Ecosystem development in short‐term postglacial chronosequences: N and P limitation in glacier forelands from Santa Inés Island,Magellan Strait

Glacier foreland moraines provide an ideal model to examine the patterns of ecosystem development and the evolution of nitrogen and phosphorous limitation over successional time. In this paper, we focus on a 400‐year soil chronosequence in the glacier forelands of Santa Inés Island in the Magellan Strait, southern Chile by examining forest development on phosphorus (P)‐poor substrates in a uniquely unpolluted region of the world. Results show a steady increase in tree basal area and a humped trend in tree species richness over four centuries of stand development. The increase in basal area suggests that the late successional tree species were more efficient nutrient users than earlier successional ones. Total contents of carbon (C) and nitrogen (N) in soils increased during the chronosequence, reaching an asymptote in late succession. The net increases in soil C : N, C : P and N : P ratios observed over successional time suggest that nutrient limitation is maximal in 400‐year‐old substrates. Foliar C : N and C : P ratios also increased over time to reach an asymptote in old‐growth stages, following soil stoichiometric relationships; however the foliar N‐to‐P ratio remained constant throughout the chronosequence. Biological N fixation was greater in early postglacial succession, associated with the presence of the symbiotic N‐fixer Gunnera magellanica. Declining trends of δ¹⁵N in surface soils through the 400‐year chronosequence are evidence of decreasing N losses in old‐growth forests. In synthesis, glacier foreland chronosequences at this high South American latitude provide evidence for increasing efficiency of N and P use in the ecosystem, with the replacement of shade‐intolerant pioneers by more efficient, shade‐tolerant tree species. This pattern of ecosystem development produces a constant foliar N : P ratio, regardless of variation in soil N‐to‐P ratio over four centuries.     

Actinotetraoses I–K: Tetrasaccharide Metabolites Produced by an Insect‐Derived Actinobacteria,Amycolatopsis sp. HCa1

An isolate of rare actinobacteria strain Amycolatopsis sp. HCa1 obtained from the gut of grasshopper produced seven different metabolites in vitro. The metabolites isolated from its mycelia cakes were characterized by NMR and MS analyses. Actinotetraose hexatiglate (or tigloside; 1 ) with nonreducing glucotetraose skeleton was isolated as a major constituent; three new tetrasaccharide derivatives actinotetraoses I–K ( 2 – 4 , resp.) and three known actinotetraoses A–C ( 5 – 7 , resp.) were also isolated.     

Cytotoxic Tetraprenylated Alkaloids from the South China Sea Gorgonian Euplexaura robusta

Nine achiral tetraprenylated alkaloids, including three new compounds, named malonganenones I–K ( 1 – 3 , resp.), together with six known analogs, 4 – 9 , were isolated from the gorgonian Euplexaura robusta collected from Weizhou Island of Guangxi Province, China. The structures of compounds 1 – 3 were elucidated by extensive spectral analyses, especially of their 1D‐ and 2D‐NMR data. Compounds 1, 4, 6 , and 7 showed moderate cytotoxicities against K562 and HeLa tumor cell lines with IC₅₀ values ranging from 0.35 to 10.82 μM . Compound 6 also showed moderate inhibitory activity against c‐Met kinase at a concentration of 10 μM .     

New Limonoids from the Seeds of a Krishna Mangrove,Xylocarpus granatum

Two new mexicanolides, named granatumins H and I ( 1 and 2 , resp.), and two phragmalins, named granatumins J and K ( 3 and 4 , resp.), were isolated from the seeds of an Indian mangrove, Xylocarpus moluccensis, collected from the swamps of Krishna estuary, Andhra Pradesh. The structures of these limonoids were established on the basis of spectroscopic data. Granatumin J ( 3 ) is a highly oxidized phragmalin with five AcO groups, whereas granatumin K ( 4 ) is the first phragmalin found in nature with conjugated C(8)?C(30) and C(14)?C(15) bonds.     

Triterpenoids from the Stem Bark of Melia toosendan and Determination of Their Absolute Configurations at C(24)

Six new triterpenoids, meliasenins S–X ( 1 – 6 , resp.), were isolated from the stem bark of Melia toosendan. Their structures were elucidated by mass spectrometry, NMR experiments, and comparison with the known compounds. Particularly, the absolute configuration at C(24) in new compounds was determined through their CD spectra of the [Pr(FOD)₃] complex (fod=1,1,1,2,2,3,3,7,7,7‐decafluoroheptane‐4,6‐dione) in CCl₄, as well as by using Mosher's method.     

