Two sarcoviolins with antioxidative and α-glucosidase inhibitory activity from the edible mushroom Sarcodon leucopus collected in Tibet

New insights into the stipitate hydnoid fungi Sarcodon, Hydnellum, and the formerly informally defined Neosarcodon, with emphasis on the edible species marketed in Southwest China

Sarcodon and Hydnellum are two ectomycorrhizal genera of important ecological and economic value in Southwest China, and they are common in the free markets in this region. It was estimated that more than 1,500 tonnes of them were sold as edible per year, but there was little information about the taxonomic placements of these edible mushrooms sold in the markets. Traditional concepts of the two genera have also been challenged recently, and circumscription of Sarcodon and the informally defined clade "Neosarcodon" remained unresolved. In the present study, specimens collected in the field and purchased from the markets in Southwest China were analyzed based on morphological characters and DNA sequences. Phylogeny of the traditional Sarcodon s. lat. and Hydnellum s. lat. was reconstructed from the combined internal transcribed spacer (ITS), nuclear large ribosomal subunit (nLSU) and RNA polymerase II second largest subunit (RPB2) dataset based on expanded samples to reevaluate the taxonomic placements of the two genera. In the present molecular analyses, four distinct clades were recovered and strongly supported: Hydnellum, Neosarcodon, Phellodon and Sarcodon. Neosarcodon is formally introduced as a generic name to include nine species previously placed in Sarcodon, and the delimitation of Sarcodon is revised based on phylogenetic and morphological studies. Phylogenetic analyses also revealed an unexpected species diversity (17 phylogenetic species) of Sarcodon and Hydnellum in the markets; nine phylogenetic species of Sarcodon and eight of Hydnellum were uncovered from the samples collected in the markets. Eight species were resolved in the traditional S. imbricatus complex, with S. imbricatus s.str. being the most common edible stipitate hydnoid fungal species. Three of the edible Hydnellum species (H. edulium, H. subalpinum, and H. subscabrosellum), and five separated from the S. imbricatus complex (Sarcodon flavidus, S. giganteus, S. neosquamosus, S. nigrosquamosus, and S. pseudoimbricatus), are described as new. Three new Chinese records (H. illudens, H. martioflavum, and H. versipelle), and the notable S. imbricatus and S. leucopus are also reported.

Antiproliferative p-terphenyl derivatives isolated from the fungus Sarcodon scabripes

The ethanol extract of the fungus Sarcodon scabripes collected from north-central British Columbia, Canada, showed strong antiproliferative activity. Bioassay-guided purification using liquid-liquid extraction and Sephadex LH-20 size-exclusion chromatography, followed by HPLC-MS and 1D/2D NMR analyses, led to the isolation of five known compounds; four p-terphenyl (1-4) derivatives and one phenolic aldehyde (5). Compounds 1, 4, and 5 were isolated for the first time from the Sarcodon genus. The cytotoxicity MTT assay showed that compounds 1-5 have antiproliferative activity against human cervical cancer cells (HeLa). For compounds 1-4, this is the first report of their antiproliferative activity against cancer cells. For compound 2, this is the first report on its bioactivity. To our knowledge, this is the first description of the isolation of bioactive constituents from S. scabripes.

Structural diversity and biological activity of natural p-terphenyls

p-Terphenyls are aromatic compounds consisting of a central benzene ring substituted with two phenyl groups, and they are mainly isolated from terrestrial and marine organisms. The central ring of p-Terphenyls is usually modified into more oxidized forms, e.g., para quinone and phenols. In some cases, additional ring systems were observed on the terphenyl-type core structure or between two benzene moieties. p-Terphenyls have been reported to have cytotoxic, antimicrobial, antioxidant and α-glucosidase inhibitory effects. In this review, we will mainly summarize the structural diversity and biological activity of naturally occurring p-Terphenyls referring to the research works published before.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-021-00117-8.

Diastereoselective synthesis of glycopyrans 1,2-annulated with dioxazinanes from 1,2-anhydrosugars and N-substituted nitrones

1,2-Annulated pyranose sugars fused with six membered rings have emerged as an important class of carbohydrates with wide biological and synthetic utility. We now describe zinc chloride catalyzed one pot diastereoselective synthesis of sugar fused dioxazinanes from 1,2-anhydro sugars and N-substituted aromatic nitrones. Various aromatic nitrones with different substituents undergo the reaction smoothly. The developed strategy works well with both ester and ether protection on the sugar and proceeds under mild reaction conditions. The mechanism seems to involve activation of the anhydrosugar by ZnCl₂ for nucleophilic attack by the nitrone followed by cyclization.

Metabolites From the Mangrove-Derived Fungus Cladosporium sp. HNWSW-1

Two new benzoic acids, cladoslide A (1) and cladoslide B (2); one new β-carboline derivative, cladospomine (3); and one new pyridin-2(1H)-one, cladoslide C (4), were isolated from the fermentation cultures of the mangrove-derived fungus Cladosporium sp. HNWSW-1, along with the previously reported N-acetyl-β-oxotryptamine (5), (4S,5S,11R)-iso-cladospolide B (6), (4S,5S,11S)-iso-cladospolide B (7), and (4R,5S,11R)-iso-cladospolide B (8). Their structures were elucidated by spectroscopic analysis, Rh₂(OCOCF₃)₄-induced ECD experiments, and Marfey’s method. Compound 1 showed cytotoxicity against the K562 cell line with IC₅₀ values of 13.10 ± 0.08 μM. Moreover, compounds 1 and 5 exhibited inhibitory activity against α-glycosidase with IC₅₀ values of 0.32 ± 0.01 mM and 0.17 ± 0.01 mM, respectively.

Secoiridoid dimers and their biogenetic precursors from the fruits of Cornus officinalis with potential therapeutic effects on type 2 diabetes

Cornusdiridoid A-F (1-6), six unusual cornuside-morroniside secoiridoid dimers, and their possible new biogenetic precursor, 3″,5″-dehydroxycornuside (7), together with four known secoiridoids (8-11), were obtained from the fruits of Cornus officinalis. Their structures were elucidated on the basis of various spectroscopic and chemical methods. A plausible biosynthetic pathway of compounds 1-11 was proposed. The α-glucosidase inhibitory, antioxidant and anti-inflammatory activities of these isolates were evaluated. Some of them emerged out as potent antidiabetic, anti-inflammatory and free radical scavenging agents. Molecular docking was also carried out for antidiabetic target α-glucosidase to investigate the possible binding modes of the most potent α-glucosidase inhibitor, vincosamide (9). These results revealed that the secoiridoids from C. officinalis fruits may be served as new potential antidiabetic agents to prevent and treat type 2 diabetes.

Dithiocarbamate derivatives inhibit α-glucosidase through an apparent allosteric site on the enzyme

Dithiocarbamate derivatives possess diverse biological activities. This work further expands their activity profile by identifying seven benzylamine-containing dithiocarbamate derivatives with piperazine and piperidine substitutions at the main moiety, and five piperazine-containing dithiocarbamates with various substitutions at the piperazine moiety as new inhibitors of α-glucosidase. Compounds bearing the benzylamine moiety exhibited more potent inhibition of the enzyme than the piperazine derivatives. Majority of the compounds non-competitively inhibited α-glucosidase that led to the identification of a new allosteric site on the enzyme with the help of molecular dynamics and docking studies. These studies suggest that the compounds regulate inhibition of the enzyme by binding to an allosteric site that is located in the vicinity of the active site. This is the first report on the allosteric inhibition of α-glucosidase by dithiocarbamate derivatives that provides insights into the mechanism of inhibition of the enzyme at molecular level. Moreover, it also explores new avenues for drug development of α-glucosidase inhibitors as antidiabetic drugs.

