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.     

New antimicrobial pregnane glycosides from the stem of Ecdysanthera rosea

Phytochemical investigation on the stem of Ecdysanthera rosea led to the isolation of eight new C-21 pregnane glycoside ecdysosides A–H (1–8), together with one known pregnane glycoside ecdysantheroside A (9). Their structures were elucidated based on extensive spectroscopic data (MS, IR, 1D and 2D NMR) analysis, as well as comparison with the reported literature data. Antimicrobial activities of all the compounds were evaluated against bacteria and yeasts. Compounds 1, 9, 3 and 5 exhibited moderate antibacterial activities against respective Enterococcus faecalis and Providensia smartii, with MIC value of 12.5 μg/mL. Compound 8 showed significant anti-yeast activity against Cryptococcus neoformans with MIC value of 12.5 μg/mL.     

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.     

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.     

Antibacterial prenylbenzoic acid derivatives from Anodendron formicinum

A phytochemical investigation on the stems of Anodendron formicinum led to the isolation of eight prenylbenzoic acid derivatives. Three of these were new compounds, designated as formicinuosides A (1), B (2), and C (3). Their structures were elucidated on the basis of extensive spectroscopic analysis, as well as by comparison with the reported spectroscopic data. This is the first report of chemical constituents from A. formicinum and their antimicrobial activities. Among the isolated compounds, compounds 4, 6 and 8 showed significant antibacterial activities against Providensia smartii with MIC values of 0.781 μg/mL. Moreover, compound 8 showed remarkable antibacterial activity against Escherichia coli with MIC value of 0.781 μg/mL.     

The antibiofilm activity of lingonberry flavonoids against oral pathogens is a case connected to residual complexity

The antimicrobial activity of lingonberry (Vaccinium vitis-idaea L.) was evaluated against two oral pathogens, Streptococcus mutans and Fusobacterium nucleatum. Long-bed gel permeation chromatography (GPC; Sephadex LH-20) yielded purified flavonoids, with the most efficient minimum inhibitory concentrations (MICs) against planktonic cells in the anthocyanin and procyanidin primary fractions against F. nucleatum (63–125 μg/ml) and in the procyanidin rich fraction against S. mutans (16–31 μg/ml). The purified flavonol glycosides and procyanidins inhibited biofilm formation of S. mutans (MICs 16–31 μg/ml), while the corresponding reference compounds showed no activity. Secondary GPC purification yielded flavonol glycosides devoid of antibiofilm activity in the 50% MeOH fraction, while elution with 70% acetone recovered a brownish material with activity against S. mutans biofilm (MIC 8 μg/ml). Even after HPLC-PDA, NMR, and MALDI-TOF analyses, the structural identity of this material remained unknown, while its color and analytical characteristics appear to be consistent with flavonoid oxidation products.     

Modulation of COX,LOX and NFκB activities by Xanthium spinosum L. root extract and ziniolide

Xanthium spinosum L. (Asteraceae) is a medicinal weed distributed worldwide. Many of its diverse ethnopharmacological uses – namely diarrhoea, inflammation, liver disorders, snake bite and fever – are linked – at least in part – to an uncontrolled release of arachidonic acid metabolites. The crude extract of X. spinosum roots from Jordanian origin dose-dependently inhibited the 5-LOX (IC₅₀ ≅ 10 μg/mL), COX-1(IC₅₀ ≅ 50 μg/mL), and 12-LOX (IC₅₀ ≅ 170 μg/mL) enzymatic pathways in intact pro-inflammatory cells. A direct activity at the level of PLA₂ is not probable, but the extract induced the synthesis of the anti-inflammatory eicosanoid 15(S)-HETE, which may in turn inhibit this enzyme. 5-LOX bioguided fractionation of the crude extract led to the isolation of ziniolide, a known 12,8-guaianolide sesquiterpene lactone, from the hydro-alcoholic fraction of the n-hexane extract (IC₅₀ = 69 μM). Both the plant extract and ziniolide are in vitro inhibitors of the phorbol-induced NFκB activation, a key regulator of the arachidonic pathway.     

Characterization and antimicrobial activity of essential oils of industrial hemp varieties (Cannabis sativa L.)

