A Survey on the Hypericum Genus: Secondary Metabolites and Bioactivity

Constituents and Selective BuChE Inhibitory Activity of the Essential Oil from Hypericum aciculare Kunth

A potential source of new inhibitors of cholinesterase enzymes are certain compounds of natural plant origin; therefore, in the study described herein we have determined the chemical composition and the acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activities of the essential oil (EO) steam distilled from aerial parts of Hypericum aciculare, which was collected in southern Ecuador. The oil qualitative and quantitative composition was determined by GC-FID and GC-MS using a non-polar and a polar chromatographic column. A total of fifty-three constituents were identified, that accounted for about 98% of the EO content. The hydrocarbon n-nonane (16.4-28.7%) and the aldehyde n-decanal (20.7-23.1%) were the predominant oil constituents. In addition, the EO showed significant inhibition of BuChE (IC₅₀ = 28.3 ± 2.7 μg/mL) and moderate activity towards AChE (IC₅₀ = 82.1 ± 12.1 µg/mL). Thus, the EO from H. aciculare aerial parts is an interesting candidate to investigate the mechanism of selective ChE inhibition by the two ChE enzymes with the aim to discover potential targets to control the progression of the Alzheimer's disease (AD).

Chemical Characterization and Antioxidant Activity of Nine Hypericum Species from Greece

Hypericum L. comprises about 500 species distributed almost worldwide. Research has mainly focused on H. perforatum with confirmed biological activity on the alleviation of depression symptoms, among others. The compounds responsible for such activity are considered naphthodianthrones and acylphloroglucinols. Other Hypericum species are less studied or not studied, and further research is needed to complete the characterization of the genus. In this study we evaluated the qualitative and quantitative phytochemical profile of nine Hypericum species native to Greece, namely H. perforatum, H. tetrapterum, H. perfoliatum, H. rumeliacum subsp. apollinis, H. vesiculosum, H. cycladicum, H. fragile, H. olympicum and H. delphicum. Qualitative analysis was performed using the LC/Q-TOF/HRMS technique, while quantitative data were calculated with the single point external standard method. Additionally, we estimated the antioxidant activity of the extracts using DPPH and ABTS assays. Three species endemic to Greece (H. cycladicum, H. fragile, H. delphicum) were studied for the first time. Our results indicated that all studied species are rich in secondary metabolites, mainly of the flavonoids family, with strong antioxidant activity.

Outstanding Antibacterial Activity of Hypericum rochelii-Comparison of the Antimicrobial Effects of Extracts and Fractions from Four Hypericum Species Growing in Bulgaria with a Focus on Prenylated Phloroglucinols

Microbial infections are by no means a health problem from a past era due to the increasing antimicrobial resistance of infectious strains. Medicine is in constant need of new drugs and, recently, plant products have had a deserved renaissance and garnered scientific recognition. The aim of this work was to assess the antimicrobial activity of ten active ingredients from four Hypericum species growing in Bulgaria, as well as to obtain preliminary data on the phytochemical composition of the most promising samples. Extracts and fractions from H. rochelii Griseb. ex Schenk, H. hirsutum L., H. barbatum Jacq. and H. rumeliacum Boiss. obtained with conventional or supercritical CO₂ extraction were tested on a panel of pathogenic microorganisms using broth microdilution, agar plates, dehydrogenase activity and biofilm assays. The panel of samples showed from weak to extraordinary antibacterial effects. Three of them (from H. rochelii and H. hirsutum) had minimum inhibitory concentrations as low as 0.625-78 mg/L and minimum bactericidal concentrations of 19.5-625 mg/L against Staphylococcus aureus and other Gram-positive bacteria. These values placed these samples among the best antibacterial extracts from the Hypericum genus. Some of the agents also demonstrated very high antibiofilm activity against methicillin-resistant S. aureus. Ultra-high-performance liquid chromatography-high-resolution mass spectrometry revealed the three most potent samples as rich sources of biologically active phloroglucinols. They were shown to be good drug or nutraceutical candidates, presumably without some of the side effects of conventional antibiotics.