Structurally Diverse Sesquiterpenoids with Anti-neuroinflammatory Activity from the Endolichenic Fungus Cryptomarasmius aucubae

Two new sterpurane sesquiterpenoids named sterpurol D (1) and sterpurol E (2), and one skeletally new sesquiterpene, cryptomaraone (3), bearing a 5,6-fused bicyclic ring system, along with five known ones, sterpurol A (4), sterpurol B (5), paneolilludinic Acid (6), murolane-2α, 9β-diol-3-ene (7) and (-)-10,11-dihydroxyfarnesol (8) were isolated from an endolichenic fungus Cryptomarasmius aucubae. The structures of the new compounds were elucidated by analysis of NMR spectroscopic spectra and HRESIMS data. The absolute configurations of 1 and 2 were established by spectroscopic data analysis and comparison of specific optical rotation, as well as the biosynthetic consideration. Additionally, compounds 1, 2, 4-6, and 8 showed significant nitric oxide (NO) production inhibition in Lipopolysaccharide (LPS)-induced BV-2 microglial cells with the IC50 values ranging from 9.06 to 14.81 μM.

p-Terphenyls From Aspergillus sp. GZWMJZ-055: Identification, Derivation, Antioxidant and α-Glycosidase Inhibitory Activities

One new (1) and fifteen known (2–16) p-terphenyls were isolated from a solid culture of the endophytic fungus Aspergillus sp. GZWMJZ-055 by adding the leaves of its host Eucommia ulmoides. Furthermore, nine p-terphenyls (17–25) were synthesized from the main compounds (5–7), among which derivatives 18, 19, 21, 22, and 25 are new p-terphenyls. Compounds 15 and 16 were also, respectively, synthesized from compounds 6 and 7 by oxidative cyclization of air in the presence of silica gel. These p-terphenyls especially those with 4,2′,4″-trihydroxy (4–7, 20, 21) or 4, 4″-dihydroxy-1,2,1′,2′-furan (15, 16) substituted nucleus, exhibited significant antioxidant and α-glucosidase inhibitory activities and lower cytotoxicity to caco-2 cells. The results indicated their potential use as lead compounds or dietary supplements for treating or preventing the diabetes.

Two New Quinazoline Derivatives from the Moss Endophytic Fungus Aspergillus sp. and Their Anti-inflammatory Activity

Two new quinazoline derivatives versicomides E (1) and F (2), and 10 known compounds (3-12) were isolated from the moss endophytic fungus Aspergillus sp. Their structures were determined on the basis of extensive spectroscopic data analysis and ECD calculations. Among them, the compound 7 (6-hydroxy-3-methoxyviridicatin) was first reported as a natural product. Inhibition on LPS-induced NO production in RAW 264.7 murine macrophages found that compounds 5, 7 and 8 showed significant inhibitory effects on NO production, with IC₅₀ values of 49.85, 22.14 and 46.02 μM respectively.

Salazinic Acid-Derived Depsidones and Diphenylethers with α-Glucosidase Inhibitory Activity from the Lichen Parmotrema dilatatum

Three new depsidones, parmosidones F - G (1 - 2), and 8'-O-methylsalazinic acid (3), and 3 new diphenylethers, parmetherines A - C (4 - 6), together with 2 known congeners were isolated from the whole thalli of Parmotrema dilatatum, a foliose chlorolichen. Their structures were unambiguously determined by extensive spectroscopic analyses and comparison with literature data. The isolated polyphenolics were assayed for their α-glucosidase inhibitory activities. Newly reported benzylated depsidones 1: and 2: in particular inhibited α-glucosidase with IC₅₀ values of 2.2 and 4.3 µM, respectively, and are thus more potent than the positive control, acarbose.

Structure-Activity Relationships and Potent Cytotoxic Activities of Terphenyllin Derivatives from a Small Compound Library

A small library of 120 compounds was established with seventy new alkylated derivatives of the natural product terphenyllin, together with 45 previous reported derivatives and four natural p-terphenyl analogs. The 70 new derivatives were semi-synthesized and evaluated for cytotoxic activities against four cancer cell lines. Interestingly, 2',4''-diethoxyterphenyllin, 2',4,4''-triisopropoxyterphenyllin, and 2',4''-bis(cyclopentyloxy)terphenyllin showed potent activities with IC₅₀ values in a range from 0.13 to 5.51 μM, which were similar to those of the positive control, adriamycin. The preliminary structure-activity relationships indicated that the introduction of alkyl substituents including ethyl, allyl, propargyl, isopropyl, bromopropyl, isopentenyl, cyclopropylmethyl, and cyclopentylmethyl are important for improving the cytotoxicity.