The present study focused on inhibitory activity of freshly extracted essential oils from three legal (THC < 0.2% w/v) hemp varieties (Carmagnola, Fibranova and Futura) on microbial growth. The effect of different sowing times on oil composition and biological activity was also evaluated. Essential oils were distilled and then characterized through the gas chromatography and gas chromatography-mass spectrometry. Thereafter, the oils were compared to standard reagents on a broad range inhibition of microbial growth via minimum inhibitory concentration (MIC) assay. Microbial strains were divided into three groups: i) Gram (+) bacteria, which regard to food-borne pathogens or gastrointestinal bacteria, ii) Gram (?) bacteria and iii) yeasts, both being involved in plant interactions. The results showed that essential oils of industrial hemp can significantly inhibit the microbial growth, to an extent depending on variety and sowing time. It can be concluded that essential oils of industrial hemp, especially those of Futura, may have interesting applications to control spoilage and food-borne pathogens and phytopathogens microorganisms.     

Quinolone alkaloids with antibacterial and cytotoxic activities from the fruits of Evodia rutaecarpa

Five new quinolone alkaloids, euocarpines A–E (16–20), four new natural products (1, 4, 12, and 14), and eleven known natural products were isolated from the fruits of Evodia rutaecarpa (Juss.) Benth. The structures of the new compounds were elucidated based on spectroscopic evidence. All compounds were evaluated for their antibacterial activity against three strains and for their cytotoxic activity against four human tumor cell lines. The results revealed that 5, 7–11, 13, 14, and 16–20 exhibited moderate antibacterial activities (MIC values: 4–128 μg/mL), and 9, 11, 14, and 17 exhibited moderate cytotoxic activities against HepG-2, Hela, BEL7402, and BEL7403 (IC₅₀ values: 15.85–56.36 μM).     

Inhibition of hepatitis C virus replication by chalepin and pseudane IX isolated from Ruta angustifolia leaves

Hepatitis C virus (HCV) infection is highly prevalent among global populations, with an estimated number of infected patients being 170 million. Approximately 70–80% of patients acutely infected with HCV will progress to chronic liver disease, such as liver cirrhosis and hepatocellular carcinoma, which is a substantial cause of morbidity and mortality worldwide. New therapies for HCV infection have been developed, however, the therapeutic efficacies still need to be improved. Medicinal plants are promising sources for antivirals against HCV. A variety of plants have been tested and proven to be beneficial as antiviral drug candidates against HCV. In this study, we examined extracts, their subfractions and isolated compounds of Ruta angustifolia leaves for antiviral activities against HCV in cell culture. We isolated six compounds, chalepin, scopoletin, γ-fagarine, arborinine, kokusaginine and pseudane IX. Among them, chalepin and pseudane IX showed strong anti-HCV activities with 50% inhibitory concentration (IC₅₀) of 1.7 ± 0.5 and 1.4 ± 0.2 μg/ml, respectively, without apparent cytotoxicity. Their anti-HCV activities were stronger than that of ribavirin (2.8 ± 0.4 μg/ml), which has been widely used for the treatment of HCV infection. Mode-of-action analyses revealed that chalepin and pseudane IX inhibited HCV at the post-entry step and decreased the levels of HCV RNA replication and viral protein synthesis. We also observed that arborinine, kokusaginine and γ-fagarine possessed moderate levels of anti-HCV activities with IC₅₀ values being 6.4 ± 0.7, 6.4 ± 1.6 and 20.4 ± 0.4 μg/ml, respectively, whereas scopoletin did not exert significant anti-HCV activities at 30 μg/ml.     

Cytotoxic sesquiterpenes from Hedychium spicatum: Isolation,structure elucidation and structure–activity relationship studies

Phytochemical investigation of chloroform extract from rhizomes of Hedychium spicatum resulted in the isolation of six new sesquiterpenes (1–6) along with fifteen known compounds (7–21). Their structures were elucidated on the basis of the extensive spectroscopic analyses (IR, Mass and NMR) and by comparison of the data with those reported in the literature. Further, cytotoxic activities of all the isolates were evaluated by determining their inhibitory effects against A-549, B-16, Hela, HT-29, NCI-H460, PC-3, IEC-6 and L-6 cancer cell lines. Results indicated that compounds 1 and 3 may serve as an important natural lead compounds for future development as they showed potent cytotoxic activity against Hela cell lines with an IC₅₀ value of 0.3 μg/mL and 1.80 μg/mL, respectively.     

