 50-fold selectivity for CaGAPDH over human GAPDH. XP-W also exhibited potent anti-biofilm activity and displayed broad-spectrum anti-Candida activities in vitro and in vivo, including multi-azole-resistant C. albicans.

CONCLUSIONS

These results demonstrate for the first time that CaGAPDH is a valuable target for antifungal drug discovery, and XP-W provides a promising lead.

α-Glucosidase Inhibitory Components from Garcinia pedunculata Fruits

From Garcinia pedunculata Roxb. fruits, two undescribed aromatic compounds including a benzofuran and a depsidone derivative, and a new natural product, together with four known compounds were isolated. Through the analysis of spectroscopic data, high resolution mass spectrum and calculated nuclear magnetic resonance, their structures were determined. The α-glucosidase inhibitory activity of the isolates was evaluated. And compound 3 exhibited a moderate inhibitory effect on α-glucosidase. The molecular docking of compound 3 was performed to elucidate the interaction with α-glucosidase.

Antidepressant polyprenylated acylphloroglucinols from Hypericum ascyron

Phytochemical investigation on the 90% EtOH extract of the air-dried aerial parts of Hypericum ascyron resulted in the isolation of three new polycyclic polyprenylated derivatives ascyronines A-C (1-3). Structural elucidation of all the compounds was performed by spectral methods such as 1D and 2D (1H-1H COSY, HMQC, and HMBC) NMR spectroscopy. All the polycyclic polyprenylated acylphloroglucinols were evaluated for their antidepressant activity by inhibiting the reuptake of tritiated serotonin ([3H]-5-HT) and noradrenalinet ([3H]-NE) in rat brain synaptosomes. Compounds 2 and 3 exhibited weak antidepressant activities in the [3H]-5-HT mode.

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

Functional characterization of a Flavonol 3-O-rhamnosyltransferase and two UDP-rhamnose synthases from Hypericum monogynum

Rhamnosyltransferase (RT) and rhamnose synthase (Rhs) are the key enzymes that are responsible for the biosynthesis of rhamnosides and UDP-l-rhamnose (UDP-Rha) in plants, respectively. How to discover such enzymes efficiently for use is still a problem to be solved. Here, we identified HmF3RT, HmRhs1, and HmRhs2 from Hypericum monogynum, which is abundant in flavonol rhamnosides, with the help of a full-length and high throughput transcriptome sequencing platform. HmF3RT could regiospecifically transfer the rhamnose moiety of UDP-Rha onto the 3-OH position of flavonols and has weakly catalytic for UDP-xylose (UDP-Xyl) and UDP-glucose (UDP-Glc). HmF3RT showed well quercetin substrate affinity and high catalytic efficiency with K_m of 5.14 μM and k_cat/K_m of 2.21 × 10⁵ S^-1 M^-1, respectively. Docking, dynamic simulation, and mutagenesis studies revealed that V129, D372, and N373 are critical residues for the activity and sugar donor recognition of HmF3RT, mutant V129A, and V129T greatly enhance the conversion rate of catalytic flavonol glucosides. HmRhs1 and HmRhs2 convert UDP-Glc to UDP-Rha, which could be further used by HmF3RT. The HmF3RT and HmRhs1 co-expressed strain RTS1 could produce quercetin 3-O-rhamnoside (quercitrin), kaempferol 3-O-rhamnoside (afzelin), and myricetin 3-O-rhamnoside (myricitrin) at yields of 85.1, 110.7, and 77.6 mg L^-1, respectively. It would provide a valuable reference for establishing a better and more efficient biocatalyst for preparing bioactive flavonol rhamnosides by identifying HmF3RT and HmRhs.

Hyperhubeins A-I, Bioactive Sesquiterpenes with Diverse Skeletons from Hypericum hubeiense

