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Lippia javanica (Burm F) Spreng: Its general constituents and bioactivity on mosquitoes

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  • Ministry of Health and Child Care, Zimbabwe

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Mosquito repellent plants are used in the rural areas of Zimbabwe despite the fact that very few of them have been biologically evaluated. Leaves of the plant Lippia javanica, were collected from Mumurwi village, Zimbabwe and evaluated for repellency against laboratory reared Aedes aegypti mosquitoes. Major plant compounds were identified using Thin Layer Chromatography (TLC) and Mass Spectrometry (MS). Fraction 'A' contained coumarins, flavonoids and essential oils and offered a protection time of 8 and 5.5hrs in choice and non-choice experiments respectively. Fraction 'B1' contained flavonoids with a protection time of 1 and 0.5hrs in choice and non choice experiments respectively. Fraction 'B2' contained coumarins and essential oils and offered a protection time of 2hrs in either test. No major compounds were identified from the following fractions: 'C1', 'C2', 'D1', 'E1', 'E2', 'F1' and 'F2' and all of them failed to give 100% repellence. The 'C1' supernatant fraction contained coumarins and provided protection from mosquito bites for 1 and 0.5 hrs in choice and non-choice experiments respectively. Fraction 'C2' did not have the major compounds but gave a protection time of 1 hr in either experiment. Fraction 'D2' contained essential oils only and it provided a protection time of 2.5hrs in choice experiments. Analysis by MS showed the presence of alpha pinene, 1,3-5 cycloheptatriene, beta phellandrene, (+)-2-carene, 3-carene, eucalyptol and caryophyllene oxide. L. javanica offered protection from mosquito bites for 8hrs (choice) and 5.5hrs (non choice experiments). The combined presence of coumarins, flavonoids and essential oils have an additive effect compared with individual plant fractions.
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Tropical Biomedicine 26(1): 85–91 (2009)
Lippia javanica (Burm F) Spreng: its general constituents
and bioactivity on mosquitoes
Nzira Lukwa1, Per Mølgaard2, Peter Furu3 and Claus Bøgh3
1 National Institute of Health Research, P. O. Box CY573, Causeway, Harare, Zimbabwe;
2 Danish University of Pharmaceutical Science, Department of Medicinal Chemistry, Universitetsparken 2, DK
2100, Copenhagen Ø, Denmark;
3 Danish Bilharziasis Laboratory, Jaegersborg Alle’ 1D, Charlottenlund, Denmark
Email: nziraa33@yahoo.co.uk
Received 14 January 2009, received in revised form 3 March 2009; accepted 5 March 2009
Abstract. Mosquito repellent plants are used in the rural areas of Zimbabwe despite the fact that
very few of them have been biologically evaluated. Leaves of the plant Lippia javanica, were
collected from Mumurwi village, Zimbabwe and evaluated for repellency against laboratory reared
Aedes aegypti mosquitoes. Major plant compounds were identified using Thin Layer
Chromatography (TLC) and Mass Spectrometry (MS). Fraction ‘A’ contained coumarins, flavonoids
and essential oils and offered a protection time of 8 and 5.5hrs in choice and non-choice
experiments respectively. Fraction ‘B1’ contained flavonoids with a protection time of 1 and 0.5hrs
in choice and non choice experiments respectively. Fraction ‘B2’ contained coumarins and essential
oils and offered a protection time of 2hrs in either test. No major compounds were identified from
the following fractions: ‘C1’, ‘C2’, ‘D1’, ‘E1’, ‘E2’, ‘F1’ and ‘F2’ and all of them failed to give 100%
repellence. The ‘C1’ supernatant fraction contained coumarins and provided protection from
mosquito bites for 1 and 0.5 hrs in choice and non-choice experiments respectively. Fraction ‘C2
did not have the major compounds but gave a protection time of 1 hr in either experiment. Fraction
‘D2’ contained essential oils only and it provided a protection time of 2.5hrs in choice experiments.
