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Nootkatone Is a Repellent for Formosan Subterranean Termite (Coptotermes formosanus)


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We examined the behavior of Formosan subterranean termites toward one of the components of vetiver grass oil, the roots of which manufacture insect repellents. We found nootkatone, a sesquiterpene ketone, isolated from vetiver oil is a strong repellent and toxicant to Formosan subterranean termites. The lowest effective concentration tested was 10 micrograms/g substrate. This is the first report of nootkatone being a repellent to insects.
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Journal of Chemical Ecology, Vol. 27, No. 3, 2001
0 2001 Plenum Publishing Corporation
SUBTERRANEAN TERMITE (Coptotermes formosanus)
Department of Biological Sciences
Department of Entomology
Louisiana State University Agricultural Center
Louisiana Agricultural Experiment Station
Louisiana State University
Baton Rouge, Louisiana
(Received July 31, 2000; accepted November 14, 2000)
Abstract—We examined the behavior of Formosan subterranean termites
toward one of the components of vetiver grass oil, the roots of which
manufacture insect repellents. We found nootkatone, a sesquiterpene ketone,
isolated from vetiver oil is a strong repellent and toxicant to Formosan
subterranean termites. The lowest effective concentration tested was
10 mg
substrate. This is the first report of nootkatone being a repellent to insects.
Key WordsVetiveria zizanioides, vetiver oil, sesquiterpenes, ketones.
The Formosan subterranean termite is the most destructive termite species
wherever it occurs in the world. These termites search for and find cellulose
largely using chemical cues from the wood itself (Amburgey and Smythe,
Reinhard et al.,
1997), and they exhibit similar chemoresponses to a variety of
chemicals. For example, trail-following behavior has been shown to naphtha-
lene, a well-known insect toxicant (Chen et al.,
1998b,c), 2-naphthalenemethanol
(Henderson et al.,
1996), and 2-phenoxyethanol, a component of some ballpoint
inks (Chen et al.,
1998a). Formosan subterranean termites live in a miasma of
chemicals present in their nests, many of which appear to be plant derived (Chen
et al.,
1998b; Henderson et al., 1999). Our recent investigations have focused
*To whom correspondence should be addressed.
on natural plant extracts that may disrupt this insects ability to recruit food
Vetiver grass (Vetiveria zizanioides, Linn Nash), a fast-growing native plant
of India, is a distant relative of maize, sorghum, sugarcane and lemongrass
(National Research Council,
1993). The plant has been used in India for weaving
mats, baskets, fans, sachets, and ornaments that have insect repellent properties.
Clothes moths, head lice, and bedbugs are thought to be repelled by vetiver grass
so fashioned (National Research Council,
1993). The Formosan subterranean
termite, Coptotermes formosanus Shiraki, readily consumes sugarcane, causing
agricultural damage to the crop in some countries (Chen and Henderson,
National Research Council,
1993). Therefore, it was not readily apparent that
termites would be repelled by components of vetiver grass. The compounds in
vetiver oil that repel cockroaches and ies are believed to include a- and b-
vetivone, khusimone, khusistone, zizanal, and epizizanal (Jain et al.,
Preliminary studies using dried vetiver root in a sand substrate (
1 : 10 ratio)
indicated that Formosan subterranean termites were effectively repelled from
tunneling to a food source (Henderson et al., unpublished data). Gas chro-
matographic and mass spectrometric analysis of vetiver oil separated on silica
columns, along with behavioral bioassays, allowed us to identify nootkatone as
a repellent to Formosan subterranean termites.
Extraction of Vetiver Oil from Roots
We examined the extracts from the roots to determine which components of
the oil were repellent. The roots of fresh Louisiana-grown vetiver grass Vetiveria
zizanioides (provided by the Donald O. Heumann Greenhouse and Laboratory,
Poydras, Louisiana) were cleaned, dried at room temperature, and ground with
a blender. Vetiver oil was obtained by petroleum ether extraction of the dried
roots. The components of vetiver oil were isolated by silica column (
2.5 × 20
cm) and eluted with hexane and increasing amounts of methylene chloride. Five
fractions were obtained by eluting with hexaneCH
: 80 : 20 for fraction 1,
70 : 30 for fraction 2, 60 : 40 for fraction 3; 40 : 60 for fraction 4, and 20 : 80
for fraction 5. Examination of sesquiterpenic ketones were visualized for their
intrinsic uorescence under UV light (Andersen,
1970) since they are potential
insect repellents. The fractions detected by UV were further isolated by prepar-
ative TLC (Analtech, Newark, Delaware) using CHCl
as a mobile phase. The
bands were visualized by charring the plate at
120 C after spraying with 50%
sulfuric acid.