A new pentacyclic triterpene with potent antibacterial activity from Limnophila indica Linn. (Druce)

A new pentacyclic triterpenoid constituent, characterized as 3-oxo-olean-12(13),18(19)-dien-29α-carboxylic acid (1) on the basis of detailed spectral studies, was isolated from the aerial parts and roots of Limnophila indica (Scrophulariaceae). Compound 1 exhibited considerable antibacterial activity against three Gram-positive bacteria viz. Bacillus subtilis, Staphylococcus aureus and Listeria monocytogenes (MICs within a range of 25–30 μg/ml) and moderate activity against four Gram-negative bacteria Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa, and Pantoea ananatis (MICs within a range of 30–100 μg/ml). The plant pathogenic bacterium P. ananatis and human pathogenic S. typhimurium responded at comparatively higher concentrations of the compound 1, which were 75 and 100 μg/ml respectively. The compound inhibited the growth of Gram-positive B. subtilis and Gram-negative P. aeruginosa completely with a clear bactericidal mode of action at their MIC values. The compound upon treatment on both B. subtilis and P. aeruginosa released substantial amount of nucleic acid in the external medium and also effected the change of morphology towards pleomorphicity, thereby indicating its probable action on cell membrane. Furthermore, the triterpenoid 1 was found not to inhibit a probiotic lactic acid bacterium Lactococcus lactis subsp. lactis LABW4 under in vitro condition and to possess no toxicity in Swiss albino mice.     

In vitro antifungal activity of phenylheptatriyne from Bidens cernua L. against yeasts

In vitro antifungal activity of phenylheptatriyne from Bidens cernua L. (Asteraceae) was studied using broth macrodilution method against 125 strains of yeasts including 104 clinical and other isolates of Candida spp. (C. albicans, C. krusei, C. tropicalis, C. guilliermondii, C. parapsilosis, C. glabrata, C. inconspicua), 16 strains of basidiomycetous yeasts (Cryptococcus neoformans, C. albidus, Trichosporon cutaneum, Rhodotorula glutinis) and five standard reference strains of Candida species. Phenylheptatriyne has shown significant activity against investigated strains, and the Minimal Inhibitory Concentrations for Candida spp. were determined as 12.5–50 µg/ml and for basidiomycetous yeasts as 12.5–100 µg/ml.     

Comparison of in vitro antiviral activity of tea polyphenols against influenza A and B viruses and structure–activity relationship analysis

Influenza poses a particular risk of severe outcomes in the elderly, the very young and those with underlying diseases. Tea polyphenols are the natural phenolic compounds in teas, and principally consist of catechins, proanthocyanidins, flavonols, and theaflavins, which antiviral activities have been reported recently. This study is to gain a further insight into potential of various tea polyphenols for inhibiting influenza virus infection. Five tea polyphenols exhibited inhibitory activity against influenza A virus in the trend of theaflavin > procyanidin B-2 > procyanidin B-2 digallate > (−)-epigallocatechin(EGC) > (−)-epigallocatechingallate(EGCG) with IC₅₀ values in the range of 16.2–56.5 μg/ml. Six of the tested compounds showed anti-influenza B virus activity in the order of kaempferol > EGCG > procyanidin B-2 > (−)-EGC ~ methylated EGC > theaflavin with IC₅₀ values in the range of 9.0–49.7 μg/ml. Based on these results, the structure–activity relationship (SAR) was explained as follows. First, the dimeric molecules, such as theaflavin and procyanidin B-2, generally displayed more potent antiviral activity against both influenza A and B viruses than the catechin monomers. Second, the kaempferol for inhibition of influenza B virus indicated that the more planar flavonol structure with only one C-4′ phenolic hydroxyl group in the B ring is necessary for the anti-influenza B virus activity. A similar SAR can be drawn from the assays of another enveloped RNA virus, such as respiratory syncytial virus. These results are expected to provide guides for rational design of antiviral drugs based on polyphenols.     

