Larvicidal potential of some plants from west Africa against Culex quinquefasciatus (Say) and anopheles gambiae giles (Diptera: Culicidae).
More than two billion people, mostly in tropical countries are at risk from mosquito-borne diseases such as malaria, dengue, haemorrhagic fever and filariasis (1). These infectious diseases mainly impact the tropic's poorest people. An estimated 50 million people are infected with dengue each year (2). Malaria has a crippling effect on Africa's economic growth and perpetuates vicious cycles of poverty (3). Approximately 300-500 million clinical cases and >1 million deaths are recorded every year (4).
The responsible pathogens are transmitted by bites of blood sucking mosquitoes which are considered to be harmful towards the populations in tropical and subtropical regions (5). The genera Culex, Aedes and Anopheles are the most important vectors involved in diseases transmission to humans.
Although there are proven strategies to control mosquito-borne diseases, mosquitoes still cause a huge public health problem in Africa. Across African people are exposed to mosquito bites because the larval habitats are widely distributed in humid areas such as flood areas and rice farms. These sites with larvae might be altered to decrease the mosquito population for the interruption of disease transmission. One of the strategies recommended by WHO is the use of organochlorines (DDT, endosulfan), organophosphates (parathion, temephos) and carbamates. However, these chemical interventions are severely compromised by the development of insecticide resistance in some mosquito vectors and environmental concerns (6-8). Also in many African countries the most widely tested interventions based on bednets treated with pyrethroid, have been difficult to implement correctly because of problems related to cost and acceptability (8),
This situation highlights the need to search for new efficient products with fewer effects on environment (9). Recently the environmentally safe and biodegradable, natural products of plants have been considered as alternative sources in the control of insects of public health importance (10). Natural products contain a range of bioactive compounds (6) and related commercial insecticides are commonly perceived as "safe" in comparison to synthetic repellents (10). Traditionally plant based repellents have been used for generations as protection measures against mosquitoes. These are still extensively used throughout rural communities in Benin (11), Tanzania (12) and Cote d'Ivoire. These plants are burned overnight in rooms to drive away nuisance mosquitoes. Some of these African plants have been shown to be larvicides (13,14).
The present study investigated 45 plants from West Africa for larvicidal activity against mosquitoes as safer natural alternatives to synthetic molecules. Most of the selected plants have been used for medicinal purposes for a long time, because these are not harmful to either humans or domestic animals.
MATERIAL & METHODS
Preparation of extracts
The plant species studied were selected on the basis of criteria (Table 1), such as lack of information on activity against Anopheles and Culex larvae, botanical families (Euphorbiaceae, Verbenaceae, and Meliaceae) from which number of larvicidal plant were reported and large distribution in West Africa. Voucher specimens are deposited at the herbarium (Base ivoire) of Centre Suisse de Recherches Scientifiques en Cote d'Ivoire, Adiopodoume.
A quantity of the different plant parts were collected from April to October 2005 in the region of Ferkessedougou (northern Cote d'Ivoire), located in the Savanna area (9-11[degrees]N, 4- 7[degrees]W) of the Cote d'Ivoire. The roots, leaves and stem bark were dried in an air-conditioned room (22[degrees]C) and pounded by hand in a mortar. A quantity of 10 g of the powder was extracted with 100 ml of 90% ethanol under mechanical stiring (150 rpm) during 24 h and then filtered. The extracts were concentrated in a rotary evaporator (Rotavapor) at 40[degrees]C and lyophilized. In all, 49 extracts have been prepared for in vitro larvicidal screening.
Mosquito larvae tested
The larvae included wild resistant An. gambiae strains, resistant Cx. quinquefasciatus strains, and sensitive Kisumu strain (from Kenya). The resistant strains were collected from breeding sites around the village of Adiopodoume, located in the northern peri-urban part of Abidjan. These sites were selected because of their proximity to Centre Suisse de Recherches Scientifiques en Cote d'Ivoire (CSRS). Breeding sites located in this village were around crop farms. After collection, the III and IV instar larvae were transferred in plastic bottles and maintained at the laboratory.
The susceptible strain (Kisumu) was provided by the insectarium of CSRS. The eggs were put in distilled water maintained at 21-22[degrees]C and safe from contaminations. Eggs hatched after 24 h and larvae were fed with powdered cat kibble.