Analysis by MS showed the presence of alpha pinene, 1,3-5 cycloheptatriene, beta phellandrene,
(+)-2-carene, 3-carene, eucalyptol and caryophyllene oxide. L. javanica offered protection from
mosquito bites for 8hrs (choice) and 5.5hrs (non choice experiments). The combined presence of
coumarins, flavonoids and essential oils have an additive effect compared with individual plant
fractions.
INTRODUCTION
Plants have to survive by all means in the
vicinity of predators and threats. Some plants
have thorns in order to deter herbivores,
which feed on them to ensure species
survival or they emit odours with a deterrent
effect on insects (Reichardt et al., 1990).
These defence mechanisms have been
utilised by man for the development of plant
– based drugs and chemicals. Watt &
Brandiwjk (1962) listed plant remedies and
pharmacological products. Other plants of
importance in traditional medicine are now
being sold as herbal medicines e.g. valerian
(Valeriana officinalis), cammone
(Chamomilla recutita) and garlic (Allium
salivum) (Tunon, 1995).
Lippia javanica is known as fever tea/
lemon bush and has dense creamy white,
flower heads. It grows in open veld, in the
bush, grassland on hillsides and stream
banks, and as a constituent of the scrub on
the fringes of forest. The plant is widely
distributed in Zimbabwe, Ethiopia, East
Africa and South Africa. Manenzhe et al.
(2004) studied the chemistry of the volatile
oil of L. javanica and concluded that it
contains several terpenoids of which 3-
methyl-6-(1-methyl-ethylidene)-cyclohex-2-
en-1-one (1) was the major component.
Results suggested that the oil was effective
86
in inhibiting cultures of Escherichia coli,
Bacillus subtilis and Staphylococcus aureus
(Manenzhe et al., 2004). Mokoka (2006)
carried out a chemical analysis L. javanica
by using Gas Liquid Chromatography (GLC)
and Mass Spectrometry (MS) and concluded
that the essential oils were alpha pinene,
sebinen, myrcene, 1.8 myrcene, ipsenone,
ipsedienone, beta caryophyllene and
germacrene D. The leaves of Lippia
origanoides are widely used as a spice in
Brazil and analysis by GLC and MS showed
a high content of oxygenated mono-terpenes,
carvacrol and thymol (Oliveira et al., 2007).
Loy et al. (2001) studied the chemical
composition of the essential oil of
Calycotome villosa leaves and isolated
falcarinol and some alcohols, terpenes, furan
derivatives, and paraffins. A total of 13
alkaloids and falcarinol were identified in the
chloroform fraction of the basic methanol
extract (Loy et al., 2001). A total of 6
flavonoids and 4 anthra-quinones were
isolated in the chloroform fraction after
acidification of the basic methanol extract
(Loy et al., 2001).
The use of repellents to avoid man/
mosquito contact is not a new concept and
is well documented (Batchelor, 1930). People
use mosquito control methods in order to
avoid mosquito bites and disease
transmission. Ethno - botanical studies were
conducted in order to collect information on
traditional uses of plants against mosquitoes
and other pests (Curtis et al., 1990; Lukwa et
al., 1999). A wide range of plants is used
against mosquitoes even though a few of
them have been biologically evaluated.
Such information is useful for planning
conservation programs targeted at natural
resources of medicinal value. Thus, people
could be discouraged from cutting down
plants perceived to be effective against
mosquitoes but proved biologically not to be
so. Plants are used to supplement several
disease control programs in Africa and
elsewhere because they are relatively cheap
and locally available.
Mosquito repellence has been ascribed
to the presence of essential oils from
camphor, citronella, lemongrass, clove,
thyme, geranium, bergamot, pine,
wintergreen, pennyroyal and eucalyptus
(Fradin, 1998). Lippia javanica and
Ocimum canum ethanolic extracts repelled
mosquitoes for 5hrs (Lukwa et al., 1996). On
the other hand, steam distilled essential oils
from Artemesia afra, Lantana angiolensis
and Syzygium huillense failed to inhibit
mosquitoes from biting (Lukwa et al., 2000).