Constituents, Enantiomeric Content, and ChE Inhibitory Activity of the Essential Oil from Hypericum laricifolium Juss. Aerial Parts Collected in Ecuador

The physical properties, chemical composition, enantiomer distribution, and cholinesterase (ChE) inhibitory activity were determined for a steam-distilled essential oil (EO), with a yield of 0.15 ± 0.05 % (w/w), from H. laricifolium aerial parts, collected in southern Ecuador. The oil qualitative and quantitative analyses were performed by GC-EIMS and GC-FID techniques, using two capillary columns containing a non-polar 5%-phenyl-methylpolysiloxane and a polar polyethylene glycol stationary phase, respectively. The main constituents (>10%) detected on the two columns were, respectively, limonene (24.29, 23.16%), (E)-β-ocimene (21.89, 27.15%), and (Z)-β-ocimene (12.88, 16.03%). The EO enantioselective analysis was carried out using a column based on 2,3-diethyl-6-tert-butyldimethylsilyl-β-cyclodextrin. Two mixtures of chiral monoterpenes were detected containing (1R,5R)-(+)-α-pinene (ee = 83.68%), and (S)-(-)-limonene (ee = 88.30%) as the major enantiomers. This finding led to some hypotheses about the existence in the plant of two enantioselective biosynthetic pathways. Finally, the EO exhibited selective inhibitory effects in vitro against butyrylcholinesterase (BuChE) (IC50 = 36.80 ± 2.40 µg/mL), which were about three times greater than against acetylcholinesterase (IC50 = 106.10 ± 20.20). Thus, the EO from Ecuadorian H. laricifolium is an interesting candidate for investigating the mechanism of the selective inhibition of BuChE and for discovering novel drugs to manage the progression of Alzheimer’s disease.

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.

Hypericum Essential Oils—Composition and Bioactivities: An Update (2012–2022)

Hypericum genus, considered to comprise over 500 species that exhibit cosmopolitan distribution, has attracted human interest since ancient times. The present review aims to provide and summarize the recent literature (2012–2022) on the essential oils of the title genus. Research articles were collected from various scientific databases such as PubMed, ScienceDirect, Reaxys, and Google Scholar. Scientific reports related to the chemical composition, as well as the in vitro and in vivo pharmacological activities, are presented, also including a brief outlook of the potential relationship between traditional uses and Hypericum essential oils bioactivity.

PSYCHE-A Valuable Experiment in Plant NMR-Metabolomics

¹H-NMR is a very reproducible spectroscopic method and, therefore, a powerful tool for the metabolomic analysis of biological samples. However, due to the high complexity of natural samples, such as plant extracts, the evaluation of spectra is difficult because of signal overlap. The new NMR “Pure Shift” methods improve spectral resolution by suppressing homonuclear coupling and turning multiplets into singlets. The PSYCHE (Pure Shift yielded by Chirp excitation) and the Zangger–Sterk pulse sequence were tested. The parameters of the more suitable PSYCHE experiment were optimized, and the extracts of 21 Hypericum species were measured. Different evaluation criteria were used to compare the suitability of the PSYCHE experiment with conventional ¹H-NMR. The relationship between the integral of a signal and the related bin value established by linear regression demonstrates an equal representation of the integrals in binned PSYCHE spectra compared to conventional ¹H-NMR. Using multivariate data analysis based on both techniques reveals comparable results. The obtained data demonstrate that Pure Shift spectra can support the evaluation of conventional ¹H-NMR experiments.

Solvent Effect in Gold(I)-Catalyzed Domino Reaction: Access to Furopyrans

We report an efficient synthesis of furopyrans through a gold(I)-catalyzed domino reaction. By starting from the same source and changing the solvent of the reaction, two classes of furopyrans are accessible. During this one-step process, which takes place in DMF, two bonds and two heterocycles are formed. DFT calculations furnish the mechanistic understanding of this transformation. The sequence includes a 5-endo-dig cyclization, a regioselective 8-endo-dig cyclization, and a retro 8π and a 6π electrocyclization.

