New Phenolic Principles from Hypericum sampsonii

Hypericum sampsonii Hance: a review of its botany, traditional uses, phytochemistry, biological activity, and safety

Ethnopharmacological relevance: Hypericum sampsonii Hance, also known as Yuanbao Cao in Chinese, is a traditional medicinal herb from the Guttiferae family and has been widely used in China to treat various conditions, including dysentery, enteritis, mastitis, scrofula, and contusion. Aim of the review: This review aims to provide a comprehensive overview of the botany, traditional uses, phytochemistry, biological activity and safety of H. sampsonii and to highlight its potential for medical application and drug development. Materials and methods: We searched several databases, i.e., Web of Science, SciFinder, PubMed, CBM, CNKI, Google Scholar, etc., for relevant information on H. sampsonii. Additionally, we also consulted some books on Chinese medicine. Results: To date, 227 secondary metabolites have been isolated from H. sampsonii, including polycyclic polyprenylated acylphloroglucinols (PPAPs), benzophenones, xanthones, flavonoids, naphthodianthrones, anthraquinones and aromatic compounds. These metabolites exhibit various biological activities such as anti-inflammatory, anti-tumor, anti-depressant, anti-oxidant, anti-viral and anti-bacterial effects. PPAPs are considered the main active metabolites with rich biological activities. Despite being known as rich source of PPAPs, the full extent of H. sampsonii biological activities, including their potential as PDE4 inhibitors, remained unclear. Since, previous studies have mainly been based on structural identification of metabolites in H. sampsonii, and efficacy evaluations of these metabolites based on clinical applications of H. sampsonii lack sufficient data. However, current evidence suggest that PPAPs are the most likely material basis for efficacy. From the limited information available so far, there is no evidence of potential safety issues and the safety data are limited. Conclusion: Collectively, this review provides a comprehensive overview of the botany, traditional uses, phytochemistry, pharmacology, and safety of H. sampsonii, a valuable medicinal plant in China with various pharmacological activities. Based on pharmacological studies, H. sampsonii shows potential for treating gastrointestinal and gynecological disorders as well as traumatic injuries, which aligns with traditional medicinal use due to the presence of PPAPs, benzophenones, xanthones, and flavonoids. Therefore, further studies are needed to evaluate the pharmacological effects and elucidate the pharmacological mechanisms. In addition, pharmacological mechanisms and safety evaluation of PPAPs on animal models need to be clarified. Yet, further comprehensive studies are required to elucidate the phytochemical constituents, pharmacological mechanisms, structure-activity relationships, safety evaluation, and quality standards of this plant. Takentogether, this review highlights the potential of H. sampsonii for medical application and drug development.

Xanthones: Biosynthesis and Trafficking in Plants, Fungi and Lichens

Xanthones are a class of secondary metabolites produced by plant organisms. They are characterized by a wide structural variety and numerous biological activities that make them valuable metabolites for use in the pharmaceutical field. This review shows the current knowledge of the xanthone biosynthetic pathway with a focus on the precursors and the enzymes involved, as well as on the cellular and organ localization of xanthones in plants. Xanthone biosynthesis in plants involves the shikimate and the acetate pathways which originate in plastids and endoplasmic reticulum, respectively. The pathway continues following three alternative routes, two phenylalanine-dependent and one phenylalanine-independent. All three routes lead to the biosynthesis of 2,3',4,6-tetrahydroxybenzophenone, which is the central intermediate. Unlike plants, the xanthone core in fungi and lichens is wholly derived from polyketide. Although organs and tissues synthesizing and accumulating xanthones are known in plants, no information is yet available on their subcellular and cellular localization in fungi and lichens. This review highlights the studies published to date on xanthone biosynthesis and trafficking in plant organisms, from which it emerges that the mechanisms underlying their synthesis need to be further investigated in order to exploit them for application purposes.

