Novel Anti-Infective Compounds from Marine Bacteria

As a result of the continuous evolution of microbial pathogens towards antibiotic-resistance, there have been demands for the development of new and effective antimicrobial compounds. Since the 1960s, the scientific literature has accumulated many publications about novel pharmaceutical compounds produced by a diverse range of marine bacteria. Indeed, marine micro-organisms continue to be a productive and successful focus for natural products research, with many newly isolated compounds possessing potentially valuable pharmacological activities. In this regard, the marine environment will undoubtedly prove to be an increasingly important source of novel antimicrobial metabolites, and selective or targeted approaches are already enabling the recovery of a significant number of antibiotic-producing micro-organisms. The aim of this review is to consider advances made in the discovery of new secondary metabolites derived from marine bacteria, and in particular those effective against the so called “superbugs”, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin resistant enterococci (VRE), which are largely responsible for the increase in numbers of hospital acquired, i.e., nosocomial, infections

Quality Profile Of Smoked African Sharptooth Catfish (Clarias Gariepinus) Treated With Uncaria Gambier (Uncaria Gambir Roxb)

The purpose of this research was to study antibacterial properties of gambier on the quality charecteristic of smoked African sharptooth catfish (Clarias gariepinus) which was marinated by antibacterial gambier, and to review the effect of concentration and marination time of gambier on the physical, chemical and microbiology characteristic of smoked African sharptooth catfish. Research applied completely randomized design with the concentration of gambier and marination time as treatment with 3 replication.The concentration of gambier consist of A1 (0%), A2 (2%), A3 (4%) and A4 (6%). The marination time consist of B1 (15 minute), B2 (30 minute) and B3 (45 minute). The parameters were Water activity (aw), Protein content, Texture, color (L*lightness, C*chroma and H*hue) and Total plate count (TPC). Test result showed that the concentration and marination time had significant effect on characteristic of smoked African sharptooth catfish. The characteristic of smoked African sharptooth catfish were: water activity (0.78-0.86), Protein content (30.57-33.47%), texture (717.6-835.2 gf), color L* (27.8-37.8), C* (4.1-6.3%), H*(21.8-34.2o), TPC (2.36-5.49 Log Cfu/g) and the best treatment was A4B3 (6% 45 m). All treatment showed the characteristic of smoked African sharptooth catfish which was introduced with gambier had better characteristic than control

Manumycin from a new Streptomyces strain shows antagonistic effect against methicillin-resistant Staphylococcus aureus (MRSA)/vancomycin-resistant enterococci (VRE) strains from Korean Hospitals

An antimicrobial compound, highly effective against multidrug-resistant (MDR) bacteria, purified from a Streptomyces strain was identified as manumycin. The minimal inhibitory concentrations (MICs) of manumycin against 8 different strains of methicillin-resistant Staphylococcus aureus (MRSA) were ranged 2 to 32 μg/ml. Similarly, MICs of manumycin against 4 vancomycin-resistant enterococci (VRE) strains were ranged 8 to 32 μg/ml while it remained ineffective against 4 other VRE strains. Compared to vancomycin, manumycin provided slightly weaker activity against MRSA strains but stronger activity against 4 VRE strains. This is the first report of antagonistic effect of manumycin against MDR pathogens.Keywords: Manumycin, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE)African Journal of Biotechnology Vol. 12(17), pp. 2249-225

Antibacterial and Antioxidant Activities of Fungal Endophytes Isolated from Medicinal Plants in Simeulue Island, Aceh

Natural products from endophytic fungi have a wide range of medicinal applications, including antibacterial and antioxidant agents. The research aimed to evaluate the antibacterial and antioxidant activities of compounds derived from endophytic fungi isolated from medicinal plants collected from Simeulue Island by TLC dot-blot and microdilution assays. Eighty-one fungal extracts were screened for antibacterial and antioxidant activities. Antibacterial activity was evaluated against Gram-positive and negative bacteria, i.e., Staphylococcus aureus InaCC B-4 and Escherichia coli InaCC B-5, respectively. Antioxidant activity was carried out by using free radical scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH). The results of the TLC bioassay revealed that the fungal extracts have activities as antibacterial and antioxidant are 65 (against S. aureus), 57 (against E. coli), and 48 extracts (DPPH free radical scavenger). Two extracts, Phomopsis sp. 48BtSi-2.1 and Xylaria sp. 55DnSi-1.1, showed strong antibacterial activity against S. aureus with MIC value of 32 μg/ml. Furthermore, nine extracts (Schizophyllum sp. 20DnSi-1; Hyphomycetes 36BhSi-1.1; Phomopsis sp. 36DnSi-2.1; Schizophyllum sp. 39DnSi-1.1; Xylaria sp. 39RpSi-2.1; Phomopsis sp. 41BtSi-1.1; Phomopsis sp. 48BtSi-2.1; Lasiodiplodia sp. 48BtSi-3.1; Schizophyllum sp. 50DnSi-3) were strong activity against E. coli with MIC value ranges from 32 to 64 μg/ml. One extract, Xylaria sp. 04BtSi-2.2 has strong antioxidant activity as DPPH free radical scavenger with an IC50 value of 21.66 μg/ml (AAI value of >1)

Chiral Binaphthoquinones: Versatile Precursors for the Synthesis of Natural Products and Ligands for Asymmetric Catalysis