MATERIALS AND METHODS
Mosquitoes
Three to five day old laboratory reared
female Aedes aegypti mosquitoes (colony
from the Danish Bilharziasis Laboratory)
were used in all the experiments. The
mosquitoes were reared in the insectary at
70-80% Relative Humidity (RH), 25ºC±2ºC
and a photo period of 12:12hrs light;
darkness. Ground dog biscuits that were
supplemented with yeast were used to rear
the larvae and female adult mosquitoes were
fed on a guinea pig. The mosquitoes were
starved for 24 hours before commencing the
studies.
Collection of plant material
Lippia javanica (Burm.f.) Spreng
(Verbenaceae) was collected from Musana
Communal Lands (17º 31’S, 22º 31’E) and
forwarded to the Zimbabwe National
Botanical Garden for the confirmation of the
plant species. A specimen was deposited as
a reference.
Preparation of plant material
The leaves of L. javanica were dried in the
shed by placing them in a single layer for 4
days before grinding them to powder. The
powder was placed in absolute ethanol by
weighing 100 grams of it into 1 litre of ethanol
(extraction was repeated 5 times) and the
preparation was placed for sonication
overnight. The extraction proceeded as
shown in Figure 1 using 50ml of ether. When
the ‘A‘ fraction was extracted in ether-ether
at pH 8, the aqueous solution gave 5 fractions
as follows: ‘B1’, ‘C2’ and ‘C2’, ‘C1’ supernatant
and ‘C2’ precipitate. The organic phase of
fraction ‘A’ gave 7 fractions namely ‘B2’, ‘D1’,
‘D2’, ‘E1’, ‘E2’, ‘F1’ and ‘F2’. According to the
87
fractionation scheme in Figure 1, ‘C1’ fraction
ought to contain mostly hydrophilic neutral
and / or charged compounds with a low
vapour pressure. Acetone precipitation was
done in order to remove carbohydrates. The
‘C2’ fraction was expected to contain mainly
neutral / or acidic compounds. The ‘F2
fraction was expected to contain lipophilic
substances with boiling points above 200ºC
that should be phenolic in nature and contain
fatty acid esters.
Distillation of essential oils
Essential oils from the leaves of L. javanica
were steam distilled by measuring 10 grams
of the plant and placing them into an
Erhlenmayer conical flask containing 100ml
distilled water. The flask was heated to
boiling at 120ºC – 140ºC. About 300ul of
toluene was used to wash the wall of the
collecting funnel and the resultant oil was
made up to 5ml toluene.
Mass spectrometry (MS)
The following parameters were used: air
(50kPa), hydrogen (60kPa), primary gas
(400kPa), carrier 2 gas (300kPa), make up
gas (65kPa), detector and injector tempera-
ture (220ºC), column initial temperature
(60ºC), initial time (10 minutes), programme
rate (5ºC/min), maximum temperature
(185ºC), running time (35 minutes) and mass
detection range (30-300). A total of 0.3ul of
the essential oil was injected into the MS.
Figure 1. Preparation of plant fractions.
88
Identification of major plant compounds
A total of 10ul of each fraction was applied
to a silica gel 60 F254 Thin Layer
Chromatography (TLC) plate measuring
5cm by 7.5cm. For the determination of
coumarins, the toluene-ethyl acetate solvent
system was used with methanolic Potassium
hydroxide as the spraying reagent. The
standards were coumarin, scopelelin and
bergapten. Flavonoids were detected in an
ethyl acetate-formic acid-glacial acetic acid-
water solvent system and detection was
done using NST Natural products. The
standards were chlorogenic acid, caffeic
acid, rutin and hyperoside. Essential oils
were detected using the toluene-ethyl
acetate solvent system and Vanillin sulphuric
acid reagent was used for detection. Carvon,
geranyl acetate, menthol and geranol were
used as standards.
Choice experiments
A special glove with an opening measuring
5cm by 5cm was used for all experiments.
The area was cut out and the edges lined with
masking tape. Plant extracts were prepared
to give a concentration of 5mg/cm2. Mosquito
cages made from perspex were used and
these had an open sleeve for introducing and
retrieving mosquitoes. A total of 50 starved
female Aedes aegypti mosquitoes were
released in the mosquito cage and left to
acclimatise for 1 hour. Two hands of the same
person were placed in the cage at the same
time (one was treated and the other one was
not for choice experiments and one hand
only for the non choice experiments ) for one
minute. The number of mosquitoes probing
to bite was recorded, excluding mosquitoes
that took off before biting. Re-testing was
done every 30 minutes until repellence was
lost. This was done for all fractions, including
the control that had ethanol only.