Identification and Antifeedant Activities of Limonoids from Azadirachta indica

Four new limonoids, azadiraindins A–D ( 1 – 4 , resp.), together with seven known analogs, were isolated from the MeOH extract of Azadirachta indica. The structures of 1 – 4 were elucidated by NMR and MS spectroscopic analyses, and the relative configuration of 1 was determined by single‐crystal X‐ray crystallography. The compounds isolated in comparatively large amount were evaluated for their antifeedant activities against Plutella xylostella; the antifeedant rate of 10 was 90.6% and the corrected mortality of 8 was 79.2%.     

Variation of Epimedins A – C and Icariin in Ten Representative Populations of Epimedium brevicornu Maxim., and Implications for Utilization

The concentration variations of main flavonoids, epimedins A–C and icariin, among ten representative populations of Epimedium brevicornu Maxim . were assessed by HPLC. The populations were collected during the flowering stage and included 419 individual samples. Remarkable variations within and among populations were detected. SXXA Population (see Fig. 1) was an outlier due to its significant low concentrations (<1.00–4.46 mg/g). But even without SXXA, significant concentration differences among populations were still observed in epimedin A (2.31–8.42 mg/g), epimedin B (6.67–55.7 mg/g), epimedin C (5.39–23.0 mg/g), icariin (8.50–39.9 mg/g), and their total (29.1–123 mg/g). All populations except SXXA showed much higher concentrations than the recommended standards (i.e. 5 mg/g for icariin and 13 mg/g for the total). A high‐concentration‐population structure, estimated both by principal component analysis (PCA) and unweighted pair group method with averaging (UPGMA) cluster analysis, based on Euclidean distances, was observed. Both methods allowed separation of the populations in four groups defined by the concentrations of four main flavonoids. The populations (SXLC and SXQS) located in north of Yellow River were clustered together and characterized by highest concentrations of epimedin B, icariin, and their total. Considering of the high concentrations of main flavonoids and abundant resources, E. brevicornu could be exploited as a good medical resource for Herba Epimedii and would offer a tremendous potential for commercial development, but SXXA population should be paid special attention, and further study is needed.     

Novel Zierane‐ and Guaiane‐Type Sesquiterpenes from the Root of Melicope denhamii

Two novel zierane‐type sesquiterpenes, named melicodenones A and B ( 1 and 2 , resp.), and three new guaiane‐type sesquiterpenes, named melicodenones C–E ( 3 – 5 ), were isolated from the root of Melicope denhamii (Seem. ) T. G. Hartley together with zierone ( 6 ). Their structures were established by extensive NMR‐spectroscopic analyses. Compounds 1 – 6 were tested for cytotoxicity using human colon cancer DLD‐1 cells, and melicodenone A ( 1 ) was found to exhibit moderate activity.     

Three new species of Pristionchus (Nematoda: Diplogastridae) show morphological divergence through evolutionary intermediates of a novel feeding‐structure polymorphism

Developmental plasticity is often correlated with diversity and has been proposed as a facilitator of phenotypic novelty. Yet how a dimorphism arises or how additional morphs are added is not understood, and few systems provide experimental insight into the evolution of polyphenisms. Because plasticity correlates with structural diversity in Pristionchus nematodes, studies in this group can test the role of plasticity in facilitating novelty. Here, we describe three new species, Pristionchus fukushimae sp. nov. , Pristionchus hoplostomus sp. nov. , and the hermaphroditic Pristionchus triformis sp. nov. , which are characterized by a novel polymorphism in their mouthparts. In addition to showing the canonical mouth dimorphism of diplogastrid nematodes, comprising a stenostomatous (‘narrow‐mouthed’) and a eurystomatous (‘wide‐mouthed’) form, the new species exhibit forms with six, 12, or intermediate numbers of cheilostomatal plates. Correlated with this polymorphism is another trait that varies among species: whereas divisions between plates are complete in P. triformis sp. nov. , which is biased towards a novel ‘megastomatous’ form comprising 12 complete plates, the homologous divisions in the other new species are partial and of variable length. In a reconstruction of character evolution, a phylogeny inferred from 26 ribosomal protein genes and a partial small subunit rRNA gene supported the megastomatous form of P. triformis sp. nov. as the derived end of a series of split‐plate forms. Although split‐plate forms were normally only observed in eurystomatous nematodes, a single 12‐plated stenostomatous individual of P. hoplostomus sp. nov. was also observed, suggesting independence of the two types of mouth plasticity. By introducing these new species to the Pristionchus model system, this study provides further insight into the evolution of polymorphisms and their evolutionary intermediates. © 2013 The Linnean Society of London     