Prenylated p-Terphenyls from a Mangrove Endophytic Fungus, Aspergillus candidus LDJ-5

Nine previously undescribed prenylated p-terphenyls, prenylterphenyllins F-J (1, 2, 4-6) and prenylcandidusins D-G (3, 7-9), were isolated from an endophytic fungus, Aspergillus candidus LDJ-5. Their structures were determined from NMR and MS data. Differing from previously reported p-terphenyls, compound 3 represents a rare 6,5,6,6-fused ring system. Compounds 4-6 are antimicrobial, and compounds 1, 4, 6, and 9 are cytotoxic.

A [5 + 1] annulation strategy for the synthesis of multifunctional biaryls and p-teraryls from 1,6-Michael acceptor ketene dithioacetals

A [5 + 1] annulation approach was used to access multifunctional biaryls and p-teraryls from ketene dithioacetals.

Two new cephalochromin derivative from the Alternaria sp. ZG22

Two new cephalochromin derivatives, prenylcephalochromin A (1), prenylcephalochromin B (2), along with cephalochromin (3) were isolated from the Alternaria sp. ZG22 obtained from a Dasymaschalon rostratum collected from the Hainan. The structures of two new compounds were elucidated by comprehensive spectroscopic methods. Compounds 1-3 showed α-glucosidase inhibitory activity.

Natural flavonoid α-glucosidase inhibitors from Retama raetam: Enzyme inhibition and molecular docking reveal important interactions with the enzyme active site

Retama raetam (Forsk.) Webb & Berthel plant has been traditionally used for the treatment of diabetes mellitus and hypertension. Interest in the medicinal chemistry of the plant in the past resulted in the isolation of a number of compounds with anti-hyperglycemic activity. The current work is a further extension of our recent work in which we isolated and characterized seven new flavonoids from Retama raetam with preliminary biological activity screening. It addresses the α-glucosidase inhibitory activity and molecular docking studies of the flavonoids. Retamasin D, G, H, and erysubin A and B noncompetitively inhibited the enzyme whereas retamasin C and F exhibited competitive inhibition. Moreover, retamasin C, F, G, and erysubin A and B carry dual activity in addition to α-glucosidase inhibition. Our previous studies have shown that they also caused significant stimulation of insulin from the blood-perfused pancreatic islets of Langerhans of mice. The C6 and C8 substituent groups greatly influenced the inhibition potency of the compounds. The most potent inhibitor was retamasin H with the γ-lactone ring substituent at C6 position of the main flavonoid moiety. Notable active chemical groups in the target compounds include γ-lactone, dihydropyran and dihydrofuran rings with hydroxyl and geminal methyl groups. Molecular modeling studies revealed that the compounds fit well in the α-glucosidase active site by interacting with important active site residues. These findings will incorporate new chemical, structural and functional diversity to the search and drug development of α-glucosidase inhibitors as anti-diabetic drugs.

Antioxidants and α-glucosidase inhibitors from Neptunia oleracea fractions using 1H NMR-based metabolomics approach and UHPLC-MS/MS analysis

Background

Neptunia oleracea is a plant cultivated as vegetable in Southeast Asia. Previous works have revealed the potential of this plant as a source of natural antioxidants and α-glucosidase inhibitors. Continuing our interest on this plant, the present work is focused in identification of the bioactive compounds from different polarity fractions of N. oleracea, namely hexane (HF), chloroform (CF), ethyl acetate (EF) and methanol (MF).

Methods

The N. oleracea fractions were obtained using solid phase extraction (SPE). A metabolomics approach that coupled the use of proton nuclear magnetic resonance (¹H NMR) with multivariate data analysis (MVDA) was applied to distinguish the metabolite variations among the N. oleracea fractions, as well as to assess the correlation between metabolite variation and the studied bioactivities (DPPH free radical scavenging and α-glucosidase inhibitory activities). The bioactive fractions were then subjected to ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) analysis to profile and identify the potential bioactive constituents.

Results

The principal component analysis (PCA) discriminated EF and MF from the other fractions with the higher distributions of phenolics. Partial least squares (PLS) analysis revealed a strong correlation between the phenolics and the studied bioactivities in the EF and the MF. The UHPLC-MS/MS profiling of EF and MF had tentatively identified the phenolics present. Together with some non-phenolic metabolites, a total of 37 metabolites were tentatively assigned.

