Botryane terpenoids produced by Nemania bipapillata, an endophytic fungus isolated from red alga Asparagopsis taxiformis - Falkenbergia stage

A chemical study of the EtOAc extract of Nemania bipapillata (AT-05), an endophytic fungus isolated from the marine red alga Asparagopsis taxiformis - Falkenbergia stage, led to the isolation of five new botryane sesquiterpenes, including the diastereomeric pair (+)-(2R,4S,5R,8S)-(1) and (+)-(2R,4R,5R,8S)-4-deacetyl-5-hydroxy-botryenalol (2), (+)-(2R,4S,5R,8R)-4-deacetyl-botryenalol (3), one pair of diastereomeric botryane norsesquiterpenes bearing an unprecedented degraded carbon skeleton, (+)-(2R,4R,8R)-(4) and (+)-(2R,4S,8S)-(5), which were named nemenonediol A and nemenonediol B, respectively, in addition to the known 4β-acetoxy-9β,10β,15α-trihydroxyprobotrydial (6). Their structures were elucidated using 1D and 2D NMR, HRESIMS and comparison with literature data of similar known compounds. The absolute configurations of 2, 3 and 4 were deduced by comparison of experimental and calculated electronic circular dichroism (ECD) spectra, while those of 1 and 5 were assigned from vibrational circular dichroism (VCD) data. Compound 4 weakly inhibited acetylcholinesterase, whereas compound 1 inhibited both acetylcholinesterase and butyrylcholinesterase. Compounds 1, 3, 5 and 6 were tested against two carcinoma cell lines (MCF-7 and HCT-116), but showed no significant citotoxicity at tested concentrations (IC₅₀ > 50 µM).

Lactone Derivatives Produced by a Phaeoacremonium sp., an Endophytic Fungus from Senna spectabilis

Three new isoaigialones, A, B, and C (1-3), along with aigialone (4), were isolated from the crude EtOAc extract of a Phaeoacremonium sp., an endophytic fungus obtained from the leaves of Senna spectabilis. The structures of these compounds were elucidated based on the analysis of spectroscopic data. Compounds 2 and 4 were active against the phytopathogenic fungi Cladosporium cladosporioides and C. sphaerospermum. This is the first report of metabolites produced by an Phaeoacremonium sp., associated with S. spectabilis.

An epigenetic modifier induces production of (10'S)-verruculide B, an inhibitor of protein tyrosine phosphatases by Phoma sp. nov. LG0217, a fungal endophyte of Parkinsonia microphylla

Incorporation of the histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA), to a culture broth of the endophytic fungus Phoma sp. nov. LG0217 isolated from Parkinsonia microphylla changed its metabolite profile and resulted in the production of (10'S)-verruculide B (1), vermistatin (2) and dihydrovermistatin (3). When cultured in the absence of the epigenetic modifier, it produced a new metabolite, (S,Z)-5-(3',4'-dihydroxybutyldiene)-3-propylfuran-2(5H)-one (4) together with nafuredin (5). The structure of 4 was elucidated by spectroscopic analyses and its absolute configuration was determined by application of the modified Mosher's ester method. The absolute structure of (10'S)-verruculide B was determined as 5-[(10'S,2'E,6'E)-10',11'-dihydroxy-3',7',11'-trimethyldodeca-2',6'-dien-1'-yl]-(3R)-6,8-dihydroxy-3-methylisochroman-1-one (1) with the help of CD and NOE data. Compound 1 inhibited the activity of protein tyrosine phosphatases (PTPs) 1B (PTP1B), Src homology 2-containing PTP 1 (SHP1) and T-cell PTP (TCPTP) with IC50 values of 13.7±3.4, 8.8±0.6, and 16.6±3.8μM, respectively. Significance of these activities and observed modest selectivity of 1 for SHP1 over PTP1B and TCPTP is discussed.

Oxaspirol B with p97 Inhibitory Activity and Other Oxaspirols from Lecythophora sp. FL1375 and FL1031, Endolichenic Fungi Inhabiting Parmotrema tinctorum and Cladonia evansii

A new metabolite, oxaspirol D (4), together with oxaspirols B (2) and C (3) were isolated from Lecythophora sp. FL1375, an endolichenic fungus isolated from Parmotrema tinctorum, whereas Lecythophora sp. FL1031 inhabiting the lichen Cladonia evansii afforded oxaspirols A (1), B (2), and C (3). Of these, oxaspirol B (2) showed moderate p97 ATPase inhibitory activity. A detailed characterization of all oxaspirols was undertaken because structures proposed for known oxaspirols have involved incomplete assignments of NMR spectroscopic data leading only to their planar structures. Thus, the naturally occurring isomeric mixture (2a and 2b) of oxaspirol B was separated as their diacetates (5a and 5b) and the structures and absolute configurations of 1, 2a, 2b, 3, and 4 were determined by the application of spectroscopic techniques including two-dimensional NMR and the modified Mosher's ester method. Oxaspirol B (2) and its diacetates 5a and 5b were evaluated for their ATPase inhibitory activities of p97, p97 mutants, and other ATP-utilizing enzymes, and only 2 was found to be active, indicating the requirement of some structural features in oxaspirols for their activity. Additional biochemical and cellular assays suggested that 2 was a reversible, non-ATP competitive, and specific inhibitor of p97.

