Vetiver (
Owing to the many usages of vetiver and its products, studies have been conducted on the chemistry of this plant, with emphasis on vetiver root oil. Plant essential oils contain secondary metabolites that are lipophilic and volatile (Ríos, 2016). Vetiver essential oil is very complex and consists of more than 300 compounds; the primary constituents are sesquiterpenes and their derivatives, including sesquiterpene alcohols, hydrocarbons, and ketones (Champagnat et al., 2006; Leite, 2012; Belhassen et al., 2015; Lim, 2016). Root extracts contain secondary metabolites such as alkaloids, flavonoids, phenols, saponins, steroids, tannins, sesquiterpenes, terpenoids, and triterpenes (Subhadradevi et al., 2010; Aarthi et al. 2014; Krishnaveni, 2016; Kumar and Gayathri, 2016). The constituents extracted from the above-ground plant parts have also been identified, and include alkaloids, cholesterol, flavonoids, flavonolignans, glycosides, phenolic acids, phenylpropanoids, glycerols saponins, steroids, tannins, and many terpenoids (e.g. monoterpenes, sesquiterpenes, and a triterpene) (Huang et al., 2004; Gao et al., 2012; Prajna et al., 2013; Soni and Dahiya, 2015).
Vetiver-derived compounds have also been investigated for pest and pathogen management. Allelopathic or repellant activity was demonstrated against multiple organisms, including bacteria and fungi (Istianto and Emida, 2011; Vázquez-Sánchez et al., 2014; Soni and Dahiya, 2015), insects, ticks and a malarial parasite (Zhu et al., 2001a, 2001b; Ibrahim et al., 2004; Panella et al., 2005; Chauhan and Raina, 2006; Sujatha, 2010; Flor-Weiler et al., 2011; Aarthi et al., 2014; Campos et al., 2015), and plants (Mao et al., 2006). Additionally, research has been conducted on vetiver as a host for plant-parasitic nematodes. Vetiver is a host for the corn cyst nematode
Despite the nonhost status of vetiver plants to RKN, few studies have been published on vetiver extracts, exudates, or oils and their effects on members of this genus. One investigation found that ethanol root extracts were nontoxic to
Although these studies with RKN did not find nematotoxic activity from vetiver constituents, the results must be considered with the knowledge that there has been little published work in this area, and that research on plant-derived compounds is affected by a complex web of factors. Vetiver age, plant part (such as stems vs. roots), vetiver cultivar and genes, environmental variation during plant growth, microbial populations in the rhizome and rhizosphere, and extraction methods used to obtain compounds can all influence the chemical components accumulated in or extracted from vetiver (Martinez et al., 2004; Adams et al., 2008; Belhassen et al., 2015; Lim, 2016). Deregistration of many synthetic nematicides has led to a need for new management agents for these plant pathogens, and the large number of compounds produced by vetiver, activity against numerous organisms, and the nonhost status to RKN all indicate that further research on vetiver activity against nematodes is warranted. Consequently, the current study was conducted to determine the effects of vetiver oil and of crude vetiver root and shoot extracts on activity and viability of
In the U.S., vetiver cv. Sierra was purchased from Agriflora Tropicals, Caguas, Puerto Rico and grown in the greenhouses of the Mycology and Nematology Genetic Diversity and Biology Laboratory (2-mon-old plants) and the Invasive Insect Biocontrol and Behavior Laboratory (4-yr-old plants) at USDA ARS, Beltsville, Maryland. Vetiver plants that were harvested after 2 mon of growth had been planted in Promix PGX (Premier Tech Horticulture, Quakertown, PA) in one-gallon (3.8 L) pots and maintained at 24°C to 29°C, with natural and supplemental lighting combined for a 16-hr daylength. Vetiver plants that were harvested after 4 yr of growth had been planted in Promix BX in 19 gallon pots (72 L) and maintained at 18°C to 24°C, with natural and supplemental lighting combined for a 16- to 18-hr daylength. Roots were chopped into 1 cm pieces and dried at room temperature (23-25°C) for 5 to 7 d. The dried material was ground by a milling machine (Thomas-Wiley, