Adesh Ramsubhag

Identification of new limonoids from Swietenia and their biological activity against insects.

BACKGROUND Natural limonoids are one group of compounds being studied for their insecticidal properties. To discover new limonoids with better activities, analogs were prepared via acylation and hydrolysis, and bioassayed. RESULTS Analogs were identified using one- and two-dimensional (COSY, HMQC and HMBC) (1) H and (13) C NMR, IR and MS. 3-O-Isovalerylswietenolide (13) and 3-O-isobutyrylswietenolide (14) showed excellent antifeedant activity, with DC(50) values of 0.19 and 0.009 mg L(-1) respectively, compared with the natural limonoid swietenolide (80.6 mg L(-1) ) against fourth-instar Spodoptera frugiperda (JE Smith) larvae. CONCLUSION This work shows that limonoid analogs prepared through semi-synthesis can be used as lead compounds for the development of new insecticides.

Detection of Helicobacter pylori in the coastal waters of Georgia, Puerto Rico and Trinidad

Fecal pollution in the coastal marine environments was assessed at eleven sampling locations along the Georgia coast and Trinidad, and nine sites from Puerto-Rico. Membrane filtration (EPA method 1604 and method 1600) was utilized for Escherichia coli and enterococci enumeration at each location. Quantitative polymerase chain reaction (qPCR) amplification of the 16S ribosomal RNA gene was used to determine the presence of the Helicobacter pylori in marine samples. There was no significant correlation between the levels of E. coli, enterococci and H. pylori in these water samples. H. pylori was detected at four of the 31 locations sampled; Oak Grove Island and Village Creek Landing in Georgia, Maracas river in Trinidad, and Ceiba Creek in Puerto Rico. The study confirms the potential public health risk to humans due to the widespread distribution of H. pylori in subtropical and tropical costal marine waters.

Phytoelicitor activity of three Caribbean seaweed species on suppression of pathogenic infections in tomato plants

Seaweed extracts are commonly used as phytoelicitors to promote crop growth and yield, worldwide. However, extracts of some seaweed species are known to induce defence processes in plants and may have potential for use as plant protection agents in the management of crop diseases. Most of the research on seaweed extracts as elicitors of plant defences have been on temperate seaweed species. Caribbean islands have an abundance of tropical seaweed species along their coasts, but their potential for use in agriculture has not been explored yet. The aim of this study was to determine the phytoelicitor potential of extracts of three seaweeds abundantly found in Trinidad and the southern Caribbean. The efficacy of the seaweed extracts in suppressing Alternaria solani and Xanthomonas campestris pv vesicatoria infections in tomato was analysed. Alkaline extracts of Ulva lactuca, Sargassum filipendula and Gelidium serrulatum were applied to tomato plants which were inoculated with the pathogens. The plants were then monitored over time for development of disease, activity of defence enzymes and expression levels of key marker genes of various plant defence pathways. Plants treated with the seaweed extracts showed reduced disease severity which was coupled with elevated rates of activities of defence enzymes. Seaweed extract-treated plants also had increased expression levels of marker genes for defence signalling pathways. The extracts of U. lactuca and S. filipendula induced jasmonate signalling defence systems. However, G. serrulatum extract was able to sequentially induce both salicylic acid and jasmonate signalling pathways and, consequently found to be very effective in controlling the intensity of both diseases. The results of this study indicate that extracts made from tropical seaweeds found locally in the southern Caribbean could be used in tomato as phytoelicitors. Local seaweed extracts therefore present a good, potentially environmentally friendly, alternative for farmers of the Southern Caribbean to manage diseases caused by A. solani and X. vesicatoria in tomato.

Molecular detection of atrazine catabolism gene atzA in coastal waters of Georgia, Puerto Rico and Trinidad

In this study, quantitative polymerase chain reaction targeting the atrazine catabolism gene, atzA, was used to detect the presence of atrazine degrading bacteria as an indicator of atrazine contamination in 11 sites in Georgia, nine coastal sites in Puerto Rico and 11 coastal sites in Trinidad. The atzA gene was detected in five stations in Georgia (Oak Grove Island entrance, Blythe Island Recreation Park, Jekyll Island., Village Creek Landing and Dunbar Creek Sea Island Rd Bridge). In Puerto Rico gene was detected in five sites (Boquilla, Oro Creek, Fishers Association, Ceiba Creek and Sabalos Creek) while seven sites in Trinidad (Carli Bay, Las Cuevas Bay, Quinam Bay, Salybia River, Salybia Bay, Maracas River and Maracas Bay) showed the presence of atzA.

Detection of verotoxin producing Escherichia coli in marine environments of the Caribbean.

The goal of this study was to determine the potential for Enterohemorrhagic Escherichia coli O157:H7 (EHEC) contamination in tropical marine waters. Samples were collected from urban, suburban, and rural sites around the islands of Puerto Rico and The Republic of Trinidad and Tobago. Quantification of E. coli and EHEC was evaluated using MI plates and qPCR. EHEC was detected in six sites in Puerto Rico: West of La Parguera Town, Boquilla, Oro Creek, Fishers Association, Joyuda Lagoon, and Boqueron Wetland Creek and in two rural sites in Trinidad: Balandra Bay and Quinam Bay. Plate count enumeration of E. coli was not a reliable indicator for the presence of EHEC. The sites where EHEC was detected on both islands are used for recreational bathing, water sports and recreational/commercial fisheries and therefore pose a public potential health risk.

Antimicrobial cholic acid derivatives from the Pitch Lake bacterium Bacillus amyloliquefaciens UWI-W23

HIGHLIGHTSFirst report of antimicrobial bile acids and bile salts from the Bacillus genus.First report of taurodeoxycholate (2) from a bacterial source.This is the first report of deoxycholate (4) from a Gram‐positive bacterium.Observed aggregation‐effect on NMR data of glycocholic acid (6) in CD3OD. ABSTRACT Six cholic acid derivatives (1–6) were isolated from broth cultures of Bacillus amyloliquefaciens UWI‐W23, an isolate from the Trinidad Pitch Lake. The compounds were extracted via solvent extraction and/or XAD resin adsorption and purified using silica gel column chromatography. Their structures were elucidated using 1D, 2D NMR and ESI‐MS spectrometry and FT‐IR spectrophotometry. One of the compounds, taurodeoxycholate (2) is for the first time being reported from a bacterial source while deoxycholate (4) is for the first time being reported from a Gram‐positive bacterium. The other compounds have not been previously isolated from Bacillus spp. viz. cholate (1), taurocholic acid (3); glycodeoxycholic acid (5) and glycocholic acid (6). All six compounds exhibited antimicrobial activity against P. aeruginosa and B. cereus with MICs ranging from 7 to 250&mgr;g/mL. Cholate (1) also showed activity against MRSA (MICs=125&mgr;g/mL) and glycocholic acid (6) against S. cerevisiae (MICs=15.6&mgr;g/mL).