Larvicidal activity was assessed as per the protocol previously described by WHO with slight modification (15). The assays were performed in two steps: (i) Detection of susceptibility of larvae to extracts; and (ii) Determination of larvicidal concentration ([LC.SUB.95]). The sensitivity of the larvae to the extracts was determined at single concentration (1000 ppm). In 220 [micro]l of distilled water or dimethylsulfoxide (DMSO) 220 mg of extract was dissolved. Then 100 of extract solution was added to 5 ml of water from breeding site (wild strain) or distilled water (Kisumu strain). The final volume was adjusted to 10 ml and 20 larvae were added to each tube. A control tube containing only distilled water or 0.1% DMSO was prepared. Mortality is assessed by direct observation of larvae movements. An extract is active if 100% of larvae died between 30 min and 24 h (16). The tests were repeated three times.
The extracts showing larvicidal activity at 1000 ppm were further diluted from 1000 to 31.2 ppm. The viability of larvae was observed after 30 min, 6, 12 and 24 h and scored according to larvae movements and physiological state: 0 = Dead larvae; 1 = Low or almost absence of movement; 2 = Activity; and 3 = Hyperactivity. The number of dead larvae was counted to determine the mortality rate and monitored for determination of KT50 the time required to kill 50% of the larvae.
Partition of active extracts
The three most active extracts were subjected to a liquid-liquid partition with different solvents of increasing polarity. In whole 10 g of plant powder was extracted with ethanol 90% using 10-fold solvent under mechanical stiring (150 rpm) during 14 h. The filtrate was successively partitioned with hexane, chloroform and water. The chloroform fraction was washed with NaCl 1% (1 g/100 ml water) in order to remove tannins. All fractions were evaporated in a rotary evaporator to dryness at 40[degrees]C and lyophilized.
Larvicidal test with fractions prepared from active extracts
The fractions obtained from active extracts were tested against III and IV instar larvae of An. gambiae and Cx. quinquefasciatus where 11 mg of each fraction was dissolved in 110 [micro]l of DMSO. The test was performed as mentioned above. Mortality was assessed visually by direct observation of larvae movements. A fraction is active if 100% of larvae died between 30 min and 24 h of exposure.
TLC phytochemical analysis
Plant extracts (hexane, and chloroform) showing larvicidal activity were investigated by thin layer chromatography (TLC). TLC plates were prepared from 10 | l of extract solution (10 mg/ml in methanol) on silicagel 60 F254 plates (aluminum), developed in hexane-ethyl acetate (1:1) as mobile phase. After drying, the chromatograms were analyzed at 254 and 366 nm, pre- and post-spraying with specific reagents according to the nature of chemicals (17-19). The retention factor (Rf) values were calculated, using the following formula:
Rf = Distance moved by the compound/Distance moved by the solvent front
In this study, we investigated the larvicidal activities of 45 plants, traditionally used in Cote d'Ivoire. Of the 49 ethanol crude extracts 7 (14.29%) showed high activity against III and IV instar larvae of Anopheles and Culex at 1000 ppm 24 h post-exposure. These seven extracts were obtained from six plant species: A. cordifolia, P. amarus, H. indicum, C. populnea, V. grandifolia and Cm. planchonii. Six of the extracts had effect on viability of susceptible and resistant larvae of Anopheles, resulting in death of larvae.
Alchornea cordifolia extract exhibited activity only against Kisumu strain. The extract of Cm. planchonii was the only active against larvae of Culex. Mere weak or no effect on larvae was observed following exposure to the remaining 42 extracts.
The decrease in viability is more pronounced at high concentrations from 1000 to 250 ppm at all examination points. At the lowest concentrations, no effect on larvae was observed with any of the extracts tested. These results show a dose response activity.
Phyllanthus amarus and Cs. populnea caused 100% mortality of resistant larvae of Anopheles after 6 h contact (Table 2). The mortality rates range between 6.67 and 100% for Anopheles and 25-100% for Culex.
The most active extracts causing 100% mortality of larvae were Cm. planchonii, P. amarus and Cs. populnea 24 h post-incubation. For these extracts, the [LC.SUB.50] were 80-180 ppm against Anopheles and 370 ppm against Culex (Table 3). Phyllanthus amarus and Cs. populnea killed resistant An. gambiae, with KT50 ranged between 41 and 42 min. Cochlospermum planchonii caused death of Anopheles and Culex with KT50 values of 125 and 145 min respectively.