Conclusions

The findings of this work supported that N. oleracea is a rich source of phenolics that can be potential antioxidants and α-glucosidase inhibitors for the management of diabetes. To our knowledge, this study is the first report on the metabolite-bioactivity correlation and UHPLC–MS/MS analysis of N. oleracea fractions.

New flavonoids from the Saudi Arabian plant Retama raetam which stimulates secretion of insulin and inhibits α-glucosidase

Retama raetam is a bush which is used in traditional medicine.

Cytotoxic p-Terphenyls from the Endolichenic Fungus Floricola striata

Eleven new p-terphenyls, floricolins K-U (1-11), together with 13 biosynthetically related known compounds (12-24) were isolated from an endolichenic fungus, Floricola striata. Their structures were elucidated by extensive spectroscopic analyses and single-crystal X-ray diffraction measurements. The newly isolated p-terphenyls inhibited the growth of A2780, MCF-7, and A549 cell lines. Further evaluation for the multidrug resistance (MDR) reversal activity of compound 5 revealed it enhanced the sensitivity of MCF-7/ADR cells toward adriamycin 39-fold at 10 μM through modulating P-glycoprotein-mediated drug exclusion.

Design, semisynthesis, α-glucosidase inhibitory, cytotoxic, and antibacterial activities of p-terphenyl derivatives

Terphenyllin (1), a naturally abundant p-terphenyl metabolite, was isolated from the coral derived fungus Aspergillus candidus together with four natural analogues 2-5. To evaluate their potency and selectivity, a series of new derivatives of 1 were designed and semisynthesized. They were evaluated for their α-glucosidase inhibitory, cytotoxic, and antibacterial activities. Compounds 1, 3, 4, 7, 8, 10, 11, 14, 15, 21, 23, 24, 29, 39, and 40 showed significant α-glucosidase inhibitory activity with IC₅₀ values of 4.79-15 μM, which were stronger than that of the positive controls, 1-deoxynojirimycin (IC₅₀ = 192.0 μM) and acarbose (IC₅₀ = 707.9 μM). Compounds 7 and 10 have relatively higher therapeutic indices (CC₅₀/IC₅₀ = 17 and 10, respectively), representing potential promising leads. The enzyme kinetic studies of compounds 1 and 24 showed a non-competitive inhibition on α-glucosidase with Ki values of 1.50 and 3.45 μM, respectively. Additionally, compounds 14, 21, 26, 29, 32, 35, and 37 were found to exhibit strong cytotoxicity against three tumor cell lines A549 (lung adenocarcinoma epithelial), HeLa (cervical carcinoma), and HepG2 (hepatocellular liver carcinoma) with IC₅₀ values ranging from 0.15 to 5.26 μM. Further study indicated that 32 could induce S-phase arrest in the cell cycle progression.

Structural and biological diversity of natural p-terphenyls

p-Terphenyls consisting of a C-18 tricyclic or polycyclic C-18 aromatic skeleton, have diverse structures because of the variation of the middle ring and the connections between the rings, and to the main skeleton. p-Terphenyls have recently been found to exhibit various biological activities such as cytotoxic, α-glucosidase inhibitory, antioxidant, and antimicrobial activity. In this review, we briefly summarized the structural varieties, biosyntheses, and bioactivities of natural p-terphenyl derivatives referring to the recent 10 years' publications.

Chemical diversity from the Tibetan Plateau fungi Penicillium kongii and P. brasilianum

Two new secondary metabolites, kongiilines A and B (1, 7), and two asperphenamate derivatives, asperphenamates B and C (5–6), together with 16 known compounds (2–4, 8–20), were isolated from Tibetan Plateau fungi Penicillium kongii and Penicillium brasilianum. This is the first report on asperphenamates B and C as naturally occurring compounds, and that aspterric acid is isolated from P. brasilianum for the first time. Their structures were elucidated by different spectroscopic techniques including high-resolution electrospray ionisation mass spectrum, 1D nuclear magnetic resonance (NMR), and 2D NMR as well as electronic circular dichroism. Compounds 4, 5, and 10 exhibited cytotoxicity activities against human colon carcinoma HCT116 cell line with IC₅₀ values of 88.16, 77.68, and 36.92 μM, respectively. Fungi from Tibetan Plateau represent important and rich resources for the investigation of new chemicals.