Gas chromatographymass spectrometry (GC-MS) was performed on a
Finnigan GCQ (Trace GC
2000 coupled with Polaris MSD). A silica capillary
MS column, DB-5MS (30 m × 0.25 mm × 0.25 mm; J&W Scientic, Folsom,
California), was operated at
60 C for 1 min, increased to 150 C at 2.5 C
held for
15 min at this temperature and increased to 260 C at 5 C
min, where
is was nally held for
10 min. The injector port was operated in splitless mode
250 C, and helium was used as carrier gas at 0.8 m
min. The mass spectral
detector (MSD) was set on full-scan mode (m
z 41400). The authentic stan-
dard of nootkatone (crystalline,
97%) was purchased from Lancaster Synthesis
Inc. (Windham, New Hampshire). Both a- and b-vetivone were kindly provided
by Professor Ekkhard Winterfeldt (Institut f
ur Organische Chemie, Technische
at, Berlin).
Termite Bioassay
1. A three-compartment plastic container (18 × 18 × 4 cm;
Pioneer Packaging Co., North Dixon, Kentucky) was used for the termite bioas-
says. A small hole (
0.5 cm diameter) was melted at the bottom of each of two
inner walls, connecting the bioassay chamber compartments. For testing,
50 mg
of nootkatone was dissolved in
10 ml ethanol as a stock solution. Five concentra-
tions of nootkatone were placed into a sand substrate in the middle compartment
of the biossay chamber:
0 (control), 10, 20, 100, and 200 mg
g sand. Four repli-
cates were conducted for each concentration. For each concentration,
500 g of
blasting sand was mixed with a series of dilutions of the stock solution (except
0 mg
g) in 25 ml of ethanol in a glass pan and dried in a hood for 2 hr.
The following day,
115 g of untreated blasting sand was added to one end of
each compartment (home compartment), and
115 g of treated sand at one of
ve concentrations was added to the middle compartment. The
0-mg concen-
tration was treated only with
25 ml of ethanol. Filter paper (Whatman No. 1,
2.3 cm diameter) was dried at 70 C for 3 hr and cooled to room temperature
30 min before weighing. A weighed lter paper with 200 ml distilled water
added was placed in the third compartment farthest from the introduction end.
Ten milliliters of distilled water was added to the treated and untreated sand in
the other compartments just prior to the introduction of termites. Fifty workers
and ve soldiers of Formosan subterranean termites from a large colony col-
lected in Algiers, Louisiana, on November
18, 1997, were placed in the home
compartment. The containers were covered with lids and kept in a dark incu-
bator at
29 C. On day 16, each apparatus was dismantled, living termites were
counted, and lter papers were cleaned, dried at
70 C for 3 hr, cooled for 30
min, and weighed. Consumption was calculated as the difference between the
weight of lter paper before and after the
16-day incubation. The tunnels ter-
mites constructed in the sand were copied using a scanner for measurement of
total tunnel lengths.
2. The materials and methods were the same as described for
experiment 1, except: (a) the concentrations of nootkatone used to treat the sand
in the middle compartment were slightly different; (b) observations of tunneling
were recorded several times during the experiment; and (c)
50 g sand was placed
in the third compartment under the lter paper disk and was moistened every
two days with
0.3 ml of distilled water. For this experiment the concentrations
of nootkatone were
0 (control), 5, 10, 20, 40, and 100 mg
g sand. Four repli-
cates were performed for each concentration. Every two days all containers were
checked for tunneling activity and the evaluating criterion was:
0 termites on
the surface (no tunneling);
1 tunneling in the rst chamber; 2 tunneling in
the rst and in the middle (treated) chamber;
3 tunneling in all chambers.
Statistical Analysis
For experiment
1, the differences among treatments in lter paper consump-
tion, tunnel length, and percentage mortality were analyzed by ANOVA. For
2, we used a nonparametric analysis of variance (Kruskal-Wallis
ANOVA) in order to analyze trends in tunneling differences between days of
observation. At the end of the experiment, differences among treatments were
analyzed as in experiment
1. For both experiments, differences between treat-
ments were analyzed by Tukeys studentized range test (HSD). Although per-
centage values were transformed to arc-sin of the square root for data analysis,
nontransformed means are reported.
Identification of Nootkatone as Active Fraction from Vetiver Oil
Three fractions (
35) contained autouorescing bands detected by UV. Each
fraction was further separated by preparative TCL with CHCl
as a mobile phase.
