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Larvicidal potential of some plants from west Africa against Culex quinquefasciatus (Say) and anopheles gambiae giles (Diptera: Culicidae).

INTRODUCTION

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.

Larval bioassays

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

RESULTS

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).

DISCUSSION

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.

CONCLUSION

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.

ACKNOWLEDGEMENTS

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.

REFERENCES

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(27.) Aouinty B, Oufara S, Mellouki F, Mahari S. Evaluation preliminaire de l'activite larvicide des extraits aqueux des feuilles du ricin (Ricinus communis L.) et du bois de thuya (Tetraclinis articulata Vahl.) sur les larves de quatre moustiques culicudes : Culex pipiens (Linn.), Aedes caspius (Pallas), Culiseta longiareolata (Aitken) et Anopheles maculipennis (Meigen). Biotechnol Agron Soc Environ 2006; 10: 67-71.

(28.) Kannaathsan K, Senthilkumar A, Chandrasekaran M, Venkatesalu V. Differential larvicidal efficacy of four species of Vitex against Culex quinquefasciatus larvae. Parasitol Res 2007; 101: 1721-3.

(29.) Karunamoorthi K, Ramanujam S, Rathinasamy R. Evaluation of leaf extracts of Vitex negundo L. (Family: Verbenaceae) against larvae of Culex tritaeniorhynchus and repellent activity on adult vector mosquitoes. Parasitol Res 2008; 103: 545-50.

Alain Azokou [1,2], Mamidou W. Kone [1,2], Benjamin G. Koudou [1,2,3] & Honora F. Tra Bi [1]

[1] UFR Sciences de la Nature, Universite Nangui Abrogoua, Abidjan, Cote d'Ivoire, [2] Centre Suisse de Recherches Scientifiques en Cote d'Ivoire, Abidjan, Cote d'Ivoire; [3] 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.

E-mail: mamidou.kone@csrs.ci

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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Article Details
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Author:Azokou, Alain; Kone, Mamidou W.; Koudou, Benjamin G.; Bi, Honora F. Tra
Publication:Journal of Vector Borne Diseases
Article Type:Report
Geographic Code:6COTE
Date:Jun 1, 2013
Words:5104
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