Cytotoxic polyprenylated phloroglucinol derivatives from Hypericum elodeoides Choisy modulating the transactivation of RXRα

Hypersine H, One Undescribed Xanthone From the Hypericum elodeoides Choisy With Anti-Neuroinflammation Activity

One undescribed xanthone, hypersine H (1), together with three known analogs, 3,7-dihydroxy-1-methoxyxanthone (2), 1,7-dihydroxy-5,6-dimethoxyxanthone (3), and 1,5-dihydroxy-6,7-dimethoxyxanthone (4), were isolated from the whole plant of Hypericum elodeoides Choisy. Their structures, including absolute configurations, were unambiguously elucidated by HR-ESI-MS, extensive NMR spectroscopy, and quantum chemical calculation of electronic circular dichroism (ECD) method. Moreover, the anti-neuroinflammation activities of isolated compounds were evaluated. As a result, Compounds 1-2 decreased the production of nitric oxide (NO) in LPS-stimulated mouse BV2 microglia. Further mechanism study indicated that 1 and 2 exerted anti-neuroinflammation effects by suppressing the expression of pro-inflammatory enzymes, including inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2. Above all, compounds 1-2 showed promise as useful therapeutic agents in the treatment of neurodegenerative diseases caused by neuroinflammation.

Filicinic acid based meroterpenoids from Hypericum elodeoides and their anti-Alzheimer's disease effects

(±)-Elodeoidileons A-L (1-12), 12 pairs of previously undescribed filicinic acid based meroterpenoids were isolated from Hypericum elodeoides with unique linear or angular 6/6/6 ring core. Modern spectroscopic techniques, modified Mosher's method and quantum chemical calculations were used to identify the planner structures and configurations of 1-12. Additionally, the potential biosynthetic pathways for 1-12 were anticipated. Moreover, biological activity assessments suggested that 1a, 5a, and 11b could activate Retinoid X receptor-α (RXRα) transcription and enhance the ATP-binding cassette transporter A1 (ABCA1) protein's expression. Fluorescence titration assay suggested that 1a might have a direct interaction with the RXRα-LBD protein, with an estimated Kd value of 5.85 μM. Moreover, molecular docking study confirmed the binding of 1a to RXRα and further validated by cellular thermal shift assay (CETSA). Thus, compound 1a may promote β-amyloid (Aβ) clearance by targeting RXRα and upregulating the expression of the ABCA1 protein, showing promise as anti-Alzheimer's agent.

Cytotoxic and Antibacterial Prenylated Acylphloroglucinols from Hypericum olympicum L

Two new bicyclo[3.3.1]nonane type bicyclic polyprenylated acylphloroglucinol derivatives (BPAPs), olympiforin A and B as well as three known prenylated phloroglucinols, were isolated from the aerial parts of Hypericum olympicum L. The structures of the isolated compounds were established by means of spectral techniques (HRESIMS and 1D and 2D NMR). All compounds were tested on a panel of human tumor (MDA-MB-231, EJ, K-562, HL-60 and HL-60/DOX) and non- tumorigenic (HEK-293 and EA.hy926) cell lines using the MTT assay. All tested compounds exerted significant in vitro cytotoxicity with IC₅₀ values ranging from 1.2 to 24.9 μM and from 0.9 to 34 μM on tumor and non-cancerous cell lines, respectively. Most of the compounds had good selectivity and were more cytotoxic to the tumor cell lines than to the normal ones. A degradation of the precursor caspase 9 for some of the compounds was observed; therefore, the intrinsic pathway of apoptosis is the most likely mechanism of cytotoxic activity. The BPAPs were examined for antibacterial and antibiofilm activity through the broth microdilution method and the protocol of Stepanović. They showed a moderate effect against Enterococcus faecalis and Streptococcus pyogenes but a very profound activity against Staphylococcus aureus with minimum inhibitory concentrations (MIC) in the range of 0.78-2 mg/L. Olympiforin B also had a great effect against methicillin-resistant S. aureus (MRSA) with an MIC value of 1 mg/L and a very significant antibiofilm activity on that strain with a minimum biofilm inhibition concentration (MBIC) value of 0.5 mg/L. The structures of the isolated compounds were in silico evaluated using ADME and drug likeness tests.