Incubation with extract of Cm. planchonii (Table 3) and related fractions (hexane, and chloroform) resulted in death of larvae of both Anopheles and Culex, at [LC.SUB.50] values ranging between 80 and 370 ppm (Table 4).
Following exposure to Cs. populnea extract, sensitive and resistant larvae of An. gambiae died at [LC.SUB.50] values of 80 and 180 ppm respectively. Its hexane fraction was more active ([LC.SUB.50] = 180 ppm) than the chloroform fraction, [LC.SUB.50] = 370 ppm (Table 4). The TLC phytochemical analysis revealed at least trace amount of monoter penoids, polyphenols and alkaloids (Table 5).
In this study P. amarus exhibited high larvicidal potential against An. gambiae ([LC.SUB.50] = 80-180 ppm). Incubation with derivatives (hexane and chloroform) caused death of larvae at [LC.SUB.50] = 180-370 ppm between 12-24 h (Table 4). No effect was observed with aqueous and tannin fractions. Preliminary phytochemical studies have shown presence of monoterpenoids, flavonoids, anthrones and anthraquinones (Table 5).
Plant phytochemicals have more specific effects and could be usefully integrated with other control measures to design comprehensive, appropriate and effective management protocols with less collateral harm to the environment and non-target species (20).
Exposures to studied plants resulted in death of susceptible and resistant larvae of An. gambiae. For the active plant species, the mortality rates range between 6.67 and 100% for Anopheles and 25-100% for Culex after 24 h exposure. In a previous study, Schinus terebinthifolia essential oil displayed activity after 72 h, the mean mortality percentage ranged from 0.5 to 96.75% for Cx. quinquefasciatus and 13.75 to 97.91% for An. gambiae (12).
Cochlospermum planchonii, Cs. populnea and P. amarus extracts caused cent percent mortality of larvae 24 h post-incubation, with [LC.SUB.50] of 80-180 ppm and [LC.SUB.95] values of 22.22-342 ppm. Other active species such as A. cordifolia, H. indicum and V. grandifolia exhibited activity with [LC.SUB.50] and [LC.SUB.95] values ranging between 180-370 and 342-703 ppm respectively. Following partition of crude extracts and larvicidal assays, only hexane and chloroform fractions exhibited activity against larvae, with [LC.SUB.50] and [LC.SUB.95] values of 180 and 342 ppm respectively for hexane. Chloroform fraction showed [LC.SUB.50] and [LC.SUB.95] values of 370 and 703 ppm respectively. The results revealed that increased larval mortality was observed with increased concentration of the extracts tested against An. gambiae and Cx. quinquefasciatus. Similar finding was obtained against An. stephensi with the leaf of Adansonia digitata (4). Chloroform extract of the plant showed [LC.SUB.50] and LC90 values of 88.55 and 168.14 ppm respectively, while its hexane extract showed [LC.SUB.50] and LC90 of 111.32 and 178.63 ppm respectively in 24 h. However, in the present study, hexane fractions displayed stronger potential than chloroform fractions against An. gambiae and Cx. quinquefasciatus.
The [KT.sub.50] values ranged between 41-125 and 145 min against resistant An. gambiae and Cx. quinquefasciatus respectively. Previous study demonstrated that the time required to knock down 50% of the wild adult An. gambiae in Tanzania was 11.29 min for S. terebinthifolia essential oil (12).
The larvicidal activity of some studied plants such as Cm. planchonii, H. indicum and A. cordifolia was reported against Ae. aegypti (14). The ethanolic extracts of these species caused death of larvae 30 min and 24 h post-incubation respectively at single concentration tested of 500 [micro]g/ml. The present study gave further data on the potential use of these plants against malaria, yellow fever, filarial and dengue vector control.
