Browsing by Author "Hassanali, Ahmed"

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    1,8-Cineole: An attractant for the banana weevil, Cosmopolites sordidus
    (Elsevier, 1996-07) Hassanali, Ahmed; Ndiege, I. O.; Budenberg, W. J.; Otieno, D. O.
    1,8-Cineole was identified as one of the electrophysiologically active components of the volatiles from banana cultivars susceptible to the banana weevil. It was also shown to be an attractant for the banana weevil Comopolites sordidus in laboratory behavioural bioassays. The resistant cultivar did not contain 1,8-cineole. β-Phellandrene, which exhibited electrophysiological activity, but did not show any attraction to the banana weevil, was found only in the resistant banana cultivar.
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    A 4-Alkyl-substituted Analogue Of Guaiacol Shows Greater Repellency To Savannah Tsetse (Glossina spp.)
    (Springer-Verlag, 2007-05) Hassanali, Ahmed; Saini, R. K.
    The responses of Glossina morsitans morsitans Westwood to guaiacol (2-methoxyphenol), a mild repellent constituent of bovid odors, and seven analogues comprising 2-methoxyfuran, 2,4-dimethylphenol, 2-methoxy-4-methylphenol (4-methylguaiacol), 4-ethyl-2-methoxyphenol (4-ethylguaiacol), 4-allyl-2-methoxyphenol (4-allylguaiacol; eugenol), 3,4-methylenedioxytoluene, and 3,4-dimethoxystyrene were compared in a two-choice wind tunnel. The 4-methyl-substituted derivative (2-methoxy-4-methylphenol) was found to elicit stronger repellent responses from the flies compared with guaiacol. None of the other analogues showed significant repellent effects on flies. 4-Methylguaiacol, guaiacol, and eugenol (which was included because of previous reports of its repellency against a number of arthropods) were further evaluated in the field with wild populations of predominantly Glossina pallidipes Austen. The presence of guaiacol or eugenol near odor-baited traps caused some nonsignificant reduction in the number of tsetse catches at relatively high release rates (∼50 mg/hr). In contrast, the 4-methyl derivative at three different release rates (2.2, 4.5, and 9.0 mg/hr) reduced trap catches of baited traps in a dose-response manner. At 10 mg/hr release rate, it reduced the catches of baited and unbaited traps by ∼80 and ∼70%, respectively. In addition, the compound not only reduced the number of tsetse attracted to natural ox odor (∼ 80%), but also had an effect on their feeding responses, reducing the proportion that fed on an ox by more than 80%. Our study shows that the presence of a methyl substituent at the 4-position of guaiacol enhances the repellency of the molecule to savannah tsetse and suggests that 4-methylguaiacol may represent a promising additional tool in the arsenal of techniques in trypanosomiasis control.
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    Airborne Volatiles from Melinis minutiflora P. Beauv., a Non-Host Plant of the Spotted Stem Borer
    (Routledge Taylor & Francis Group, 2011-12-08) Hassanali, Ahmed; Pickett, J. A.; Khan, Z. R.; Lwande, W.; Chhabra, S. C.; Kimani, S. M.
    Airborne volatiles released by Melinis minutiflora P. Beauv., a non-host plant of the spotted stem borer, Chilo partellus (Swinhoe), were trapped from the live plant by air entrainment into porous polymer Porapak Q and analyzed by GC and GC/MS. The main hydrocarbons identified and confirmed by co-injection with authentic samples on two columns of different polarities were (3E)-4,8-dimethylnona-1,3,7-triene (28.1% of isolated volatiles) and β-caryophyllene (24.2% of isolated votatiles). Of these, (3E)-4,8-dimethylnona-1,3,7-triene is electroantenographically active (EAG) against Chilo partellus (Swinhoe).
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    Anti-bacterial Activities and Phytochemical Screening of Extracts of Different Parts of Thalictrum Rhynchocarpum.
    (African Journal of Traditional, Complementary and Alternative Medicine, 2013-09) Odalo, Josiah Ochieng; Mayeku, P. W.; Hassanali, Ahmed; Kiremire, B. T.; Hertweck, C.