Rickenyls A-E, antioxidative terphenyls from the fungus Hypoxylon rickii (Xylariaceae, Ascomycota)

Our screening efforts for new natural products with interesting bioactivity have revealed the neotropical ascomycete Hypoxylon rickii as a prolific source. We isolated five secondary metabolites with a p-terphenyl backbone from the mycelial extract of a fermentation of this fungus in 70 l scale by using RP-HPLC, which were named rickenyls A-E (1-5). Their structures were elucidated by X-ray crystallography and NMR spectroscopy, complemented by HRESIMS. Two of the compounds contained a quinone core structure in ortho (2) and para-position (5), respectively. We obtained 2 spontaneously and by lead tetraacetate oxidation from 1. All compounds were screened for antimicrobial, antioxidative and cytotoxic activities. Rickenyl A (1) exhibited strong antioxidative effects and moderate cytotoxic activity against various cancer cell lines.

Polyketides with α-Glucosidase Inhibitory Activity from a Mangrove Endophytic Fungus, Penicillium sp. HN29-3B1

Five new compounds, pinazaphilones A and B (1, 2), two phenolic compounds (4, 5), and penicidone D (6), together with the known Sch 1385568 (3), (±)-penifupyrone (7), 3-O-methylfunicone (8), 5-methylbenzene-1,3-diol (9), and 2,4-dihydroxy-6-methylbenzoic acid (10) were obtained from the culture of the endophytic fungus Penicillium sp. HN29-3B1, which was isolated from a fresh branch of the mangrove plant Cerbera manghas collected from the South China Sea. Their structures were determined by analysis of 1D and 2D NMR and mass spectroscopic data. Structures of compounds 4 and 7 were further confirmed by a single-crystal X-ray diffraction experiment using Cu Kα radiation. The absolute configurations of compounds 1-3 were assigned by quantum chemical calculations of the electronic circular dichroic spectra. Compounds 2, 3, 5, and 7 inhibited α-glucosidase with IC50 values of 28.0, 16.6, 2.2, and 14.4 μM, respectively, and are thus more potent than the positive control, acarbose.

Lanostane Triterpenes from the Tibetan Medicinal Mushroom Ganoderma leucocontextum and Their Inhibitory Effects on HMG-CoA Reductase and α-Glucosidase

Sixteen new lanostane triterpenes, ganoleucoins A-P (1-16), together with 10 known tripterpenes (17-26), were isolated from the cultivated fruiting bodies of Ganoderma leucocontextum, a new member of the Ganoderma lucidum complex. The structures of the new compounds were elucidated by extensive spectroscopic analysis and chemical transformation. The inhibitory effects of 1-26 on HMG-CoA reductase and α-glucosidase were tested in vitro. Compounds 1, 3, 6, 10-14, 17, 18, 23, 25, and 26 showed much stronger inhibitory activity against HMG-CoA reductase than the positive control atorvastatin. Compounds 13, 14, and 16 presented potent inhibitory activity against α-glucosidase from yeast with IC₅₀ values of 13.6, 2.5, and 5.9 μM, respectively. In addition, the cytotoxicity of 1-26 was evaluated against the K562 and PC-3 cell lines by the MTT assay. Compounds 1, 2, 6, 7, 10, 12, 16, 18, and 25 exhibited cytotoxicity against K562 cells with IC₅₀ values in the range 10-20 μM. Paclitaxel was used as the positive control with an IC₅₀ value of 0.9 μM. This is the first report of secondary metabolites from this medicinal mushroom.