The active plants contain phytochemicals such as monoterpenoids and flavonoids. The fresh rhizomes of Cm. planchonii yield essential oils, with a high rate of oxygenated compounds (86.4% of ketones and esters) (21). Cissus populnea and P. amarus also contained essential oils (22,23). Several authors have demonstrated strong responses of mosquito odour receptors to volatiles produced by plants. Essential oils were found to be larvicidal against Anopheles and Culex (17,24,25). The finding of the present study is in line with the high potential of non-polar (dichloromethane, chloroform and hexane) extracts (4,19) demonstrated against mosquito larvae.
The selection of plants based on their botanical family or genus can be valuable criteria for identifying high larvicidals. Of the 7 active species, 2 were Euphorbiaceae. Several species of this family were reported to be larvicidal against mosquitos. Ricinus communis (26), Acalypha indica (27), and Acalypha alnifolia (1) have shown activity against resistant and susceptible Anopheles and Culex larvae. Alchornea cordifolia, Bridelia aubrevillei and B. grandis caused death of Ae. aegypti (18). Thus, Euphorbiaceae is a promising family for vector control.
Vitex grandifolia displayed activity on resistant and susceptible larvae of Anopheles; disappointingly in this study, the species lacked activity against Cx. quinquefasciatus. Other species of the same genus, V. trifolia, V. peduncularis and V. altissima exhibited activity on IV instar larvae of Cx. quinquefasciatus (28). The extract of V. negundo was repellent against adult mosquitoes (29). Therefore, there is no doubt that Vitex spp are of great interest in control of mosquitoes.
This is the first hand report of the larvicidal activity of studied plants discussing whether some are well-known for treating malaria. Phytochemical investigations, repellent study and field evaluation are ongoing.
In the present study, the larvicidal potential of 45 plants from West Africa was evaluated against sensitive and resistant An. gambiae and Cx. quinquefasciatus. Some of these plants exhibited high larvicidal activity. The results show that some of plants traditionally used in West Africa could gain place in control of African malaria vectors. The efficacy exhibited by these plants has given an opportunity for further investigation on eggs and adult mosquitoes and to evaluate them in small-scale field trials.
The authors would like to sincerely address their deepest acknowledgements to the Centre Suisse de Recherches Scientifiques en Cote d'Ivoire (CSRS) for financially supporting this study. They would also like to thank the Nangui Abrogoua University for the scientific and academic support.
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Alain Azokou [1,2], Mamidou W. Kone [1,2], Benjamin G. Koudou [1,2,3] & Honora F. Tra Bi 
 UFR Sciences de la Nature, Universite Nangui Abrogoua, Abidjan, Cote d'Ivoire,  Centre Suisse de Recherches Scientifiques en Cote d'Ivoire, Abidjan, Cote d'Ivoire;  Vector Group/Liverpool School of Tropical Medicine, Liverpool, UK
Correspondence to: Prof. M.W. Kone, Centre Suisse de Recherches Scientifiques en Cote d'Ivoire, 01 BP 1303, Abidjan 01, Cote d'Ivoire.
Received: 23 October 2012
Accepted in revised form: 17 February 2013