Repellence tests were done following the
test method previously described by Curtis
et al. (1990) and Tunon (1995). Percentage
mosquito repellence was calculated
following the method previously described
by Mehr et al. (1985). The calculation was
carried out as follows:
Where
_
B c = mean number of bites on control
and
_
B t = mean number of bites on treated.
Data analysis
Data was analysed using the Analysis Of
Variance (ANOVA) method at 95%
confidence limit.
RESULTS
The major constituents of L. javanica
extract are shown in Table 1. MS was done
on steam distilled essential oils from L.
javanica and the results are shown in
Figure 2. 1,3,5 Cycloheptatriene was the
most abundant and it constituted 41.97% of
all the constituents as compared to alpha
pinene (6.77%). Beta phellandrene
constituted 1.22% of all the constituents and
(+)-2-Carene was 0.54%. Eucalyptol
constituted 5.77% of the compounds and 3-
Carene was 1.11%. Caryophyllene oxide and
Alloparinol constituted 0.97% and 0.33%
respectively.
In experiments where mosquitoes were
not given a choice, fraction ‘A’ had a
protection time of 5.5 hours from mosquito
bites (Table 1). The mean protection times
in choice experiments were 1.19 hours and
those in no choice experiments were 0.73
hours and the results were not significantly
different using t-test (p=0.543698).
In choice experiments, fractions
containing flavonoids and coumarins offered
protection from mosquito bites for 1 hour
and the results are shown in Figure 3. The
longest protection time was realised with
fractions containing essential oils,
coumarins and flavonoids. When non-choice
experiments were conducted, protection
times were less than those obtained in choice
experiments (Table 1).
DISCUSSION
The process of fractionation applied to L.
javanica produced different fractions that
were analysed. Our results showed that the
‘A‘ fraction contained coumarins, flavonoids
and essential oils as compared to the basified
89
Table 1. Protection times of L. javanica on Ae. aegypti mosquitoes
Fraction Major plant compounds Non choice Choice
experiments experiments
A Coumarins, flavonoids and essential oils 5.5 hours 8 hours
B1Flavonoids 0.5 hour 1 hour
B2Coumarins and essential oils 2 hours 2 hours
C1——
C1 supernatant Coumarins 0.5 hour 1 hour
C1 precipitate Coumarins and flavonoids ——
C21 hour 1 hour
D1——
D2Essential oils 2.5 hours
E1——
E2——
F1——
F2——
Figure 2. Compounds detected by mass spectrometry.
90
aqueous solution of ‘ B1‘ that had flavonoids
only. Loy et al. (2001) detected flavonoids
after acidification of the basic methanol
extract of C. villosa leaves but we failed to
detect any flavonoids after undergoing the
same process in fractions ‘E1’, ‘E2’, ‘F1’ and
‘F2’ of L. javanica. The resultant aqueous
solution from ‘ B1’ (C1) did not have the major
compounds and this might be due to the
basic nature of the extract (pH 8). However,
after precipitation, the supernatant
contained coumarins and the precipitate
contained coumarins and flavonoids. Our
results suggest that the process of
precipitation is required in order to make the
detection of major compounds easy.
Flavonoids and essential oils could not be
detected in fractions ‘C1’, ‘C2’, ‘D1’, ‘E1’, ‘E1’,
‘F1’ and ‘F2’ and only coumarins were
detected in ‘B1’ and ‘C1’ supernatant. Our
results suggest that individual fractions do
not contain all major compounds found in
the parent plant. Our results on MS revealed
the presence of 1,3,5 cycloheptatriene, alpha
pinene, beta phellandrene, (+)-2-carene,
eucalyptol, 3-carene, caryophyllene oxide
and alloparinol. Studies by Mokoka (2006)
showed the presence of alpha pinene and
caryophyllene in L. javanica.