Cytotoxic Constituents of the Bark of Hypericum roeperianum towards Multidrug-Resistant Cancer Cells

The global cancer burden remains a serious concern with the alarming incidence of one in eight men and one in eleven women dying in developing countries. This situation is aggravated by the multidrug resistance (MDR) of cancer cells that hampers chemotherapy. In this study, the cytotoxicity of the methanol extract (HRB), fractions (HRBa, HRBb, and HRBa1-5), and compounds from the bark of Hypericum roeperianum (HRB) was evaluated towards a panel of 9 cancer cell lines. The mode of action of the HRB and trichadonic acid (1) was also studied. Column chromatography was applied to isolate the constituents of HRB. The cytotoxicity of botanicals and phytochemicals was evaluated by the resazurin reduction assay (RRA). Caspase-Glo assay was used to evaluate the activity of caspases, and reactive oxygen species (ROS) (H₂DCFH-DA) were assessed by flow cytometry. Phytochemicals isolated from HRB were trichadonic acid (1), fridelan-3-one (2), 2-hydroxy-5-methoxyxanthone (3), norathyriol (4), 1,3,5,6-tetrahydroxyxanthone (5), betulinic acid (6), 3′-hydroxymethyl-2′-(4″-hydroxy-3″,5″-dimethoxyphenyl)-5′,6′:5,6-(6,8-dihydroxyxanthone)-1′,4′-dioxane (7), and 3′-hydroxymethyl-2′-(4″-hydroxy-3″,5″-dimethoxyphenyl)-5′,6′:5,6-(xanthone)-1′,4′-dioxane (8). Botanicals HRB, HRBa, HRBa2-4, HRBb, and doxorubicin displayed cytotoxic effects towards the 9 tested cancer cell lines. The recorded IC₅₀ values ranged from 11.43 µg/mL (against the P-glycoprotein (gp)-overexpressing CEM/ADR5000 leukemia cells) to 26.75 µg/mL (against HCT116 (p53^+/+) colon adenocarcinoma cells) for the crude extract HRB. Compounds 1, 5, and doxorubicin displayed cytotoxic effects towards the 9 tested cancer cell lines with IC₅₀ values varying from 14.44 µM (against CCRF-CEM leukemia cells) to 44.20 µM (against the resistant HCT116 (p53^−/−) cells) for 1 and from 38.46 µM (against CEM/ADR5000 cells) to 112.27 µM (against the resistant HCT116 (p53^−/−) cells) for 5. HRB and compound 1 induced apoptosis in CCRF-CEM cells. The apoptotic process was mediated by enhanced ROS production for HRB or via caspases activation and enhanced ROS production for compound 1. This study demonstrated that Hypericum roeperianum is a potential source of cytotoxic phytochemicals such as trichadonic acid and could be further exploited in cancer chemotherapy.

Benzophenone and Benzoylphloroglucinol Derivatives from Hypericum sampsonii with Anti-Inflammatory Mechanism of Otogirinin A

Three new compounds, 4-geranyloxy-2-hydroxy-6-isoprenyloxybenzophenone (1), hypericumone A (2) and hypericumone B (3), were obtained from the aerial parts of Hypericum sampsonii, along with six known compounds (4–9). The structures of these compounds were determined through spectroscopic and MS analyses. Hypericumone A (2), sampsonione J (8) and otogirinin A (9) exhibited potent inhibition (IC₅₀ values ≤ 40.32 μM) against lipopolysaccharide (LPS)-induced nitric oxide (NO) generation. Otogirinin A (9) possessed the highest inhibitory effect on NO production with IC₅₀ value of 32.87 ± 1.60 μM. The well-known proinflammatory cytokine, tumor necrosis factor-alpha (TNF-α) was also inhibited by otogirinin A (9). Western blot results demonstrated that otogirinin A (9) downregulated the high expression of inducible nitric oxide synthase (iNOS). Further investigations on the mechanism showed that otogirinin A (9) blocked the phosphorylation of MAPK/JNK and IκBα, whereas it showed no effect on the phosphorylation of MAPKs/ERK and p38. In addition, otogirinin A (9) stimulated anti-inflammatory M2 phenotype by elevating the expression of arginase 1 and Krüppel-like factor 4 (KLF4). The above results suggested that otogirinin A (9) could be considered as potential compound for further development of NO production-targeted anti-inflammatory agent.