In fraction
4, bands 1 and 2 autouoresced, and were examined by GC-MS.
Nootkatone was a major constituent of band
2 (Figure 1A). The chromatograph
of authentic nootkatone is shown in Figure
1B. The nootkatone identication
was veried by comparing the mass spectrum of its GC peak (Figure
2A) with
authentic nootkatone (Figure
Termite Bioactivity of Nootkatone
1. The mean consumption of lter paper decreased signicantly
in the presence of nootkatone; the decrease in consumption was concentration
dependent (Table
1). Even at the lowest concentration tested (10 mg
g sand),
nootkatone signicantly decreased feeding as compared with the control. Little
consumption of lter paper was found when concentrations of nootkatone were
higher than
20 mg
g. Termite mortality increased as nootkatone concentrations
FIG. 1. Gas chromatography of band 2 (A) and the standard of nootkatone (B). The reten-
tion time of nootkatone in band
2 is 53.22 min (rst peak) and in the standard is 53.35
increased (Table 1). All concentrations of nootkatone had a signicant impact on
mortality when compared with the control. Ninety percent mortality or greater
was observed in all chambers when nootkatone concentrations were
100 mg
sand. The presence of nootkatone substantially decreased the tunneling activity
even at the lowest concentration of
10 mg
g sand (Table 1). At higher concentra-
tions of nootkatone (
20 mg
g and higher), no tunneling was visible in the middle
2. Units treated with different concentration of nootkatone
showed signicantly different levels of tunneling activity. On day two, signi-
cant differences were detected among treatments (H
20.47, df 5, P 0.001,
Kruskal-Wallis ANOVA); almost all groups treated with lowest concentrations
were able to tunnel in the rst and even in the middle (treated) chamber, while
termites faced with the highest concentration remained on the surface. The same
trend is conrmed on day
6 (H 17.39, df 5, P 0.0038), where some ter-
mite groups (control and concentration
3) tunneled into the feeding chamber,
FIG. 2. Mass spectrum of the nootkatone peak in band 2 (A) and authentic nootkatone (B).
Concentration of Weight loss of Termite
nootkatone lter paper mortality Tunneling length
g sand) (mg) (%) (cm)
010.500 ± 2.867A 58.50 ± 8.72A 27.000 ± 6.072A
10 1.900 ± 0.641B 88.50 ± 10.12B 7.225 ± 2.155B
20 0.525 ± 0.709B 87.00 ± 18.22B 0.000 ± 0.000B
100 0.025 ± 0.050B 90.50 ± 11.72B 0.000 ± 0.000B
200 0.275 ± 0.050B 95.00 ± 8.718B 0.000 ± 0.000B
Four replicates were included for each treatment. Means within a column followed by the same
letter are not signicantly different (ANOVA: F
9.39, df 4 and P < 0.0005 for paper
consumption; F
4.22, df 4, P < 0.0174 for percentage mortality and F 43.1, df 4, P < 0.0001
for tunneling length.)
and on day 11 (H 14.52, df 5, P 0.0126) (Table 2). As in experiment
1, signicant differences were detected in lter paper consumption, where only
the controls and groups treated with
20 and 40 mg
g sand of nootkatone could
eat some lter paper. Differences were also detected in tunnel length: only the
controls and units treated with the lowest concentration of nootkatone showed
tunneling behavior. Due to high variability between units belonging to the same
treatment group, no signicant differences were detected on termite mortality.