Nine new sesquiterpenes, hyperhubeins A-I (1-9), and 14 known analogues (10-23) were isolated from the aerial portions of Hypericum hubeiense. Their structures and absolute configurations were determined unambiguously via spectroscopic analysis, single-crystal X-ray diffraction, and electronic circular dichroism calculations. Compounds 1-3 possess an unprecedented sesquiterpene carbon skeleton. Further, a plausible biosynthetic pathway from farnesyl diphosphate (FPP) is proposed. The isolated phytochemicals were evaluated for neuroprotective and anti-neuroinflammatory properties in vitro. Compounds 1, 2, 5-8, 14, and 21 displayed notable neuroprotective activity against hydrogen peroxide (H₂O₂)-induced lesions in PC-12 cells at 10 μM. Additionally, compounds 1, 2, 12, and 13 exhibited inhibition of lipopolysaccharide (LPS)-induced nitric oxide (NO) production in BV-2 microglial cells, with their IC₅₀ values ranging from 4.92 to 6.81 μM. Possible interactions between these bioactive compounds and inducible nitric oxide synthase (iNOS) were predicted via molecular docking. Moreover, Western blotting indicated that compound 12 exerted anti-neuroinflammatory activity by suppressing LPS-stimulated expression of toll-like receptor-4 (TLR-4) and inhibiting consequent activation of nuclear factor-kappa-B (NF-κB) signaling.

Diverse polycyclic polyprenylated acylphloroglucinols with anti-neuroinflammatory activity from Hypericum beanii

A phytochemical investigation on the roots of Hypericum beanii resulted in the isolation of six new polycyclic polyprenylated acylphloroglucinols (PPAPs), hyperberlones A-F, along with fourteen known analogues. The structural characterization of these compounds was carried out by analyzing the HRESIMS data, 1D and 2D NMR spectroscopic data, electronic circular dichroism (ECD) calculations, and gauge-independent atomic orbital (GIAO) NMR calculations. Hyperberlone A (1) was a caged PPAP with a rare tricyclo[4.3.1.0^3,8]decane carbon skeleton. It was deduced to be biosynthetically generated from hyperbeanol C (8) through key Paternò-Büchi reaction, radical cascade cyclizations, and retro-aldol reaction. Compounds 4, 6, 7, 9, 14, and 16 exhibited significant nitric oxide (NO) production inhibitory effects in lipopolysaccharide (LPS)-induced BV-2 microglial cells with IC₅₀ values of 6.11-25.28 μM. Moreover, compound 4 significantly decreased the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in LPS-induced BV-2 microglia, as well as the phosphorylation of JNK.

Xanthone Biosynthetic Pathway in Plants: A Review

Xanthones are secondary metabolites rich in structural diversity and possess a broad array of pharmacological properties, such as antitumor, antidiabetic, and anti-microbes. These aromatic compounds are found in higher plants, such as Clusiaceae, Hypericaceae, and Gentianaceae, yet their biosynthetic pathways have not been comprehensively updated especially within the last decade (up to 2021). In this review, plant xanthone biosynthesis is detailed to illuminate their intricacies and differences between species. The pathway initially involves the shikimate pathway, either through L-phenylalanine-dependent or -independent pathway, that later forms an intermediate benzophenone, 2,3',4,6-tetrahydoxybenzophenone. This is followed by a regioselective intramolecular mediated oxidative coupling to form xanthone ring compounds, 1,3,5-trihydroxyxanthone (1,3,5-THX) or 1,3,7-THX, the core precursors for xanthones in most plants. Recent evidence has shed some lights onto the enzymes and reactions involved in this xanthone pathway. In particular, several biosynthetic enzymes have been characterized at both biochemical and molecular levels from various organisms including Hypericum spp., Centaurium erythraea and Garcinia mangostana. Proposed pathways for a plethora of other downstream xanthone derivatives including swertianolin and gambogic acid (derived from 1,3,5-THX) as well as gentisin, hyperixanthone A, α-mangostin, and mangiferin (derived from 1,3,7-THX) have also been thoroughly covered. This review reports one of the most complete xanthone pathways in plants. In the future, the information collected here will be a valuable resource for a more directed molecular works in xanthone-producing plants as well as in synthetic biology application.

Chemical constituents from the flowers of Hypericum monogynum L. with COX-2 inhibitory activity

Hypericum monogynum L. (Hypericaceae) has been used as a folk Chinese medicine for the treatment of inflammatory related diseases. Cyclooxygenase-2 (COX-2) is a crucial target for the development of agents to treat inflammation. To search for anti-inflammatory compounds from traditional Chinese medicines, a chemical constituent study along with COX-2 inhibitory activity analysis was performed for this plant. In this study, sixteen chemical monomers, including three undescribed oxidative degradation polycyclic polyprenylated acylphloroglucinols (PPAPs, hypemoins C-E), two undescribed PPAPs (hypemoins A and B), and 11 known compounds, were identified from the flowers of H. monogynum. Their structures were characterized by HRESIMS, NMR techniques, ECD, and single crystal X-ray diffraction. Four flavonoid derivatives showed remarkable COX-2 inhibitory activities, with IC₅₀ values ranging from 0.220 ± 0.006 to 1.655 ± 0.098 μM. Among these compounds, the possible recognition mechanism between quercetin 3-(6″-O-caffeoyl)-β-3-D-galactoside and COX-2 was predicted by molecular docking analysis. Moreover, the multidrug resistance reversal activities for the selected compounds were evaluated.

