Mycosporine‐glutamicol‐glucoside: a natural UV‐absorbing secondary metabolite of rock‐inhabiting microcolonial fungi

The original article to which this Erratum refers was published in Rapid Commun. Mass Spectrom. 2003; 17 : 897–902     

Synthesis of a new microbial secondary metabolite: anti-Helicobacter pylori CJ-13,015

A six-step, first synthesis of an anti-Helicobacter pylori secondary metabolite, CJ-13,015 (1a), in 65% overall yield, is described, starting from 5-methylfurfural (2), via a Wittig reaction of the ylide generated in situ from (8-hydroxyoctyl)triphenylphosphonium bromide, selective reduction of the newly formed carbon-carbon double bond, conversion of the alcohol to a halide, coupling with the anion of 3,5-dimethoxyphthalide and a chemoselective conversion of the protective furan group to a 1,4-dicarbonyl system as a key reaction.     

Chemical ecology of endophytic fungi: origins of secondary metabolites

Endophytes constitute a remarkably multifarious group of microorganisms ubiquitous in plants and maintain an imperceptible association with their hosts for at least a part of their life cycle. Their enormous biological diversity coupled with their capability to biosynthesize bioactive secondary metabolites has provided the impetus for a number of investigations on endophytes. Here, we highlight the possible current and future strategies of understanding the chemical communication of endophytic fungi with other endophytes (fungi and bacteria) and with their host plants, which might not only allow the discovery and sustainable production of desirable natural products but also other mostly overlooked bioactive secondary metabolites.     

Epicoccamide,a novel secondary metabolite from a jellyfish-derived culture of Epicoccum purpurascens

From the inner tissue of the jellyfish Aurelia aurita a marine strain of the fungus Epicoccum purpurascens was obtained. After mass cultivation the fungus was investigated for its secondary metabolite content and found to contain the new, and most unusual tetramic acid derivative, epicoccamide (1). Epicoccamide is quite unusual since it is composed of three biosynthetically distinct subunits; glycosidic, fatty acid and tetramic acid (amino acid). The structure of the new compound was elucidated using spectroscopic methods, mainly 1D and 2D NMR, ESI-MS, and chemical degradations.     

One metabolite, two pathways: convergence of polypropionate biosynthesis in fungi and marine molluscs

Structural similarity or even the identity of polyketide compounds does not necessarily imply unique biosynthesis. Feeding experiments with a (13)C labeled precursor establish that the C(3) units in 7-methyl-cyercene-1 (1) are derived from intact propionate in the marine mollusc Ercolania funerea. The same compound in the terrestrial fungus Leptosphaeria maculans/Phoma lingam is synthesized by an acetate/SAM pathway thus proving for the first time metabolic convergence of polyketide biosynthesis in eukaryotes. Traditional (1)H-(13)C NMR correlation spectroscopy has been successfully applied to estimate (13)C incorporation in biosynthetic experiments.     

Volatile secondary metabolite pattern of callus cultures of Chamomilla recutita

The effects of various plant growth regulators and culture conditions on the production of volatile secondary metabolites from callus cultures of Chamomile (Chamomilla recutita) inflorescence were investigated and the most efficient conditions were determined. The essential oil composition was assayed by GC-MS analysis and found to contain chamomillol, gossonorol, cubenol, alpha-cadinol, (-)-alpha-bisabolol, 1-azulenethanol acetate and (-)-alpha-bisabolol acetate.     

Characterization of the secondary metabolite biosynthetic gene clusters in archaea

Secondary metabolites are a range of bioactive compounds yielded by bacteria, fungi and plants, etc. The published archaea genomic data provide the opportunity for efficient identification of secondary metabolite biosynthetic gene clusters (BGCs) by genome mining. However, the study of secondary metabolites in archaea is still rare. By using the antiSMASH, we found two main putative secondary metabolite BGCs, bacteriocin and terpene in 203 Archaea genomes. Compared with the genomes of Euryarchaeota that usually lives in less complexity of environment, the genomes of Crenarchaeota usually contained more abundant bacteriocin. In these archaea genomes, we also found the positive correlation between the abundance of bacteriocin and the abundance of CRISPR spacer, suggesting the bacteriocin might be a crucial component of the innate immune system that defense the microbe living in the common environment. The structure analysis of the bacteriocin gene clusters gave a clue that the assisted genes located at the edge of clusters evolved faster than the core biosynthetic genes. To the best of our knowledge, we are the first to systematically explore the distribution of secondary metabolites in archaea, and the investigation of the relationship between BGC and CRISPR spacer expands our understanding of the evolutionary dynamic of these functional molecules.     