Concentration of Weight loss of
nootkatone lter paper % termite Tunneling length
g sand) (mg) mortality (cm)
03.675 ± 3.500 A 27.727 ± 10.111 A 29.450 ± 8.065 A
50.150 ± 0.300 B 36.364 ± 7.120 A 24.975 ± 14.558 A
10 0.650 ± 1.300 AB 52.273 ± 45.281 A 11.000 ± 16.818 AB
20 0.300 ± 0.600 AB 48.182 ± 36.980 A 2.250 ± 2.872 B
40 0 ± 0B 39.091 ± 32.710 A 0 ± 0 B
100 0 ± 0B 58.636 ± 33.008 A 0 ± 0 B
Four replicates were included for each treatment. Means within a column followed by the same
letter are not signicantly different (ANOVA: F
3.416, df 5, P 0.024 for paper consumption;
0.580, df 5, P 0.715 for percentage mortality and F 7.215, df 5, P 0.0007 for tunneling
Vetiver oil is a complex essential oil containing several hundred individual
compounds. Of them,
92 compounds have been characterized and can be divided
33 esters, 36 sesquiterpenic hydrocarbons, 5 bi- and tricyclic sesquiterpenic
9 ketones, 3 aldehydes, and 6 acids (Cazaussus et al., 1989). Nootka-
4,4a,5,6,7,8-hexahydro-6-isopropenyl-4,4a-dimethyl-2(3H)-naphthalone, is
a mildly pungent sesquiterpene ketone found in the oil of Alaska yellow cedar,
Chamaecyparis nootkatensis (Lamb) Spach (Erdtman and Hirose,
1962) and in
a great number of citrus oils, especially oil from grapefruit, Citrus pavadisi Calli
(MacLeod and Buigues,
1964). Nootkatone is widely used in the perfume and
avor industries, being essentially nontoxic to humans (National Research Coun-
Our studies determined that nootkatone has potential as a termite repel-
lent barrier. Considering tunneling behavior as a measurement of termite activ-
ity, these results conrmed that nootkatone effects termite vigor. Termites from
colonies treated with lower concentrations of nootkatone were able to dig tun-
nels in the home and in the treated chamber, and this ability was negatively
correlated with the concentration of nootkatone. Termites treated with the high-
est concentrations of nootkatone were not able to dig tunnels, even in the home
chamber, possibly because of the nootkatone vapors acting as an inhibitor of
termite mobility. We believe that a concentration of nootkatone bewteen
10 and
1000 mg
g, preferably between 10 and 200 mg
g, may be useful in repelling
and killing termites. We are also evaluating nootkatone as a chemical that could
be of value against termites in structural wood treatments or cellulose mulch
applications (Henderson et al., unpublished data).
A barrier created by plants that manufacture a termite repellent could poten-
tially provide long-lasting repellency. Vetiver grass is a fast growing plant with
a huge spongy mass of roots. The roots grow to depths of
3 m, and with a little
attention the plant could live for
5060 years (National Research Council, 1993).
Since the oil occurs primarily in the roots, a low-cost way to prevent invasion by
subterranean termites and other insidious underground insects may be to plant a
solid band of vetiver grass around a house. Recently, we found that some of the
insect repellents found in the roots also occur in the soil surrounding the plant
(Henderson et al., in preparation).
Vetiver oil is one of the most complex essential oils (Cazaussus et al.,
In addition to nootkatone, we also have found that vetiver oil itself and its major
components a- and b-vetivone were powerful repellents and toxicants against
Formosan subterranean termite (Zhu et al., in preparation). Jain et al. (
reported six substances in vetiver oil that have potent topical irritant activity on
cockroaches and ies.
AcknowledgmentsThis project was approved for publication by the Louisiana State Univer-
sity Agricultural Center and Louisiana Agricultural Experiment Station as manuscript
Partial funding was provided through a specic cooperative agreement with the USDA
Orleans (
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... The compounds in VZ EO, including α-vetivone, β-vetivone, khusimone, zizanal, and epizizanal, were found to be repellent to insects as well (Jain et al. 1982). Zhu et al. (2001) also reported that VZ EO was found to be the most effective repellent with a major bioactive ingredient α-and β-vetivone. In this study, GC-MS analysis revealed that β-vetivone, khusimol, and α-vetivone are the main component of VZ EO, with nootkatone as one of the minor components. ...
... Table 2. Mean percent escape response and percent mortality of Culex quinquefasciatus (field strain) exposed to each plant extracts and their binary mixture with AP CE (2.5% w/v) at different blending ratios in contact and noncontact trials 2009). Study of Zhu et al. (2001) found that two compounds including nootkatone and sesquiterpene ketone, isolated from VZ EO was a strong repellent and toxicant to the Formosan subterranean termites, Coptotermes formosanus Shiraki. Some studies showed that the repellent activity of EO combinations against mosquito was better than that of single EO (Das et al. 2015, Uniyal et al. 2015. ...
