Philip O. Owuor

Comparative evaluation of ELISA kit and HPLC DAD for the determination of chlorpyrifos ethyl residues in water and sediments.

Enzyme linked immunosorbent assay (ELISA) kit is a versatile, cheap and relatively available tool that can be used in remote areas. In this study, performance of ELISA kit was evaluated in terms of accuracy, recovery, precision, sensitivity, cross reactivity and matrix interference for pesticide residue determination in water and sediment samples. This method was compared with high performance liquid chromatography (HPLC) which is not a commonly available analytical technique for chlorpyrifos ethyl residue analysis in developing countries. The ELISA kit had limits of detection (LOD) of 0.37 µg L(-1) and 0.42 µg Kg(-1) dry weight (dw), for chlorpyrifos ethyl in water and sediment samples, respectively using deionized water and a control sediment sample. Mean percentage recoveries and coefficients of variation (CV) for ELISA kit varied from 96.0±5.8% to 108.0±3.4% for water and sediment samples. Comparison between ELISA and HPLC analysis results using water and sediment samples from Lake Naivasha showed no significant difference in results (p≤0.05). Strong correlations (r2=0.9878 water samples and r1=0.9670, p<0.0001 for sediment samples, n=48) were reported between the methods for the two samples analyzed. Bland-Altman bias plot analysis showed that the two methods were in agreement within 95% confidence interval of limits -2.9 to 3.8 and -2.2 to 3.6 for water and sediment, respectively. Given the high sensitivity reported and the obtained acceptable limits of coefficient of variation and percentage recovery, ELISA appears to be a suitable rapid analytical tool in analysis of chlorpyrifos ethyl in water and sediment samples. Results demonstrate comparability to HPLC and could complement conventional tools in regular monitoring program particularly in developing countries. This will hasten results delivery for ecological risk assessment and timely execution of mitigation measures.

Presence and Distribution of Mosquito Larvae Predators and Factors Influencing their Abundance along the Mara River, Kenya and Tanzania.

Among all the malaria controlling measures, biological control of mosquito larvae may be the cheapest and easiest to implement. This study investigated baseline predation of immature mosquitoes by macroinvertebrate predators along the Mara River, determined the diversity of predators and mosquito larvae habitats and the range of their adaptive capacity to water physico-chemical parameters. Between July and August 2011, sampling sites (n=39) along the Mara River were selected and investigated for the presence of macroinvertebrate predators and mosquito larvae. The selected sampling sites were geocoded and each dipped 20 times using standard mosquito larvae dipper to sample mosquito larvae, while a D-frame dip net was used to capture the macroinvertebrate predators. Water physico-chemical parameters (dissolved oxygen, temperature, pH, conductivity, salinity and turbidity) were taken in situ at access points, while hardness and alkalinity were measured titrimetically. The influence of macroinvertebrate predator occurrence was correlated with mosquito larvae and water quality parameters using Generalized Linear Model (GLM). Predators (n=297) belonging to 3 orders of Hemiptera (54.2%), Odonata (22.9%) and Coleoptera (22.9%), and mosquito larvae (n=4001) belonging to 10 species, which included An.gambiae s.l (44.9%), Culex spp. (34.8%) and An. coustani complex (13.8%), An. maculipalpis (3.6%), An. phaorensis (1.2%), An. funestus group (0.5%), An. azaniae (0.4%), An. hamoni (0.3%), An. christyi (0.3%), An. ardensis (0.08%), An. faini (0.07%), An. sergentii (0.05%) and 0.05% of Aedes mosquito larvae which were not identified to species level, due to lack of an appropriate key, were captured from different habitats along the Mara river. It was established that invasion of habitats by the macroinvertebrate predators were partially driven by the presence of mosquito larvae (p < 0.001), and the prevailing water physico-chemical parameters (DO, temperature, and turbidity, p <0.001). Understanding abiotic and biotic factors which favour mosquitoes and macroinveterbrate co-occurrence may contribute to the control of malaria.

Isolation of a new β-carboline alkaloid from aerial parts of Triclisia sacleuxii and its antibacterial and cytotoxicity effects

Abstract A new β-carboline alkaloid named sacleuximine A (1) together with known compounds palmatine (2), isotetrandrine (3), trans-N-feruloyltyramine (4), trans-N-caffeoyltyramine (5), yangambin (6), syringaresinol (7), sesamin (8), (+) epi-quercitol (9), 4-hydroxybenzaldehyde (10), β-sitosterol (11), quercetin 3-O-rutinoside (12) and myricetin 3-O-β-glucose (1→6) α-rhamnoside (13) have been isolated from methanol extract of Triclisia sacleuxii aerial parts. Compounds 1–10 were evaluated for their cytotoxicity against human adenocarcinoma (HeLa), human hepatocarcinoma (Hep3B) and human breast carcinoma (MCF-7) cells lines and also for antibacterial activities against both Gram-positive and Gram-negative bacteria. The cytotoxicity (IC50) values ranged between 0.15 and 36.7 μM while the minimum inhibitory concentrations were found to be in the range of 3.9 and 125 μM, respectively. This is the first report of antibacterial compounds and the isolation of lignans together with a β-carboline alkaloid from T. sacleuxii.