Chemical Composition and Antimicrobial Activity of the Essential Oils of Three Closely Related Hypericum Species Growing Wild on the Island of Crete, Greece

The volatile compositions of three closely related Hypericum species growing wild on the island of Crete were studied, all belonging to the section Coridium. Hydro-distillation in a modified Clevenger-type apparatus was performed according to the Hellenic Pharmacopoeia in order to obtain the essential oils, which were analyzed by GC-MS. Identification of the compounds was carried out by comparison of MS spectra and retention indices with literature data, as well as by co-chromatography with authentic samples. In total, 123 different compounds were identified and the main compounds were by order of their abundance as follows: H. empetrifolium: α-pinene, germacrene D, β-pinene, E-caryophyllene; H. amblycalyx: β-elemene, β-selinene, α-pinene, E-caryophyllene, α-selinene; H. jovis: trans-calamenene, α-selinene, β-elemene. The chemical results revealed the differences and similarities (qualitative and quantitative) between the studied oils, supporting the hypothesis that essential oils from Hypericum spp. do not serve as chemotaxonomic markers. Moreover, the essential oils were subjected to antimicrobial screening. According to the given results, the essential oils possessed better antifungal and anticandidal activities than antibacterial activities.

Three new prenyloxy chromanones from aerial parts of Hypericum aucheri

Three new prenyloxy chromanone derivatives, aucherine A-C (6, 7 and 9) as well as six known prenylated phloroglucinols (1-5 and 8) were isolated from the aerial parts of Hypericum aucheri Jaub. Et Spach. The structures of the isolated compounds were established by means of spectral techniques (HRESIMS, 1D and 2D NMR). The new compounds were tested on а panel of human tumor cell line using MTT assay. All tested compounds exerted moderate cytotoxicity with IC₅₀ values ranging from 19.6 to 57.8 μM. The influence of the new compounds on some key signaling molecules (procaspase-9 and Bcl-xL), implicated in the regulation of programmed cell death was assessed by Western blot analysis.

Remarkable rutin-rich Hypericum capitatum extract exhibits anti-inflammatory effects on turpentine oil-induced inflammation in rats

BACKGROUND

Natural extracts with beneficial biological activities are nowadays of high interest, in various treatment or prophylaxis. Hypericum capitatum has been known for its curative effects for centuries and its extracts have become of interest due to their distinct activity among other Hypericaceae members. In this study, further light is aimed to be shed on the secondary-metabolites composition of H. capitatum extracts, using chromatographic techniques and Electron paramagnetic resonance profiles in alkaline medium. Considering that no previous works explored the anti-inflammatory activity of H. capitatum, here, an in vivo study is also designed in order to evaluate this property by assessing the impact of one of H. capitatum extracts in ameliorating turpentine oil-induced inflammation on rats and to quantify their blood antioxidants level.

METHODS

Chromatographic techniques and Electron paramagnetic resonance spectroscopy were used in order to describe the chemical profile in different parts of the plant. The in vivo study on turpentine-oil induced inflammation in rats included three doses of H. capitatum extract expressed in rutin concentration. Oxidative stress was measured using total oxidative status, total antioxidant capacity, oxidative stress index, 3-nitrotyrosine, nitric oxide, malondialdehyde, superoxide dismutase, catalase and the inflammatory response was evaluated by performing a complete blood cells count and C reactive protein.

RESULTS

The extract was remarkably rich in rutin; however, other polyphenolic-like minor components appeared important in explaining the observed biological properties. The tested extract prevents the increase of inflammation-induced white blood cell count, number of neutrophils, and serum nitric oxide, and did so in a dose-dependent manner, similarly to the positive control-diclofenac. In addition, the same extract appeared to be a good alternative to diclofenac to restore total oxidative status, thiobarbituric active reactive species, total proteins and C reactive proteins. Moreover, antioxidant enzymes such as catalase, superoxide dismutase and total serum thiol concentration were significantly increased by the tested extract.

CONCLUSIONS

Due to its powerful reservoir rich in rutin, H. capitatum extract depicted its in vivo antioxidant and anti-inflammatory effects indicating it to be a good alternative to conventional drugs for oxidative stress protection.

