New Diterpenes and Diterpene Glycosides with Antibacterial Activity from Soft Coral Lemnalia bournei.

Five new biflorane-type diterpenoids, biofloranates E-I (1-5), and two new bicyclic diterpene glycosides, lemnaboursides H-I (6-7), along with the known lemnabourside, were isolated from the South China Sea soft coral Lemnalia bournei. Their chemical structures and stereochemistry were determined based on extensive spectroscopic methods, including time-dependent density functional theory (TDDFT) ECD calculations, as well as a comparison of them with the reported values. The antibacterial activities of the isolated compounds were evaluated against five pathogenic bacteria, and all of these diterpenes and diterpene glycosides showed antibacterial activities against Staphylococcus aureus and Bacillus subtilis, with MICs ranging from 4 to 64 µg/mL. In addition, these compounds did not exhibit noticeable cytotoxicities on A549, Hela, and HepG2 cancer cell lines, at 20 µM.

Aurantoside L, a New Tetramic Acid Glycoside with Anti-Leishmanial Activity Isolated from the Marine Sponge Siliquariaspongia japonica.

A new tetramic acid glycoside, aurantoside L (1), was isolated from the sponge Siliquariaspongia japonica collected at Tsushima Is., Nagasaki Prefecture, Japan. The structure of aurantoside L (1) composed of a tetramic acid bearing a chlorinated polyene system and a trisaccharide part was elucidated using spectral analysis. Aurantoside L (1) showed anti-parasitic activity against L. amazonensis with an IC50 value of 0.74 µM.

Highly oxidized rearranged derivatives of quinochalcone C-glycosides from Carthamus tinctorius.

Safflopentsides A-C (1-3), three highly oxidized rearranged derivatives of quinochalcone C-glycosides, were isolated from the safflower yellow pigments. Their structures were determined based on a detailed spectroscopic analysis (UV, IR, HR-ESI-MS, 1D and 2D NMR), and the absolute configurations were confirmed by the comparison of experimental ECD spectra with calculated ECD spectra. Compounds 1-3 have an unprecedented cyclopentenone or cyclobutenolide ring A containing C-glucosyl group, respectively. The plausible biosynthetic pathways of compounds have been presented. At 10 µM, 2 showed strong inhibitory activity against rat cerebral cortical neurons damage induced by glutamate and oxygen sugar deprivation.

Tepuazines A-E: Phenazine Glycosides from a Venezuelan Quartz-Rich (Tepui) Cave Soil-Derived Streptomyces virginiae CMB-CA091.

Investigation of the secondary metabolites of Streptomyces virginiae CMB-CA091 isolated from the quartz-rich (tepui) soil of a cave in Venezuela yielded two new dimeric phenazine glycosides, tepuazines A and B (1 and 2); three new monomeric phenazine glycosides, tepuazines C-E (3-5); and a series of known analogues, baraphenazine G (6), phenazinolin D (7), izumiphenazine C (8), 4-methylaminobenzoyl-l-rhamnopyranoside (9), and 2-acetamidophenol (10). Structures were assigned to 1-10 on the basis of detailed spectroscopic analysis and biosynthetic considerations, with 1 and 2 featuring a rare 2-oxabicyclo[3.3.1]nonane-like ring C/D bridge shared with only a handful of known Streptomyces natural products. We propose a plausible convergent biosynthetic relationship linking all known members of this structure class that provides a rationale for the observed ring C/D configuration.

Isolation and characterization of dihydrohomoisoflavonoids from Portulaca oleracea L.