Table 1. Plant species selected for larvicidal screening Voucher No. Plant species Common names (English) 6470 Acacia flava Forsk. Flood-plain acacia 2308295 Acacia nilotica L. Babul acacia 2308811 Acacia polyacantha Wild Catechu tree 5867 Aframomum spectrum Oliv. Hanb Bear berry 8429 Afzelia africana Sn et Perr Apa, Pod mahogany 19839 Alchornea cordifolia Christmas bush, Muell. Arg dovewood 16004 Allophyllus africanus Beauv. African false currant, African Allophyllus 2309690 Andira inermis Kunth ex DC Angelin, Dog almond, Bastard mahogany 6138 Apodostigma pallens Planch. Not found ex Oliv. 4650 Baissea multiflora A. DC Not found 2308107 Bobgunnia madagascariensis Snake-bean tree (Desv.) J.H. Kirkbr & Wiersema 19945 Bridelia ferruginea Benth Ira 2288053 Cissus populnea Guill. & Perr Food gum 18546 Cochlospermum planchonii False cotton, Cotton Hook ex Planch plant 2288334 Cola cordifolia R. Br. Mandingo kola 11772 Combretum molle R. Br ex Don Velvet-leaved combretum 113612 Daniellia oliveri Hutch West African copal, et Dalz African copaiba, balsam tree, nigercopal, maaje 115451 Eleusine indica L. Goose grass, Bermuda grass, wiregrass, fowl foot 66252 Entada africana Guill et Perr Entada 68854 Erythrina senegalensis DC Senegal coral tree, Parrot tree, coral tree 2314388 Fadogia erythrophloea Not found Hutch & Dalziel 39365 Ficus congensis Engl Swamp or hippo fig 2308048 Heliotropium indicum L. Indian heliotrope, Heliotrope, cock's comb 2309989 Jatropha curcas L. Jatropha, Physic nu 2303193 Keetia hispida (Benth.) Bridson 16507 Khaya senegalensis Desr. Dry-zone mahogany A. Juss 2309941 Kigelia africana Lam. Benth Sausage tree 2316413 Landolphia owariensis Smith White-ball rubber, Vine rubber, rubber vine, ciwo 113251 Leptadenia pyrotechica L. Leptadenia 1774 Lonchocarpus cyanescens West African indigo (Schum. & Thonn.) Benth. 63592 Lophira lanceolata Van Tiegh Dwarf red ironwood, Ironwood, ekki, meni oil tree, nambanchi 2313051 Mimusops kummel Bruce Red milkwood, Bullet wood 115154 Parkia biglobosa Jacq R. Br West African locust bean, Dadawa tree 2177601 Phyllanthus amarus Black catnip, Schumach & Thonn Phyllanthus, amarus plant 8693 Phyllanthus muellerianus Myrobalan Kuntze 2177703 Premna lucens A. Chev Not found 2291444 Pseudocedrela kostchyi Harms Dry-zone cedar 113985 Sclerocarya birrea A. Rich Marula 70889 Securidaca longepedunculata Violet-tree Fres 2308860 Syzygium guineense Willd DC Water berry, Water Pear 2308288 Tapinanthus dodeneifolius DC Not found 20656 Uapaca togoensis Pax Charcoal, somon 19621 Vernonia guineensis Benth Guinean ginseng 2316528 Vitex grandifolia Gurke Black plum, Chocolate berry tree 2293337 Ximenia americana Wild False sandalwood, Blue Sourplum Voucher No. Families Tested organ 6470 Mimosaceae Leaves 2308295 Mimosaceae Leaves 2308811 Mimosaceae Stem bark 5867 Zingiberaceae Leaves 8429 Caesalpiniaceae Leaves 19839 Euphorbiaceae Leaves 16004 Sapindaceae Roots 2309690 Fabaceae Leaves 6138 Hyppochrateaceae Leaves and stem 4650 Apocynaceae Roots 2308107 Caesalpiniaceae Roots 19945 Euphorbiaceae Roots 2288053 Vitaceae Roots 18546 Cochlospermaceae Roots 2288334 Sterculiaceae Bark 11772 Combretaceae Roots, leaves and stem 113612 Caesalpiniaceae Young leaves 115451 Poaceae Leaves 66252 