New Polyprenylated Acylphloroglucinol Derivatives and Xanthones From Hypericum wilsonii

Four new polyprenylated acylphloroglucinol derivatives, hyperwilone A-D (1–4), and two new xanthones, wilsonxanthone A (5) and wilsonxanthone B (6), together with eight known compounds were isolated from the aerial parts of Hypericum wilsonii. Their structures were expounded by comprehensive analysis of the 1D and 2D NMR spectra and HRESIMS. The relative configurations and absolute configurations of 1-6 were determined by NMR calculations and comparing their experimental and computed ECD data. All compounds were evaluated for GLUT4 translocation effects in L6 myotubes. Compound 5 showed the strongest GLUT4 translocation effects with 2.57 folds at a concentration of 30 μg/ml.

Characteristic metabolites of Hypericum plants: their chemical structures and biological activities

Plants belonging to the genus Hypericum (Hypericaceae) are recognized as an abundant source of natural products with interesting chemical structures and intriguing biological activities. In the course of our continuing study on constituents of Hypericum plants, aiming at searching natural product-based lead compounds for therapeutic agents, we have isolated more than 100 new characteristic metabolites classified as prenylated acylphloroglucinols, meroterpenes, ketides, dibenzo-1,4-dioxane derivatives, and xanthones including prenylated xanthones, phenylxanthones, and xanthonolignoids from 11 Hypericum plants and one Triadenum plant collected in Japan, China, and Uzbekistan or cultivated in Japan. This review summarizes their chemical structures and biological activities.

Acmoxanthones A-E, New Lavandulated Xanthones from Hypericum acmosepalum N. Robson

Acmoxanthones A-E (1-5), five new lavandulylated xanthones, were isolated from the aerial parts of Hypericum acmosepalum, together with four known xanthones. Their structures with absolute configurations were elucidated on the basis of analysis of MS, NMR and chiroptical properties. A bioassay against high glucose-induced damage on human umbilical vein endothelial cells (HUVECs) showed ananixanthone (6) and osajaxanthone (7) had potential antioxidative damage activity with EC₅₀ values of 10.5 μg/mL and 7.6 μg/mL, respectively, while 3-hydroxy-2,4-dimethoxyxanthone (8) exhibited cytotoxic effect on the damaged cells with IC₅₀ values of 7.1 μg/mL.

Type B polycyclic polyprenylated acylphloroglucinols from the roots of Hypericum beanii

Two new type B polycyclic polyprenylated acylphloroglucinols (PPAPs) (1 and 2) and a known biogenetic precursor hyperbeanol Q (3) were isolated from the root extract of Hypericum beanii, a medicinal plant widespread in southwest China. Their chemical structures were elucidated by 1D/2D NMR and HRESIMS data analysis, and absolute configurations were determined through detailed electric circular dichroism (ECD) analysis including ECD exciton chirality, Mo₂(OAc)₄-induced ECD, and ECD comparison. Of these compounds, hyperbeone A (1) is a typical [3.3.1]-type B PPAP with an unusual C-1 geranyl side chain, and hyperberin C (2) possesses a rare bicyclo[5.3.1]hendecane core. Taking compound 3 as a starting point, a plausible biosynthetic pathway to the bicyclic type B frameworks of 1 and 2 was proposed.

