Clionasterol, a triterpenoid from the Kenyan marine green macroalga halimeda macroloba

Peer reviewedPublisher PD

Clionasterol, a Triterpenoid from the Kenyan Marine Green Macroalga Halimeda macroloba

The triterpenoid clionasterol (1), a 29 carbon structure compound was isolated from the less polar extract (20% EtOAc in hexanes) of the green alga Halimeda macroloba collected at Shimoni near Mombasa, Kenya. The structure and relative stereochemistry of this compound was elucidated by spectroscopic data, mainly NMR and mass spectrometry. This metabolite was inactive against DLD-1 cells on the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Further experiments on mosquito larvae and brine shrimp lethality confirmed this result

Cyclodepsipeptides from a Kenyan marine cyanobacterium

An examination of an organic extract of the cyanobacterium Lyngbya majuscula collected from Wasini Island off the southern Kenyan coast led to the isolation of the known cyclodepsipeptide antanapeptin A (7), recently isolated from a Madagascan collection of L. majuscula, and a new bioactive cyclodepsipeptide, homodolastatin 16 (42). Although L. majuscula is a common, pantropical cyanobacterium this study represents the first investigation of the natural product chemistry of a Kenyan population of L. majuscula. The structures of the two cyclodepsipeptides were determined from 2D NMR and mass spectrometry data. The L- stereochemistry of the proline, valine, and N-methylphenylalanine amino acids in 7 and the L – proline configuration in 42, was confirmed by Marfey’s HPLC method. Chiral GC was used to determine the absolute stereochemistry of the hydroxyisovaleric acid moiety in 7 and 42, the lactate residue in 42 and tentatively propose an L-stereochemistry for the Nmethylisoleucine amino acid in 42. Homodolastatin 16, a higher homologue of the potential anti-cancer agent, dolastatin 16, exhibited moderate activity against two oesophageal cancer cell lines

Micrococcin P1 and P2 from Epibiotic Bacteria Associated with Isolates of Moorea producens from Kenya

Epibiotic bacteria associated with the filamentous marine cyanobacterium Moorea producens were explored as a novel source of antibiotics and to establish whether they can produce cyclodepsipeptides on their own. Here, we report the isolation of micrococcin P1 (1) (C48H49N13O9S6; obs. m/z 1144.21930/572.60381) and micrococcin P2 (2) (C48H47N13O9S6; obs. m/z 1142.20446/571.60370) from a strain of Bacillus marisflavi isolated from M. producens’ filaments. Interestingly, most bacteria isolated from M. producens’ filaments were found to be human pathogens. Stalked diatoms on the filaments suggested a possible terrestrial origin of some epibionts. CuSO4·5H2O assisted differential genomic DNA isolation and phylogenetic analysis showed that a Kenyan strain of M. producens differed from L. majuscula strain CCAP 1446/4 and L. majuscula clones. Organic extracts of the epibiotic bacteria Pseudoalteromonas carrageenovora and Ochrobactrum anthropi did not produce cyclodepsipeptides. Further characterization of 24 Firmicutes strains from M. producens identified extracts of B. marisflavi as most active. Our results showed that the genetic basis for synthesizing micrococcin P1 (1), discovered in Bacillus cereus ATCC 14579, is species/strain-dependent and this reinforces the need for molecular identification of M. producens species worldwide and their epibionts. These findings indicate that M. producens-associated bacteria are an overlooked source of antimicrobial compounds

Ethnopharmacological Screening of some East Kimberley Native Australian Plants for Antimicrobial Activity

1 page(s

UV Resistance of bacteria from the Kenyan Marine cyanobacterium Moorea producens

Abstract UV resistance of bacteria isolated from the marine cyanobacterium Moorea producens has not been observed previously, findings which highlight how unsafe germicidal UV irradiation for sterilization of air, food, and water could be. Further, UV resistance of Bacillus licheniformis is being observed for the first time. This study focused on bacteria isolated from the marine cyanobacterium M. producens collected off the Kenyan coast at Shimoni, Wasini, Kilifi, and Mida. UV irradiance of isolates (302 nm, 70 W/m2, 0–1 hr) established B. licheniformis as the most UV resistant strain, with the following order of taxon resistance: Bacilli> γ proteobacteria > Actinobacteria. UV resistance was independent of pigmentation. The maximum likelihood phylogenetic distance determined for both B. licheniformis and Bacillus aerius relative to M. producens CCAP 1446/4 was 2.0. Survival of B. licheniformis upon UV irradiance followed first‐order kinetics (k = 0.035/min, R2 = 0.88). Addition of aqueous extracts (2, 10, 20 and 40 mg/ml) of this B. licheniformis strain on the less resistant Marinobacterium stanieri was not significant, however, the commercial sunscreen benzophenone‐3 (BP‐3) positive control and the time of irradiance were significant. Detection of bacteria on M. producens filaments stained with acridine orange confirmed its nonaxenic nature. Although the chemistry of UV resistance in cyanobacteria has been studied in depth revealing for example the role of mycosporine like amino acids (MAAs) in UV resistance less is known about how bacteria resist UV irradiation. This is of interest since cyanobacteria live in association with bacteria

Bush Medicine Research Partnerships for Drug Discovery and Cultural Preservation

1 page(s

Phytochemical characterization of the Australian (Aboriginal) medicinal plant Dolichandrone heterophylla and influence of selected isolated compounds on human keratinocytes

The Miriwoong Aboriginal people of Eastern Kimberley, Western Australia use the leaves and bark of Dolichandrone heterophylla (R. Br.) F. Muell., Bigoniaceae, to treat sores, rashes, grazes, scabies, boils and wounds. Bioassay guided fractionation of an aqueous extract of the leaves and twigs led to the isolation of the known compounds caffeic acid, the phenylethanoids isoacteoside (1) and acteoside (2), and the flavonoids chrysoeriol and luteolin. The structures of these compounds were determined using mass spectrometric and 1D- and 2D-NMR spectroscopic data and verified by comparison with those in the literature. Studies of the effect of isoacteoside (1) and chrysoeriol on HaCaT keratinocytes using the MTT assay revealed that chrysoeriol had growth inhibitory properties towards the cell line in a dose dependent manner (IC 50 = 31 μM) whereas 1 was well tolerated up to 50 μM. On the other hand, 1 inhibited the growth of Pseudomonas aeruginosa.8 page(s