Sequential regiospecific gem-diprenylation of tetrahydroxyxanthone by prenyltransferases from Hypericum sp

Polyprenylated acylphloroglucinol derivatives, such as xanthones, are natural plant products with interesting pharmacological properties. They are difficult to synthesize chemically. Biotechnological production is desirable but it requires an understanding of the biosynthetic pathways. cDNAs encoding membrane-bound aromatic prenyltransferase (aPT) enzymes from Hypericum sampsonii seedlings (HsPT8px and HsPTpat) and Hypericum calycinum cell cultures (HcPT8px and HcPTpat) were cloned and expressed in Saccharomyces cerevisiae and Nicotiana benthamiana, respectively. Microsomes and chloroplasts were used for functional analysis. The enzymes catalyzed the prenylation of 1,3,6,7-tetrahydroxyxanthone (1367THX) and/or 1,3,6,7-tetrahydroxy-8-prenylxanthone (8PX) and discriminated nine additionally tested acylphloroglucinol derivatives. The transient expression of the two aPT genes preceded the accumulation of the products in elicitor-treated H. calycinum cell cultures. C-terminal yellow fluorescent protein fusions of the two enzymes were localized to the envelope of chloroplasts in N. benthamiana leaves. Based on the kinetic properties of HsPT8px and HsPTpat, the enzymes catalyze sequential rather than parallel addition of two prenyl groups to the carbon atom 8 of 1367THX, yielding gem-diprenylated patulone under loss of aromaticity of the gem-dialkylated ring. Coexpression in yeast significantly increased product formation. The patulone biosynthetic pathway involves multiple subcellular compartments. The aPTs studied here and related enzymes may be promising tools for plant/microbe metabolic pathway engineering.

Polycyclic Polyprenylated Acylphloroglucinol Derivatives from Hypericum acmosepalum

Hypericum acmosepalum belongs to the Hypericum genus of the Guttiferae family. The characteristic components in Hypericum are mainly a series of polycyclic polyprenylated acylphloroglucinols (PPAPs), flavonoids, and xanthones. Among them, the PPAPs have received much attention due to their novel structures and diverse pharmacological activities and have become hot spots in organic chemistry and medicinal chemistry. However, there are few reports about the chemical constituents of Hypericum acmosepalum at present, especially the PPAPs. This research is dedicated to the study of the air-dried aerial parts of Hypericum acmosepalum, which were extracted with 95% EtOH under reflux, then suspended and successively partitioned with petroleum ether and ethyl acetate. Five PPAP derivatives were obtained using various chromatographic techniques, and their structures were determined by NMR spectroscopic data, including two new phloroglucinol derivatives, hyperacmosin A (1) and hyperacmosin B (2). Those compounds were evaluated for their neuroprotective effect using two models.

Methylated Polycyclic Polyprenylated Acylphloroglucinol Derivatives from Hypericum ascyron

Hyperascyrins A-H (1-11) and four known compounds (12-15) were acquired from the air-dried aerial parts of Hypericum ascyron and were all identified as methylated polycyclic polyprenylated acylphloroglucinol derivatives. Their structures were established by NMR spectroscopy, experimental and calculated electronic circular dichroism (ECD) data, and comparison with established compounds. Compounds 8 and 9 showed protection against paracetamol-induced HepG2 cell damage at 10 μM. The neuroprotective activities of all compounds (10 μM) were evaluated, and compounds 1 and 8 exhibited mild neuroprotection against glutamate-induced toxicity in SK-N-SH cells.