Eight pairs of dihydrohomoisoflavonoids (1-8), including four pairs of enantiomeric aglycones [(R,S)-portulacanones B (1) and C (2) and (R,S)-oleracones C (3) and Q (4)] and four pairs of epimeric glycosides [portulacasides A-D and epiportulacasides A-D (5-8)], were obtained from Portulaca oleracea L. Among them, (R,S)-oleracone Q (4) and four pairs of epimeric glycosides (5-8) were reported for the first time. The 50% EtOH fraction from the 70% EtOH extract prevented HepG2 human liver cancer cell damage induced by N-acetyl-p-aminophenol (APAP), and the cell survival rate was 62.3%. Portulacaside B (6a), which was isolated from the 50% EtOH fraction, exhibited hepatoprotective and anti-inflammatory effects. The compound increased the survival rate of APAP-damaged HepG2 human liver cancer cells from 40.0% to 51.2% and reduced nitric oxide production in RAW 264.7 macrophages, resulting in an inhibitory rate of 46.8%.

Bioactive neolignan, iridoid and flavonoid glycosides from the leaves of Vaccinium bracteatum.

Two neolignan glycosides including a new one (1), along with seven iridoid glycosides (3 - 9) and nine flavonoid glycosides (10 - 18), were isolated from the leaves of Vaccinium bracteatum. Their structures were established mainly on the basis of 1D/2D NMR and ESIMS analyses, as well as comparison to known compounds in the literature. The structure of 1 with absolute stereochemistry was also confirmed by chemical degradation and ECD calculation. Selective compounds showed antiradical activity against ABTS and/or DPPH. Moreover, several isolates also suppressed the production of ROS in RAW264.7 cells and exerted neuroprotective effect toward PC12 cells.

A "biphasic glycosyltransferase high-throughput screen" identifies novel anthraquinone glycosides in the diversification of phenolic natural products.

The sugar moieties of many glycosylated small molecule natural products are essential for their biological activity. Glycosyltransferases (GTs) are enzymes responsible for installing these sugar moieties on a variety of biomolecules. Many GTs active on natural products are inherently substrate promiscuous and thus serve as useful tools in manipulating natural product glycosylation to generate new combinations of sugar units (glycones) and scaffold molecules (aglycones) in a process called glycodiversification. It is important to have an effective screening tool to detect the activity of promiscuous enzymes and their resulting glycoside products. Toward this aim, we developed a strategy for screening natural product GTs in a high-throughput fashion enabled by rapid isolation and detection of chromophoric or fluorescent glycosylated natural products. This involves a solvent extraction step to isolate the resulting polar glycoside product from the unreacted aglycone acceptor substrate and the detection of the formed glycoside by the innate absorbance or fluorescence of the aglycone moiety. Using our approach, we screened a collection of natural product GTs against a panel of precursors to therapeutically important molecules. Three GTs showed previously unreported promiscuity toward anthraquinones resulting in novel ε-rhodomycinone glycosides. Considering the pharmaceutical value of clinically used anthraquinone glycosides that are biosynthesized from an ε-rhodomycinone precursor, and the significance that the sugar moiety has on the biological activity of these drugs, our results are of particular importance toward the glycodiversification of therapeutics in this class. The GTs identified and the novel compounds they produce show promise toward new biocatalytic tools and therapeutics.

New polyphenolic glycosides from the stems of Caesalpinia cucullata and their inhibitory effect on methicillin-resistant Staphylococcus aureus with different ways.

Anti-virulence strategy represents an emerging alternative strategy in the war against increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) due to its milder selection pressure on bacterial resistance. Sortase A (SrtA), as an important virulence factor, is a membrane-localized cysteine transpeptidase which anchors cell surface proteins to the cell wall. Natural products in medicinal plants are the source of targeting bacterial virulence factors. Here, we found polyphenolic glycosides (1-15), including thirteen new derivatives isolated from the stems of Caesalpinia cucullata, exhibited weak to moderate SrtA inhibitory activity without affecting the growth of MRSA, and compound 7 (53.7 % inhibition at 100 µM) was superior to the positive control curcumin. Meanwhile, compounds 2, 4 and 8 could effectively reduce the dose of ceftiofur in combination in vitro with fractional inhibitory concentration index (FICI) ranging from 0.188 to 0.375, which meant polyphenolic glycosides have got antibacterial activity with different ways. Here, we reported all new compounds structures determined by spectroscopy methods and their antibacterial activities, together, the relationship between structures with the inhibitory efficiency. The results indicated that polyphenolic glycosides could be used as promising therapeutic agents to prevent resistance development for S. aureus infections.