Experiments were conducted in
situations were mosquitoes were either
given a choice of biting one treated hand only
or a combination of a treated and untreated
hand at the same time. Our results suggest
that more protection from mosquito bites is
obtained when mosquitoes have a choice
than when there is no choice at all. The
results also indicate that an 8-hour protection
time can be obtained with the main
preparation (fraction ‘A’) when there is a
choice than when there is no choice (5.5).
Our results compare well with studies done
on DEET as reported by studies performed
by Tunon (1995) and Curtis et al. (1990).
Lukwa et al. (1996) recorded a repellent
activity of O. canum of 5 hours and our
results on choice experiments appear
superior. Curtis et al. (1990) ascribed
mosquito repellence properties to the
presence of essential oils but our results
suggest that the oils alone are not very
effective since they give a short repellent
period and this has been observed by Lukwa
et al. (2000).
The level of protection from mosquito
bites becomes less important from fraction
‘A’ to E2, suggesting that all the compounds
in a plant have a synergistic effect. It was
also interesting to note that fractions where
no major compounds were detected did not
offer any protection from mosquito bites.
Figure 3. Mosquito repellence in choice and no choice experiments (n=5; SD=2.37641)
91
Acknowledgements. This study could
have not been possible without financial
support from DANIDA. We would like to
acknowledge technical support provided by
Mr Peter Mashamba, Mr Johane Muchenje
and Miss Bente Gauguin. The Director of the
National Institute for Health Research, Dr
S.L. Mutambu offered support during the
study.
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... (Verbenaceae) (Figure 1(a)) has a long history of traditional uses in tropical Africa as indigenous herbal tea or tisane (Figure 1(b)), refreshing beverage, or food additive based on its perceived health and medicinal properties. Lippia javanica is rich in volatile oil, particularly caryophyllene, carvone, ipsenone, ipsdienone, limonene, linalool, myrcene, myrcenone, ocimenone, p-cymene, piperitenone, sabinene, and tagetenone [1][2][3][4][5]. Research by Viljoen et al. [3] revealed that the essential oil profiles of L. javanica are characterized by inter-and intraspecies variations because they are produced by different metabolic pathways. ...
... Leaves, twigs, and whole plant Used in washes and poultices or as steam or sprayed or burnt to chase away mosquitoes Ethiopia, South Africa, and Zimbabwe [4,26,34,[47][48][49][50][51] Malaria Leaves, roots Decoction taken orally Mozambique, South Africa [17,33,52] Prophylactic against malaria Leaves Infusion taken orally South Africa [40] Evidence-Based Complementary and Alternative Medicine 5 [6] and leafy vegetable in India [12,13]. Lippia javanica is popular as herbal tea, particularly in Botswana, South Africa, and Zimbabwe [7][8][9][10][11]. ...
... In India, the whole plant is used to repel lice in poultry [61]. In South Africa and Zimbabwe, whole plant or leaves are burnt to repel mosquitoes [4,34,35,48,49,58]. In South Africa and Zimbabwe, L. javanica is widely used to get rid of ticks and other ectoparasites; for example, ticks are sprayed with crushed leaves mixed with water or twigs are used as bedding in fowl runs [58][59][60]. ...
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Lippia javanica occurs naturally in central, eastern, and southern Africa and has also been recorded in the tropical Indian subcontinent. The potential of L. javanica as herbal or recreational tea and herbal medicine and its associated phytochemistry and biological properties are reviewed. The extensive literature survey revealed that L. javanica is used as herbal tea and has ethnomedicinal applications such as in colds, cough, fever, malaria, wounds, diarrhoea, chest pains, bronchitis, and asthma. Multiple classes of phytochemicals including volatile and nonvolatile secondary metabolites such as alkaloids, amino acids, flavonoids, iridoids, and triterpenes as well as several minerals have been identified from L. javanica . Scientific studies on L. javanica indicate that it has a wide range of pharmacological activities which include anticancer, antiamoebic, antidiabetic, antimalarial, antimicrobial, antioxidant, antiplasmodial, and pesticidal effects. Although many of the traditional uses of L. javanica have been validated by phytochemical and pharmacological studies, there are still some gaps where current knowledge could be improved. Lippia javanica is popular as both herbal and recreational tea, but there is need for more precise studies to evaluate the safety and clinical value of its main active crude and pure compounds and to clarify their mechanisms of action.
