New nitrogenous constituents from the South African marine Ascidian Pseudodistoma sp

A Quarter Century of Marine Biodiscovery in Algoa Bay, South Africa

Algoa Bay, the largest crenulate bay on the southeastern coast of South Africa, is currently one of the most well-studied marine ecosystems in southern Africa. A plethora of endemic marine invertebrates inhabits the benthic reefs on the western edge of the Bay in close proximity to South Africa's sixth largest city. Over the past 25 years, South African marine natural products chemists, together with international collaborators from the US National Cancer Institute and other US institutions, have focused their attention on Algoa Bay's benthic marine invertebrates as a potential source of new anticancer compounds. This review commemorates a quarter of a century of marine biodiscovery in Algoa Bay and presents the structures and bioactivities of 49 new and 36 known specialized metabolites isolated from two molluscs, eight ascidians, and six sponges. Thirty-nine of these compounds were cytotoxic to cancer cells in vitro with 20 exhibiting moderate to potent cytotoxicity. Six other compounds exhibited antimicrobial activity. Foremost among the potential anticancer compounds is mandelalide A (38) from the Algoa Bay ascidian Lissoclinum species.

Evaluation of Wound Healing Activity of Sea Cucumber Holothuria parva Hydroalcoholic Extract in Rat

A significant challenge in biomedicine is the development of Biomaterials with the potential to accelerate wound healing. The aim of this study was to investigate the effect of the gel prepared from sea cucumber on wound healing in rats. Full-thickness wounds were created in male rats divided into five experimental groups, negative control (NC), positive control (PC), and treatments. The NC and PC groups received respectively gel base and phenytoin cream 1%. Treatment groups were treated topically by gels of 1%, 3%, and 5% Holothuria parva extract (HPE) in the gel base. The rats were sacrificed on days 7, 14, and 21. Pathological reports revealed the proliferation of keratinocytes in the borders of the wound in treatment groups and controls. Formation of granulation tissue was seen on day 7 in treatment groups, collagen fibers in granulation tissue were randomly organized, and the rate of fibroblast decreased. Results showed that there were statistically significant differences in wound contraction between all groups in comparison to the NC group (P < .05) on day 8. It was concluded that the 1% HPE gel has a good potential for promoting wound healing. [Formula: see text].

Feeding cessation alters host morphology and bacterial communities in the ascidian Pseudodistoma crucigaster

BACKGROUND

Ascidians can associate with abundant and diverse consortia of microbial symbionts, yet these communities remain unexamined for the majority of host ascidians and little is known about host-symbiont interactions.

METHODS

We coupled electron microscopy and 16S rRNA gene tag pyrosequencing to investigate the bacterial communities associated with the colonial ascidian Pseudodistoma crucigaster, a species endemic to the Mediterranean Sea that has a life cycle with two phases: actively-filtering (active) and non-filtering (resting) forms.

RESULTS

Resting colonies exhibited a reduced branchial sac (feeding apparatus) and a thickened cuticle. Electron microscope images also suggested higher abundance of colonizing microorganisms on surfaces of resting colonies. Accordingly, bacterial sequences associated with environmental sources (sediment and biofilms, >99 % similarity) were detected exclusively in resting colonies. Bacterial communities of P. crucigaster colonies (active and resting) were dominated by 3 core taxa affiliated (>94 % similarity) with previously described symbiotic Alphaproteobacteria in marine invertebrates. Shifts in rare bacteria were detected when ascidians entered the resting phase, including the appearance of strictly anaerobic lineages and nitrifying bacterial guilds.

CONCLUSIONS

These findings suggest that physical (thickened cuticle) and metabolic (feeding cessation) changes in host ascidians have cascading effects on associated bacteria, where modified oxygen concentrations and chemical substrates for microbial metabolism may create anaerobic microhabitats and promote colonization by environmental microorganisms.

Isolation of marine natural products

Marine macro- and micro-biota offer a wealth of chemically diverse compounds that have been evolutionary preselected to modulate biochemical pathways. Many industrial and academic groups are accessing this source using advanced technology platforms. The previous edition of this chapter offered some practical guidance in the process of extraction and isolation of marine natural products with more emphasis on the procedures adapted to the physical and chemical characteristics of the isolated compounds. Automation and direct integration of the isolation technology into high-throughput screening (HTS) systems were also reported. In this edition, we refer to some new topics which are heavily represented in the literature. These include methods for sampling the deep ocean and the procedures for culturing high-pressure-adapted (piezophilic) marine microorganisms to be amenable to laboratory investigation. A brief discussion on genomic-guided approaches to detect the presence of biosynthetic loci even those that are silent or cryptic is also included.

New cytotoxic N-methylated beta-carboline alkaloids from the marine ascidian Eudistoma gilboverde

Bioassay-guided fractionation of an extract of the marine ascidian Eudistoma gilboverde provided three new beta-carboline alkaloids identified as 2-methyleudistomin D (1), 2-methyleudistomin J (2), and 14-methyleudistomidin C (3). Six known metabolites, eudistomins C, D (4), E, J (5), K, and L, were also isolated and characterized. The structures of the new metabolites were elucidated by spectroscopic analyses and by comparison of their spectral data with related literature values. Of the three new compounds, 14-methyleudistomidin C (3) exhibited the most potent cytotoxic activity with IC(50)'s of < 1.0 microg/mL against four different human tumor cell lines.