Phenolics in buckwheat hull extracts and their antioxidant activities on bulk oil and emulsions.

Buckwheat hulls are discarded as waste, although they have more phenolic compounds than buckwheat groats. The antioxidant activities of buckwheat hull extracts prepared with water, 50% ethanol, and 100% ethanol were investigated in bulk oil, oil-in-water (O/W), and water-in-oil (W/O) emulsions. The relationship between the phenolic compositions of the extracts and their antioxidant activities in the three different lipid systems was also evaluated. Fifty percent ethanol extract had the highest total phenolic content (327 mg gallic acid equivalent [GAE]/g extract) followed by water and 100% ethanol extracts (211 and 163 mg GAE/g extract, respectively). The total oxidation rate (k) was not significantly different among the bulk oils added with the buckwheat hull extracts. However, in the O/W emulsion, the k was more reduced by the 50% and 100% ethanol extracts than by the water extract at the concentration of 100 µg GAE/g (2.9, 2.8, and 3.7 Totox/day, respectively). The k of the W/O emulsion was more reduced by the 100% ethanol extract than by the water and 50% ethanol extract at the concentration of 100 µg GAE/g (3.8, 4.7, and 4.5 Totox/day, respectively). Multivariate statistical analysis revealed that the contents of phenolic acids and their derivatives were the highest in the water extract among the extracts, while the contents of flavonoid glycosides and methylated polyphenols were the highest in the 50% and 100% ethanol extracts, respectively. The results suggest that flavonoid glycosides and methylated polyphenols could be potential candidates for retarding the oxidation of the emulsion system. PRACTICAL APPLICATION: Buckwheat hull extracts could retard lipid oxidation. Flavonoid glycosides and methylated polyphenols in buckwheat hull extracts may have an antioxidative effect on lipids. Thus, buckwheat hulls could be used as an antioxidant in lipid systems, as flavonoid glycosides and methylated polyphenols are properly extracted from buckwheat hulls.

Sesquiterpene and Sorbicillinoid Glycosides from the Endophytic Fungus Trichoderma longibrachiatum EN-586 Derived from the Marine Red Alga Laurencia obtusa.

An unusual sesquiterpene glycoside trichoacorside A (1) and two novel sorbicillinoid glycosides sorbicillisides A (2) and B (3), together with a known compound sorbicillin (4), were isolated and identified from the culture extract of an endophytic fungus Trichoderma longibrachiatum EN-586, obtained from the marine red alga Laurencia obtusa. Trichoacorside A (1) is the first representative of a glucosamine-coupled acorane-type sesquiterpenoid. Their structures were elucidated based on detailed interpretation of NMR and mass spectroscopic data. The absolute configurations were determined by X-ray crystallographic analysis, chemical derivatization, and DP4+ probability analysis. The antimicrobial activities of compounds 1-4 against several human, aquatic, and plant pathogens were evaluated.

In Vitro Anticancer and Cancer-Preventive Activity of New Triterpene Glycosides from the Far Eastern Starfish Solaster pacificus.