The efforts described in this dissertation initially focus on the asymmetric synthesis of axially chiral binaphtho-para- and binaphtho-ortho-quinones, followed by an exploration of their utility in natural product synthesis, development of ligands for asymmetric catalysis, and development as potential sensors. Axially chiral binaphtho-para- and in-in-binaphtho-ortho-quinones were synthesized through a concerted route involving the enantioselective coupling of a hindered 8-substituted 2-naphthol, with a diaza-cis-decalin copper catalyst developed previously by the Kozlowski group. The coupling was achieved in 62% yield and 87% ee (a single trituration produced material of \u3e99% ee). Subsequent transformations led to an 8,8\u27-hydroxylated binaphthol, which was selectively oxidized to a binaphtho-para-quinone using a Co-salen catalyst or transformed to the in-in-binaphtho-ortho-quinone with o-iodoxybenzoic acid (IBX). Similarly, the out-out-binaphtho-ortho-quinone was synthesized from a 6,6\u27-hydroxylated binaphthol, using IBX. Binaphtho-para-quinones were used as key intermediates for the synthesis of the bisanthraquinone natural product (S)-bisoranjidiol. (S)-Bisoranjidiol was synthesized from a 6,6\u27-dibrominated binaphtho-para-quinone and mixed vinyl ketene acetal, through a regioselective tandem Diels-Alder/aromatization reaction. This transformation was achieved in 80% yield (~95% per transformation). The synthesis of (S)-bisoranjidiol was completed in 4% yield over 12 steps, and \u3e99% ee. In addition, the synthesis of a reported binaphthalene tetraol natural product was achieved through reduction of an out-out-binaphtho-ortho-quinone. This synthesis led to the structural reassignment of the proposed compound to a tetrabrominated diphenyl ether. Condensation of various phenylenediamines with binaphtho-ortho-quinones led to bisbenzo[a]phenazines, which represent BINOL derivatives with electron-withdrawing groups (pyrazine ring). The in-in-bisbenzo[a]phenazines performed better than BINOL, but did not offer improvements over the electron-deficient BINOL based catalysts/ligands reported for those reactions. The bisbenzo[a]phenazines, in particular the tetrachlorinated derivatives, also displayed a series of interesting properties and colorimetric responses to various stimuli (chromism), which may lead to the development of colorimetric sensors. The properties include mechanochromism, thermochromism, solvatochromism, vapochromism, acidochromism, and fluorescence

The ascidian-derived metabolites with antimicrobial properties

Among the sub-phylum of Tunicate, ascidians represent the most abundant class of marine invertebrates, with 3000 species by heterogeneous habitat, that is, from shallow water to deep sea, already reported. The chemistry of these sessile filter-feeding organisms is an attractive reservoir of varied and peculiar bioactive compounds. Most secondary metabolites isolated from ascidians stand out for their potential as putative therapeutic agents in the treatment of several illnesses like microbial infections. In this review, we present and discuss the antibacterial activity shown by the main groups of ascidian-derived products, such as sulfur-containing compounds, meroterpenes, alkaloids, peptides, furanones, and their derivatives. Moreover, the direct evidence of a symbiotic association between marine ascidians and microorganisms shed light on the real producers of many extremely potent marine natural compounds. Hence, we also report the antibacterial potential, joined to antifungal and antiviral activity, of metabolites isolated from ascidian-associate microorganisms by culture-dependent methods

Antifungal and Antibacterial Activities of Isolated Marine Compounds

To combat the ineffectiveness of currently available pharmaceutical medications, caused by the emergence of increasingly resistant bacterial and fungal strains, novel antibacterial and antifungal medications are urgently needed. Novel natural compounds with antimicrobial activities can be obtained by exploring underexplored habitats such as the world’s oceans. The oceans represent the largest ecosystem on earth, with a high diversity of organisms. Oceans have received some attention in the past few years, and promising compounds with antimicrobial activities were isolated from marine organisms such as bacteria, fungi, algae, sea cucumbers, sea sponges, etc. This review covers 56 antifungal and 40 antibacterial compounds from marine organisms. These compounds are categorized according to their chemical structure groups, including polyketides, alkaloids, ribosomal peptides, and terpenes, and their organismal origin. The review provides the minimum inhibitory concentration MIC values and the bacterial/fungal strains against which these chemical compounds show activity. This study shows strong potential for witnessing the development of new novel antimicrobial drugs from these natural compounds isolated and evaluated for their antimicrobial activities

Progress Toward the Asymmetric Total Synthesis of Chaetoglobin A Selective Oxidative Homo- and Cross-Coupling of Phenols Using Aerobic Catalysts

The chaetoglobins are a structurally unique class of azaphilone alkaloid dimers with reported anticancer activity. They are also a potential platform for the development of antibacterial and botulinum antitoxin. Notably, this class of compounds has not been synthesized to date. Chaetoglobin A (1) and B (2) were originally isolated from the endophytic fungus Chaetomium globosum.1 Chaetoglobin A has been shown to be potentially active against human colon and breast cancer. However, the bioactivity of chaetoglobin B has not been studied due lack of material, suggesting the need of further research. The main goal of this project is the design and optimization of a synthetic route for chaetoglobin natural products. Achiral phenol coupling has been studied for many years; however, the regioselective methods reported to date are substrate-dependent and limited in scope. - Previously, we developed a regio- and enantioselective method for oxidative phenol coupling applying a series of bimetallic and monomeric vanadium catalysts. The aim of this project is to develop a new complementary method for regioselective oxidative phenol coupling. In collaboration with Trung Cao and Young Lee, 84 catalysts were synthesized and screened against a collection of phenolic substrates using High-Throughput Experimentation (HTE). We successfully identified catalysts that give high reactivity toward different substrates, and upon scale-up isolated the products in good yields