Phytochemical investigation of sesquiterpenes from the fruits of Schisandra chinensis and their cytotoxic activity

Phytochemical investigation of ethanolic extract from the fruits of Schisandra chinensis led to the isolation of four new sesquiterpenes (1–4); their structures were determined by a combination of NMR (1D and 2D) and MS spectroscopic techniques. In addition, all these isolates were screened for their cytotoxic activities against MCF-7, Caco-2, Hela, Lncap, Hep G2 and MDA-MB231 cancer cell lines. Results indicated that compounds 2 and 3 displayed potent cytotoxic activity against Caco2 cell lines with IC₅₀ values of 17.10 μg/mM and 16.46 μg/mM, respectively.     

Phytic acid enhances the oral absorption of isorhamnetin,quercetin, and kaempferol in total flavones of Hippophae rhamnoides L.

AimTotal flavones of Hippophae rhamnoides L. (TFH) have a clinical use in the treatment of cardiac disease. The pharmacological effects of TFH are attributed to its major flavonoid components, isorhamnetin, kaempferol, and quercetin. However, poor oral bioavailability of these flavonoids limits the clinical applications of TFH. This study explores phytic acid (IP₆) enhancement of the oral absorption in rats of isorhamnetin, kaempferol, and quercetin in TFH.MethodsIn vitro Caco-2 cell experiments and in vivo pharmacokinetic studies were performed to investigate the effects of IP₆. The aqueous solubility and lipophilicity of isorhamnetin, quercetin, and kaempferol were determined with and without IP₆, and mucosal epithelial damage resulting from IP₆ addition was evaluated by MTT assays and morphology observations.ResultsThe P_app of isorhamnetin, kaempferol, and quercetin was improved 2.03-, 1.69-, and 2.11-fold in the presence of 333 μg/mL of IP₆, respectively. Water solubility was increased 22.75-, 15.15-, and 12.86-fold for isorhamnetin, kaempferol, and quercetin, respectively, in the presence of 20 mg/mL IP₆. The lipophilicity of the three flavonoids was slightly decreased, but their hydrophilicity was increased after the addition of IP₆ in the water phase as the logP values of isorhamnetin, kaempferol, and quercetin decreased from 2.38 ± 0.12 to 1.64 ± 0.02, from 2.57 ± 0.20 to 2.01 ± 0.04, and from 2.39 ± 0.12 to 1.15 ± 0.01, respectively. The absorption enhancement ratios were 3.21 for isorhamnetin, 2.98 for kaempferol, and 1.64 for quercetin with co-administration of IP₆ (200 mg/kg) in rats. In addition, IP₆ (200 mg/kg, oral) caused neither significant irritation to the rat intestines nor cytotoxicity (400 μg/mL) in Caco-2 cells.ConclusionsThe oral bioavailability of isorhamnetin, kaempferol, and quercetin in TFH was enhanced by the co-administration of IP₆. The main mechanisms are related to their enhanced aqueous solubility and permeability in the presence of IP₆. In summary, IP₆ is a potential absorption enhancer for pharmaceutical formulations that is both effective and safe.     

Synthesis and antimycobacterial evaluation of natural oridonin and its enmein-type derivatives

A series of enmein-type derivatives were synthesized and assayed for their antimycobacterial effects. The structures of the synthesized compounds were established by ¹H NMR, ¹³C NMR and mass spectral analysis. All the compounds were screened for their antimycobacterial properties against Mycobacterium phlei, Mycobacterium smegmatis and Mycobacterium marinum. Compounds 2, 6g and 6i were found to exhibit potent antimycobacterial activity against M. phlei at a concentration of 0.5 μg/mL, which was comparable to that of positive drug streptomycin. Furthermore, five compounds were tested against Mycobacterium tuberculosis H₃₇Rv based on the promising preliminary screening results. Among them, compound 10 showed potent activity with IC₅₀ value of 17.1 μg/mL against M. tuberculosis H₃₇Rv strain. Thus, compound 10 could emerge as a promising lead for further research work.     