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... Their occurrence is also well reported in West Godavari, Visakhapatnam, and Vizianagaram districts of Andhra Pradesh and in Ranga Reddy district of Telangana state of India (Narayana and Narasimharao 2015). Its usual habitats are open fields, bushy grasslands on the hillside, stream banks, and as part of the scrub along forest margins (Lukwa et al. 2009). The leaves are hairy on both sides and are 3-4 cm long. ...
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... Their occurrence is also well reported in West Godavari, Visakhapatnam, and Vizianagaram districts of Andhra Pradesh and in Ranga Reddy district of Telangana state of India (Narayana and Narasimharao 2015). Its usual habitats are open fields, bushy grasslands on the hillside, stream banks, and as part of the scrub along forest margins (Lukwa et al. 2009). The leaves are hairy on both sides and are 3-4 cm long. ...
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Lippia javanica is a multipurpose medicinal plant of the Verbenaceae family, which is commonly known for its volatile and essential oil compounds with numerous pharmaceutical applications. Due to medicinal importance, the plant was overexploited, which has been resulted in the rare availability of plant material. Through this study, an efficient and reproducible protocol was established for its in vitro micropropagation using nodal explants. Maximum number of shoots (7.11 ± 0.12) per nodal explant was induced on Murashige and Skoog (MS) medium augmented with 2.0 mg L⁻¹ of 6-benzylaminopurine (BAP). When combination of phytohormones tested, highest number of multiple shoots (25.76 ± 0.37) was obtained on 2.0 mg L⁻¹ of BAP and 0.5 mg L⁻¹ of kinetin (Kn). Rooting of shoots with good response and maximum number of roots (21.19 ± 0.54) per explant was induced on half-strength MS medium with 1.0 mg L⁻¹ of indole-3-butyric acid (IBA). Well rooted in vitro raised plantlets were hardened in paper cups possessing soilrite. The hardened plantlets were initially maintained in the pots for 3 weeks and finally acclimatized to soil conditions with an 80% of survival rate. The micro-morpho-anatomical characterization of in vitro and ex vitro hardened plantlets revealed detailed developmental information about structural features of leaf, stem, and the type and density of trichomes while adapting to natural conditions. Similarly, the genetic fidelity of micropropagated plantlets were screened by SCoT and ISSR molecular markers and the results confirmed the true to type nature of regenerated plantlets with the mother plant.
... It promotes bone growth and repair, 855 and has insecticidal and repellent qualities. [856][857][858] Terpinene can be found in tea tree oil and some other plants. It is often used in the cosmetic and food industries. ...
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... Combining various pesticidal compounds will also allow for the exploitation of synergistic activity which may result in enhanced activity and hence reduced applications of the pesticide. Studies by Innocent and Hassanali (2015), Lukwa et al. (2009) andMukandiwa et al. (2016b) in which crude extracts had better activity compared to the isolated compounds supports this notion. Standardizing such extracts is a possible next step to their pharmaceutical development and commercialization. ...
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Lippia origanoides H.B.K. (Verbenaceae) is a plant known in Oriximiná (Brazil) as “Salva-de-Marajó”. Its leaves are widely used as of a spice in cooking and in traditional medicine. The chemical composition of the essential oil obtained from its leaves, analyzed by GC and GC/MS, showed a high content of oxygenated monoterpenes (66.0%), carvacrol (38.6%) and thymol (18.5%) being the major constituents. Considering that previous studies on the same plant species showed carvacrol as a trace or absent compound, we propose the existence of a new chemotype for this species. A high carvacrol content in the essential oil determines the plant’s suitability for the preparation of oregano condiment. The antimicrobial activity of this essential oil was determined by the drop diffusion method, showing highly significant inhibition zones for all microorganisms tested.
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Seven microcapsule formulations and two polymer formulations of deet were tested on white rabbits for their repellency against the mosquito, Aedes aegypti. Two microcapsule formulations and one polymer formulation provided more than 80% protection for 12 hours. Results demonstrated that the protection period of deet can be extended through controlled-release techniques.