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Efficacies of essential oils (EOs) of Vetiveria zizanioides (L.) Nash. (Poales: Poaceae) (VZ EO), Cananga odorata (Lam) Hook. F. & Thomson (Magnoliales: Annonaceae) (CO EO), and crude extract (CE) of Andrographis paniculata (Burm.F.) Wall ex. Nees (Lamiales: Acanthaceae) (AP CE), against laboratory (lab) and field strains of Culex quinquefasciatus Say were investigated. Irritant and repellent activities of individual and binary mixtures of plant extracts were compared with N,N-diethyl-m-toluamide (DEET) using an excito-repellency system. The irritant activity (direct tarsal contact), the mean percent escape response of VZ EO (91.67%, 83.33%), and CO EO (80%, 88.33%) were not significantly different compared with DEET (88.33%, 95%) against lab and field strains, respectively. Similarly, irritant responses in combinations (1:1 and 1:2, v:v) of either VZ EO or CO EO with AP CE were not significantly different from DEET against both strains (P > 0.001). The repellent activity (no tarsal contact), the mean percent escape response of VZ EO (68.33%), CO EO (61.67%), and VZ EO+AP CE (1:1, v:v) (81.67%) against lab strain and CO EO (85%) against field strain were not significantly different from that of DEET (P > 0.001). Interestingly, the greatest contact irritancy of VZ EO+AP CE (1:1, v:v) (96.67%) (P = 0.0026) and a stronger repellency response of CO EO (85%) (P = 0.0055) produced significantly different patterns of escape response compared with DEET against both lab and field strains, respectively. The EOs of VZ EO and CO EO or their mixture with AP CE showed potential as plant-based active ingredients for mosquito repellents. In addition, the major chemical constituents of VZ EO were β-vetivone (6.4%), khusimol (2.96%), and α-vetivone (2.94%) by gas chromatograpy-mass spectrometry.
... The major components of VZ EO are β-vetivone, khusimol, α-vetivone, vitiveryl acetat, vetiverol, vitivone, and terpenes [27,36]. VZ EO has been reported to repel several insects, such as termites, mosquitoes, weevils, and beetles [12,37,38]. Recently, Nararak et al. [35] demonstrated that VZ EO and two of their constituents (valencene and vetiverol) had potential as active ingredients for repelling Ae. ...
... Most plant essential oils are volatile and act on mosquitoes in the volatile phase. Therefore, their effectiveness and protection time are time-limited [38,43]. Improved repellency of plant-derived topical repellents has been shown after formulation with some bases or fixative materials, such as liquid paraffin, vanillin, and salicyluric acid [44][45][46][47]. ...
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Each binary mixture formulation of Vetiveria zizanioides (L.) Nash (VZ) with Andrographis paniculata (Burm.f.) Wall. ex Nees (AP) or Cananga odorata (Lam.) Hook.f. & Thomson (CO) and AP with CO at 1:1, 1:2, 1:3, and 1:4 ratios (v:v) was investigated for behavioral responses on laboratory and field strains of Aedes aegypti. Irritant and repellent activities of each formulation were compared with N,N-diethyl-3-methylbenzamide (DEET) using an excito-repellency test system. The result demonstrated that the mixture of VZ:AP in all combination ratios was the most effective in inducing an irritancy response against the laboratory strain (56.57–73.33%). The highest percentage of escaped mosquitoes exposed to the mixture at a 1:4 ratio (73.33%) was significantly different from DEET (26.67%) (p < 0.05). Against the field strain, the strongest escape response of AP:CO at a 1:1 ratio in the contact trial (70.18%) was significantly different compared with DEET (38.33%) (p < 0.05). There was a weak non-contact escape pattern in all combinations of VZ:CO against the laboratory strains (6.67–31.67%). These findings could lead to the further development of VZ and AP as active ingredients in a repellent that could advance to human use trials.
... Vetiver ( Vitiveria zizanioides (L.) Nash, Poaceae) essential oil consists of a complex mixture of more than 200 compounds, a major portion of oil consisting of sesquiterpenoids, hydrocarbons and their oxygenated derivatives, but also phenols and nitrogen compounds. Vetiver oil has been reported to repel several insects such as termites, mosquitoes, weevils, beetles ( Nararak et al., 2016 ;Sujatha, 2010 ;Zhu et al., 2001 ). St. Pfau and Plattner (1939) identified in vetiver oil -and -vetivones comprising the major constituents. ...
... The constituents in vetiver oil, including -and -vetivone, khusimone, zizanal, and epizizanal, were found to be repellent to insects ( Jain et al., 1982 ). Zhu et al. (2001) also reported that vetiver oil was found to be the most effective repellent with a major bioactive ingredient -and -vetivone. In this study, GC-MS analysis revealed thatvetivone, khusimol, and -vetivone are the main components of vetiver oil, with nootkatone as one of the minor components ( Boonyuan et al., 2022 ). ...
