Caged xanthones displaying protein tyrosine phosphatase 1B (PTP1B) inhibition from Cratoxylum cochinchinense

Four new caged xanthones (1–4) and two known compounds (5, 6) were isolated from the roots of Cratoxylum cochinchinense, a polyphenol rich plant, collected in China. The structures of the isolated compounds (1–6) were characterized by obtaining their detailed spectroscopic data. In particular, compounds 1 and 6 were fully identified by X-ray crystallographic data. The isolated compounds (1–6) were evaluated against protein tyrosine phosphatase 1B (PTP1B), which plays an important role in diabetes, obesity, and cancer. Among these compounds, 3, 4, and 6 displayed significant inhibition with IC₅₀ values of 76.3, 43.2, and 6.6 µM, respectively. A detailed kinetic study was conducted by determining K_m, V_max, and the ratio of K_ik and K_iv, which revealed that all the compounds behaved as competitive inhibitors.     

Xanthones from the stem bark of Garcinia bracteata with growth inhibitory effects against HL-60 cells

Five xanthones, 1,4,5,6-tetrahydroxyxanthone (1) and bracteaxanthones III–VI (2–5) together with twenty-six known compounds (6–31), were isolated from the ethanol extract of the stem bark of Garcinia bracteata. Their structures were elucidated via spectroscopic analyses. Growth inhibitory activities of these compounds against the human leukaemic HL-60 cell line were measured in vitro. Compounds 7, 11, and 29 exhibited moderate activities with GI₅₀ values of 2.8, 3.4, and 3.1 μM, respectively, and a preliminary structure–activity relationship is discussed.     

Two furanoxanthones from the bark of Cratoxylum cochinchinense

Two undescribed furanoxanthones, cratocochinones A (1) and B (2), along with eight known xanthones (3–10), were isolated from the bark of Cratoxylum cochinchinense. Their structures were elucidated using spectroscopic methods, mainly 1D and ²D NMR. The isolated compounds were investigated for α-glucosidase inhibitory activity. Seven compounds, 3-6 and 8-10, displayed stronger inhibitory effects than the positive control, acarbose. Especially, cochinxanthone A (6) showed remarkable inhibition with an IC₅₀ value of 59.6 μM, which was approximately 16-fold more potent than acarbose.     

A pair of new tetrahydro-naphthalenone enantiomers from Eremurus altaicus (Pall.) Stev.

A new racemic mixture of a 4-hydroxytetralone derivative, altaicusin A (1), was isolated from the whole plant of Eremurus altaicus (Pall.) Stev., together with three anthraquinones (compounds 2–4) and two naphthalene derivatives (5–6). The racemic altaicusin A (1) was further purified by chiral HPLC to yield a pair of enantiomers, (+)-(4S)-altaicusin A (1a) and (−)-(4R)-altaicusin A (1b). Their structures were established on the basis of spectroscopic analysis, including IR, HR-TOF-MS, and NMR. The absolute configurations of compounds 1a and 1b were elucidated by quantum chemical ECD calculations. Compounds 3 and 6 exhibited inhibitory activity against protein tyrosine phosphatase 1B (PTP1B).     

Isolation and characterization of three pairs of indolediketopiperazine enantiomers containing infrequent N-methoxy substitution from the marine algal-derived endophytic fungus Acrostalagmus luteoalbus TK-43

Three pairs of new N-methoxy-containing indolediketopiperazine enantiomers, acrozines A–C (1–3), were isolated from the culture extract of Acrostalagmus luteoalbus TK-43, an endophytic fungus obtained from the marine green alga Codium fragile. The optical resolution of compounds 1–3 by chiral HPLC successfully afforded individual enantiomers (+)-1/(–)-1, (+)-2/(–)-2, and (+)-3/(–)-3, respectively. The structures of all these compounds were established on the basis of detailed interpretation of their NMR and mass spectroscopic data. X-ray crystallographic analysis confirmed the structures of compounds 1–3, while the absolute configurations were determined by TDDFT-ECD calculations. All these compounds containing a N-methoxy group which is uncommon in indolediketopiperazines. The enantiomers, (+)-2/(–)-2, showed different antimicrobial activities against several plant-pathogenic fungi, while (+)-1 displayed better inhibitory activity against acetylcholinesterase than that of (–)-1.     