Bioactive compounds from the aerial parts of Hypericum sampsonii

Hypericum sampsonii is an important medicinal plant used in Vietnam to treat many diseases such as backache, burns, diarrhea, and swelling. In order to study the chemical constituents in the aerial parts of H. sampsonii, five compounds, including two xanthones (1-2), and three benzophenones (3-5) were isolated from the aerial parts of the H. sampsonii with various chromatographic separations. Their chemical structures were established on the basis of spectroscopic data such as 1D- and 2D-NMR, HR-ESI-MS. Their anti-inflammatory activities were investigated by measuring nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW264.7 cells. Moreover, the DPPH radical scavenging was evaluated. As the obtained results, compound 5 showed the strongest inhibitory activity against LPS-stimulated NO production in RAW264.7 cells with IC₅₀ value ranging from 2.00 ± 0.34 µM.

Phenotyping the genus Hypericum by secondary metabolite profiling: emodin vs. skyrin, two possible key intermediates in hypericin biosynthesis

A wide range of compounds that occur in the genus Hypericum are listed as effective drugs of natural origin. The main biological activities of several Hypericum representatives are due to the presence of naphthodianthrones, phloroglucinols, and other diverse groups of secondary metabolites that synergistically contribute to their therapeutic effects. The regulation of biosynthesis of hypericin as the key bioactive naphthodianthrone remains uncertain. Here, we present liquid chromatography mass spectrometry-based phenotyping of 17 Hypericum species, the results of which suggest an important role for skyrin and its derivatives in the polyketide pathway that leads to hypericin formation. Moreover, we report for the first time the presence of new metabolites in the genus Hypericum that are related to classes of anthraquinones, their derivatives, and phloroglucinols. As skyrin and other species of anthraquinones are rarely found in higher plants but frequently occur in fungal microorganisms, the obtained results suggest that further research on the synthesis pathways of hypericin and the role of anthraquinone derivatives in plant metabolism should be carried out. The fact that these compounds are commonly synthesized in endophytic fungi and perhaps there is some similarity in the metabolic pathways between these organisms should also be investigated.

Tricyclic Acylphloroglucinols from Hypericum lanceolatum and Regioselective Synthesis of Selancins A and B

The chemical investigation of the chloroform extract of Hypericum lanceolatum guided by (1)H NMR, ESIMS, and TLC profiles led to the isolation of 11 new tricyclic acylphloroglucinol derivatives, named selancins A-I (1-9) and hyperselancins A and B (10 and 11), along with the known compound 3-O-geranylemodin (12), which is described for a Hypericum species for the first time. Compounds 8 and 9 are the first examples of natural products with a 6-acyl-2,2-dimethylchroman-4-one core fused with a dimethylpyran unit. The new compounds 1-9 are rare acylphloroglucinol derivatives with two fused dimethylpyran units. Compounds 10 and 11 are derivatives of polycyclic polyprenylated acylphloroglucinols related to hyperforin, the active component of St. John's wort. Their structures were elucidated by UV, IR, extensive 1D and 2D NMR experiments, HRESIMS, and comparison with the literature data. The absolute configurations of 5, 8, 10, and 11 were determined by comparing experimental and calculated electronic circular dichroism spectra. Compounds 1 and 2 were synthesized regioselectively in two steps. The cytotoxicity of the crude extract (88% growth inhibition at 50 μg/mL) and of compounds 1-6, 8, 9, and 12 (no significant growth inhibition up to a concentration of 10 mM) against colon (HT-29) and prostate (PC-3) cancer cell lines was determined. No anthelmintic activity was observed for the crude extract.