    Parts of the plant Thalictrum rhyncocarpum are used in herbal medicine in Kenya to treat various infections. The aim of this study was to evaluate in-vitro anti-bacteria activities and phytochemical profiles of solvent extracts of the leaves, stem bark and root of Thalictrum rhyncocarpum against Bacillus subtilis-6633, Staphylococcus aures-SG 511, Escherichia coli SG 458, Pseudomonus aeruginosa-K799/61 and Mycobacterium vaccae-10670. Anti-bacterial activity tests were carried out using disc diffusion assay and tube dilution technique, and phytochemical screening was carried out through Thin Layer Chromatography. The crude extracts showed antibacterial effects on M. vaccae, P. aeruginosa and B. subtilis. M. vaccae was most sensitive, particularly to the methanol root extract. Phytochemical screening of the extracts suggested the presence of glycosides and alkaloids in the stem bark and root extracts, and flavonoids and triterpenes in the leaf extracts. The study showed interesting levels of activities of solvent extracts of different parts of T. rhyncocarpum against some of the bacteria tested (M. vaccae, P. aeruginosa and B. subtilis). The results provide some scientific rationale for the traditional use of the plant in Kenya to treat different microbial infections.
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    Anti-bacterial Properties and GC-MS Analysis of Extracts and ,Essential Oils of Selected Plant Products
    (2013-10-17) Nyaitondi, Ombuna Dinah; Wanjau, R. N.; Nyambaka, H. N.; Hassanali, Ahmed
    Bacteria, as common microorganisms found in air, food, water and soil remain a major problem in developing countries where disease. outbreaks frequently occur in congested areas. Antibiotics are used to treat common bacterial diseases such as respiratory, ear, gastrointestinal and skin infections but bacteria develop resistance to most of the drugs. The drugs also have serious side effects and the cost of medication is high. Plants are traditionally used for treatment of bacterial infections though they are not clinically regulated due to lack of awareness and enough data to support the reported therapeutic claims. Some plants used as food and vegetables are hardly considered in such studies. The aim of this study was to investigate the antibacterial properties associated with garlic, ginger, lemon, turmeric and onion. The bioactivities of juices, methanol extracts and essential oils of these materials were tested, individually and as blends, against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Salmonella typhi. Bioassay data obtained from the active extracts and oils were subjected to analysis of variance (ANOV A). Treatment means showing significant difference (p :s 0.05) were separated using Student-Newman-Keuls test (SNK). Identification of suspected antibacterial compounds was done by comparison of retention indices and the mass spectra with those in National Institute of Standards and Technology (NIST) libraries using GC-MS analysis. Garlicjuice was bactericidal against Salmonella typhi (17.7±2.5), Staphylococcus aureus (14.7±2.5), Pseudomonas aeruginosa (10.O±O.O)and Escherichia coli (11. 7±O.6). Lemon/garlic juice exhibited significantly higher activity against Escherichia coli (15.O±O.O) and Salmonella typhi (12.O±O.O). Turmeric/lemon/garlic methanol extracts blend was most active against S. aureus (I2.O±I.0). Preliminary screening of the essential oils indicated significant antibacterial activity of lemon/garlic essential oil blend (10.O±O.O) against Pseudomonas aeruginosa. Garlic recorded timecourse increasing activity against pseudomonas aeruginosa, Staphylococcus aureus and. Escherichia coli from day 1 to day.S, ·GC-MS analysis of the active samples confirmed the presence of compounds containing -OOH, -OH, -N, -CI, -F, -NH2 and -S groups which are associated with bacterial inhibition in conventional antibiotics. The 10 major constituents obtained from samples suspected to contain antibacterial activity include limonene (85.08%);)-vinyl-l,2-dithiacyclohex-4-ene (21.43%); u-zingiberene (33.75%); diallyl disulphide (10.84%); 2-butanone,4-(-hydroxy-3-methoxyphenyl)- (14.14%); 3- chlorothiophene (8.93%); methanehydrazonic acid,N-[3-(methylthio)-I,-2,4-thiadiazol-5- . yl]-,ethyl ester (8.87%); n-hexadecanoic acid (8_01%); 'Y-sitosterol (8.00) and propanamide,2-amino-3-phenyl (6.71%). Since juices of garlic, lemon and lemon/garlic blend were found to be active against one or more of the bacteria tested unlike methanol extracts and essential oils, they should be used in raw form as heating and drying is likely to render them inactive. Further studies on methanol extract and fresh juice of lemon/garlic blend need to be undertaken in order to elucidate the active principles in these extracts. These may provide novel antimicrobial agents and/or models for new generation of synthetic antibiotics.