Effect of Hypericum humifusum aqueous and methanolic leaf extracts on biochemical and histological parameters in adult rats

Hypericum genus is traditionally known for its medicinal use and its therapeutic and antioxidant effects. However, the toxic effect of this plant has not been much explored. Our study aimed at investigating the effect of Hypericum humifusum (Hh) leaf extracts on oxidative stress parameters in male rats. For it, we first focused on the phytochemical analysis of the aqueous and methanolic extracts of Hh leaves. Hence, Wistar rats were treated per gavage for 30 days and divided into Control (1 mL/rat, distilled water), A200 group (200 mg/kg body weight (bw) aqueous extract), A400 group (400 mg/kg bw aqueous extract), M10 group (10 mg/kg bw methanolic extract), M20 group (20 mg/kg bw methanolic extract). The phytochemical analysis revealed the presence of tannins, flavonoids, steroids, carbohydrates, and phenolic compounds. Biochemical and histological investigations were performed in plasma and liver tissue. Liver tissue homogenates were used for the measurement of malondialdehyde (MDA), catalase (CAT) and superoxide dismutase (SOD) levels. At the same time, alanine transaminase (ALT), aspartate transaminase (AST) and lactate dehydrogenase (LDH) were assayed in plasma samples. Histological study was also conducted in liver. We showed that Hh extracts reduced relative liver weight and increased ALT, AST, LDH activities in treated groups compared to control group. These results were associated with an increase of MDA levels and a decrease of antioxidant enzyme activities (CAT and SOD) in liver tissues of treated rats. Histology of liver demonstrated several alterations showing necrosis, altered hepatocytes and lymphocyte migration mainly in A200 group and dilated sinusoids, foamy appearance of hepatocytes and lymphocyte accumulation in the other treated groups. This original work indicated that chronic consumption of Hh leaf extracts has no antioxidant effect but instead it induces oxidative stress and enhances markers of cell damage which was confirmed by histological study of liver rats.

Hyperdioxane A, a Conjugate of Dibenzo-1,4-dioxane and Sesquiterpene from Hypericum ascyron

Two new dibenzo-1,4-dioxane derivatives, hyperdioxanes A (1) and B (2), were isolated from the roots of a Hypericaceous plant, Hypericum ascyron. Hyperdioxane A (1) is a conjugate of dibenzo-1,4-dioxane and sesquiterpene with an unprecedented heptacyclic ring system. The structures of 1 and 2 were assigned by detailed spectroscopic analyses, including application of a modified Mosher's method. A possible biogenetic pathway of hyperdioxane A (1) from hyperdioxane B (2) and a sesquiterpene, eremophil-9,11(13)-dien-8β,12-olide (3), is presented.

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).

Chemical composition and antioxidant activities of the essential oil of Hypericum gaitii Haines - an endemic species of Eastern India

The present study reports the chemical composition and antioxidant activities of the essential oil extracted from the leaves and tender branches of Hypericum gaitii Haines (Hypericaceae) - an endemic plant of Eastern India. On hydrodistillation, the fresh leaves and tender parts of H. gaitii yielded 0.43% (v/w) of pale yellowish essential oil. Gas chromatography mass spectrometry analysis revealed the presence of 40 compounds, which represent 96.9% of the total oil. Monoterpene hydrocarbons (79.3%) predominated followed by sesquiterpene hydrocarbons (12.6%). Of these, α-pinene (69.5%), β-caryophyllene (10.5%), sabinene (5.6%), myrcene (3.0%) and geranyl acetate (2.0%) were the main constituents. Antioxidant activities of oil were evaluated by three different systems namely 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and reducing power assay. Essential oil exhibited moderate antioxidant activities compared to butylated hydroxytoluene (BHT) and ascorbic acid.

Synthesis of the furo[2,3-b]chromene ring system of hyperaspindols A and B

The synthesis of the unique furo[2,3-b]chromene ring system found in hyperaspidinols A and B, acylphloroglucinols from Hypericum chinense has been achieved in twelve steps. By comparison of the NMR spectra of the synthesized compounds with those of the natural products, a relative stereochemistry is suggested, especially that of the ketal carbon.

Spirocyclic Acylphloroglucinol Derivatives from Hypericum pyramidatum

Five spirocyclic acylphloroglucinol derivatives (1–5) have been isolated from a hexanes extract of the leaves of Hypericum pyramidatum. Pyramidatones A-D (1–3, 5) are new, and chipericumin C (4) has been previously reported. The acylphloroglucinols were characterized based on spectroscopic (NMR, IR, UV-VIS) and mass spectrometric data.