Xanthones from the stems of Cudrania tricuspidata and their inhibitory effects on pancreatic lipase and fat accumulation

Nine new xanthones, cudracuspixanthones I - Q (12–14, 25, 32–36), and 30 known xanthones (1–11, 15–24, 26–31, 37–39) were isolated from the stems of Cudrania tricuspidata (Moraceae). The structures of isolated compounds were established by using 1D and 2D NMR in combination with HR-TOF-MS. Xanthones from the stems of C. tricuspidata exerted pancreatic lipase inhibitory activity. In addition, cudracuspixanthone P (35), a new xanthone, reduced the fat accumulation in liver cells stimulated with fatty acids. Therefore, these compounds might be beneficial in the treatment of metabolic diseases.     

Chemical constituents from Lomatogonium carinthiacum (Gentianaceae)

Lomatogonium carinthiacum (Wulfen) Rchb. (Gentianaceae) is an annual plant which used in the Mongolian system of medicine against liver and bile diseases. In the present study, three flavones (1–3), four xanthones (4–7), and two iridoids (8, 9) were isolated and identified. Among them, compounds 3–5, 7, 8 were firstly isolated from the species L. carinthiucum, compounds 3-5 were isolated from the genus Lomatogonium for the first time. The Chemotaxonomic significance of these compounds was discussed in the article.     

Four new triterpenoid saponins isolated from Schefflera kwangsiensis and their inhibitory activities against FBPase1

Four new triterpenoid saponins, schekwangsiensides H–K (1–4) were isolated from the aerial parts of Schefflera kwangsiensis, together with fifteen esters (5–19) of known saponins. The structures of these compounds were elucidated on the basis of spectroscopic data analysis and chemical evidence. Furthermore, in in vitro assays, compounds 3, 8, 17, and 18 exhibited weak inhibitory activities against fructose-1,6-bisphosphatase (FBPase1).     

Anti-inflammatory activity of benzophenone and xanthone derivatives isolated from Garcinia (Clusiaceae) species

Species of the genus Garcinia have been the source of many benzophenone and xanthone derivatives. Recent data regarding potent biological properties of natural compounds in Garcinia species led us to investigate the in vitro anti-inflammatory effect of three known xanthones, lichexanthone (1), 1,3,6,7-tetrahydroxyxanthone (2), 1,3,5,6-tetrahydroxyxanthone (3), two new xanthones 1-hydroxy-3,6,7-tri-O,O,O-triprenylxanthone (4), 1,6-dihydroxy-3,7-di-O,O-diprenylxanthone (5) and two benzophenones isoxanthochymol (6), guttiferone E (7), isolated from Garcinia nobilis and Garcinia punctata. The Griess assay was used for the measurement of nitric oxide (NO) production in RAW264.7 macrophages and the ferrous oxidation-xylenol orange assay was used to determine the 15-lipoxygenase (15-LOX) inhibitory activity. All the compounds had inhibitory effect on 15-LOX activity to different extents. Compound (7) had the highest anti-LOX activity with an IC₅₀ value of 43.05 μg/mL. At the highest studied concentration (25 μg/mL), compound (4) had the most potent inhibitory activity against NO release with a% of inhibition of 95.42% and less cytotoxic effect on RAW264.7 cells (% of cell viability of 81.40).The results presented here suggest that 1,3,5,6-tetrahydroxyxanthone (3) and guttiferone E (7) are promising inhibitors of NO production and 15-LOX activity. Further studies should be considered in order to elucidate the mechanism by which these compounds exert their inhibitory activities.     

New pyranonaphthazarin and 2-naphthoic acid derivatives from the mangrove endophytic fungus Leptosphaerulina sp. SKS032

Two new compounds, named leptospyranonaphthazarin A (1) and leptosnaphthoic acid A (2), together with four known compounds (3–6) were isolated from an endophytic fungus Leptosphaerulina sp. SKS032. Their structures were assigned using spectroscopic methods, computational methods, and single-crystal X-ray diffraction analysis. In the antibiotic assay, compounds 1, 2, and 6 exhibited antibacterial activities against Staphylococcus aureus with minimal inhibitory concentration (MIC) values of 25.0, 50.0, and 50.0 μg/mL, respectively.     