A novel secondary metabolite of Chinese ted alga Laurencia karlae

A novel skeleton compound benkarlaol (1) was isolated from the red alga Laurencia karlae Zhang et Xia, collected from the Nansha Islands in the South China Sea. Its structure and relative stereochemistry were determined by spectroscopic data, especially extensive 1D and 2D NMR experiments.     

Advances in Aspergillus secondary metabolite research in the post-genomic era

This review studies the impact of whole genome sequencing on Aspergillus secondary metabolite research. There has been a proliferation of many new, intriguing discoveries since sequencing data became widely available. What is more, the genomes disclosed the surprising finding that there are many more secondary metabolite biosynthetic pathways than laboratory research had suggested. Activating these pathways has been met with some success, but many more dormant genes remain to be awakened.     

Optimization of secondary metabolite production using singular approximation and minimum principle

Optimal control profiles as calculated with two control algorithms, singular approximation and minimum principle, are compared in this article. Switching points were determined using the singular approximation by mathematical calculation. The optimal growth rate was calculated using minimum principle. With an increased number of switching points, the calculated optimal control profiles approached the theoretical optimal control profile as calculated using the minimum principle. With three switching times, the product concentration approached 96% of the theoretical optimal control profile. From these results, optimal control can be achieved with more than a three-switching-point approximation.     

Bacterial sunscreen: layer-by-layer deposition of UV-absorbing polymers on whole-cell biosensors

UV-protective coatings on live bacterial cells were created from the assembly of cationic and UV-absorbing anionic polyelectrolytes using layer-by-layer (LbL) methodology. A cationic polymer (polyallylamine) and three different anionic polymers with varying absorbance in the UV range (poly(vinyl sulfate), poly(4-styrenesulfonic acid), and humic acid) were used to encapsulate Escherichia coli cells with two different green fluorescent protein (GFP) expression systems: constitutive expression of a UV-excitable GFP (GFPuv) and regulated expression of the intensely fluorescent GFP from amphioxus (GFPa1) through a theophylline-inducible riboswitch. Riboswitches activate protein expression after specific ligand-RNA binding events. Hence, they operate as a cellular biosensor that will activate reporter protein synthesis after exposure to a ligand target. E. coli cells coated with UV-absorbing polymers demonstrated enhanced protection of GFP stability, metabolic activity, and viability after prolonged exposure to radiation from a germicidal lamp. The results show the effectiveness of LbL coatings to provide UV protection to living cells for biotechnological applications.     

A new ring-opening access to aeroplysinin-1, a secondary metabolite of Verongia aerophoba

An improved synthetic methodology of spiroisoxazolines by employing anodic oxidation of the corresponding phenol derivative has been established. An alternative efficient synthesis of aeroplysinin-1 1 has been achieved by employing the ring-opening reaction of spiroisoxazolines 10b, 10c as a key step.     

Metabolic diversity of lichen-forming ascomycetous fungi: culturing, polyketide and shikimate metabolite production, and PKS genes

Lichens are composite and symbiotic organisms. Biologically, they often have been interpreted as one organism (fungi and algae associated within a common thallus), but taxonomically as a life form of ascomycetous fungi; as the lichen-forming fungus or "mycobiont" has been, in most cases, classified as the dominant symbiotic partner. About 46% of the ascomycota are lichen-forming, however, about 2-3% of the lichen fungi are basidiomycota. Lichen-forming fungi produce a great variety of secondary metabolites, biosynthetically derived from the acetyl polymalonyl, mevalonic and shikimate pathways. Thus, secondary metabolites comprise a significant proportion of the lichen thallus dry weight (0.1-5% or even more). The majority of secondary lichen products are aromatic polyketides, and a number of them has been shown to exhibit marked biological activity.     

豆荚软珊瑚Lobophytum sp. 的次生代谢产物研究

从海南岛三亚海域采集的软珊瑚Labophytumsp.中分离得五个甾醇苷(1)～(5)。通过波谱分析，确定它们的化学结构依次为3'-O-乙酰基-4-O-[β-D-吡喃木糖苷]-孕甾-20-烯-3β,4α-二醇(1)，4-O-[β-D-吡喃木糖苷]-孕甾-20-烯-3β,4α-二醇(2),4'-O-乙酰基-4-O-[β-D-吡喃木糖苷]-孕甾-20-烯-3β,4α-二醇(3),4'-O-乙酰基-4-O-[β-D-吡喃阿拉伯糖苷]-孕甾-20-烯-3β,4α-二醇(4)和4-O-[β-D-吡喃阿拉伯糖苷]-孕甾-20-烯-3β,4α-二醇(5),其中1为新化合物。体外细胞毒性实验表明：化合物(1),(2)和(5)对SKMG-4,Hep-G2和CNE2三种人体癌细胞具有抑制作用。