Penialidins A–C with strong antibacterial activities from Penicillium sp., an endophytic fungus harboring leaves of Garcinia nobilis

Three new polyketides named penialidins A–C (1–3), along with one known compound, citromycetin (4), were isolated from an endophytic fungus, Penicillium sp., harbored in the leaves of the Cameroonian medicinal plant Garcinia nobilis. Their structures were elucidated by means of spectroscopic and spectrometric methods (NMR and HRMSⁿ). The antibacterial efficacies of the new compounds (1–3) were tested against the clinically-important risk group 2 (RG2) bacterial strains of Staphylococcus aureus and Escherichia coli. The ecologically imposing strains of E. coli (RG1), Bacillus subtilis and Acinetobacter sp. BD4 were also included in the assay. Compound 3 exhibited pronounced activity against the clinically-relevant S. aureus as well as against B. subtilis comparable to that of the reference standard (streptomycin). Compound 2 was also highly-active against S. aureus. By comparing the structures of the three new compounds (1–3), it was revealed that altering the substitutions at C-10 and C-2 can significantly increase the antibacterial activity of 1.     

NorA efflux pump inhibitory activity of coumarins from Mesua ferrea

The purpose of this investigation was to study the modulator and efflux pump inhibitor activity of coumarins isolated from Mesua ferrea against clinical strains as well as NorA-over expressed strain of Staphylococcus aureus 1199B. Seven coumarins were tested for modulator activity using ethidium bromide (EtBr) as a substrate. Compounds 1, 4–7 modulated the MIC of EtBr by ≥ 2 fold against wild type clinical strains of S. aureus 1199 and S. aureus 1199B, whereas compounds 4–7 modulated the MIC of EtBr by ≥ 16 fold against MRSA 831. Compounds 1, 4–7 also reduced the MIC of norfloxacin by ≥ 8 fold against S. aureus 1199B, and 4–6 reduced the MIC of norfloxacin by ≥ 8 fold against MRSA 831 at half of their MICs. Inhibition of EtBr efflux by NorA-overproducing S. aureus 1199B and MRSA 831 confirmed the role of compounds 4–6 as NorA efflux pump inhibitors (EPI). Dose-dependent activity at sub-inhibitory concentration (6.25 μg/mL) suggested that compounds 4 and 5 are promising EPI compared to verapamil against 1199B and MRSA 831 strains.     

Antibacterial dihydrobenzopyran and xanthone derivatives from Garcinia cowa stem barks

Two new compounds, garciniacowol (1) and garciniacowone (2) along with 15 known compounds were isolated from the stem barks of Garcinia cowa. Their structures were determined by intensive spectroscopic methods. The structure of 1 was a symmetrical dimeric dihydrobenzopyran derivative, whereas the framework of 2 was a triprenyl caged-xanthone precursor. The antibacterial activities against Escherichia coli TISTR 780, Salmonella typhimurium TISTR 292, Staphylococcus aureus TISTR 1466, and methicillin-resistant S. aureus (MRSA) SK1 of the isolated compounds were also evaluated. Compounds 2 and 9 exhibited good antibacterial activity against MRSA SK1 with the same minimum inhibitory concentration (MIC) value of 2 μg/mL. Moreover, compound 2 also showed good antibacterial activity against S. aureus with an MIC value of 2 μg/mL.     

Antiparasitic antioxidant phenylpropanoids and iridoid glycosides from Tecoma mollis

A radical scavenging guided phytochemical study on the stem bark of Tecoma mollis afforded seven active phenylpropanoid glycosides (1–7), including a new one (4), and one iridoid (8). The structures of the isolated compounds were elucidated on the basis of spectroscopic evidences and correlated with known compounds. Compounds (1–7) displayed promising antioxidant activity (DPPH assay) in relation to ascorbic acid (positive control). The antimicrobial activity for compounds (1–8) was evaluated against five bacterial and five fungal strains. The isolated compounds exhibited nonselective weak to moderate antimicrobial activity. The highest antileishmanial activity against Leishmania donovani was observed for compound (7) with an IC₅₀ value of 6.71 μg/ml, using pentamidine and amphotericin B as drug controls. Compound (5) exhibited moderate antimalarial activity (45% inhibition) against chloroquine sensitive (D6) clones of Plasmodium falciparum.     