Hypermoins A-D: Rearranged Nor-Polyprenylated Acylphloroglucinols from the Flowers of Hypericum monogynum

Hypermonins A-D (1-4), four rearranged nor-polycyclic polyprenylated acylphloroglucinols (PPAPs) with unprecedented skeletons, together with two new biosynthesis related PPAPs (5 and 6) were isolated and identified from the flowers of Hypericum monogynum. Hypermoins A-D represented the first examples of highly modified norPPAPs characterized by a rare 7/6/6/5-tetracyclic system. From the biogenic synthesis pathway analysis, all isolates shared the same biosynthetic intermediate, and the addition of two methyls or one methyl to this intermediate through methyltranferase could generate different types of PPAPs (1-7). Their planner structures as well as absolute configuration were confirmed via spectroscopic analysis, ECD calculation, and X-ray crystallography. All isolates potentially reversed multidrug resistance (MDR) activity in both two cancer cells, HepG2/ADR and MCF-7/ADR. Specifically, hypermoin E (5) and hyperielliptone HA (7) were found to be the best MDR modulators with the reversal fold ranging from 41 to 236, which is higher than the positive control verapamil.

Anti-Inflammatory, Antioxidant, and Anti-Nonalcoholic Steatohepatitis Acylphloroglucinol Meroterpenoids from Hypericum bellum Flowers

In this work, 26 methylated acylphloroglucinol meroterpenoids with diverse skeletons, including 18 new ones (bellumones A-R, 1-18), were identified from the flowers of Hypericum bellum. Their structures including absolute configurations were elucidated by detailed spectroscopic data, calculated electronic circular dichroism (ECD), and X-ray diffraction (XRD). Through methylation at C-5, prenylation with different chain lengths of the acylphloroglucinol-derived core, along with different types of secondary cyclization, type A bicyclic polyprenylated acylphloroglucinols (BPAPs) (1-5 and 19-24) and dearomatized isoprenylated acylphloroglucinols (DIAPs) (6-18 and 25-26) were obtained. The significant results of anti-inflammatory, antioxidant, and anti-nonalcoholic steatohepatitis (anti-NASH) activities suggest its usefulness in daily health care.

In Vivo Screening of Xanthones from Garcinia oligantha Identified Oliganthin H as a Novel Natural Inhibitor of Convulsions

Epilepsy is a chronic neurological disorder, characterized by recurrent, spontaneous, and transient seizures, and affects more than 70 million people worldwide. Although two dozen antiepileptic drugs (AEDs) are approved and available in the market, seizures remain poorly controlled in one-third of epileptic patients who are suffering from drug resistance or various adverse effects. Recently, the xanthone skeleton has been regarded as an attractive scaffold for the discovery and development of emerging anticonvulsants. We had isolated several dihydroxanthone derivatives previously, including oliganthin H, oliganthin I, and oliganthin N, whose structures were similar and delicately elucidated by spectrum analysis or X-ray crystallographic data, from extracts of leaves of Garcinia oligantha. These xanthone analogues were evaluated for anticonvulsant activity, and a novel xanthone, oliganthin H, has been identified as a sound and effective natural inhibitor of convulsions in zebrafish in vivo. A preliminary structure-activity relationship analysis on the relationship between structures of the xanthone analogues and their activities was also conducted. Oliganthin H significantly suppressed convulsant behavior and reduced to about 25% and 50% of PTZ-induced activity, in 12.5 and 25 μM treatment groups (P < 0.01 and 0.001), respectively. Meanwhile, it reduced seizure activity, velocity, seizure duration, and number of bursts in zebrafish larvae (P < 0.05). Pretreatment of oliganthin H significantly restored aberrant induction of gene expressions including npas4a, c-fos, pyya, and bdnf, as well as gabra1, gad1, glsa, and glula, upon PTZ treatment. In addition, in silico analysis revealed the stability of the oliganthin H-GABAA receptor complex and their detailed binding pattern. Therefore, direct interactions with the GABAA receptor and involvement of downstream GABA-glutamate pathways were possible mechanisms of the anticonvulsant action of oliganthin H. Our findings present the anticonvulsant activity of oliganthin H, provide a novel scaffold for further modifications, and highlight the xanthone skeleton as an attractive and reliable resource for the development of emerging AEDs.

Ethnopharmacology of Hypericum species in China: A comprehensive review on ethnobotany, phytochemistry and pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Hypericum species have been used traditionally as astringent, antipyretic, diuretic, antiphlogistic, analgesic, and antidepressant in Europe, America, Africa, and Asia. One of the most extensively investigated medicinal herbs, H. perforatum L. (St. John's wort), is widely used in many countries to treat mild to moderate mental depression. Hypericum species are abundant throughout China, including 30 used as ethnomedicines. There are limited publications describing the ethnobotanical uses and biological activities associated with Hypericum species in China. Some reported activities include the treatment of wounds and bruises, irregular menstruation, dysentery, hepatitis, mastitis, jaundice, hemoptysis, and epistaxis.