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    Anti-mosquito and antimicrobial nor-halimanoids, isocoumarins and an anilinoid from Tessmannia densiflora
    (Elselvier, 2009-07) Kihampa, C; Nkunya, M.H.; Joseph, C.C.; Magesa, S.M.; Hassanali, Ahmed; Heydenreich, Matthias; Kleinpeter, E.
    The nor-halimane diterpenoid tessmannic acid and its methyl, 2-methylisopropyl and 1-methylbutyl esters, the unusual isocoumarins 8-hydroxy-6-methoxy-3-pentylisocoumarin and 7-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin, and 5-pentyl-3-methoxy-N-butylaniline were isolated from the stem and root bark extracts of Tessmannia densiflora Harms (Caesalpiniaceae) that showed mosquito larvicidal activity. The structures were determined on interpretation of spectroscopic data. Tessmannic acid and its methyl ester exhibited antibacterial and antifungal activity. The compounds also caused high larvae and adult Anopheles gambiae mosquitoe mortality effects, and stronger mosquito repellency than that shown by the standard repellent DEET, hence indicating Tessmannia species to be potential sources of bioactive natural products.
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    Anti-mosquito plants as an alternative or incremental method for malaria vector control among rural communities of Bagamoyo District, Tanzania
    (BioMed Central, 2014-07-11) Hassanali, Ahmed; Innocent, E.; Kisinza, W. N. W.; Mutalemwa, P. P. P.; Magesa, S.; Kayombo, E.
    Background Plants represent one of the most accessible resources available for mosquito control by communities in Tanzania. However, no documented statistics exist for their contribution in the management of mosquitoes and other insects except through verbal and some publications. This study aimed at assessing communities' knowledge, attitudes and practices of using plants as an alternative method for mosquito control among selected communities in a malaria-prone area in Tanzania. Methods Questionnaires were administered to 202 respondents from four villages of Bagamoyo District, Pwani Region, in Tanzania followed by participatory rural appraisal with village health workers. Secondary data collection for plants mentioned by the communities was undertaken using different search engines such as googlescholar, PubMED and NAPRALERT. Results Results showed about 40.3% of respondents used plants to manage insects, including mosquitoes. A broad profile of plants are used, including "mwarobaini" (Azadirachta indica) (22.5%), "mtopetope" (Annona spp) (20.8%), "mchungwa/mlimau" (Citrus spp) (8.3%), "mvumbashi/uvumbati" (Ocimum spp) (7.4%), "mkorosho" (Anacadium occidentale) (7.1%), "mwembe" (5.4%) (Mangifera indica), "mpera" (4.1%) (Psidium spp) and "maganda ya nazi" (4.1%) (Cocos nucifera). Majority of respondents collected these plants from the wild (54.2%), farms (28.9%) and/or home gardens (6%). The roles played by these plants in fighting mosquitoes is reflected by the majority that deploy them with or without bed-nets (p > 0.55) or insecticidal sprays (p >0.22). Most respondents were aware that mosquitoes transmit malaria (90.6%) while few respondents associated elephantiasis/hydrocele (46.5%) and yellow fever (24.3%) with mosquitoes. Most of the ethnobotanical uses mentioned by the communities were consistent with scientific information gathered from the literature, except for Psidium guajava, which is reported for the first time in insect control. Conclusion This survey has indicated some knowledge gap among community members in managing mosquito vectors using plant. The communities need a basic health education and sensitization for effective exploitation of this valuable tool for reducing mosquitoes and associated disease burdens. On the other hand, the government of Tanzania should strengthen advocacy of botanical pesticides development, registration and regulation for public health benefits because they are source of pest control tools people rely on them.
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    Anti-protozoal activity of aporphine and protoberberine alkaloids from Annickia kummeriae (Engl. & Diels) Setten & Maas (Annonaceae)"
    (BMC Complementary and Alternative Medicine, 201) Malebo, H. M.; Wenzler, Tanja; Cal, Monical; Swaleh, Sauda M.; Omolo, Maurice O; Hassanali, Ahmed; Séquin, Urs; Häussinger, Daniel; Dalsgaard, P.; Hamburger, Matthias; Brun, Reto; Ndiege, I. O.