Pharmacokinetic study of eight coumarins of Radix Angelicae Dahuricae in rats by gas chromatography–mass spectrometry

A sensitive, specific gas chromatography–mass spectrometry (GC–MS) method was established for the quantitative determination of eight coumarins of Radix Angelicae Dahuricae including coumarin, isopsoralen, psoralen, xanthotoxin, bergapten, osthole, imperatorin and oxypeucedanin in rat plasma. Nitrendipine was used as the internal standard (IS). The plasma samples were extracted by acetonitrile. GC separation was accomplished on a DB-5MS column with temperature programmed from 160 °C (17 min) to 190 °C (10 min) at the rate of 20 °C/min, then to 240 °C (5 min) at 20 °C/min, and finally to 280 °C (14 min) at 20 °C/min. The detection was performed on a quadrupole mass spectrometer detector operated by full-scan mode (m/z 50–500). The lower limit of quantitation was 5–10 ng/mL for eight coumarins, and the linear range was 5–1000 ng/mL for the coumarins (R² > 0.9990). All the validation data were within the required limits. After oral administration, the plasma concentration–time curves showed that the time for maximum concentration (T_max) was 1.29 for coumarin, 1.83 for isopsoralen, 1.93 for psoralen, 1.30 for xanthotoxin, 2.04 for bergapten, 0.64 for osthole, 1.41 for imperatorin and 0.51 h for oxypeucedanin. The plasma concentration of the eight coumarins was low, with a mean maximum plasma concentration (C_max) < 6.41 μg/mL. Pharmacokinetic data analysis showed that the eight coumarins had different pharmacokinetic characteristics after oral administration. The method was successfully applied to pharmacokinetic studies of eight coumarins after oral administration in rats.     

Pharmacokinetic and metabolism studies of rohitukine in rats by high performance liquid-chromatography with tandem mass spectrometry

A sensitive, selective, and rapid high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed for the quantification of rohitukine in rat plasma. HPLC was performed using a Symmetry-Shield C₁₈ (5 μ, 4.6 × 150 mm) column, and isocratic elution with ammonium acetate buffer (pH 4; 10 mM):methanol (08:92, v/v) at a flow rate of 0.6 mL/min. Sample clean-up involved solid phase extraction (SPE) of analyte and internal standard (phenacetin) from 100 μL plasma. The parent → product ion transitions (MRM) for analyte and IS were 306.1 → 245.1 m/z and 180.1 → 138.1 m/z respectively, and were monitored on a triple quadrupole mass spectrometer, operating in positive ion mode. The method was validated across the dynamic concentration range of 5–500 ng/mL for rohitukine, with a fast run time of 4.5 min. The analytical method measured concentrations of rohitukine with accuracy (% bias) of <± 10% and precision (% RSD) of <± 12%. Rohitukine was stable during the battery of stability studies viz., bench-top, auto-sampler, freeze/thaw cycles and 30 days of storage in a freezer at − 70 ± 10 °C. Finally, the applicability of this assay has been successfully demonstrated in vivo pharmacokinetic and in vitro metabolism studies in Sprague–Dawley rat. This method will therefore be highly useful for future preclinical and clinical pharmacokinetic studies of rohitukine.     

Chemical constituents from Aphanamixis grandifolia

Four new terpenoids, nemoralisins D–G (1–4), were isolated from the leaves and stems of Aphanamixis grandifolia, along with two known diterpenoids, nemoralisin C and nemoralisin. Among them, compound 1 is the first example of norsesquiterpenoid with δ-lactone moiety, and nemoralisins E–G (2–4), are a class of acyclic diterpenoids, which are structurally related nemoralisin C and nemoralisin. These structures were established on the basis of spectroscopic methods and the absolute configuration of 1 was determined by comparison of quantum chemical TDDFT calculated and experimental ECD spectra. Nemoralisins D–G (1–4) were tested for their cytotoxicities on HL-60, SMMC-7721, A-549, MCF-7, and SW480 human tumor cell lines (IC₅₀ > 40 μM), as well as the antimicrobial activities on Staphylococcus aureus, Pseudomonas aeruginosa, MRSA92^# and MRSA98^# (MIC > 50 μg/mL).