Sea stars or starfish (class Asteroidea) and holothurians or sea cucumbers (class Holothuroidea), belonging to the phylum Echinodermata (echinoderms), are characterized by different sets of glycosidic metabolites: the steroid type in starfish and the triterpene type in holothurians. However, herein we report the isolation of eight new triterpene glycosides, pacificusosides D−K (1−3, 5−9) along with the known cucumarioside D (4), from the alcoholic extract of the Far Eastern starfish Solaster pacificus. The isolated new compounds are closely related to the metabolites of sea cucumbers, and their structures of 1−3 and 5−9 were determined by extensive NMR and ESIMS techniques. Compounds 2, 5, and 8 have a new type of tetrasaccharide chain with a terminal non-methylated monosaccharide unit. Compounds 3, 6, and 9 contain another new type of tetrasaccharide chain, having 6-O-SO3-Glc as one of the sugar units. The cytotoxic activity of 1−9 against non-cancerous mouse epidermal cells JB6 Cl41 and human melanoma cell lines SK-MEL-2, SK-MEL-28, and RPMI-7951 was determined by MTS assay. Compounds 1, 3, 4, 6, and 9 showed potent cytotoxicity against these cell lines, but the cancer selectivity (SI > 9) was observed only against the SK-MEL-2 cell line. Compounds 1, 3, 4, 6, and 9 at the non-toxic concentration of 0.1 µM significantly inhibited neoplastic cell transformation of JB6 Cl41 cells induced by chemical carcinogens (EGF, TPA) or ionizing radiation (X-rays and UVB). Moreover, compounds 1 and 4 at the non-toxic concentration of 0.1 µM possessed the highest inhibiting activity on colony formation among the investigated compounds and decreased the colonies number of SK-MEL-2 cells by 64% and 70%, respectively. Thus, triterpene glycosides 1 and 4 can be considered as prospective cancer-preventive and anticancer-compound leaders.

Potential active constituents responsible for treating acute pharyngitis in the flowers of Hosta plantaginea (Lam.) Aschers and their pharmacokinetics.

In Asia, the flower of Hosta plantaginea (Lam.) Aschers (hosta flower) is both an edible food and medicine. The hosta flower is often used as a material for cooking porridge and scented tea and in combination with other plants for alleviating pharyngitis. To clarify the anti-pharyngitis effect of the hosta flower and evaluate its potential active ingredients, an ethanol extract of the hosta flower was prepared and partially purified via chromatography on a column packed with D101 macroporous resin, which was eluted with different concentrations of ethanol. The anti-pharyngitis effect of the crude extract and the various partially purified fractions was examined in an ammonia-induced acute pharyngitis rat model. The 30% ethanol-eluted fraction significantly alleviated the severity of pharyngitis in the rat, as evaluated by changes in the levels of cytokines (IL-1ß, IL-6, and TNF-α) and histological changes in the pharynx tissues. Subsequent HPLC-QTOF/MS (high-performance liquid chromatography coupled with quadrupole-time of flight tandem mass spectrometry) analysis of this fraction revealed kaempferol and its glycosides as the main components. Three of the main components were isolated and identified by 1D NMR. Their pharmacokinetics were studied for the first time by UHPLC-QQQ/MS (ultrahigh-performance liquid chromatography coupled with mass spectrometry). The findings suggested that the 30% ethanol-eluted fraction of the hosta flower extract may be a potential functional food for treating pharyngitis.

Bioconversion of Glycosidic Precursors from Sour Guava (Psidium friedrichsthalianum Nied.) Fruit by the Oral Microbiota into Odor-Active Volatile Compounds.

The ability of the human oral microbiota to hydrolyze the glycosidic aroma precursor extract isolated from sour guava (Psidium friedrichsthalianum Nied.) fruits was studied herein. The glycosidic extract (GP) was incubated with a mixture of the oral microbiota isolated from three individuals' saliva to evaluate the hydrolytic capacity of oral bacteria in the generation of odor-active compounds. The oral microbiota was able to release 1-hexanol from GP, under both aerobic and anaerobic conditions. Additionally, the aroma precursor extracts showed a decrease in the growth of harmful oral bacteria (Streptococcus and Actinomyces). This effect can be considered beneficial to human health because these bacteria have been related to different diseases of the bucco-respiratory tract.

Chemical Components in Hedera rhombea Leaves and Their Cytotoxicity.

Two novel triterpene glycosides (1 and 2), 17 known triterpene glycosides (3-19), two known flavonoid glycosides (20 and 21), and two known norsesquiterpene glucosides (22 and 23) were isolated from Hedera rhombea (Araliaceae) leaves. The structures of 1 and 2 were determined by spectroscopic analysis, including two-dimensional NMR spectroscopy, and chromatographic analysis of the hydrolyzed products. The cytotoxicity of the isolated triterpene glycosides (1-19) against HL-60 human promyelocytic leukemia cells was evaluated. Compounds 9, 10, and 11 were cytotoxic to HL-60 cells with IC50 values of 7.2, 21.9, and 32.8 µM, respectively. Other compounds isolated from the leaves were not cytotoxic at sample concentrations of 50 µM.