    Background: Malaria, trypanosomiasis and leishmaniasis have an overwhelming impact in the poorest countries in the world due to their prevalence, virulence and drug resistance ability. Currently, there is inadequate armory of drugs for the treatment of malaria, trypanosomiasis and leishmaniasis. This underscores the continuing need for the discovery and development of new anti-protozoal drugs. Consequently, there is an urgent need for research aimed at the discovery and development of new effective and safe anti-plasmodial, anti-trypanosomal and anti-leishmanial drugs. Methods: Bioassay-guided chromatographic fractionation was employed for the isolation and purification of antiprotozoal alkaloids. Results: The methanol extract from the leaves of Annickia kummeriae from Tanzania exhibited a strong anti-plasmodial activity against the multi-drug resistant Plasmodium falciparum K1 strain (IC50 0.12 ± 0.01 µg/ml, selectivity index (SI) of 250, moderate activity against Trypanosoma brucei rhodesiense STIB 900 strain (IC50 2.50 ± 0.19 µg/ml, SI 12) and mild activity against Leishmania donovani axenic MHOM-ET-67/82 strain (IC50 9.25 ± 0.54 µg/ml, SI 3.2). Bioassay-guided chromatographic fractionation led to the isolation of four pure alkaloids, lysicamine (1), trivalvone (2), palmatine (3), jatrorrhizine (4) and two sets of mixtures of jatrorrhizine (4) with columbamine (5) and palmatine (3) with (-)-tetrahydropalmatine (6). The alkaloids showed low cytotoxicity activity (CC50 30 - >90 µg/ml), strong to moderate anti-plasmodial activity (IC50 0.08 ± 0.001 - 2.4 ± 0.642 µg/ml, SI 1.5-1,154), moderate to weak anti-trypanosomal (IC50 2.80 ± 0.001 - 14.3 ± 0.001 µg/ml, SI 2.3-28.1) and anti-leishmanial activity IC50 2.7 ± 0.001 - 20.4 ± 0.003 µg/ml, SI 1.7-15.6). Conclusion: The strong anti-plasmodial activity makes these alkaloids good lead structures for drug development programs.
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    Anti-protozoal and structure-activity relationships of chemical constituents of Acridocarpus chloropterus Oliver (Malpighiaceae) from Tanzania
    (Universal Research Publications, 2013) Hassanali, Ahmed; Malebo, H. M.; Wenzler, T.; Cal, M.; Swaleh, Sauda M.; Machocho, Alex K.; Häussinger, D.; Dalsgaard, P.; Omolo, M. O.; Séquin, U.; Hamburger, M.; Brun, R.; Ndiege, I. O.
    Chromatographic separation of Acridocarpus chloropterus extract led to the isolation and identification of five triterpenes: β-sitosterol (1), stigmasterol (2), friedelin (3), oleanolic acid (4), ursolic acid (5); and five flavonoids: apigenin (6), luteolin (7), vitexin (8), kaempferol (9) and quercetin (10). Quercetin (10) exhibited moderate in vitro anti-plasmodial activity (IC50 2.6+0.05 μg/ml) while the rest of compounds were inactive. Mild to weak in vitro anti-trypanosomal activity was observed in quercetin (10) (IC50 3.60+0.1 μg/ml), ursolic acid (5) (IC50 7.80+0.1 μg/ml) and apigenin (6) (IC50 9.0+0.1 μg/ml). Ursolic acid (5) exhibited strong in vitro anti-leishmanial activity (IC50 0.80+0.001 μg/ml) while oleanolic acid (4), apigenin (6), kaempferol (9) and quercetin (10) showed moderate to mild activity (2.10+0.1, 2.20+0.1, 5.90+ 0.1 and 3.5+0.2 μg/ml, respectively) whereas favorable selectivity was observed with all flavonoids. Structure-activity-relationship (SAR) comparison of the isolated triterpenoids confirmed that the hydroxyl group at C-3 together with C-23, C-25, C-26 and C-30 methyl groups, C-12/C-13 double bond, the C-28 carboxylic acid group, and H-20 in ursolic acid (5) and related compounds are all responsible for the strong anti-leishmanial activity. The 3-OH and 3′-OH in the apigenin (6) and related compounds are responsible for the strong anti-protozoal activity observed in the isolated flavonoids. The strong to moderate anti-leishmanial activity of the isolated triterpenes and flavonoids make them good candidates or templates for new anti-protozoal drug devel
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    Antifeedant and ovicidal activities of a new cassane and other compounds from Caesalpinia welwitschiana Oliv. and Caesalpinia bonduc L. against Tuta absoluta (Lepidoptera: Gelechiidae)
    (Taylor & Francis Group, 2020) Flaure, Rosette Ehawa Essounga; Mba’ning, Brice Mitterant; Tcho, Alain Tadjong; Chhabra, Sumesh Chander; Mohamed, Samira Abuelgasim; Lenta, Bruno Ndjakou; Ngouela, Silvere Augustin; Tsamo, Etienne; Hassanali, Ahmed; Cox, Russell John
    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/ml. Overall, the present study, conclude that the two species of the plant could be a promising source of ecofriendly botanical constituents.