AIM OF THE REVIEW

This review aims to critically examine how Hypericum species are used ethnomedicinally in China, to see if the ethnobotanical data may be useful to help prioritize Hypericum species and certain phytochemical constituents that may be new drug leads, and consider the focus and lack of the phytopharmacological study on Hypericum species in China.

MATERIALS AND METHODS

Classic medicinal books and ethnomedicinal publications were reviewed for the genus Hypericum (called jin si tao in Chinese). In addition, relevant information about ethnobotany, phytochemistry, and pharmacology were from online databases including SciFinder, Science Direct, PubMed, Google Scholar, and China National Knowledge Infrastructure (CNKI). "Hypericum", "", "ethnobotany", "traditional use", "ethnomedicine", "phytochemistry", "pharmacology" and "bioactivity" were used as keywords when searching the databases. Thus, available articles from 1959 to 2019 were collected and analyzed.

RESULTS

Among 64 Hypericum species recorded in China, 30 have been used as ethnomedicines by 15 linguistic groups such as Dai, Dong, Han, Miao, and Mongolian people. Hypericum species in China possess traditional uses which are also mirrored in Europe, America, Africa, and other countries in Asia. However, there are some unique ethnomedicinal uses in China. For example, several Hypericum species are used as a local remedy in southwest China, and H. attenuatum Fisch. ex Choisy is used to treat cardiac disorders in northeast China. Antitumor, anti-inflammatory, antimicrobial, neuroprotective, antidepressant, hepatoprotective, cardioprotective, and antiviral activities have been reported in numerous biological studies. The main phytochemical constituents in Hypericum consist of phloroglucinols, naphthodianthrones, xanthones, flavonoids, and terpenoids.

CONCLUSIONS

There is a rich traditional knowledge regarding the ethnomedicinal uses of Hypericum species in China. Through phytochemical and pharmacological studies, several medicinal Hypericum from China have yielded many bioactive phytochemicals, possessing antitumor, anti-inflammatory, antimicrobial, and neuroprotective properties. Hypericum species from China are potential sources of drugs to fight cancer and other chronic diseases. Remarkably, nearly half of Hypericum species in China have rarely been studied, and their ethnomedicinal potential have not been scientifically evaluated. Thus, in vitro mechanistic studies, in vivo pharmacology, and clinical efficacy are all needed, prioritizing those studies that relate most closely with their traditional uses. In addition, a comprehensive plant-resource evaluation, quality control, and toxicology studies are needed.

Hypericum spp.: An Update on the Biological Activities and Metabolic Profiles

Plants from the genus Hypericum, one genus of the Hypericaceae family, have attracted a lot of attention for their potential pharmaceutical applications. Most of the studies in the literature focus on H. perforatum L. (common St. John's wort), whose complex spectrum of bioactive compounds makes this species one of the top herbal remedies and supplements in the world. It is also important to compare the studies on other Hypericum species, both from the phytochemical and biological point of view. The aim of this review was to provide an update of most recent studies about biological investigations of plants belonging to Hypericum genus. The metabolic profiles of Hypericum spp. were also discussed in order to present a spectrum of secondary metabolites not previously identified in this genus.

Xanthones and Cancer: from Natural Sources to Mechanisms of Action

Xanthones are a class of heterocyclic natural products that have been widely studied for their pharmacological potential. In fact, they have been serving as scaffolds for the design of derivatives focusing on drug development. One of the main study targets of xanthones is their anticancer activity. Several compounds belonging to this class have already demonstrated cytotoxic and antitumor effects, making it a promising group for further exploration. This review therefore focuses on recently published studies, emphasizing their natural and synthetic sources and describing the main mechanisms of action responsible for the anticancer effect of promising xanthones.