Two new chamigrane metabolites from fermentation broth of Steccherinum ochraceum

Two new chamigrane-type metabolites named steperoxides C (1) and D (2) were isolated from the basidiomycetes Steccherinum ochraceum. The structures of 1 and 2 were established on the basis of spectral methods (MS, IR, ID and 2D NMR experiments). Compounds 2 showed significant antimicrobial activity against Staphylococcus aureus at 10 and 5 μg/disk.     

Bioactive cis-stilbenoids from the tubers of Scirpus yagara

Two new cis-stilbenoids, sciryagarol I (1) and II (2) were isolated from the EtOAc extract of the tubers of Scirpus yagara, together with four known compounds. The structures of all compounds were determined by comprehensive analyses of their spectroscopic data and comparison with literature information. The compounds 3, 4 and 6 were isolated for the first time from this genus. Some compounds were tested for their cytotoxicity against human tumor cell lines and antimicrobial activity. Compounds 1–4 showed significant cytotoxicity against the Hela cell lines with IC₅₀ values ranging from 7.21 to 61.21 μM. 1 and 2 exhibited some antimicrobial activity against Staphylococcus aureus and Candida albicans with uniform MICs of 79.3 μl/ml for 2, and 152 μl/ml for 1, respectively.     

Four new bis-iridoids isolated from the traditional Tibetan herb Pterocephalus hookeri

Pterocenoids A–E (1–4), which Pterocenoids A(1) is one novel dimer containing a pyridine monoterpene alkaloid; and Pterocenoids B–E (2–4) are rare arranged non-glycosidic bis-iridoids were isolated from Pterocephlus hookeri. The structures of the compounds were established by 1D and 2D NMR spectroscopy and mass spectrometry. All bis-iridoids isolated from P. hookeri were found to possess secoiridoid/iridoid subtype skeletons. Hence, bis-iridoids can be regarded as the chemotaxonomic markers of P. hookeri. The origins of the new bis-iridoids (1–4) were postulated and their activities of inhibition of the NF-κB pathway were assayed and compounds 1–3 showed moderate activity in inhibiting NF-κB.     

Antibacterial tetraoxygenated xanthones from the immature fruits of Garcinia cowa

A phytochemical investigation of the acetone extract from the immature fruits of Garcinia cowa led to the isolation of two novel tetraoxygenated xanthones, garcicowanones A (1) and B (2), together with eight known tetraoxygeanted xanthones. Their structures were determined by spectroscopic analysis. All isolated compounds were evaluated for their antibacterial activity against Bacillus cereus TISTR 688, Bacillus subtilis TISTR 008, Micrococcus luteus TISTR 884, Staphylococcus aureus TISTR 1466, Escherichia coli TISTR 780, Pseudomonas aeruginosa TISTR 781, Salmonella typhimurium TISTR 292 and Staphylococcus epidermidis ATCC 12228. α-Mangostin showed potent activity (MIC 0.25–1 μg/mL) against three Gram–positive strains and garcicowanone A and β-mangostin exhibited strong antibacterial activity against B. cereus with the same MIC values of 0.25 μg/mL.     

Mangostanaxanthones I and II,new xanthones from the pericarp of Garcinia mangostana

Two new xanthones: mangostanaxanthones I (3) and II (5) were isolated from the pericarp of Garcinia mangostana, along with four known xanthones: 9-hydroxycalabaxanthone (1), parvifolixanthone C (2), α-mangostin (4), and rubraxanthone (6). Their structures were elucidated on the basis of IR, UV, 1D, 2D NMR, and MS spectroscopic data, in addition to comparison with literature data. The isolated compounds were evaluated for their antioxidant, antimicrobial, and quorum-sensing inhibitory activities. Compounds 3 and 5 displayed promising antioxidant activity with IC₅₀ 12.07 and 14.12 μM, respectively using DPPH assay. Compounds 4–6 had weak to moderate activity against Escherichia coli and Staphylococcus aureus, while demonstrated promising action against Bacillus cereus with MICs 0.25, 1.0, and 1.0 mg/mL, respectively. The tested compounds were inactive against Candida albicans. However, they showed selective antifungal potential toward Aspergillus fumigatus. Compounds 3 and 4 possessed quorum-sensing inhibitory activity against Chromobacterium violaceum ATCC 12472.     