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Numerous plant-based repellents are widely used for personal protection against host-seeking mosquitoes. Vitiveria zizanioides (L.) Nash essential oil and its constituents have demonstrated various mosquito repellent activities. In this study, three chemical actions of vetiver oil and five constituents (terpinen-4-ol, α-terpineol, valencene, vetiverol and vetivone) were characterized against Aedes aegypti, Aedes albopictus and Culex quinquefasciatus by using the high-throughput screening assay system (HITSS). Significant contact escape responses in Ae. aegypti and Ae. albopictus to all test compounds at concentrations between 2.5 and 5% were observed. Spatial repellency responses were also observed in some tested mosquito populations depending upon concentrations. The most significant toxic response on mosquitoes was found at the highest concentration, except for vetivone which had no toxic effect on Ae. aegypti and Ae. albopictus. Results on phototoxic and genotoxic hazard revealed that vetiver oil and their constituents showed no phototoxic potential or any significant genotoxic response. In conclusion, vetiver oil and two constituents, valencene and vetiverol, are potentials as active ingredients for mosquito repellency and present no toxicity.
... [18] Zhu et. al., [46] indicated that one of the components of vetiver roots, nootkatone (Fig. 8), was a strong repellent and toxicant to Formosan subterranean termites; Coptotermes formosans ( Isoptera :Rhinotermitidae) and suggested planting of a barrier of plants that manufacturers a termite repellent could potentially provide repellence to this pest. ...
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The push-pull strategy is a behavioural manipulation method that uses repellent/deterrent (push) and attractive/stimulant (pull) stimuli to direct the movement of pest or beneficial insects for pest management. Stimuli used for behavioural manipulation in push pull strategies include visual and semiochemical cues or signals that work by nontoxic mechanisms. Such strategies are therefore integrated with other population-reducing methods. Sustainable and environmentally sensitive components are favoured, and the use of insecticides can be reduced. The push-pull strategy undertakes a holistic approach in exploiting chemical ecology and agrobiodiversity. Push-pull strategies targeted at pest insects are being developed in all major areas of pest management. However, their use is currently underexploited. Changing attitudes toward replacing broad-spectrum insecticides with new technologies, particularly semiochemical tools, to manipulate the behaviour of natural enemies for biological control will enable improved push-pull strategies to be developed and used more widely in the future. This paper summarizes the principles of the push pull strategy. Its potential components like semiochemicals, host-plant resistance, trap crops and selective pesticides or biological control agents and examples of practical applications of push pull strategies in integrated pest management.
... VO consists of a complex mixture of more than 300 compounds, with the major ones being vetiverol, vetivene, alpha-and beta-vetivone, khusimol, elemol, vetiselinenol, beta-eudesmol, terpenes, zizanoic acid, vanillin, hydrocarbons, sesquiterpenes, alcohols, and ketones 9 . Vetiver grass has been reported to have insect repellent properties against ants, ticks, cockroaches, termites, mosquitoes, weevils, and beetles [10][11][12][13] . Besides essential oils, a pure compound named β-caryophyllene oxide (BCO) is a bicyclic sesquiterpene, a representative of an epoxide derived from the ole n of (E)-caryophyllene. ...
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Mosquito repellents play a major role in reducing the risk of mosquito borne diseases by preventing mosquito bites. The present study evaluated the mosquito-repellent activity of β-caryophyllene oxide 1% (BCO), vetiver oil 2.5% (VO) and their binary mixtures [BCO+VO (1:1), BCO+VO (2:1), BCO+VO (1:2)] against four laboratory-colonized mosquito species: Aedes aegypti (L.), Aedes albopictus (Skuse), Anopheles minimus (Theobald), and Culex quinquefasciatus Say using an excito-repellency assay system. In general, the compound mixtures produced a much stronger response by the mosquitoes than single compounds, regardless of the test conditions and species. The greatest synergetic effect was achieved for the combination of BCO+VO (1:2) in both the contact and non-contact trials with An. minimus (74.07–78.18%) and Cx. quinquefasciatus (55.36–83.64%). Knockdown responses to the binary mixture of BCO+VO were observed for Ae. albopictus, An. minimus and Cx. quinquefasciatus, in the range 18.18–33.33%. The synergistic repellent activity of BCO and VO used in the study may support increased opportunities to develop safer alternatives to synthetic repellents for personal protection against mosquitoes.
... Due to its pleasant aroma to humans, (+)-nootkatone is commonly used in the flavour and fragrance industries. It has also been used as an ingredient in insect repellents 29 . Several studies have concentrated on (+)-nootkatone production using E. coli 30,31 , but none achieved one-step de novo production. ...