Bioactive Metabolites Produced by Penicillium sp.1 and sp.2, Two Endophytes Associated with Alibertia macrophylla (Rubiaceae)

In the course of our continuous search for bioactive metabolites from endophytic fungi living in plants from the Brazilian fl ora, leaves of Alibertia macrophylla (Rubiaceae) were submitted to isolation of endophytes, and two species of Penicillium were isolated. The acetonitrile fraction obtained in corn from a culture of Penicillium sp.1 afforded orcinol (1). On the other hand, Penicillium sp.1 cultivated in potato-dextrose-broth furnished two different compounds, cyclo-(L-Pro-L-Val) (2) and uracil (3). The chromatographic fractionation of the acetonitrile fraction obtained from Penicillium sp.2 led to three dihydroisocoumarins, 4-hydroxymellein (4), 8-methoxymellein (5) and 5-hydroxymellein (6). Compounds 5 and 6 were obtained from the Penicillium genus for the fi rst time. Additionally, metabolites 1 - 6 were evaluated for their antifungal and acetylcholinesterase (AChE) inhibitory activities. The most active compounds 1 and 4 exhibited detection limits of 5.00 and 10.0 μg against Cladosporium cladosporioides and C. sphaerospermum, respectively. Compound 2 showed a detection limit of 10.0 μg, displaying potent AChE inhibitory activity.

Biologically active eremophilane-type sesquiterpenes from Camarops sp., an endophytic fungus isolated from Alibertia macrophylla

Two new eremophilane-type sesquiterpenes, xylarenones F (3) and G (4), have been isolated from solid substrate cultures of a Camarops sp. endophytic fungus isolated from Alibertia macrophylla, together with the known compounds xylarenones C (1) and D (2). The structures and relative configurations of 1-4 were elucidated by extensive NMR and HRESIMS spectroscopic analysis. Due to their effects on the respiratory burst of neutrophils, which included inhibition of the reactive oxygen species production, these sesquiterpenes exhibited potential anti-inflammatory and antioxidant properties.

Anti-Mycobacterium tuberculosis activity of fungus Phomopsis stipata

Our purpose was to determine the anti-Mycobacterium tuberculosis activity of the metabolites produced by the endophitic fungus Phomopsis stipata (Lib.) B. Sutton, (Diaporthaceae), cultivated in different media. The antimycobacterial activity was assessed through the Resazurin Microtiter Assay (REMA) and the cytotoxicity test performed on macrophage cell line. The extracts derived from fungi grown on Corn Medium and Potato Dextrose Broth presented the smallest values of Minimum Inhibitory Concentration (MIC) and low cytotoxicity, which implies a high selectivity index. This is the first report on the chemical composition and antitubercular activity of metabolites of P. stipata, as well as the influence of culture medium on these properties.

Identification and control of dynamical systems using the self-organizing map

In this paper, we introduce a general modeling technique, called vector-quantized temporal associative memory (VQTAM), which uses Kohonen's self-organizing map (SOM) as an alternative to multilayer perceptron (MLP) and radial basis function (RBF) neural models for dynamical system identification and control. We demonstrate that the estimation errors decrease as the SOM training proceeds, allowing the VQTAM scheme to be understood as a self-supervised gradient-based error reduction method. The performance of the proposed approach is evaluated on a variety of complex tasks, namely: i) time series prediction; ii) identification of SISO/MIMO systems; and iii) nonlinear predictive control. For all tasks, the simulation results produced by the SOM are as accurate as those produced by the MLP network, and better than those produced by the RBF network. The SOM has also shown to be less sensitive to weight initialization than MLP networks. We conclude the paper by discussing the main properties of the VQTAM and their relationships to other well established methods for dynamical system identification. We also suggest directions for further work.

Context in temporal sequence processing: a self-organizing approach and its application to robotics

A self-organizing neural net for learning and recall of complex temporal sequences is developed and applied to robot trajectory planning. We consider trajectories with both repeated and shared states. Both cases give rise to ambiguities during reproduction of stored trajectories which are resolved via temporal context information. Feedforward weights encode spatial features of the input trajectories, while the temporal order is learned by lateral weights through delayed Hebbian learning. After training, the net model operates in an anticipative fashion by always recalling the successor of the current input state. Redundancy in sequence representation improves noise and fault robustness. The net uses memory resources efficiently by reusing neurons that have previously stored repeated/shared states. Simulations have been carried out to evaluate the performance of the network in terms of trajectory reproduction, convergence time and memory usage, tolerance to fault and noise, and sensitivity to trajectory sampling rate. The results show that the model is fast, accurate, and robust. Its performance is discussed in comparison with other neural-networks models.

Communiols E-H: new polyketide metabolites from the coprophilous fungus Podospora communis

Communiols E-H (1-4), four new polyketide-derived natural products containing furanocyclopentane, furanocyclopentene, cyclopentene, or gamma-lactone moieties, have been isolated from two geographically distinct isolates of the coprophilous fungus Podospora communis. The structures of these compounds were determined by analysis of NMR and MS data.