Anatomy,histology, and systematic implications of the head ornamentation in the males of four species of Limnonectes (Anura: Dicroglossidae)

The males of four species of the Asian frog genus Limnonectes [Limnonectes dabanus (Smith, 1922a), Limnonectes gyldenstolpei (Andersson, 1916), Limnonectes macrognathus (Boulenger, 1917), and Limnonectes plicatellus (Stoliczka, 1873)] exhibit remarkable ornamentation in the form of a swollen, or cap‐like, structure (caruncle) on the top of their heads. These caruncles vary in their appearance among species, and neither their function nor their actual systematic value is known. We compared their anatomy via dissections, morphometrics, radiography, and histology, and analysed the available mitochondrial DNA sequences as well as new data to place these species within the context of a larger phylogenetic hypothesis for Limnonectes. Despite the externally different morphology, the underlying histological structure is virtually identical. Beneath skin that is densely packed with mucous glands lies a pad of connective tissue overlaying the parietal bone. The actual function of the caruncle, however, remains enigmatic. In addition to the presence of the caruncle, independent evidence from osteological characters and molecular data support the monophyly of a clade comprising of L. dabanus, L. gyldenstolpei, L. macrognathus, and L. plicatellus. The caruncles are therefore interpreted as a robust autapomorphy for this clade, and suggest that the subgenus Elachyglossa should be restricted to the four species in question. © 2014 The Linnean Society of London     

Three New Phenylpropanoids from the Roots of Piper taiwanense and Their Inhibitory Activities on Platelet Aggregation and Mycobacterium tuberculosis

Bioassay‐guided fractionation of the active AcOEt‐soluble fraction from the roots of Piper taiwanense has led to the isolation of two new phenylpropanoids, taiwanensols A and B ( 1 and 2 , resp.), a new natural product, taiwanensol C ( 3 ), and 3‐acetoxy‐4‐hydroxy‐1‐allylbenzene ( 4 ). The compounds were obtained as two isomer mixtures ( 1 / 2 and 3 / 4 , resp.). Their structures were elucidated by spectroscopic analyses, including 1D‐ and 2D‐NMR spectroscopy and mass spectrometry, and by the comparison of their NMR data with those of related compounds. Compounds 1 – 4 were evaluated for their antiplatelet and antitubercular activities. The mixtures 1 / 2 and 3 / 4 showed potent inhibitory activities against platelet aggregation induced by collagen, with IC₅₀ values of 35.2 and 8.8 μM , respectively. In addition, 1 / 2 and 3 / 4 showed antitubercular activities against Mycobacterium tuberculosis H37Rv, with MIC values of 30.0 and 48.0 μg/ml, respectively.     

Characteristic Steroids from the South China Sea Gorgonian Muricella sibogae and Their Cytotoxicities

Twenty‐four steroid‐based natural products, 9,10‐secosteroids ( 1 – 10 ), 1,4‐dien‐3‐one steroids ( 11 – 19 ), and 4‐en‐3‐one steroids ( 20 – 24 ), containing varying side‐chains, were isolated from the South China Sea gorgonian Muricella sibogae. The structures of one new 9,10‐secosteroid, sibogol D ( 1 ), and two new 1,4‐dien‐3‐one steroids, sibogols E and F ( 11 and 12 ), were elucidated by extensive spectroscopic analyses and by comparison with the literature data. Cytotoxicities for all the isolates were evaluated against four selected tumor cell lines, HL‐60, HCT116, K562, and P388. Compounds 3, 9 , and 13 exhibited potent cytotoxic activities against the HL‐60 cell line, with IC₅₀ values ranging from 1.27 to 10.05 μM , and compound 3 was also cytotoxic against HCT116 with an IC₅₀ value of 5.8 μM . The bioassay results also indicated a potential relationship between structural patterns and activity. The newly presented series of 1,4‐dien‐3‐one and 4‐en‐3‐one types of steroids relating to the unique 9,10‐secosteroids in biogenesis were found in this species for the first time, which is of considerable chemotaxonomic significance.     