Mimosaceae Stem bark 68854 Fabaceae Roots 2314388 Rubiaceae Leaves 39365 Moraceae Stem bark 2308048 Boraginaceae Leaves 2309989 Euphorbiaceae Leaves 2303193 Rubiaceae Leaves and stem 16507 Meliaceae Stem bark 2309941 Bignoniaceae Roots 2316413 Apocynaceae Leaves 113251 Asclepiadaceae Leaves 1774 Fabaceae Leaves 63592 Ochnaceae Bark 2313051 Sapotaceae Roots 115154 Mimosaceae Roots and stem bark 2177601 Euphorbiaceae Whole plant 8693 Euphorbiaceae Leaves 2177703 Verbenaceae Roots 2291444 Meliaceae Roots 113985 Anacardiaceae Roots 70889 Polygalaceae Roots 2308860 Myrtaceae Stem bark 2308288 Loranthaceae Leaves 20656 Euphorbiaceae Leaves and stem bark 19621 Asteraceae Leaves 2316528 Verbenaceae Leaves and stem bark 2293337 Olacaeae Roots Table 2. Mortality rates of resistant larvae of Anopheles gambiae and Culex quinquefasciatus in the presence of active plant species Mosquito Concentrations Mortality [+ or -] S.D. species (ppm) 0.5 h 1 h Control (DMSO) 0 [+ or -] 0 0 [+ or -] 0 Anopheles Phyllanthus gambiae amarus 1000 28.33 [+ or -]7.64 83.33 [+ or -] 7.64 500 23.33 [+ or -]7.64 70 [+ or -] 1 250 16.67 [+ or -] 7.67 18.33 [+ or -] 7.64 125 0 [+ or -] 0 0 [+ or -] 0 62.5 0 [+ or -] 0 0 [+ or -] 0 31.2 0 [+ or -] 0 0 [+ or -] 0 Cissus populnea 1000 33.33 [+ or -] 7.64 78 [+ or -] 7.64 500 28.33 [+ or -] 7.64 73 [+ or -] 1.00 250 0 [+ or -] 0 11.67 [+ or -] 2.89 125 0 [+ or -] 0 0 [+ or -] 0.00 62.5 0 [+ or -] 0 0 [+ or -] 0 31.2 0 [+ or -] 0 0 [+ or -] 0 Cochlospermum planchonii 1000 0 [+ or -] 0 0 [+ or -] 0 500 0 [+ or -] 0 0 [+ or -] 0 250 0 [+ or -] 0 0 [+ or -] 0 125 0 [+ or -] 0 0 [+ or -] 0 62.5 0 [+ or -] 0 0 [+ or -] 0 31.2 0 [+ or -] 0 0 [+ or -] 0 Culex Cochlospermum quinque- planchonii fasciatus 1000 0 [+ or -] 0 0 [+ or -] 0 500 0 [+ or -] 0 0 [+ or -] 0 250 0 [+ or -] 0 0 [+ or -] 0 125 0 [+ or -] 0 0 [+ or -] 0 62.5 0 [+ or -] 0 0 [+ or -] 0 31.2 0 [+ or -] 0 0 [+ or -] 0 Mosquito Mortality [+ or -] S.D. species 6 h 12 h 0 [+ or -] 0 0 [+ or -] 0 Anopheles gambiae 100 [+ or -] 0 100 [+ or -] 0 100 [+ or -] 0 100 [+ or -] 0 66.67 [+ or -] 7.64 100 [+ or -] 0 5[+ or -]0 15[+ or -]0 6.67 [+ or -] 2.89 8.33 [+ or -] 1 0 [+ or -] 0 0 [+ or -] 0 100 [+ or -] 0 100 [+ or -] 0 100 [+ or -] 0 100 [+ or -] 0 11.67 [+ or -] 2.89 81.67 [+ or -]10.41 1.67 [+ or -] 2.89 3.33 [+ or -] .5.77 0 [+ or -] 0 0 [+ or -] 0 0 [+ or -] 0 0 [+ or -] 0 11.67 [+ or -] 7.64 76.67 [+ or -] 2.89 8.33 [+ or -] 2.89 71.67 [+ or -] 2.89 3.33 [+ or -] 2.89 66.67 [+ or -] 2.89 3.33 [+ or -] 2.89 18.33 [+ or -] 2.89 0 [+ or -] 0 0 [+ or -] 0 0 [+ or -] 0 0 [+ or -] 0 Culex quinque- fasciatus 25 [+ or -] 0 83.33 [+ or -] 7.64 16.67 [+ or -] 2.89 75 [+ or -] 1 0 [+ or -] 0 20[+ or -] 1 0 [+ or -] 0 0 [+ or -] 0 0 [+ or -] 0 0 [+ or -] 0 0 [+ or -] 0 0 [+ or -] 0 Mosquito Mortality [+ or -] S.D. species 24 h 0 [+ or -] 0 Anopheles gambiae 100 [+ or -] 0 100 [+ or -] 0 100 [+ or -] 0 35[+ or -]0 33.33 [+ or -] 2.89 0 [+ or -] 0 100 [+ or -] 0 100 [+ or -] 0 100 [+ or -] 0 6.67 [+ or -] 7.64 0 [+ or -] 0 0 [+ or -] 0 100 [+ or -] 0 100 [+ or -] 0 100 [+ or -] 0 23.33 [+ or -].2.89 0 [+ or -] 0 0 [+ or -] 0 Culex quinque- fasciatus 100 [+ or -] 0 100 [+ or -] 0 25 [+ or -]1 0 [+ or -] 0 0 [+ or -] 0 0 [+ or -] 0 S.D. : Standard deviation. Table 3. [LC.sub.50] and [LC.sub.95] (ppm) of ethanol extracts of active plant species on III and IV instar larvae of Anopheles gambiae and Culex quinquefasciatus Plant species Plant parts Anopheles gambiae Sensitive strain Kissumu [LC.sub.50] [LC.sub.95] Cochlospermum planchonii Roots 80 22.22 Phyllanthus amarus Whole plant 80 22.22 Heliotropium indicum Leaves 180 342 Cissus populnea Roots 80 22.22 Vitex grandifolia Leaves 180 22.22 Vitex grandifolia Stem bark 180 342 Plant species Anopheles gambiae Resistant strain [LC.sub.50] [LC.sub.95] Cochlospermum planchonii 180 342 Phyllanthus amarus 180 342 Heliotropium indicum 370 703 Cissus populnea 180 342 Vitex grandifolia 370 703 Vitex grandifolia 370 703 Plant species Culex quinquefasciatus Resistant strain [LC.sub.50] [LC.sub.50] Cochlospermum planchonii 370 703 Phyllanthus amarus ND ND Heliotropium indicum ND ND Cissus populnea ND ND Vitex grandifolia ND ND Vitex grandifolia ND ND ND = Not determined. Table 4. LC95 and LC50 (ppm) of chloroform and hexane fractions Plant species Mosquitos Hexane fraction species [LC.sub.95] [LC.sub.95] Cochlospermum Anopheles 342 180 planchonii gambiae Cochlospermum Culex 342 180 planchonii quinquefasciatus Cissus Anopheles 342 180 populnea gambiae Phyllanthus Anopheles 342 180 amarus gambiae Plant species Mosquitos Chloroform fraction species [LC.sub.95] [LC.sub.95] Cochlospermum Anopheles 703 370 planchonii gambiae Cochlospermum Culex 703 370 planchonii quinquefasciatus Cissus Anopheles 703 370 populnea gambiae Phyllanthus Anopheles 703 370 amarus gambiae Table 5. Possible compounds present in fractions of the most active plants Plant fractions Pre-derivatization Rf Visible 254 nm 366 nm Cissus 0.65 Visible Blue populnea (Chloroform) Cissus 0.65 Visible Blue populnea (Hexane) Phyllanthus 0.65 Visible Violet amarus 0.70 Orange (Chloroform) 0.08 Orange Phyllanthus 0.65 Green Visible Orange amarus Orange (Hexane) Plant fractions Post-derivatization Godin Folin-Ciocalteu Visible 366 nm Rf Visible Rf Cissus populnea Blue 0.53 (Chloroform) Violet 0.56 Blue 0.59 Cissus 0.65 populnea Violet 0.8 (Hexane) Violet 0.56 Blue 0.36 Blue 0.8 Blue 0.59 Phyllanthus amarus (Chloroform) Blue 0.56 Blue 0.53 Phyllanthus 0.65 amarus (Hexane) Violet 0.79 Orange 0.69 Yellow 0.56 Blue 0.8 Blue 0.59 Blue 0.53 Plant fractions Post-derivatization Dragendorff KOH Visible Rf Visible 366 nm Rf Cissus populnea (Chloroform) Yellow 0 Cissus 0.65 populnea (Hexane) Orange 0.59 Phyllanthus amarus (Chloroform) Red 0.71 Yellow 0 Phyllanthus 0.65 amarus (Hexane) Red 0.71 Plant fractions Possible types of compounds Cissus ND populnea Monoterpenoids (Chloroform) Monoterpenoids Polyphenols Anthrones Cissus 0.65 ND populnea Monoterpenoids (Hexane) Monoterpenoids Monoterpenoids Polyphenols Polyphenols Alkaloids Phyllanthus ND amarus ND (Chloroform) ND Monoterpenoids Polyphenols Anthraquinones Anthrones Phyllanthus 0.65 ND amarus ND (Hexane) Monoterpenoids Flavonoids Flavonoids Polyphenols Polyphenols Polyphenols Anthraquinones ND : Not determined.
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|Author:||Azokou, Alain; Kone, Mamidou W.; Koudou, Benjamin G.; Bi, Honora F. Tra|
|Publication:||Journal of Vector Borne Diseases|
|Date:||Jun 1, 2013|
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