Highly Potent Inhibition of Tyrosinase by Mulberrosides and the Inhibitory Mechanism in Vitro.

Many stilbene glycosides can alleviate skin hyperpigmentation due to their inhibitory effect on tyrosinase. Mulberrosides in Morus alba L. are stilbene glycosides. In the present study, the inhibition of tyrosinase by five mulberrosides (S1-5), isolated from Morus alba L. was investigated and compared, and the inhibitory mechanism was explored. These five mulberrosides exhibited obvious inhibitory effects on tyrosinase only in a concentration-dependent manner, without time-dependence, indicating that they are reversible inhibitors of tyrosinase. S2, S1 and S5 inhibited tyrosinase activity with IC50 values of 28.93, 75.94 and 151.72 µM, respectively, and were more active than kojic acid (IC50 =169.13 µM). Kinetic studies revealed that S1, S2 and S4 were competitive inhibitors, while S3 and S5 were mixed inhibitors. Analysis of the fluorescent spectra showed that mulberrosides S1, S2 and S4 quenched the intrinsic fluorescence intensity of tyrosinase. A molecular docking study indicated that the interaction of tyrosinase with mulberrosides was reflected by compound scores as follows: S2>S5>S1>S3/S4>kojic acid, and hydroxy groups in the side chain of mulberrosides may play a crucial role in the binding of the enzyme. Our results suggest that mulberrosides in Morus alba L. could be further developed as whitening agents for enhanced performance against hyperpigmentation.

Isolation and characterization of a novel flavanone glycoside from an endemic plant Haplanthodes neilgherryensis.

The chemical characterization study of an endemic plant, Haplanthodes neilgherryensisis (Wight) R.B. Majumdar from Western Ghats of India, resulted in to the isolation of a new flavanone glycoside, 5-hydroxy-7-methoxy-8-O-ß-D-glucopyranosyl-2S-flavanone (1), along with 3 known flavonoids, 7-O-methyl dihydrowogonin (2), 7-O-methyl wogonin (3), andrographidine C (4). The structure of 1 was elucidated by using 1 D and 2 D NMR and HRMS experimental data, while for the known compounds, 1H NMR and mass spectrometry data were compared with the reported literature. Compound 1 was tested in vitro to check the improvement in uptake of glucose by the L6 rat skeletal muscle tissues and the observed EC50 value was 5.8 µM, while rosiglitazone showed EC50 of 2.7 µM.

Isolation and characterization of secondary metabolites from the leaves of Sauropus spatulifolius Beille and their potential biological assays.

Eight new compounds (1-8), along with three known related compounds (9-11) were isolated from the leaves of Sauropus spatulifolius Beille. Their structures and configurations were elucidated by means of spectrometric and the modified Mosher's method. Among the new compounds, compounds 1 and 2 were identified as ethyl 3, 6-anhydro-2-deoxy-ß-D-arabino-hexofuranoside (1) and ethyl 3, 6-anhydro-2-deoxy- hexofuranoside (2). Compounds 3-5 were the 2-acetylpyrrole derivatives and identified as 2-(2-acetyl-1H-pyrrol-1-yl)-4-hydroxybutyric acid (3), methyl 4-(2-acetyl-lH-pyrrol- 1-yl) butanoate (4) and 1, 4-bis (2-acetyl-1H-pyrrol-1-yl) butane (5), respectively. Compound 6 was elucidated as 7-megastigmane-3, 8, 9-triol. Compounds 7, 8 were identified as kaempferol-3-O-2-deoxy-ß-D-glucoside (7) and kaempferol-3-O-ß-D- glucopyranosyl-(1-6)-2-deoxy-ß-D-glucoside (8). In addition, the cytotoxic activities of all the compounds were also evaluated, where compounds 3, 5, 7, 9\10 and 11 exhibited the magnificent inhibition activity on lung fibroblast differentiation induced by TGF-ß1with low toxicity against the RLE-6TN cell.