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    Antimosquito and antimicrobial clerodanoids and a chlorobenzenoid from Tessmannia species
    (Pubmed, 2010-02) Kihampa, C.; Nkunya, M. H.; Joseph, C.C.; Magesa, S.M.; Hassanali, Ahmed; Heydenreich, Matthias; Kleinpeter, E.
    The clerodane diterpenoids trans-kolavenolic acid, 18-oxocleroda-3,13(E)-dien-15-oic acid, ent-(18-hydroxycarbonyl)-cleroda-3,13(E)-dien-15-oate, 2-oxo-ent-cleroda-3,13(Z)-dien-15-oic acid and trans-2-oxo-ent-cleroda-13(Z)-en-15-oic acid, and the chlorobenzenoid O-(3-hydroxy-4-hydroxycarbonyl-5-pentylphenyl)-3-chloro-4-methoxy-6-pentyl-2-oxybenzoic acid were isolated from Tessmannia martiniana var pauloi and T. martiniana var matiniana. Structures were established based on interpretation of spectroscopic data. Some of the compounds exhibited significant antimosquito, antifungal and antibacterial activities.
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    Antiplasmodial, anti-trypanosomal, anti-leishmanial and cytotoxicity activity of selected Tanzanian medicinal plants.
    (Tanzania Journal of Health Research, 2009-10-04) Hassanali, Ahmed; Malebo, H. M.; Tanja, W.; Swaleh, S A M; Omolo, M O; Hamburger, M; Brun, R; Ndiege, I. O.
    The antiplasmodial, anti-trypanosomal and anti-leishmanial activity of 25 plant extracts obtained from seven Tanzanian medicinal plants: Annickia (Enantia) kummeriae (Annonaceae), Artemisia annua (Asteraceae), Pseudospondias microcarpa (Anacardiaceae), Drypetes natalensis (Euphorbiaceae), Acridocarpus chloropterus (Malpighiaceae), Maytenus senegalensis (Celastraceae) and Neurautanenia mitis (Papilonaceae), were evaluated in vitro against Plasmodium falciparum K1, Trypanosoma brucei rhodesiense STIB 900 and axenic Leishmania donovani MHOM-ET-67/82. Out of the 25 extracts tested, 17 showed good antiplasmodial activity (IC50 0.04-5.0 μg/ml), 7 exhibited moderate anti-trypanosomal activity (IC50 2.3- 2.8 μg/ml), while 5 displayed mild anti-leishmanial activity (IC50 8.8-9.79 μg/ml). A. kummeriae, A. annua, P. microcarpa, D. natalensis, M. senegalensis and N. mitis extracts had good antiplasmodial activity (IC50 0.04-2.1 μg/ml) and selectivity indices (29.2-2,250 μg/ml). The high antiplasmodial, moderate anti-trypanosomal and mild anti-leishmanial activity make these plants good candidates for bioassay-guided isolation of anti-protozoal compounds which could serve as new lead structures for drug development.
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    Arm-in-cage testing of natural human-derived mosquito repellents
    (Biomed Central, 2010) James, Logan G.; Nina, Stanczyk M.; Hassanali, Ahmed; Kemei, Joshua; Santana, Antônio E.G.; Karlos, Ribeiro A.L.; John, Pickett A.; Mordue, Jennifer A.