Cytotoxic Xanthones from Hypericum stellatum, an Ethnomedicine in Southwest China

Hypericum stellatum, a species endemic to China, is used to treat hepatitis by several ethnic groups in Guizhou Province. This research was inspired by the traditional medicinal usage of H. stellatum, and aims to explore the phytochemistry and bioactivity of H. stellatum to explain why local people in Guizhou widely apply H. stellatum for liver protection. In this study, two new prenylated xanthones, hypxanthones A (8) and B (9), together with seven known compounds, were isolated from the aerial parts of the plant. Spectroscopic data as well as experimental and calculated ECD spectra were used to establish the structures of these compounds. Six xanthones isolated in this study, together with four xanthones previously isolated from H. stellatum, were evaluated for their growth-inhibitory activities against five human liver carcinoma cell lines to analyze the bioactivity and structure-activity relationship of xanthones from H. stellatum. Isojacareubin (6) showed significant cytotoxicity against five human liver carcinoma cell lines, with an IC₅₀ value ranging from 1.41 to 11.83 μM, which was stronger than the positive control cisplatin (IC₅₀ = 4.47–20.62 μM). Hypxanthone B (9) showed moderate cytotoxicity to three of the five cell lines. Finally, structure-activity analysis revealed that the prenyl and pyrano substituent groups of these xanthones contributed to their cytotoxicity.

Hyperforatins L-U: Prenylated acylphloroglucinols with a terminal double bond from Hypericum perforatum L. (St John's Wort)

Hyperforatins L-U, ten undescribed polycyclic polyprenylated acylphloroglucinols (PPAPs) bearing a terminal double bond, together with a known compound hypericumoxide J, were isolated from the aerial parts of Hypericum perforatum L. Their structures were elucidated by spectroscopic methods, including HRESIMS, IR, UV, and NMR (¹H, ¹³C, DEPT, HSQC, HMBC, ¹H-¹H COSY, and NOESY experiments). Their absolute configurations were determined by comprehensive analyses of their experimental ECD spectra in conjunction with a modified Mosher's method. Evaluation of their neuroprotective activities highlighted hyperforatin L, which displayed mild activity at a concentration of 10 μM.

Gentianella turkestanerum Showed Protective Effects on Hepatic Injury by Modulating the Endoplasmic Reticulum Stress and NF-κB Signaling Pathway

OBJECTIVE

To investigate the protective effects of Gentianella turkestanerum extraction by butanol (designated as GBA) on hepatic cell line L02 injury induced by carbon tetrachloride (CCl4) and hydrogen peroxide (H2O2).

METHODS

L02 cells were incubated with 5 µg/mL, 10 µg/mL, 20 µg/mL, 40 µg/mL, 60 µg/mL, 80 µg/mL and 100 µg/mL GBA for 24 hours, and then MTT assay was used to screen the cytotoxicity for GBA. Cells were divided into blank control group, CCl4/H2O2 model group, treated by CCl4 (20 mmol/L) or H2O2 (100 µmol/L); silymarin+CCl4/H2O2 group, treated by CCl4 (20 mmol/L) or H2O2 (100 µmol/L) and 5 µg/mL silymarin; GBA+CCl4/H2O2 group, treated by CCl4 (20 mmol/L) or H2O2 (100 µmol/L) and GBA (5 µg/mL, 10 µg/mL and 20 µg/mL). MTT assay was performed to determine the cellular activity. Malondialdehyde (MDA) content was determined using a commercial kit. The alanine transaminase (ALT), aspartate transaminase (AST) in the supernatant was determined. PE-Annexin V/7-ADD method was utilized to determine the apoptosis of cells. RT-PCR was used to evaluate the expression of endoplasmic reticulum stressrelated genes (CHOP, PERK, IRE1 and ATF6) mRNA. Western blot analysis was performed to determine the expression of CHOP, Caspase 12 and NF-κB protein.

RESULTS

Cellular survival after GBA (5 µg/mL, 10 µg/mL and 20 µg/mL) incubation was ≥ 75%. After GBA incubation, levels of ALT and AST showed a significant decrease (P < 0.05), while that of the MDA showed a significant decrease (P < 0.05). The apoptosis in the CCl4 or H2O2 group showed a significant increase compared to the control group (P < 0.05). In contrast, GBA-preincubation could attenuate the cellular apoptosis compared to the CCl4 or H2O2 group, which displayed a dose-dependent manner (P < 0.05). The expression of CHOP, PERK, IRE1 and ATF6 mRNA was significantly up-regulated in the presence of CCl4 or H2O2 (P < 0.05). Whereas, GBA induced a significant decrease in these mRNA thereafter (P < 0.05), together with a decrease in CHOP and Caspase 12 proteins (P < 0.05). Besides, it could attenuate the expression of NF-κB p65 in nuclear protein.