A new megastigmane from Kalanchoe tubiflora (Harvey) Hamet

One new megastigmane, (6S,7R,8R,9S)-6-oxaspiro-7,8-dihydroxymegastigman-4-en-3-one (1) (tubiflorone, 1), and ten known compounds were isolated and characterized from the EtOH extract of Kalanchoe tubiflora (Harvey) Hamet. Structures of these isolates were assigned based on spectroscopic analyses that included 1D and 2D NMR techniques, such as HMQC, HMBC, and NOESY. The anti-inflammatory activities of selected isolated compounds (1–6 and 9–11) were evaluated as inhibitory activities against lipopolysaccharide (LPS) induced nitric oxide (NO) production in RAW264.7 cell lines. Compounds 1–4, 6, 9, and 11 possessed nitric oxide inhibitory activity with IC₅₀ values ranging from 15.1 ± 0.9 to 98.9 ± 1.3 μM.     

Structures and biological evaluation of phenylpropanoid derivatives from Murraya koenigii

Four new phenylpropanoid derivatives (1–4), together with eleven known analogues (5–15) were isolated and identified by comparison with their references and extensive spectroscopic methods from Murraya koenigii for the first time. Compounds (1–15) were assayed for their inhibitory activities by measuring IL-6-induced STAT3 promoter activities in HepG2 cells, and found compounds 1, 2, 6, and 15 showed inhibitory effects with IC₅₀ values of 11.5, 18.7, 8.9, and 22.7 μM, respectively. The inhibitory activities of compounds (1–15) were screened against NO production in lipopolysaccharide (LPS)-induced RAW264.7 macrophage cells, and found compounds 3, 4, 9, 11, and 14 exhibited inhibitions against LPS-induced NO production in RAW264.7 macrophages, with IC₅₀ values of 32.7, 7.9, 42.1, 58.9, and 62.4 μM, respectively.     

Phenolic derivatives from Garcinia multiflora Champion ex Bentham and their chemotaxonomic significance

A phytochemical investigation of the leaves and twigs of Garcinia multiflora Champion ex Bentham led to the isolation of eleven phenolic derivatives, including a new polycyclic polyprenylated acylphloroglucinol (PPAP, 1), five known PPAPs (2–6), three xanthones (7–9), a benzophenone (10), and a methyl phenyl acetate derivative (11). Their structures were established by extensive spectroscopic analysis, including HR-ESI-MS and NMR. Five compounds (1, 2, 4, 5, and 11) were first found in the genus Garcinia, of which compounds 1 and 11 were reported from the family Guttiferae for the first time. The chemotaxonomic significance of the isolated compounds was discussed. Furthermore, six PPAPs showed good cytotoxicities with IC₅₀ values ranging from 1.79 to 9.40 μM.     

Three new xanthones from the stems of Garcinia oligantha and their anti-TMV activity

For more bioactive compounds, phytochemical investigations of the acetone extract of the stems of Garcinia oligantha resulted in the isolation of three new xanthones (1–3) and five known analogues (4–8). Structural elucidations of 1–3 were performed by spectral methods such as 1D and 2D (HMQC, HMBC, and ROESY) NMR spectroscopy, in addition to high resolution mass spectrometry. Compounds 1, 2, 6, 7, and 8 showed anti-tobacco mosaic virus (anti-TMV) activities with inhibition rates above 10%.     

Three new prenylated xanthones from Comastoma pedunculatum and their anti-tobacco mosaic virus activity

Comastomaxanthones A–C (1–3), three new xanthones with a rare 2-oxoprenyl substituent, along with three known ones (4–6) were isolated from the aerial parts of Comastoma pedunculatum. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. In addition, compounds 1–6 were tested for their anti-tobacco mosaic virus activity. The results showed that all isolated compounds exhibited weak anti-TMV activity with IC₅₀ values ranging from 122.7 to 242.9 μM.     