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The biosynthesis of natural products often requires eukaryotic cytochrome P450s (P450s) in combination with P450 reductase, in physical proximity, to perform electron-transfer reactions. Unfortunately, functional expression of eukaryotic P450s in bacteria remains generally difficult. Here we report an electron channelling strategy based on the application of Photorhabdus luminescens CipB scaffold protein, which allows efficient electron transfer between P450s and reductases by bringing these enzymes in close proximity. The general applicability of this electron channelling strategy is proved by developing recombinant Escherichia coli strains producing lutein, (+)-nootkatone, apigenin and l-3,4-dihydroxyphenylalanine (l-DOPA), each of which requires P450s in its biosynthetic pathway. The production titres are then further enhanced by increasing the haem pathway flux or by optimization of the culture conditions. Remarkably, the final lutein strain produced 218.0 mg l−1 of lutein with a productivity of 5.01 mg l−1 h−1 in fed-batch fermentation under optimized culture conditions. Eukaryotic cytochrome P450s (P450s) are often required for the biosynthesis of natural products, but their performance in bacteria is usually reduced. Now, scaffold enzymes bring eukaryotic P450s and a reductase in close proximity for efficient electron channelling, increasing the production of natural products in Escherichia coli.
... [35] Similarly, vetiver oil, nootkatone, and disodium octaborate tetrahydrate imposed feeding, inhibition and obstruction of wood digestion inside the termite gut. [36] Vetiver oil was found highly effective against subterranean termites without any side effect on environment. [37] Hexaflumuron and copper chloride are used in poison baits to control fungus-growing termite, Odontotermes formosanus. ...
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In present investigation Tagetes erecta and its combinatorial formulations were evaluated to observe the anti-termite efficacy against Indian white termite Odontotermes obesus. These have shown very high termiticidal activity and repellency against present termite species. It was proved by very low LD 50 values obtained i.e. B-AST-A 261.930 and S-AST-C 507.666 respectively. Tagetes erecta termiticidal potential was enhanced when other bio-material were added to them in a defined ratio. This synergistic action caused very high mortality in termites. Besides this, combinatorial mixtures significantly repelled termites in two Choice bioassays. These also have shown strong anti-feedant action in termite workers.
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Repellents play a major role in reducing the risk of mosquito-borne diseases by preventing mosquito bites. The present study evaluated the mosquito-repellent activity of β-caryophyllene oxide 1% (BCO), vetiver oil 2.5% (VO), and their binary mixtures (BCO + VO (1:1), BCO + VO (2:1), BCO + VO (1:2)) against four laboratory-colonized mosquito species, Aedes aegypti (L.), Aedes albopictus (Skuse), Anopheles minimus Theobald, and Culex quinquefasciatus Say, using an excito-repellency assay system. In general, the compound mixtures produced a much stronger response in the mosquitoes than single compounds, regardless of the test conditions or species. The greatest synergetic effect was achieved with the combination of BCO + VO (1:2) in both contact and noncontact trials with An. minimus (74.07–78.18%) and Cx. quinquefasciatus (55.36–83.64%). Knockdown responses to the binary mixture of BCO + VO were observed for Ae. albopictus, An. minimus, and Cx. quinquefasciatus, in the range of 18.18–33.33%. The synergistic repellent activity of BCO and VO used in this study may support increased opportunities to develop safer alternatives to synthetic repellents for personal protection against mosquitoes.
In Brazil, two tick species are mainly involved in public health and livestock issues: Amblyomma sculptum and Rhipicephalus microplus, respectively. Nootkatone, a sesquiterpenoid isolated from Chamaecyparis nootkatensis, has been described in the literature as an environmentally friendly alternative method of control, with repellent and toxic action against different insect and tick species from the Northern Hemisphere. The objective of the present study was to evaluate the effect of nootkatone on the in vitro mortality of R. microplus and A. sculptum. Different dilutions of nootkatone (0.5, 1, 2, 5 and 10%) were used on instars of both tick species. In A. sculptum engorged larvae, unfed nymphs, and unfed adults, 2% nootkatone resulted in 95% mortality in almost all tests. An in vitro mortality rate of 95% was observed for larvae and engorged females of R. microplus with 1% and 0.5% nootkatone, respectively. Additionally, 5% and 10% nootkatone were at least 97% effective against engorged larvae, unfed nymphs, and unfed adults of A. sculptum and larvae and engorged females of R. microplus. This was the first study to use nootkatone against ticks from Brazil and the data suggest that nootkatone has great potential as a tool for tick control.