New phenyl derivatives from endophytic fungus Aspergillus flavipes AIL8 derived of mangrove plant Acanthus ilicifolius

Two new aromatic butyrolactones, flavipesins A (1) and B (2), two new natural products (3 and 4), and a known phenyl dioxolanone (5) were isolated from marine-derived endophytic fungus Aspergillus flavipes. The structures of compounds 1–5 were elucidated by 1D- and 2D-NMR and MS analysis, the absolute configurations were assigned by optical rotation and CD data, and the stereochemistry of 1 was determined by X-ray crystallography analysis. 1 demonstrated lower MIC values against Staphylococcus aureus (8.0 μg/mL) and Bacillus subtillis (0.25 μg/mL). 1 also showed the unique antibiofilm activity of penetration through the biofilm matrix and kills live bacteria inside mature S. aureus biofilm.     

A new 9-nor-atractylodin from Atractylodes lancea and the antibacterial activity of the atractylodin derivatives

A new compound, namely, 9-nor-atractylodin (1) and one known atractylodin (2) were isolated from the rhizomes of Atractylodes lancea. The structural modifications of atractylodin were carried out and a series of atractylodin derivatives (3-10) were obtained. The antibacterial activities of 1-10 were examined against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Candida albicans. Compounds 4 and 8, which contained the α, β-unsaturated carbonyl fragment, were found to be active against E. coli and S. aureus.     

Iridoid and bis-iridoid glucosides from the fruit of Gardenia jasminoides

Three new iridoid glucosides, 6″-O-trans-feruloylgenipin gentiobioside (1), 2′-O-trans-caffeoylgardoside (2), jasmigeniposide A (3), and one new bis-iridoid glucoside, jasmigeniposide B (4), along with six known analogues (5–10), were isolated from the fruit of Gardenia jasminoides. Their structures were established on the basis of spectroscopic analyses and chemical methods. Anti-virus activity of isolated compounds were evaluated in vitro and only compound 9 showed moderate inhibitory activity against H1N1 with 50% effective concentration (EC₅₀) value of 104.36 μM, and selective index (SI) value greater than 4.79.     

Antibacterial triterpenes from the threatened wood-decay fungus Fomitopsis rosea

From a biologically active extract from the fungus Fomitopsis rosea, two new lanostane triterpenes were isolated, 3α-(3′-butylcarboxyacetoxy)oxepanoquercinic acid C 1 and 3α-hydroxy-24-methylene-23-oxolanost-8-en-26-carboxylic acid 2, along with three known triterpenes, 3–5, and the epidioxy sterol derivative 6. The structures of the compounds were elucidated based on their spectral properties. All triterpenes demonstrated antibacterial activity against S. aureus but possessed no antiradical activity against DPPH radicals.     

New biologically active compounds from Kenyan propolis

From propolis samples from Kenya, two new arylnaphtalene lignans were isolated, tetrahydrojusticidin B 1 and 6-methoxydiphyllin 2, along with four known phenolic compounds 5–8, found for the first time in propolis. The structures of the compounds were elucidated based on their spectral properties. The geranylstilbenes 7 and 8 demonstrated antibacterial activity against S. aureus, and the geranylflavon macarangin 6 possessed antiradical activity against DPPH radicals.     

Ophiobolins P–T,five new cytotoxic and antibacterial sesterterpenes from the endolichenic fungus Ulocladium sp.

Five ophiobolane sesterterpenes, ophiobolins P–T, and three known compounds, 6-epi-21,21-O-dihydroophiobolin G, 6-epi-ophiobolin G and 6-epi-ophiobolin K, were isolated from the acetone extract of the endolichenic fungus Ulocladium sp. by using OSMAC method. Their structures were elucidated on the basis of spectroscopic analysis. The absolute configuration of the 18,19-diol moieties in ophiobolin Q was assigned using the Frelek's method. The cytotoxic effects on KB and HepG2 cell lines, antibacterial activity against Bacillus subtilis, methicillin-resistant Staphylococcus aureus, and Bacille Calmette–Guerin were evaluated for all isolated compounds. Ophiobolin T and 6-epi-ophiobolin G exhibited the most potent cytotoxic activity against HepG2 with IC₅₀ of 0.24 and 0.37 μM, respectively. In antibacterial assay, ophiobolins P and T showed moderate antibacterial activity against B. subtilis and meticillin-resistant S. aureus. Ophiobolin T also displayed moderate antibacterial activity against the Bacille Calmette–Guerin strain.     

