Antifeedant and ovicidal activities of a new cassane and other compounds from Caesalpinia welwitschiana Oliv. and Caesalpinia bonduc L. against Tuta absoluta (Lepidoptera: Gelechiidae).

Methanolic extracts of liana of Caesalpinia welwitschiana and leaves of C. bonduc were found to possess moderate antifeedant and ovicidal activities against Tuta absoluta. Bioassay-guided isolation of constituents from the most active fraction of C. welwitschiana led to the identification of four known compounds [isobonducellin 1a and bonducellin 1 b, intricatinol 2, (-)-epigallocatechin-3-O-gallate 4] and one new constituent [welwitschianic acid 3]. The most active fraction of C. bonduc afforded two known constituents neocaesalpin L 5 and neocaesalpin A 6. The isolated structures were elucidated on the basis of their MS, UV, IR and 1 & 2 D NMR spectra and by comparison with literature data. Compounds 2, 4-6 were showed antifeedant and ovicidal properties against T. absoluta, some comparable to that of azadirachtin at 50, 100 and 200 ng/µl. Overall, the present study, conclude that the two species of the plant could be a promising source of eco-friendly botanical constituents.

Repellence and fumigant toxicity of essential oils of Ocimum gratissimum and Ocimum kilimandscharicum on Tuta absoluta (Lepidoptera: Gelechiidae).

Tuta absoluta Meyrick originates in South America and is now one of the most important insect pests of Solanaceae in different parts of the world, including Africa. Its control has relied primarily on chemical insecticides, which are associated with negative ecological effects. In the present study, essential oils of Ocimum gratissimum and O. kilimandscharicum were tested for repellence and fumigant toxicity on the adult stages under laboratory conditions. The oil of O. gratissimum was more repellent, but its toxicity was comparable with that of O. kilimandscharicum. The major constituents of O. gratissimum were methyl eugenol (39.5%) and eugenol (29.7%). Those of O. kilimandscharicum were camphor (47.1%) and 1.8-cineole (19.3%). Eugenol (LC50 of 0.24 µl/ml, 83.3%, RI50 = 0.15) and camphor (LC50 of 0.23 µl/ml, 89.5%, RI50 = 0.13) were more toxic (at 1 µl/ml for 24 h) and repellent than the other constituents. The results show potential of the essential oils for use in integrated management of the tomato pest.

Eucleanal: a new napthalene derivative from Euclea divinorum.

A new naphthalene derivative, named eucleanal (1), was isolated from Euclea divinorum Hiern., and its structure elucidated by detailed spectroscopic (1H, 13C NMR, COSY, HMQC, HMBC) and HREIMS analysis.

Drypetdimer A: a new flavone dimer from Drypetes gerrardii.

A new flavone dimer, drypetdimer A (1), was isolated from Drypetes gerrardii J.Hutch The structure of the new compound was elucidated by detailed spectroscopic analysis such as 1H, 13C NMR, COSY, HMQC, HMBC and HREIMS.

Augustamine type alkaloids from Crinum kirkii.

Sixteen more Amaryllidaceae alkaloids have been isolated from bulbs of Crinum kirkii Baker of which noraugustamine and 4a,N-dedihydronoraugustamine are hitherto unknown. Their structures and those of earlier known alkaloids have been established by physical and spectroscopic analysis. Application of 2D NMR techniques was used for complete characterization of the alkaloids as well as of 3-O-acetylsanguinine. 1,2-Diacetyllycorine and 3-O-acetylsanguinine showed activity against Trypanosoma brucci rhodesiense, the parasite associated with sleeping sickness. 3-O-acetylsanguinine also showed some activity against Trypanosoma cruzi.

Fermentation and antimicrobial activities of extracts from different species of fungus belonging to Genus, Trichoderma.

The present paper discusses the effects of the crude extracts of Trichoderma spp. on a number of fungal and bacterial organisms. These include Paecilomyces variotii, Penicillium notatum, Nematospora corylii, Mucor miehei, Bacillus brevis, Bacillus subtilis, Enterobacter dissolvens and Sarcina lutea. The culture broth extracts of different isolates of Trichoderma harzianum, T. longibrachiatum and T. koningii cultured in different media were investigated individually for in-vitro antifungal and antibacterial activities by agar diffusion technique. The culture broth extracts of T. harzianum produced definite antifungal and antibacterial activities against most of the test organisms. The results indicate that the extracts were fungicidal and antibacterial at a concentration of 100 microg per 6mm paper disks. Trichoderma harzianum showed the highest activity while T. koningii showed the least activity against most of the test organisms especially the yeast Nematospora coryli. The results of this study indicate that the Trichoderma species especially T. harzianum is a possible source of useful antimicrobial agents against pathogenic microorganisms which include gram-negative, gram-positive, fungi and yeasts.

Dissolved organic carbon (DOC) and coliform bacteria in underground waters in areas around Nairobi.

Most people in areas surrounding Nairobi use untreated underground waters for their domestic chores. A study was carried out during the wet season (April-June) and the dry season (September-November) of the year 1994 to find out if these untreated underground waters contain dissolved organic carbon (DOC) and coliform bracteria. Out of the 40 sites sampled during both the wet and dry seasons, 11 contained colifrorm bacteria during the wet season, while only 2 contained the microbes during the dry season. The microbes were detected only in the wells. DOC was detected in 37 sites during the wet season and in 31 sites during the dry season within a range of 2.0-30.8 mg L(-1 ). DOC which mainly consists of humic and fulvic acids was quantified by measuring their absorbance at 360nm by UV-VIS spectrophotometry. The presence of coliform bacteria was detected by use of microbiological techniques.

Ring A-seco mosquito larvicidal limonoids from Turraea wakefieldii.

Five novel limonoids, 1-5, were isolated from the root bark of Turraea wakefieldii and were characterized as tecleaninoid derivatives. This is the first report of the natural occurrence of tecleanin-type limonoids with a five-membered-ring A-seco structure for which we propose the name neotecleanins. The relative stereochemical structures of compounds 1-5 were established on the basis of NMR spectroscopy. The absolute stereochemical structure of 5 was confirmed by X-ray diffraction methods. In mosquito larvicidal assays, compounds 1, 2 and 4 showed dose-dependent larvicidal activity against larvae of Anopheles gambiae s.s.

Molluscicidal and antimicrobial activity of Solanum aculeastrum.

The methanolic extract of the fresh root bark and berries of Solanum aculeastrum showed significant activity against host snails of schistosomiasis. The berries extract was more potent with 100% snail kill at 50 ppm. Fractionation increased activity with 100% mortality at 20 ppm. The aqueous and methanolic extracts of the berries showed moderate antimicrobial activity, increasing by fractionation.

Flavonoids from Tephrosia aequilata.

From the roots of the plant Tephrosia aequilata Baker, five flavonoids were isolated of which, 3,4:8,9-dimethylenedioxypterocarpan is reported for the first time. Its structure and those of the already known flavonoids were established by physical and spectroscopic analysis. Application of 2D NMR techniques was useful for complete characterization of the new pterocarpan as well as the other known flavonoids.

Bioactive steroidal alkaloid glycosides from Solanum aculeastrum.

Solanum aculeastrum Dunal was investigated for the presence of molluscicidal compounds. This led to the isolation of solaculine A, from the root bark in addition to known steroidal alkaloids; solamargine and beta-solamarine from the berries. The structures were elucidated by spectroscopic techniques. Molluscicidal activity of the aqueous extracts of the berries and root bark, and the isolated compounds were investigated.