Triterpene Glucosides from the Leaves of Aralia elata and Their Cytotoxic Activities

Three new triterpene glucosides, named congmuyenosides C–E ( 1 – 3 , resp.), along with four known ones, were isolated from an EtOH extract of Aralia elata (Miq .) Seem . leaves. The structures of the new compounds were identified as 3‐O‐{β‐D ‐glucopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐(1→3)‐[β‐D ‐glucopyranosyl‐(1→2)]‐β‐D ‐glucopyranosyl}caulophyllogenin ( 1 ), 3‐O‐{β‐D ‐glucopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐(1→3)‐[β‐D ‐glucopyranosyl‐(1→2)]‐β‐D ‐glucopyranosyl}hederagenin 28‐O‐β‐D ‐glucopyranosyl ester ( 2 ), 3‐O‐{β‐D ‐glucopyranosyl‐(1→3)‐β‐D ‐glucopyranosyl‐(1→3)‐[β‐D ‐glucopyranosyl‐(1→2)]‐β‐D ‐glucopyranosyl}echinocystic acid 28‐O‐β‐D ‐glucopyranosyl ester ( 3 ) on the basis of spectral analyses, including MS, ¹H‐NMR, ¹³C‐NMR, DEPT, HSQC, HMBC, NOESY, and HSQC‐TOCSY experiments. All isolates obtained were evaluated for their cytotoxic activities against three human tumor cell lines (HepG2, SKOV3, and A549). Compound 3 showed significant cytotoxicity against A549 cell line (IC₅₀ 9.9±1.5 μM ).     

Genetic differentiation,speciation, and phylogeography of cactus flies (Diptera: Neriidae: Odontoloxozus) from Mexico and south‐western USA

Nucleotide sequences from the mitochondrial cytochrome c oxidase subunit I (COI) gene, comprising the standard barcode segment, were used to examine genetic differentiation, systematics, and population structure of cactus flies (Diptera: Neriidae: Odontoloxozus) from Mexico and south‐western USA. Phylogenetic analyses revealed that samples of Odontoloxozus partitioned into two distinct clusters: one comprising the widely distributed Odontoloxozus longicornis (Coquillett) and the other comprising Odontoloxozus pachycericola Mangan & Baldwin, a recently described species from the Cape Region of the Baja California peninsula, which we show is distributed northward to southern California, USA. A mean Kimura two‐parameter genetic distance of 2.8% between O. longicornis and O. pachycericola, and eight diagnostic nucleotide substitutions in the COI gene segment, are consistent with a species‐level separation, thus providing the first independent molecular support for recognizing O. pachycericola as a distinct species. We also show that the only external morphological character considered to separate adults of the two species (number of anepisternal bristles) varies with body size and is therefore uninformative for making species assignments. Analysis of molecular variance indicated significant structure among populations of O. longicornis from three main geographical areas, (1) Arizona, USA and Sonora, Mexico; (2) Santa Catalina Island, California, USA; and (3) central Mexico (Querétaro and Guanajuato), although widely‐separated populations from Arizona and Sonora showed no evidence of structure. A TCS haplotype network showed no shared haplotypes of O. longicornis among the three main regions. The potential roles of vicariance and isolation‐by‐distance in restricting gene flow and promoting genetic differentiation and speciation in Odontoloxozus are discussed. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 245–256.     