Chemoenzymatic total synthesis of hyperiones A and B

The first asymmetric total synthesis of hyperiones A and B, two norlignans from Hypericum chinense, has been accomplished following a chemoenzymatic approach. Key features of this synthesis include the lipase-catalyzed enantioselective desymmetrization of a prochiral allenic diol and a silver-mediated cycloisomerization of the resulting axially chiral product to furnish the furan core structure. Two alternative pathways, a ruthenium-catalyzed redox isomerization on the one side and a platinum-catalyzed hydrogenation on the other, are described to finally obtain the desired norlignans.

Bioactive polyprenylated acylphloroglucinol derivatives from Hypericum cohaerens

Nine new polyprenylated acylphloroglucinol derivatives, hypercohins B-J (1-9), and nine known analogues were isolated from the aerial parts of Hypericum cohaerens. The structures of 1-9 were elucidated based on spectroscopic analysis, and the absolute configuration of 1 was confirmed by X-ray crystallographic analysis. The inhibitory activities of these isolates on acetylcholinesterase and five human tumor cell lines were tested, and hypercohins B-D (1-3) exhibited moderate inhibitory activity (IC₅₀ 5.8-17.9 μM) against the tested tumor cell lines.

Hypercohones A–C, acylphloroglucinol derivatives with homo-adamantane cores from Hypericum cohaerens

Three new homo-adamantanyl type natural products were derived from polyprenylated polycyclic acylphloroglucinol. Hypercohones A-C (1–3), along with five other known hypercohones (4–8), were isolated from the aerial parts of Hypericum cohaerens. The structures of 1–3 were elucidated on the basis of comprehensive spectroscopic analysis. The inhibitory activities of these isolates against five human cancer cell lines in vitro were tested.

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.

Phloroglucinol derivatives from Hypericum empetrifolium with antiproliferative activity on endothelial cells

Five acylphloroglucinols substituted with monoterpenoids (empetrifelixin A-D and empetrikajaforin), three known monocyclic acylphloroglucinols and one monocyclic acylphloroglucinol were isolated from a petrol ether extract of Hypericum empetrifolium after fractionation by flash chromatography on silica gel, RP-18 and subsequent purification by preparative HPLC (RP-18). Their structures were elucidated by 1D, 2D NMR techniques and HREIMS. To determine a possible anti-angiogenic activity, inhibition of cell proliferation was measured using a human microvascular endothelial cell line (HMEC-1). Subconfluent grown HMEC-1 cells were treated with all compounds isolated in sufficient amounts and stained with crystal violet. Highest activity was observed for empetrifelixin A and empetrifelixin D showing a concentration dependent inhibition of cell proliferation with IC(50) values of 6.5 ± 0.1 and 7.3 ± 0.4 μM, respectively. Empetrifelixin A also showed activity in a cell migration assay with HMEC-1 cells in low micromolar concentrations.

Chemical Composition and Possible in vitro Antigermination Activity of Three Hypericum Essential Oils

The essential oils of Hypericum perforatum, H. perfoliatum and H. hircinum, growing in Southern Italy, were analyzed by GC and GC/MS. In the three oils, 111 compounds in all were identified: 53 for the oil of H. hircinum (93.7% of the total oil), 55 for H. perforatum (96.5% of the total oil) and 63 for H. perfoliatum (98.7% of the total oil). The major fraction of the essential oils of H. perforatum and H. hircinum was represented by sesquiterpene hydrocarbons, while the monoterpene α-pinene, and the phenol thymol were the most abundant compounds in the essential oil of H. perfoliatum.

The oils were evaluated for their potential in vitro phytotoxic activity against germination and early radicle elongation of Raphanus sativus and Lepidium sativum. The germination of this latter was significantly inhibited by the essential oil of H. hircinum, at the highest doses tested, whereas radicle elongation of garden cress was significantly inhibited by the essential oils of H. perfoliatum and H. hircinum. The radicle elongation of radish was inhibited by the essential oil of H. hircinum to a major extent and by H. perforatum and perfoliatum in a minor measure.