Meroterpenes and azaphilones from marine mangrove endophytic fungus Penicillium 303#

Three new metabolites (compounds 1–2 and 6), one azaphilone, and two meroterpenes, together with eleven known compounds have been isolated from a mangrove endophytic fungus, Penicillium 303#. Structure elucidation was achieved by 1D and 2D NMR spectroscopy. The absolute configurations of 1 and 2 were determined by electronic circular dichroism (ECD). Cytotoxic activities of new compounds 1–2 and 6 and compound 7were evaluated in vitro against human cancer lines MDA-MB-435, HepG2, HCT-116, and A549. Those compounds showed weak to moderate cytotoxic activities.     

Indole alkaloids from the roots of Isatis indigotica and their inhibitory effects on nitric oxide production

Three rare indole-2-S-glycosides, indole-3-acetonitrile-2-S-β-D-glucopyranoside (1), indole-3-acetonitrile-4-methoxy-2-S-β-D-glucopyranoside (2) and N-methoxy-indole-3-acetonitrile-2-S-β-D-glucopyranoside (3), together with 11 known indole alkaloids were isolated from the roots of Isatis indigotica Fort. (Cruciferae). The structures of 1–3 were elucidated on the basis of mass spectrometry and extensive 1D and 2D NMR spectroscopy. All of the isolated compounds were tested for inhibitory activity against LPS-induced nitric oxide production in RAW 264.7 macrophages. A plausible biosynthesis pathway of 1–3 is also proposed.     

Triterpene saponins from the roots of Ilex pubescens

Five new triterpene saponins, Ilexpublesnins N–R (1–5), along with seven known analogs were isolated from the root of Ilex pubescens. Their structures were elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D NMR experiments. Ilexpublesnin N (1) possessed a rare 20-hydroxyursolic acid scaffold from natural resource. These compounds were evaluated in vitro for their cytotoxic effects on human cancer cell lines HepG2, HLE, BEL7402, BEL7403, BEL7405, MCF-7, HeLa. Among them, only compounds 5 and 10 showed cytotoxic potentiality against BEl-7403 and HEL cell lines [inhibition (%): 35.38 and 45.12, respectively].     

Iridoid and phenylpropanoid glycosides from Scrophularia ningpoensis Hemsl. and their α-Glucosidase inhibitory activities

A new phenylpropanoid glycoside, designated Scrophuside (1) and two new iridoid glycosides, respectively named Ningposide I (2) and Ningposide II (3), along with twelve known (4–15) iridoid and phenylpropanoid glycosides were obtained from the roots of Scrophularia ningpoensis Hemsl. by various chromatographic techniques and their structures were established through chemical methods and spectroscopic analyses. Most of the obtained compounds have been screened for α-Glucosidase inhibitory activity, in which compounds 4, 5, 7, 11, 12, 13, and 14 show significant activity.     

Two new sesquiterpenes from Artemisia sieversiana

Two new sesquiterpenes, together with 32 known compounds(3–34), were isolated from Artemisia sieversiana Ehrhart ex willd. and the compounds 3–21 were isolated from this plant for the first time. The new compounds were elucidated as 2α,9α-dihydroxymuurol-3(4)-en-12-oic acid (1) and 13α-methyl-(5αH,6αH,7αH,8αH)-austricin 8-O-β-D-glucopyranoside (2), respectively. The structural identification of these compounds was mainly achieved by spectroscopic methods including 1D and 2D NMR techniques, and the structure of compound 1 was confirmed by a single crystal X-ray diffraction experiment. Compounds 1–2 were evaluated for cytotoxic activity in vitro against MCF-7, NCI-H460 and Hep-G2 cell lines, respectively.