Physicochemical, structural and rheological properties of pectin isolated from citrus canning processing water.

In order to better utilize the citrus pectin (CP) resource, the crude citrus pectin (CCP), obtained from the citrus fruit canning processing waste water, was purified by cellulose DEAE-52 column, providing neutral polysaccharide CP0 and two acidic polysaccharides (CP1 and CP3). CP1 had the highest yield among the three fractions, being 44.29%. The chemical composition, structure and morphology of these pectin components were analyzed. Monosaccharide composition analysis revealed that arabinose was the most abundant composition in these pectin samples. CCP, CP1 and CP3 were mainly composed of rhamnogalacturonan-I (RG-I) regions. Compared with CP3, CCP and CP1 had longer side chains, which are mainly consisted of arabinose. FT-IR and NMR analysis indicated that α-type glycosidic bonds are the main linkage in the four pectin components. These CP samples were found to possess different conformation, but no triple-helical conformation was observed in all these CP fractions. Scanning electron microscopy revealed that CCP, CP1 and CP3 all had irregular sheet-like structures and partly porous structures. The four pectin components showed the characteristics of non-Newtonian fluids and possessed good viscoelasticity. Due to these properties, the pectin might have potential application in food industry as food thickening agent.

Abieshanesides A and B, two unique ent-18,19-dinoricetexane diterpenoid glycosides from Abies beshanzuensis M.H. Wu.

Two unprecedented ent-18,19-dinoricetexane diterpenoid glycosides, named abieshanesides A (1) and B (2), together with seven known compounds, have been isolated from the dead trunks and branches of Abies beshanzuensis M.H. Wu. To our knowledge, abieshanesides A and B represent the first ent-18,19-dinoricetexane diterpenoid glycosides found in natural sources. Their structures and absolute configurations were elucidated by using a combination of spectroscopic techniques and comparison of experimental and calculated electronic circular dichroism (ECD) data. The MTT experiments showed that (E)-resveratrol (7) could inhibit viability of MH7A cells with the IC50 value of 12.5 µM. Compound 7 was able to block MH7A cell proliferation and was associated with G0/G1-phase cell cycle arrest. Flow cytometric analysis showed that the treatment by 7 significantly induced the proliferation of MH7A cells in a dose-dependent manner.

Diarylheptanoid glycosides from Zingiber officinale peel and their anti-apoptotic activity.

Four new diarylheptanoid glycosides (1-4), (1S,3R,5S)-2-(4-hydroxy-3- methoxyphenyl)-6-[2-(4-hydroxyphenyl)ethyl]-tetrahydropyran-4-ol-4'-O-ß-D-glucopyranoside (1), (1S,3R,5S)-2-(4,5-dihydroxy-3-methoxyphenyl)-6-[2-(4-hydroxyphenyl) ethyl]-tetrahydropyran-4-ol-4'-O-ß-D-glucopyranoside (2), (1S,3R,5S)-2-(4-hydroxy- 3,5-dimethoxyphenyl)-6-[2-(4-hydroxy-3-methoxyphenyl)ethyl]-tetrahydropyran-4-ol-4'-O-ß-D-glucopyranoside (3), and (1R,3R,5R)-2-(4-hydroxy-3,5-dimethoxyphenyl)- 6-[2-(4-hydroxy-3-methoxyphenyl)ethyl]-tetrahydropyran-4-ol-3-O-ß-D-glucopyranoside (4) were isolated from the 50% ethanol extract of Zingiber officinale peel. The structures of the isolated compounds were determined by HR-ESI-MS and extensive spectroscopic techniques (UV, IR, 1D-NMR, and 2D-NMR). Compounds 1-4 significantly increased the survival rate of human normal lung bronchial epithelial cells (BEAS-2B) induced by lipopolysaccharide (LPS) at the concentration of 10 µM.