Acylphloroglucinol and xanthones from Hypericum ellipticum

An acylphloroglucinol, elliptophenone A, and two xanthones, elliptoxanthone A and elliptoxanthone B, were isolated from the aerial portions of Hypericum ellipticum together with three known xanthones, 1,3,7-trihydroxy-8-(3-methyl-2-butenyl)-9H-xanthen-9-one, 1,6-dihydroxy-4-methoxy-9H-xanthen-9-one, and 1,4,5-trihydroxy-9H-xanthen-9-one. Their structures were determined by spectroscopic analyses. The acylphloroglucinol and xanthones were evaluated for cytotoxicity using three human colon cancer cell lines cell lines (HT-29, HCT-116 and Caco-2) and a normal human colon cell line (CCD-18Co).

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.

Acylphloroglucinol, biyouyanagiol, biyouyanagin B, and related spiro-lactones from Hypericum chinense

Biyouyanagiol (1), an acylphloroglucinol-related compound having a unique cyclopenta-1,3-dione moiety, was isolated from a Japanese traditional medicinal plant, Hypericum chinense, together with three new spiro-lactone-related derivatives, biyouyanagin B (2), 5,6-dihydrohyperolactone D (3), and 4-hydroxyhyperolactone D (4). Their structures were established on the basis of spectroscopic evidence. In a cytotoxicity assay against human cancer cell lines including multidrug-resistant (MDR) cancer cell lines, several compounds demonstrated enhanced cytotoxicity against MDR KB cells in the presence of colchicine.

Chromone and chromanone glucosides from Hypericum sikokumontanum and their anti-Helicobacter pylori activities

Chromone glucosides, takanechromones A-C (1, 2 and 5) and chromanone glucosides, named takanechromanones A and B (3 and 4), were isolated from the methanolic extracts of Hypericumsikokumontanum together with 27 known compounds. Their structures were established based on spectroscopic evidence. The isolated compounds and some chromone derivatives were assayed for antimicrobial activity against Helicobacter pylori and cytotoxicity against human cancer cell lines.

Tomoeones A-H, cytotoxic phloroglucinol derivatives from Hypericum ascyron

Phloroglucinol derivatives tomoeones A-H (1-8) and three known compounds were isolated from leaves of Hypericum ascyron. Their structures were established based on spectroscopic analyses. They are all acylphloroglucinol derivatives possessing a spiro skeleton with geminal isoprenyl groups and a monoterpene moiety, and they are stereoisomers to each other at C-4 and C-13. They appear to be a class of phloroglucinol derivatives. Cytotoxicities of the isolated phloroglucinol derivatives against human tumor cell lines, including multidrug-resistant (MDR) cancer cell lines, were evaluated. Tomoeone F (6) demonstrated significant cytotoxicity against KB cells with an IC50 value of 6.2 microM. Compound 6 was also cytotoxic against MDR cancer cell lines (KB-C2 and K562/Adr), which was more potent than doxorubicin.

Anti-inflammatory phloroglucinol derivatives from Hypericum empetrifolium

Phytochemical investigation of Hypericum empetrifolium Willd. (Clusiaceae), a species native to Greece and Turkey has led to the bioassay-guided identification of two acylphloroglucinol derivatives with potent in vitro anti-inflammatory activity. Using NMR spectroscopy and mass spectrometry, the acylphloroglucinol derivatives were characterized as 3-geranyl-1-(2'-methylpropanoyl)phloroglucinol (1) and 3-geranyl-1-(2'-methylbutanoyl)phloroglucinol (2). Hypotheses are proposed regarding the biosynthetic origin of these and similar acylphloroglucinols from related Hypericum species. Compounds 1 and 2 were evaluated for in vitro inhibitory activity against COX-1, COX-2 and 5-LOX catalyzed LTB(4) formation. Compound 1 displayed good activity (IC(50) values: 6.0, 29.9, and 2.2 μM, respectively) in all three assays. Compound 2 showed good activity (IC(50) value: 5.8 μM) against LTB(4) formation and moderate activity (IC(50) value: 26.2 μM) against COX-1.