Didemnaketals F and G,New Bioactive Spiroketals from a Red Sea Ascidian Didemnum Species

In continuation of our ongoing efforts to identify bioactive compounds from Red Sea marine organisms, a new collection of the ascidian Didemnum species was investigated. Chromatographic fractionation and HPLC purification of the CH₂Cl₂ fraction of an organic extract of the ascidian resulted in the identification of two new spiroketals, didemnaketals F (1) and G (2). The structure determination of the compounds was completed by extensive study of 1D (¹H, ¹³C, and DEPT) and 2D (COSY, HSQC, and HMBC) NMR experiments in addition to high-resolution mass spectral data. Didemnaketal F (1) and G (2) differ from the previously reported compounds of this class by the lack the terminal methyl ester at C-1 and the methyl functionality at C-2. Instead, 1 and 2 possess a methyl ketone moiety instead of the terminal ester. Furthermore, didemnaketal F possesses a disubstituted double bond between C-2 and C-3, while the double bond was replaced by a secondary alcohol at C-3 in didemnaketal G. In addition, they possess the unique spiroketal/hemiketal functionality which was previously reported in didemnaketal E. Didemnaketals F (1) and G (2) displayed moderate activity against HeLa cells with of IC_50s of 49.9 and 14.0 µM, respectively. In addition, didemnaketal F (1) displayed potent antimicrobial activity against E. coli and C. albicans. These findings provide further insight into the biosynthetic capabilities of this ascidian and the chemical diversity as well as the biological activity of this class of compounds.     

Diameter-Selective Raman Scattering from Vibrational Modes in Carbon Nanotubes

Single wall carbon nanotubes (SWNTs) that are found as close-packed arrays in crystalline ropes have been studied by using Raman scattering techniques with laser excitation wavelengths in the range from 514.5 to 1320 nanometers. Numerous Raman peaks were observed and identified with vibrational modes of armchair symmetry (n, n) SWNTs. The Raman spectra are in good agreement with lattice dynamics calculations based on C-C force constants used to fit the two-dimensional, experimental phonon dispersion of a single graphene sheet. Calculated intensities from a nonresonant, bond polarizability model optimized for sp2 carbon are also in qualitative agreement with the Raman data, although a resonant Raman scattering process is also taking place. This resonance results from the one-dimensional quantum confinement of the electrons in the nanotube.     

Toxicity in three dogs from accidental oral administration of a topical endectocide containing moxidectin and imidacloprid

Three dogs were presented with a history of oral administration of a topical endectocide containing imidacloprid and moxidectin. They were diagnosed with imidacloprid and moxidectin intoxication, having ingested doses ranging from 7.5 to 1.4 mg/kg of imidacloprid and 1.9 to 2.8 mg/kg of moxidectin. The three dogs were affected to different degrees of severity, but all displayed signs of ataxia, generalised muscle tremors, paresis, hypersalivation and disorientation. Temporary blindness occurred in two cases. The three dogs were tested for the presence of the multi-drug resistance 1 gene deletion, which can cause an increased sensitivity to the toxic effects of moxidectin, and were found to be negative. Treatment included gastrointestinal decontamination, intravenous fluid therapy and benzodiazepines to control muscle tremors. All three dogs made a complete recovery within 48 h of ingestion.     

Capability of some agricultural wastes for removing some heavy metals from polluted water stocked in combination with Nile tilapia,Oreochromis niloticus (L.)

Heavy metal (HM) pollution is one of the major problems that adversely affect the aquatic ecosystem and inhabiting biota. Heavy metals adsorption by low-cost adsorbents is one of the techniques used for HM removing from polluted water. In the present study, agricultural wastes (AW), i.e., rice straw, sugarcane bagasse, and maize stalks, were washed with distilled water, dried in a dry-oven, cut into small pieces (<0.5 cm long), and immersed at 1.0 g/L in aquaria containing synthetic mixture of lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn). Nile tilapia, Oreochromis niloticus (L.), fingerlings (25.2 ± 0.88 g) were stocked at a density of ten fish per 100-L aquarium for 72 h, during which fish were fed on a fish diet containing 25% crude protein ad libitum twice daily. Samples of water, AW, and fish were collected at different times to determine HM concentrations. The HM removal from polluted water was depending on the type of the metal ions, AW, and the contact time. However, HM concentrations in aquaria waters of all AW treatments decreased significantly by increasing contact time up to 24 h after which their concentrations were almost the same. Concentrations of waterborne Pb, Cd, Cu, and Zn in AW-containing aquaria were significantly lower than those of AW-free aquaria. The presence of any AW reduced significantly HM concentrations. In AW-free aquaria, HM-exposed fish accumulated more HM in their body than those reared in AW-containing aquaria. The results of this experiment showed that all AW had the capability to remove HM levels from the polluted water and reduce their bioaccumulation in fish body. However, rice straw was the more efficient adsorbent for all metals.