    Background: Individual human subjects are differentially attractive to mosquitoes and other biting insects. Previous investigations have demonstrated that this can be attributed partly to enhanced production of natural repellent chemicals by those individuals that attract few mosquitoes in the laboratory. The most important compounds in this respect include three aldehydes, octanal, nonanal and decanal, and two ketones, 6-methyl-5- hepten-2-one and geranylacetone [(E)-6,10-dimethylundeca-5,9-dien-2-one]. In olfactometer trials, these compounds interfered with attraction of mosquitoes to a host and consequently show promise as novel mosquito repellents. Methods: To test whether these chemicals could provide protection against mosquitoes, laboratory repellency trials were carried out to test the chemicals individually at different concentrations and in different mixtures and ratios with three major disease vectors: Anopheles gambiae, Culex quinquefasciatus and Aedes aegypti. Results: Up to 100% repellency was achieved depending on the type of repellent compound tested, the concentration and the relative composition of the mixture. The greatest effect was observed by mixing together two compounds, 6-methyl-5-hepten-2-one and geranylacetone in a 1:1 ratio. This mixture exceeded the repellency of DEET when presented at low concentrations. The repellent effect of this mixture was maintained over several hours. Altering the ratio of these compounds significantly affected the behavioural response of the mosquitoes, providing evidence for the ability of mosquitoes to detect and respond to specific mixtures and ratios of natural repellent compounds that are associated with host location. Conclusion: The optimum mixture of 6-methyl-5-hepten-2-one and geranylacetone was a 1:1 ratio and this provided the most effective protection against all species of mosquito tested. With further improvements in formulation, selected blends of these compounds have the potential to be exploited and developed as humanderived novel repellents for personal protection.
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    Aromatic plants of Kenya II: Volatile constituents of leaf oil of Psiadia Punculata (DC) Vatke
    (Faculty of Pharmacy, University of Nairobi, 1999) Hassanali, Ahmed; Mwangi, J. W.; Thoithi, Grace N.; Lwande, W.
    Psiadia punculata (DC) Vatke (P. arabica Jaub. and Spach)(Compositae) is a shrub 0.5-2.5 m (1]. The leaves arc shiny and sticky, narrowly elliptic (ovate), base cuneate or decurrent. apex narrowly acuminate, margin entire or ere¬ nate. Flowers are yellow in many-flowered heads. The plant is found in grassland, bushland and dry forest edges in Kenya. Powdered leaf decoction is used to trcat abdominal pains
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    Aromatic plants of Kenya: volatile constituents of leaf oils of Sphaeranthus suaveolens (Forsk) D.C. and S. bullatus Mattf
    (The International Centre of Insect Physiology and Ecology (ICIPE), 1998) Hassanali, Ahmed; Mwangi, J. W.; Achola, K. J.; Lwande, W.
    The essential oils isolated by hydrodistillation from Sphaeranthus su av eolens (Forsk) D.C. (0.47%) and S. bullatus Mattf. (0.5%) were analyzed by GC and GC-MS. Seventy eight compounds consisting about 95% of the oil of S. suaveolens were identified while 97 constituents accounting for about 83% were identified from the leaf oil of S. bullatus, The major constituents of the leaf oil of S. sauveolens was cis-pinocamphone (63.5 %) while those of S. bullatus oil were thymol (22.0%), bornyl acetate (8.1%) and germacrene-D (7.9%).
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    Assessment of Different Legumes for the Control of Striga hermonthica in Maize and Sorghum
    (Madison, 2007-03) Hassanali, Ahmed; Khan, Z. R.; Midega, C. A.O.; Pickett, J. A.; Wadhams, L. J.