Photoluminescence properties of LiTi2 − xEux(PO4)3 phosphor

A solid‐state reaction route‐based LiTi_{2 ? x}Eu_x(PO₄)₃ was phosphor synthesized for the first time to evaluate its luminescence performance by excitation, emission and lifetime (τ) measurements. The LiTi_{2 ? x}Eu_x(PO₄)₃ phosphor was excited at λ_exci. = 397 nm to give an intense orange–red (597 nm) emission attributed to the ⁵D₀ → ⁷F₁ magnetic dipole (ΔJ = ±1) transition and red (616 nm) emission (⁵D₀ → ⁷F₂), which is an electric dipole (ΔJ = ±2) transition of the Eu³⁺ ion. Beside this, excitation and emission spectra of host LiTi₂(PO₄)₃ powder were also reported. The effect of Eu³⁺ concentration on luminescence characteristics was explained from emission and lifetime profiles. Concentration quenching in the LiTi_{2 ? x}Eu_x(PO₄)₃ phosphor was studied from the Dexter's model. Dipole–quadrupole interaction is found to be responsible for energy transfer among Eu³⁺ ions in the host lattice. The LiTi_{2 ? x}Eu_x(PO₄)₃ phosphor displayed a reddish‐orange colour realized from a CIE chromaticity diagram. We therefore suggest that this new phosphor could be used as an optical material of technological importance in the field of display devices. Copyright © 2016 John Wiley & Sons, Ltd.     

Antituberculosis Agents and an Inhibitor of the para‐Aminobenzoic Acid Biosynthetic Pathway from Hydnocarpus anthelminthica Seeds

Investigation on the extracts of Hydnocarpus anthelminthica seeds led to the isolation of three new compounds, anthelminthicins A–C ( 1 – 3 , resp.), and two known ones, namely chaulmoogric acid ( 4 ) and ethyl chaulmoograte ( 5 ). Their structures were determined mainly by using spectroscopic techniques. The absolute configuration at the cyclopentenyl moiety of compound 2 was rationalized by quantum calculations. Base hydrolysis, followed by optical‐rotation comparison, allowed assignment of the configuration of chaulmoogric‐acid moiety of compounds 3 and 5 . Biological assays revealed that compounds 1 – 5 significantly inhibit Mycobacterium tuberculosis (MTB) growth with MIC values of 5.54, 16.70, 4.38, 9.82, and 16.80 μM , respectively. Compound 3 was found to inhibit the pathway between chorismate and para‐aminobenzoic acid (pAba) with a MIC value of 11.3 μM , representing a new example of pAba inhibitor isolated from a natural source. All compounds were not toxic to Candida albicans SC5314 at a concentration up to 100 μM .     

A comparative study of viral capsids and bacterial compartments reveals an enriched understanding of shell dynamics

In this work, we carry out a comparative study of the homo 360‐mer structures of viral capsids and bacterial compartments. Different from viral 360‐mers that all are arranged on a skewed right‐handed icosahedral lattice with a triangulation number T of 7, the new 360‐mer structure of AaLS‐13, an engineered bacterial compartment, offers a novel open conformation that has a unique unskewed lattice arrangement with a triangulation number T of 1 and large keyhole‐shaped pores in the shell. By comparing their differences, we are able to predict a closed conformation of AaLS‐13 that has the same lattice arrangement as existing viral capsid structures and in which all the keyhole‐shaped pores are shut. We find that there is a smooth transition pathway between the open and closed conformations. There exists another close conformation but with an opposite, left handedness, which, however, is not kinetically accessible from the open conformation. Our finding thus provides a clue why existing 360‐mer capsid structures all share the same right handedness. We further show that the conformation transition between the open and closed forms aligns extremely well with the intrinsic dynamics of the system as revealed from normal mode analysis, indicating that conformation transition can be fully driven by thermal fluctuations. The significance of this work is that it provides a better understanding of shell dynamics of both viral capsids and bacterial compartments, paving a way for future study of pore dynamics and the selective permeability of these systems.     

A New Cytotoxic Carbazole Alkaloid and Two New Other Alkaloids from Clausena excavata

One new carbazole alkaloid, excavatine A ( 1 ), and two additional new alkaloids, excavatine B ( 2 ) and excavatine C ( 3 ), were isolated from the stems and leaves of Clausena excavata Burm .f. (Rutaceae). Their structures were determined on the basis of detailed spectroscopic analyses, especially 2D‐NMR and HR‐EI‐MS data. Compounds 1 – 3 were tested for their cytotoxic activities against A549, HeLa, and BGC‐823 cancer cell lines, and for their antimicrobial activities against Candida albicans and Staphylococcus aureus. Only 1 exhibited cytotoxicity against A549 and HeLa cell lines with the IC₅₀ values of 5.25 and 1.91 μg/ml, respectively.