Valencene and nootkatone, two sesquiterpenes, extracted from natural sources, have great market potential with diverse applications. This paper aims to comprehensively review the recent advances in valencene and nootkatone, including source, production, physicochemical and biological properties, safety and pharmacokinetics evaluation, potential uses, and their industrial applications as well as future research directions. Microbial biosynthesis offers a promising alternative approach for sustainable production of valencene and nootkatone. Both compounds exert various beneficial activities, including antimicrobial, insecticidal, antioxidant, anti-inflammatory, anticancer, cardioprotective, neuroprotective, hepatoprotective, and nephroprotective and other activities. However, most of the studies are performed in animals and in vitro, making it difficult to give a conclusive description about their health benefits and extend their application. Hence, more attention should be paid to in vivo and long-term clinical studies in the future. Moreover, valencene and nootkatone are considered safe for consumption and show great promise in the applications of food, cosmetic, pharmaceutical, chemical, and agricultural industries.
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Termite nests provide a controlled environment and physical defence for the colonies of insects they house. Another important factor involved in colony defence may be volatile chemicals present in the nest: we have found the hydrocarbon naphthalene in extracts of the nest material produced by Formosan subterranean termites. This is the first time naphthalene has been found naturally associated with any insect species.
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The search for food in subterranean termites is investigated in the French species Reticulitermes santonensis De Feytaud (Isoptera, Rhinotermitidae). Not accompanied by soldiers, only few pioneer workers explore a new territory systematically in every direction by means of short exploratory trails (median: 1.3 cm). Following these trails, termites build subterranean tunnels and/or galleries in the open, hereby forming an extensive regularly branched net. Food is detected over distance by perceiving volatiles emanating from the wood. Then foragers appear more frequently and undertake longer exploratory runs (up to 15 cm), which are directed towards the odour source. Following contact with the wood, sucessful workers return to the nest precisely along their exploratory trail and hereby lay a recruitment trail. This recruitment trail is immediately followed by further workers as well as by single soldiers. Following the course of this trail, termites build a non‐branched subterranean tunnel or a gallery above ground leading straight to the wood. This direct access requires less investment and provides workers with a shelter ensuring a rapid and safe exploitation of the food source.
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Isolation and identification of 2-phenoxyethanol from a ballpoint pen ink as a termite trail-following substance was accomplished by using trail-following bioassays, column chromatography, high performance liquid chromatography, and gas chromatography-mass spectrometry. This chemical elicited trail-following in both C. formosanus Shiraki and Reticulitermes sp.
A choice feeding test using 21 amino acids was conducted to determine the feeding preference of Formosan subterranean termite,Coptotermes formosanus Shiraki, in the laboratory. Significantly more filter paper treated withD-aspartic acid orL-glutamic acid was consumed by Formosan subterranean termites than was control filter paper treated with water. In two-choice feeding tests, termites consumed significantly more filter paper treated withD-aspartic acid orL-aspartic acid than paper treated with water. AddingL-proline,L-lysine, orL-isoleucine to filter paper significantly increased consumption compared with control filter paper in no-choice tests. The use of amino acid additives in termite baits is briefly discussed.
Oil of vetiver samples of Haiti, Reunion, and North Indian origin have been examined by GLC. The North Indian variety (Khus Oil) is distinctly different and represents a chemically distinct race of Vetiveria zizanioides (Gramineae) or perhaps a distinct species. The biogenetic implications of the antipodal sesquiterpenes isolated from vetiver oil varieties are reevaluated in light of these results.
The acetylated fraction of aVetiver oil from Java has been analyzed by GC/MS and GC/MS/MS with different ionization methods. 92 compounds were characterized and nine of them identified. The differentiation of isomers as methyl isozizanoate and methyl zizanoate confirmed the sensitivity, specificity, speed and accuracy of tandem mass spectrometry.
On the basis of spectral data and partial syntheses, structure 1 and 2 are established for zizanal and epizizanal, two new insect-repelling aldehydes isolated from Javanese vetiver oil (Vetiveria zizanoides).
Naphthalene was detected in nest cartons of Formosan subterranean termites, Coptotermes formosanus Shiraki. The concentration of naphthalene ranges from 50.56 to 214.6 μg/kg. This is the first report of naphthalene being associated with termites. Some possible functions of naphthalene in a termite society are discussed. Keywords: Naphthalene; Coptotermes formosanus; termite nest
The bicyclic conjugated sesquiterpene ketone, nootkatone, has been found in grapefruit peel oil and in peel-oil-free grapefruit juice. The flavor intensity of grapefruit oil appears to be related to the relative abundance of nootkatone. A combination of gas-liquid chromatography and thin-layer chromatography revealed the presence of this ketone, which was identified by its infrared spectrum and the melting point of its 2,4-dinitrophenylhydrazone derivative. Traces of nootkatone were found also in bergamot, lemon, lime, orange, and tangerine oils.