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This paper is intended to provide the clinician with the detailed and scientific information needed to advise patients who seek safe and effective ways of preventing mosquito bites. For this review, clinical and analytical data were selected from peer-reviewed research studies and review articles, case reports, entomology texts and journals, and government and industry publications. Relevant information was identified through a search of the MEDLINE database, the World Wide Web, the Mosquito-L electronic mailing list, and the Extension Toxicology Network database; selected U.S. Army, U.S. Environmental Protection Agency, and U.S. Department of Agriculture publications were also reviewed. N,N-diethyl-3-methylbenzamide (DEET) is the most effective, and best studied, insect repellent currently on the market. This substance has a remarkable safety profile after 40 years of worldwide use, but toxic reactions can occur (usually when the product is misused). When DEET-based repellents are applied in combination with permethrin-treated clothing, protection against bites of nearly 100% can be achieved. Plant-based repellents are generally less effective than DEET-based products. Ultrasonic devices, outdoor bug "zappers," and bat houses are not effective against mosquitoes. Highly sensitive persons may want to take oral antihistamines to minimize cutaneous reactions to mosquito bites.
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To assess peoples' perceptions and knowledge about malaria transmission and control with special reference to the use of plants as mosquito repellents. Cross sectional study. Mandeya ward "A" (33 degrees E and 18 degrees 30' S), Honde Valley, Zimbabwe. 226 household heads present when interview was conducted. Mosquito control methods, spraying coverage, plants used to repel mosquitoes and reasons for using them. 215 (95.0%) of the respondents' homes had been sprayed and their understanding of malaria transmission was not related to compliance with the National Malaria Control Programme (NMCP). Taking mosquito control measures was related to knowledge of malaria transmission, with 24 (75.0%) of those who did not know, taking no measures of their own. The use of plants was mentioned by 50 (23.5%) of the respondents and the reasons given were that they were cheap 43 (86.0%), effective five (10.0%) and locally available two (4.0%). The plant which was mentioned as being used by all age groups was L. javanica 25 (50.0%) and the other plants were used to a lesser extent. Forty six (92.0%) of the people said that they had used plants for mosquito control. The leafy part of the plant was used by 43 (86.0%) and a fresh preparation 43 (86.2%) gave better protection than a dry one. The plants were crushed and applied on the skin by eight people (14.6%), burnt by 36 people (72.8%) and used in their original form by six people (12.6%) and used once per by day 42 people (84.0%). One of the important points to emerge from this study is that, despite widespread knowledge about the morbidity of malaria, understanding about its prevention was generally low and this has negative implications on an integrated control programme.
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The chemical composition of the essential oil and methanol extract of Calycotome villosa (Poiret) Link leaves collected in Sardinia (Italy) has been studied by analytical and spectroscopic methods. Falcarinol and some alcohols, terpenes, furan derivatives, and paraffins have been isolated from the essential oil. Thirteen alkaloids and falcarinol have been identified in the chloroform fraction of the basic methanol extract. Six flavonoids and four anthraquinones have been isolated in the chloroform fraction after acidification of the basic methanol extract. The cytotoxic and antimicrobial activities have also been evaluated. The essential oil, the methanol extract in toto, and the fraction of the basic extract showed strong cytotoxicity, whereas the fraction of the acid extract showed lower cytotoxicity. Furthermore, this fraction showed good antibacterial activity against Staphylococcus aureus, Bacillus lentus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Providencia rettgeri, and Morganella morganii. It can therefore be stated that this plant's cytotoxicity is prevalently due to falcarinol.
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The volatile oil of Lippia javanica was prepared by hydrodistillation of leaves, flowers and stems, and characterized by GC-MS. The major component was 3-methyl-6-(1-methylethylidene)-cyclohex-2-en-1-one. The oil was tested for antimicrobial activity on cultures of Escherichia coli, Bacillus subtilis and Staphylococcus aureus, and found to inhibit E. coli and S. aureus at 1% dilution. The oil was also active against Plasmodium falciparum in micromolar concentrations.