A multilayer screening approach toward the discovery of novel Pf-DHFR inhibitors

A small yet diverse xanthone library was build and computationally docked against wild type Pf-DHFR by Molegro Virtual Docker (MolDock). For analysis of results an integrated approach based on re-ranking, scaling (based on heavy atom counts), pose clustering and visual inspection was implemented. Standard methods such as self-docking (for docking), EF analysis, average rank determinations (for size normalization), and cluster quality indices (for pose clustering) were used for validation of results. Three compounds X5, X113A and X164B displayed contact footprints similar to the known inhibitors with good scores. Finally, 16 compounds were extracted from ZINC data base by similarity based screening, docking score and drug/lead likeness. Out of these 16 compounds, 11 displayed very close contact footprints to experimentally known inhibitors, indicating there potential utility in further drug discovery efforts.

Sampbenzophenones A–G, prenylated benzoylphloroglucinol derivatives from Hypericum sampsonii

Seven prenylated benzoylphloroglucinol derivatives, named sampbenzophenones A–G (1–7), together with two known analogues (8 and 9), were isolated from the aerial parts of Hypericum sampsonii.

A new 3,4-seco-oleanane-type triterpenoid with an unusual enedione moiety from Hypericum ascyron

A novel 3,4-seco-oleanane-type triterpenoid named 3,4-seco-olean-13(18)-ene-12,19-dione-3-oic acid (1), bearing an unusual enedione moiety, was isolated from the aerial parts of Hypericum ascyron, together with a known feiedelane-type triterpenoid friedelin (2). The structure of 1 with absolute configuration was elucidated on the basis of spectroscopic methods and a single-crystal X-ray diffraction analysis.

Novel polyprenylated phloroglucinols from Hypericum sampsonii

Hypericum sampsonii Hance (Clusiaceae) is a folk medicine used in Taiwan to treat blood stasis, relieve swelling, and as an anti-hepatitis drug. Two new polyprenylated phloroglucinol derivatives, hypersampsone R (1) and hypersampsone S (2), and a known prenylated benzophenone, hyperibone K (3) were isolated from the aerial parts of H. sampsonii. Their structures were determined by extensive 1D and 2D NMR, and MS spectral analyses.

Naturally Occurring Xanthones: Chemistry and Biology

Xanthones are one of the biggest classes of compounds in natural product chemistry. A number of xanthones have been isolated from natural sources of higher plants, fungi, ferns, and lichens. They have gradually risen to great importance because of their medicinal properties. This review focuses on the types, isolation, characterization, biological applications, and biosynthesis of naturally occurring xanthones isolated so far. Different physicochemical and instrumental methods such as liquid-solid and liquid-liquid extraction, TLC, flash chromatography, column chromatography, IR, 1H NMR and 13C NMR spectroscopy, GLC, HPLC, GC, and LCMS have been widely used for isolation and structural elucidation of xanthones. Hepatoprotective, anticarcinogenic, antileprosy, antimalarial, antioxidant, anticholinergic, mutagenicity, radioprotective, immunomodulatory, antibone resorption, antiparasitic, neuraminidase inhibitory, anticomplement, antibacterial, antifungal, algicidal, anti-HIV, cardioprotective, antitumoral, antidiabetes, antihyperlipidemic, antiatherogenic, anti-inflammatory, antiulcer, antidiabetic, hypolipidemic, analgesic, antiasthmatic, antihistaminic, antiamoebic, diuretic, antidiarrheal, larvicidal, and ovicidal activities have been reported for natural occurring xanthones. To a certain extent, this review provides necessary foundation for further research and development of new medicines.