Isolation of three new meroterpenoids and seven known compounds from Albatrellus yasudae and their Aβ-aggregation inhibitory activity

Alzheimer’s disease is a serious neurologic disorder that cannot be cured completely. In this study, we targeted compounds that inhibit amyloid-beta (Aβ) aggregation, based on the amyloid cascade hypothesis. Ten compounds (1–10) were isolated from CHCl₃ extracts of the mushroom Albatrellus yasudae using Aβ-aggregation inhibitory activity–guided separation. The structures of these compounds were elucidated from 1D and 2D NMR and MS spectral data. Compounds 1–3 were novel, whereas 4–10 were identified as the known compounds grifolin, grifolic acid, neogrifolin, confluentin, 2-hydroxyneogrifolin, daurichromenic acid, and a cerebroside derivative. Compounds 1–10 were tested for Aβ-aggregation inhibitory activity. Compounds 1, 3, 5, 6, 8, and 9 have potential as Aβ-aggregation inhibitory activity.     

Fatty acid synthase inhibitors of phenolic constituents isolated from Garcinia mangostana

Natural inhibitors of fatty acid synthase (FAS) are emerging as potential therapeutic agents to treat cancer and obesity. The bioassay-guided chemical investigation of the hulls of Garcinia mangostana led to the isolation of 13 phenolic compounds (1–13) mainly including xanthone and benzophenone, in which compounds 7, 8, 9, 10, and 11 were isolated from this plant for the first time and compound 9 was a new natural product. These isolates possess strong inhibitory activity of FAS with the IC₅₀ values ranging from 1.24 to 91.07 μM. The study indicates that two types of natural products, xanthones and benzophenones, could be considered as promising FAS inhibitors.     

Neuraminidase inhibitory activities of flavonols isolated from Rhodiola rosea roots and their in vitro anti-influenza viral activities

Five flavonols (3, 5, and 9–11) were isolated from Rhodiola rosea, and compared with commercially available flavonoids (1, 2, 4, 6–8, and 12–14) to facilitate analysis of their structure–activity relationship (SAR). All compounds (1–14) showed neuraminidase inhibitory activities with IC₅₀ values ranging from 0.8 to 56.9 μM. The in vitro anti-influenza virus activities of flavonoids 1–6, 8–12, and 14 were evaluated using two influenza viral strains, H1N1 (A/PR/8/34) and H9N2 (A/Chicken/Korea/MS96/96), testing their ability to reduce virus-induced cytopathic effect (CPE) in MDCK cells. We found that the activity of these compounds ranged from 30.2 to 99.1 μM against H1N1- and 18.5 to 133.6 μM against H9N2-induced CPE. Of compounds 1–14, gossypetin (6) exhibited the most potent inhibitory activity, with IC₅₀ values of 0.8 and 2.6 μM on neuraminidases from Clostridium perfringens and recombinant influenza virus A (rvH1N1), respectively. In contrast, kaempferol (3) exhibited the highest activity against two influenza viruses, H1N1 and H9N2 with EC₅₀ values of 30.2 and 18.5 μM, respectively. Activity depended on the position and number of hydroxy groups on the flavonoids backbone. In kinetic studies, all isolated compounds behaved as noncompetitive inhibitors.     

A new cerebroside and bioactive compounds from Celtis adolphi-friderici Engl. (Cannabaceae)

A phytochemical investigation of the roots of Celtis adolphi-friderici Engl. led to the isolation of a previously undescribed cerebroside named, eloundemnoside (1), alongside with seventeen known compounds (2–18). Their chemical structures were elucidated based on the analysis of their NMR and MS data. All the compounds were isolated from this specie for the first time, while eight known compounds (4–5, 12–13, 15–18) are obtained from the genus Celtis for the first time. The isolates were screened for their antioxidant, lipoxygenase, urease, and butyrylcholinesterase enzyme inhibitory activities. Compounds 4, 7 and 12 showed good antioxidant activities with IC₅₀ values of 22.2, 29.3, and 13.2 μM, respectively. In addition, azelaic acid (12) showed the best lipoxygenase inhibition (IC₅₀ value of 16.3 μM), while friedelin (2) exhibited the highest inhibition of urease with an IC₅₀ value of 15.3 μM. However, all the compounds tested had moderate butyrylcholinesterase inhibitory properties. The chemophenetic relationship of the isolates and their significance were discussed.