New ceramide from the aerial part of Tinospora oblongifolia with cytotoxic activities.

A new ceramide, 2,3-dihydroxy-N-[(2S,3S,4R)-1,3,4-trihydroxyicosan-2-yl[tetracosanamide (1) along with four known compounds: 2-(4′-hydroxyphenyl)-ethyl lignocerate (2), docosyl-3,4-dihydroxy-trans-cinnamate (3), β-sitosterol (4) and β-sitosterol glycoside (5) were isolated from Tinospora oblongifolia (Menispermaceae). Their structures were determined on the basis of spectroscopic methods, mass spectrometry analysis as well as chemical transformation and by comparing their physical and spectral data with those reported in the literature. Compound 1 exhibited strong cytotoxic activity against KB cells with IC50 = 3.4 μM although less than that of camptothecin IC50 = 0.3 μM (positive control).

Phytoecdysteroids from the stem bark of Vitex doniana and their anti-inflammatory effects.

With reference to the ethnopharmacological significance of Vitex doniana Sweet (Lamiaceae) leaves in the treatment of stomach and rheumatic pains as well as inflammatory disorders, biological studies on its stem bark extracts have also reported anti-inflammatory and analgesic activities, with no attempt to identify the active components. Chromatographic and spectroscopic procedures identified three new phytoecdysteroids: 21-hydroxyshidasterone (1), 11β-hydroxy-20-deoxyshidasterone (2), and 2,3-acetonide-24-hydroxyecdysone (3) from the stem bark methanol extracts along with known ecdysteroids shidasterone (4), ajugasterone C (5), 24-hydroxyecdysone (6), and 11β,24-hydroxyecdysone (7). The compounds (1-7) showed significant (p ≤ 0.05) inhibitory effect at 100 mg/kg dose on rat paw oedema development due to carrageenan-induced inflammation in Sprague Dawley rats. These results suggest a possible contribution of ecdysteroids to the anti-inflammatory effect of some V. doniana stem bark extracts.

Recent Advances on Mercury Speciation in Aquatic Ecosystems, Health Effects and Analytical Techniques

Elemental mercury is not as poisonous as its congeners such as methyl mercury and dimethyl mercury, especially at trace levels. However, understanding the speciation mechanisms of mercury in aquatic ecosystems offers an opportunity to appreciate the dangers emanating from elemental mercury in the environment. Notably, elemental mercury is occasionally used in dental filling therapy which presents it as a non-poisonous element. Recent advances on mechanisms of elemental mercury speciation, health effects of different mercury congeners and analytical techniques of identifying/quantifying them in aquatic ecosystems are outlined. The effects of Review Article Omwoma et al.; BJAST, 19(1): 1-37, 2017; Article no.BJAST.31635 2 anthropogenic activities employing the use of elemental mercury such as gold amalgamation are highlighted through a case study. Kenya Gold mines are identified as a potential risk zone amenable to mercury health effects.

Effects of Senna didymobotrya Root Extract and Compounds on Tritoninduced Hyperlipidaemic Rats and Differentiation of 3T3-Li Preadipocytes

The lipid lowering effects of Senna didymobotrya (Leguminoceae) root extract (250 mg/kg) and pure isolates (100 mg/kg) were investigated for hypolipidemic activity on Triton-induced hyperlipidemic rats (in-vivo). The extracts and isolates showed significant (p�0.01) reduction in serum lipid contents, and reactivation of the lipolytic enzymes, relative to the Triton-treated group. Ethyl acetate extract exhibited the highest lipid lowering (p�0.01) compared to other fractions. Seven anthraquinones, obtusifolin (1), 1,6-di-O-methylemodin (2), nataloemodin-8-methyl ether (3), chrysophanol (4), physcion (5), chrysophanol-10,10-bianthrone (6), physcion-10,10-bianthrone (7) and stigmasterol (8) were isolated from the ethyl acetate extract. Compounds 3, 5 and 7 displayed significant (p�0.01) lipid lowering effects. The hypolipidaemic activities prompted the determination of inhibition of differentiation of 3T3-L1 preadipocytes into adipocytes by the compounds 3, 5 and 7. Only compound 7 exhibited potent anti-adipogenic activity without significant cytotoxicity. The result indicated that extracts of S. didymobotrya root extract can provide good antidyslipidaemic and adipocytes maturation inhibitors.

Changes in the Composition of Elements in Non-Aerated Green Teas Processed from Seedling Tea (Camellia sinensis) Due to Variations in Nitrogenous Fertilizer Rates and Seasons.

National Commission for Science, Technology and Innovation (NACOSTI) and Kenya Agricultural and Livestock Organization-Tea Research Institute (KALRO-TRI)