Re-exploring promising α-glucosidase inhibitors for potential development into oral anti-diabetic drugs: Finding needle in the haystack

Treatment of diabetes mellitus by oral α-glucosidase inhibitors is currently confined to acarbose, miglitol and voglibose marred by efficacy problems and unwanted side effects. Since the discovery of the drugs more than three decades ago, no significant progress has been made in the drug development area of anti-diabetic α-glucosidase inhibitors. Despite existence of a wide chemical diversity of α-glucosidase inhibitors identified to date, majority of them are simply piled up in publications and reports thus creating a haystack destined to be forgotten in the scientific literature without given consideration for further development into drugs. This review finds those "needles" in that haystack and lays groundwork for highlighting promising α-glucosidase inhibitors from the literature that may potentially become suitable candidates for pre-clinical or clinical trials while drawing attention of the drug development community to consider and take already-identified promising α-glucosidase inhibitors into the next stage of drug development.

α-Glucosidase and tyrosinase inhibitory effects of an abietane type diterpenoid taxoquinone from Metasequoia glyptostroboides

Background

Nowadays plant derived natural compounds have gained huge amount of research attention especially in food and medicine industries due to their multitude of biological and therapeutic properties as alternative medicines.

Methods

In this study, a diterpenoid compound taxoquinone, isolated from Metasequoia glyptostroboides was evaluated for its α–glucosidase and tyrosinase inhibitory efficacy in terms of its potent anti-diabetic and depigmentation potential, respectively.

Results

As a result, taxoquinone at the concentration range of 100–3,000 μg/mL and 200–1,000 μg/mL showed potent efficacy on inhibiting α-glucosidase and tyrosinase enzymes by 9.24-51.32% and 11.14-52.32%, respectively.

Conclusions

The findings of this study clearly evident potent therapeutic efficacy of an abietane diterpenoid taxoquinone isolated from M. glyptostroboides with a possibility for using it as a novel candidate in food and medicine industry as a natural alternative medicine to prevent diabetes mellitus type-2 related disorders and as a depigmentation agent.

Erinacerins C-L, isoindolin-1-ones with α-glucosidase inhibitory activity from cultures of the medicinal mushroom Hericium erinaceus

The well-known edible and medicinal mushroom Hericium erinaceus produces various bioactive secondary metabolites. Ten new isoindolin-1-ones, named erinacerins C-L (1-10), together with (E)-5-(3,7-dimethylocta-2,6-dien-1-yl)-4-hydroxy-6-methoxy-2-phenethylisoindolin-1-one (11) were isolated from the solid culture of H. erinaceus. The structures of new metabolites were established by spectroscopic methods. The absolute configurations of 3, 4, 9, and 10 were assigned by comparing their specific rotations with those of related phthalimidines (13-20). Compounds 5 and 6, 7 and 8, and 9 and 10 are double-bond positional isomers. In a α-glucosidase inhibition assay, compounds 2-11 showed inhibitory activity with IC50 values ranging from 5.3 to 145.1 μM. Preliminary structure-activity analysis indicated that the terpenoid side chain and the phenolic hydroxy groups contributed greatly to the α-glucosidase inhibitory activity of 1-11. In a cytotoxicity assay, compound 11 also presented weak cytotoxicity against two cell lines, A549 and HeLa, with IC50 values of 49.0 and 40.5 μM.

New α-glucosidase inhibitors with p-terphenyl skeleton from the mushroom Hydnellum concrescens

The purpose of this study is to elucidate the bioactive components responsible for the the α-glucosidase inhibitory activity detected in the EtOAc extract of the mushroom Hydnellum concrescens. Two new p-terphenyl derivatives, concrescenins A (1) and B (2), in along with six known compounds thelephantins L (3), I (4), J (5), K (6), dihydroauran-tiacin dibenzoate (7), and curtisian A (8) were isolated from the fruiting bodies of H. concrescens. Their chemical structures were elucidated by NMR experiments. Compounds 1-4 and 6-8 showed the inhibitory activity against α-glucosidase with the IC50 of 0.99, 3.11, 4.53, 18.77, 2.98, 5.16, and 8.34 μM, respectively. Kinetic analysis of α-glucosidase indicated that compounds 1 and 2 inhibited the activity of α-glucosidase in a noncompetitive fashion with a Ki value of 0.02 and 0.21 μM, respectively. In antioxidant evaluation, compounds 1 and 4 showed weak DPPH scavenging activity (EC50=82.50 and 161.75 μM) and weak reducing ability (EC50=193.57 and 152.94 μM). The current research supports the potential use of mushroom-derived p-terphenyl derivatives for the treatment of diabetes.