    The witchweed, Striga hermonthica (Del.) Benth., is a major constraint to maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench] production in sub-Saharan Africa. Intercropping maize and sorghum with desmodium (Desmodium spp.) effectively controls Striga and enhances grain yields. Studies were thus conducted to assess the potential role of intercropping maize and sorghum with different food legumes for control of Striga Seasonal Striga counts in the intercrops, other than greenleaf desmodium where the counts consistently remained close to zero, were generally not significantly different from those in the control in both crops. A pooled analysis across seasons, however, showed that intercropping sorghum with cowpea [Vigna unguiculata (L.) Walp.], greengram [Vigna radiata (L.) Wilczek], and crotalaria (Crotalaria ochroleuca G. Don), and maize with crotalaria significantly reduced Striga populations. Within-season analysis showed that it was only the greenleaf desmodium intercrop that maintained significantly enhanced grain yields relative to the control. On the other hand, multiseason analysis showed that it was only the crotalaria, cowpea, and greenleaf desmodium intercrops in maize and greenleaf desmodium intercrop in sorghum that significantly enhanced grain yields. These results indicate that intercropping sorghum with cowpea, greengram, or crotalaria and maize with crotalaria could be combined with other cultural methods for a sustainable control of S. hermonthica
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    Attraction of Amblyomma variegatum (ticks) to the attraction-aggregation-attachment-pheromone with or without carbon dioxide
    (Springer Verlag, 2003) Hassanali, Ahmed; Maranga, R. O.; Kaaya, G. P.; Mueke, J. M.
    The responses of adult Amblyomma variegatum ticks released from various distances to different doses of the synthetic attraction-aggregation-attachment pheromone (AAAP) (made up of ortho-nitrophenol, methyl salicylate and nonanoic acid in paraffin oil), dispensed from the center of circular field plots, were studied in the presence or absence of elevated levels of CO2. Up to 90% of the ticks released were attracted to the pheromone source in the presence of CO2 within 3h. CO2 alone was unattractive, similar to previous findings in Zimbabwe, but unlike results from a Caribbean A. variegatum population, which was significantly attracted to this signal. In the absence of CO2, smaller but significant proportions of the released ticks were attracted to the pheromone, albeit more slowly, suggesting another variation in the responses of this bont tick to inter- and intra-specific signals. Our results are interpreted in the light of a study undertaken elsewhere demonstrating relatively high heterozygosity among tick populations. Possible directions of further research to explore the use of the pheromone in off-host control of the tick are also highlighted.
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    Augmentation of host's naturally acquired immunity by solubilized membrane-bound midgut proteins of the tick Rhipicephalus appendiculatus.
    (PubMed, 1992-01-07) Hassanali, Ahmed; Essuman, S.; Nyindo, M.; Ole-Sitayo, E N
    Immune resistance of rabbits to the hard tick Rhipicephalus appendiculatus induced by combined tick infestations and immunization with solubilized midgut membrane proteins were compared with resistance due to 1-3 infestations or immunization alone. Results demonstrate that the level of exposure of rabbits to ticks used in the study does not significantly affect the immune expression resulting from immunization and that the latter augments the resistance due to infestation.
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    Behaviour and Biology of Chilo partellus (Swinhoe) on Striga Hermonthica (Del.) Benth. Infested and Uninfested Maize Plants.
    (2007) Hassanali, Ahmed; Mohamed, H. M.; Khan, Z. R.; Mueke, J. M.; Kairu, E. W.; Pickett, J. A.
    Stemborers and Striga hermonthica co-exist in cereal fields in sub-Saharan Africa where together they cause crop damage that sometimes results in total crop loss. Striga alters both the chemistry and morphology of cereals and this may influence behaviour and performance of stemborers on the host plants. Studies were undertaken to compare the effects of various levels of Striga infestation of maize on oviposition preference and survival of Chilo partellus. Potted maize plants were exposed to different densities of Striga seeds (0, 1000, 2000 and 3000/pot) and subsequent effects on C. partellus oviposition evaluated in no-choice and choice-tests. In addition, larval arrestment, settlement, feeding, growth and development were assessed. Results showed that Striga infestation and plant height had non-significant influence on oviposition preference of C. partellus, except in 2-choice assays involving uninfested maize and one under high Striga infestation, in which case they preferred to oviposit on the latter. Similarly, Striga infestation had no influence on larval arrest and settlement. The larvae, however, consumed significantly more of the leaves and stems from uninfested than infested maize plants, with a progressive decline in the consumed proportions with increasing level of Striga infestation. Larval food assimilation was not influenced by Striga infestation, but larval period, percentage of pupation and growth rate were significantly higher on uninfested plants as compared to medium and high Striga infested plants. Possible reasons underlying these observations and their implications are discussed.
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