Hypericum Genus as a Natural Source for Biologically Active Compounds

Hypericum L. genus plants are distributed worldwide, with numerous species identified throughout all continents, except Antarctica. These plant species are currently used in various systems of traditional medicine to treat mild depression, wounds and burns, diarrhea, pain, fevers, and their secondary metabolites previously shown, and the in vitro and/or in vivo cytotoxic, antimicrobial, anti-inflammatory, antioxidant, antihyperglycemic, and hepatoprotective activities, as well as the acetylcholinesterase and monoamine oxidase inhibitory activities. We conducted a systematic bibliographic search according to the Cochrane Collaboration guidelines to answer the question: "What is known about plants of Hypericum genus as a source of natural products with potential clinical biological activity?" We documented 414 different natural products with confirmed in vitro/in vivo biological activities, and 58 different Hypericum plant species as sources for these natural products. Phloroglucinols, acylphloroglucinols, xanthones, and benzophenones were the main chemical classes identified. The selective cytotoxicity against tumor cells, cell protection, anti-inflammatory, antimicrobial, antidepressant, anti-Alzheimer's, and adipogenesis-inhibition biological activities are described. Acylphloroglucinols were the most frequent compounds with anticancer and cell-protection mechanisms. To date, no work has been published with a full descriptive list directly relating secondary metabolites to their species of origin, plant parts used, extraction methodologies, mechanisms of action, and biological activities.

Seco-polyprenylated acylphloroglucinols from Hypericum elodeoides induced cell cycle arrest and apoptosis in MCF-7 cells via oxidative DNA damage

Four undescribed seco-polyprenylated acylphloroglucinols (seco-PAPs), elodeoidesones A-D (1-4), were characterized from Hypericum elodeoides. Compound 1 represents the 1,6-seco-PAPs with fascinating 5/5 fused ring, while 2-4 possess a 1,2-seco-PAPs skeleton with a five-membered lactone core. Their structures including absolute configurations were established by spectroscopic analyses and quantum chemical computations. A possible biosynthetic pathway of 1-4 from normal PAPs was proposed. All the isolates were investigated for their cytotoxicity against tumor cells. Notably, 1 inhibited the proliferation of MCF-7 cells with the IC₅₀ value of 7.34 μM. Mechanism investigation indicated that 1 induced MCF-7 cells apoptosis by blocking cell cycle at S phase via inducing oxidative DNA damage.

Bioinspired Total Synthesis of Erectones A and B, and the Revised Structure of Hyperelodione D

The field of biomimetic synthesis seeks to apply biosynthetic hypotheses to the efficient construction of complex natural products. This approach can also guide the revision of incorrectly assigned structures. Herein, we describe the evolution of a concise total synthesis and structural reassignment of hyperelodione D, a tetracyclic meroterpenoid derived from a Hypericum plant, alongside some biogenetically related natural products, erectones A and B. The key step in the synthesis of hyperelodione D forms six stereocentres and three rings in a bioinspired cascade reaction that features an intermolecular Diels-Alder reaction, an intramolecular Prins reaction and a terminating cycloetherification.

Unprecedented Monoterpenoid Polyprenylated Acylphloroglucinols with a Rare 6/6/5/4 Tetracyclic Core, Enhanced MCF-7 Cells' Sensitivity to Camptothecin by Inhibiting the DNA Damage Response

(±)-Hypersines A-C (1-3), the three pairs of enantiomerically pure monoterpenoid polyprenylated acylphloroglucinols with an unprecedented 6/6/5/4 fused ring system, were isolated from Hypericum elodeoides. Their structures, including absolute configurations, were elucidated by comprehensive spectroscopic data, single-crystal X-ray diffraction, and quantum chemical calculations. The plausible, biosynthetic pathway of 1-3 was proposed. Moreover, the bioactivity evaluation indicated that 1a might be a novel DNA damage response inhibitor, and could enhance MCF-7 cell sensitivity to the anticancer agent, camptothecin.