CONCLUSION

G. turkestanerum could inhibit the lipid peroxidation and increase the antioxidant activity. Also, it could inhibit the cellular apoptosis through down-regulating the transcriptional level of ERS related genes and proteins. This process was associated with the nuclear translocation of NF-κB p65 protein.

Polycyclic polyprenylated acylphloroglucinol and phenolic metabolites from the aerial parts of Hypericum elatoides and their neuroprotective and anti-neuroinflammatory activities

A phytochemical study on the aerial parts of Hypericum elatoides led to the isolation of a previously undescribed polycyclic polyprenylated acylphloroglucinol derivative, hyperelatone A, seven previously undescribed phenolic metabolites, hyperelatones B-H, along with ten known analogues. The structures of hyperelatones A-H were elucidated by 1D and 2D NMR spectroscopy, HRESIMS experiment, single-crystal X-ray diffraction and comparison of experimental and calculated ECD spectra, as well as chemical derivatization. All compounds were evaluated for their neuroprotective activity against hydrogen peroxide (H₂O₂)-induced cell injury in rat pheochromocytoma PC-12 cells and inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in BV-2 microglial cells. Hyperelatones B-D and H, cinchonain Ib, and tenuiside A showed noticeable neuroprotection at concentrations of 1.0-100.0 μM. Hyperelatones D, G, and H, (-)-epicatechin, tenuiside A, and (Z)-3-hexenyl-β-D-glucopyranoside exhibited significant anti-neuroinflammatory activity with IC₅₀ values ranging from 0.75 ± 0.02 to 5.83 ± 0.23 μM.

Hyperbeanols F-Q, diverse monoterpenoid polyprenylated acylphloroglucinols from the flowers of Hypericum beanii

Hyperbeanols F-Q, which are twelve undescribed monoterpenoid polyprenylated acylphloroglucinols, and four known analogues were isolated from the dried flowers of Hypericum beanii. Their structures were elucidated by detailed HRESIMS and 1D and 2D NMR data analyses. The absolute configurations of hyperbeanols FH were established by the circular dichroism (CD) exciton chirality method. The plausible biosynthetic pathway speculation of hyperbeanols F-Q indicated that diverse reactions, including prenylation, 1,6-ene reaction, rearrangement, epoxidation and dehydration, contributed to their diverse skeletons. Hyperbeanols FI, O and hypercalin B exhibited moderate nitric oxide (NO) inhibitory activities in LPS-induced RAW 264.7 macrophages, with IC₅₀ values in the range of 17.11-28.74 μM.

New depsidone and dichromone from the stems of Garcinia paucinervis with antiproliferative activity

A new depsidone, paucinervin Q (1), a new dichromone, paucinervin R (2), and a known compound, paucinervin B (3), were isolated from the stems of Garcinia paucinervis by various chromatographic methods. Their structures were determined by analysis of spectroscopic data. The isolates were evaluated for their antiproliferative activity against three cancer cell lines HL-60, PC-3 and CaCo-2. Compound 1 showed significant inhibitory activities.

Hyperelatosides A-E, biphenyl ether glycosides from Hypericum elatoides, with neurotrophic activity

Five new biphenyl ether glycosides, hyperelatosides A-E (1-5), one new benzoate glycoside, hyperelatoside F (6), along with nine known phenolic compounds (7-15), were isolated from the aerial parts of Hypericum elatoides. Their structures were elucidated by 1D and 2D NMR spectroscopy and HRESIMS, as well as chemical derivatization. This is the first report of the identification of biphenyl ether glycosides as plant metabolites and their possible biosynthetic pathway is proposed. Except for 3, the new phenolic metabolites exhibited significant neurotrophic activities to enhance nerve growth factor-induced neurite outgrowth in PC12 cells. In addition, the anti-neuroinflammatory and antioxidant activities of compounds 1-15 were preliminarily evaluated in vitro.