Differential Expression of Benzophenone Synthase and Chalcone Synthase in Hypericum Sampsonii

cDNAs encoding Hypericum sampsonii benzophenone synthase (HsBPS) and chalcone synthase (HsCHS) were isolated and functionally characterized. Differential expressions of HsBPS and HsCHS were monitored using quantitative polymerase chain reaction (PCR). In the vegetative stage, HsBPS was highly expressed in the roots; its transcript level was approx. 100 times higher than that of HsCHS. Relatively high transcript amounts of HsBPS were also detected in older leaves, whereas the youngest leaves contained higher transcript amounts of HsCHS. In the reproductive stage, maximum HsCHS expression was detected in flowers, the transcript level being approx. 5 times higher than that of HsBPS. The inversed situation with a 10-fold difference in the expression levels was observed with fruits. High transcript amounts for both proteins were found in roots.

Prenylated phloroglucinol derivatives from Hypericum sampsonii

Six new acylphloroglucinol derivatives, sampsonols A-F (1-6), were isolated from the petroleum ether extract of the aerial parts of Hypericum sampsonii. The structures and relative configurations of sampsonols A-F were elucidated by extensive spectroscopic analyses. All these compounds were tested for their in vitro cytotoxic and anti-inflammatory activities. Sampsonols A and B (1 and 2) showed significant cytotoxicity against four human tumor cell lines with IC(50) values in the range of 13-28μM, whereas sampsonols C and F (3 and 6) showed potent inhibitory activities against LPS-induced NO production in RAW 264.7 macrophages with IC(50) values of 27.3 and 29.3μM, respectively.

Two new xanthones from Hypericum sampsonii and biological activity of the isolated compounds

Phytochemical investigation of the CH(2) Cl(2) extract of the aerial part of Hypericum sampsonii yielded two new prenylated xanthones, hypericumxanthone A and B, together with three known xanthones. Their structures were elucidated by analysis of physical and spectral (UV, IR, mass and NMR) data and comparison of spectroscopic data with those reported previously. All these compounds were evaluated for in vitro antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Two new compounds were also tested for their cytotoxicity against human breast (MCF-7), hepatoma (HepG2), colon (HT-29) and lung (A549) tumour cell lines. Two new compounds showed moderate antibacterial activities at minimum inhibitory concentrations (MIC) of 16 and 32 µg/mL, respectively, whereas the positive standard antibacterial drug, vancomycin, showed an MIC of 8 µg/mL. The other compounds were inactive against MRSA. In addition, hypericumxanthone B showed weak inhibitory activities against four human tumour cell lines.

Prenylated benzophenone peroxide derivatives from Hypericum sampsonii

Two new prenylated benzophenone peroxide derivatives, peroxysampsones A and B (1 and 2, resp.), together with a known compound, plukenetione C (3), were isolated from the roots of the Chinese medicinal plant Hypericum sampsonii, and their structures were elucidated by detailed spectral analysis. These compounds are the unusual peroxides of polyprenylated benzophenone derivatives, containing the unique caged moiety of 4,5-dioxatetracyclo[9.3.1.1(9,13).0(1,7)]hexadecane-12,14,15-trione. In the biological test, peroxysampsone A (1) showed comparable activity with norfloxacin against a NorA over-expressing multidrug-resistant (MDR) strain of Staphylococcus aureus SA-1199B.

Polyisoprenylated benzoylphloroglucinol derivatives from Hypericum sampsonii

Bioassay-directed fractionation using multidrug-resistant (MDR) Staphylococcus aureus resulted in the isolation of four new polyprenylated benzophloroglucinol derivatives, sampsoniones N-Q (1-4), and four known compounds, 7-epiclusianone (5) and sampsoniones B, L, and R, from the roots of Hypericum sampsonii. The structures of these compounds were established by analysis of spectroscopic data, and the structures of 4 and 5 were determined by single-crystal X-ray diffraction crystallography. In the bioassay, 7-epiclusianone (5) showed promising activity with a minimum inhibitory concentration (MIC) of 7.3 microM against the NorA overexpressing MDR S. aureus strain SA-1199B; the positive control antibiotic norfloxacin showed activity at MIC 100 microM.