Phenolic metabolites from Hypericum kelleri Bald., an endemic species of Crete (Greece)

Thirteen compounds were isolated from the aerial parts of Hypericum kelleri Bald., growing as an endemic on the island of Crete (Greece). These compounds comprise four previously unknown prenylated xanthones 1,2-dihydro-3,8-dihydroxy-6-methoxy-1,1,5-tri(3-methylbut-2-enyl)xanthen-2,9-dione (kellerine A), 1,2-dihydro-3,6,8-trihydroxy-1,1,5-tri(3-methylbut-2-enyl)xanthen-2,9-dione (kellerine B), 1,2-dihydro-3,8-dihydroxy-6-methoxy-1,1-bi(3-methylbut-2-enyl)xanthen-2,9-dione (6-methylpatulone), (R/S)-1,3,5-trihydroxy-2-(3-methyl-2-buten-1-yl)-4-[2-(3-methylbut-2-enyl)-3-methylbut-3-enyl]-6-methoxy-9H-xanthen-9-one ((2″R/S)-kellerine C) and the hitherto undescribed depsidone (R/S)-1,3,6-trihydroxy-5-methoxy-2-(3-methyl-2-buten-1-yl)-4-[2-(3-methylbut-2-enyl)-3-methylbut-3-enyl]-11Η-dibenzo[b,e] [1,4]dioxepin-9-one ((2″R/S)-creticine). As known compounds, brevipsidone D, 4-geranyl-2-(2'-isobutyryl)-phloroglucinol, 4-geranyl-2-(2'-methylbutyryl)-phloroglucinol, I3, II8-biapigenin, quercetin, avicularin, pseudohypericin and neochlorogenic acid have been isolated. The structures were elucidated on the basis of their 1D, 2D NMR, CD and MS data. The study confirms the typical occurrence of xanthones in Hypericum section Oligostema (Boiss.) Stef., and is also the first report on the simultaneous isolation of acylphloroglucinols in this section. Furthermore the first evidence of depsidones in the genus Hypericum L. is reported. Cytotoxicity was investigated in HeLa cells for prenylated xanthones and the depsidones. Both triprenylated 1,2-dihydroxanthones (kellerine A and B) showed significant in vitro cytotoxicity with IC₅₀ values of 2.5 ± 0.1 (kellerine A) and 5.9 ± 0.9 (kellerine B) μM, whereas other compounds were less cytotoxic (IC₅₀ > 20 μM).

Lipid and Phenolic Constituents from Seeds of Hypericum perforatum L. and Hypericum tetrapterum Fr. and their Antioxidant Activity

Seeds of Hypericum perforatum and H. tetrapterum were extracted with dichloromethane and methanol and investigated by chromatographic and mass spectrometric methods. Both species yielded a fatty oil fraction amounting to 30.5% and 18.0% of the seed weight, respectively. Linoleic acid (C18:2n-6) was shown to be the predominant fatty acid constituent. Moreover, xanthone derivatives, i.e. tetrahydroxyxanthones (THX), xanthone-glycosides and xanthone-sulfonates, were assigned in methanolic extracts. For structure elucidation, one representative xanthone, namely 1,3,6,7-THX, was synthesized and analyzed via HPLC-DAD/MSⁿ and GC/MS. Total THX contents were quantitated applying a validated HPLC-DAD method, resulting in 1.25 g/kg (H. perforatum) and 0.27 g/kg (H. tetrapterum), respectively. Moreover, the free radical scavenging capacity of the methanol extracts was tested using the DPPH antioxidant assay. Both, H. perforatum (IC₅₀ = 8.7 mg/l) and 1,3,6,7-THX (IC₅₀ = 3.0 mg/l), exhibited good DPPH free radical scavenging activity compared to Trolox (IC₅₀ = 6.6 mg/l).

Beyond the Antagonism: Self-Labeled Xanthone Inhibitors as Modeled "Two-in-One" Drugs in Cancer Therapy

Self-labeled inhibitors (SLIs) are promising for creating links, ranging from cancer therapy and metastatic pathways to mechanistic elucidation. In this study, a new category of "two-in-one" fluorescent xanthone inhibitors was developed for the systematic evaluation of anticancer activity and the selective imaging of cytoplasm in vitro. These xanthone inhibitors presented high fluorescent brightness, working over a wide pH range enabled by a "switchable reaction" of the heterocyclic backbone. The strength and nature of fluorescence were probed via spectroscopic methods and density functional theory calculations on the molecular level, respectively. Along with the potent anticancer activity, which was demonstrated using MTT and clonogenic assays with high fluorescent brightness in the cytoplasm, SLI 3fd could be established as a modeled self-monitoring drug in cancer therapy.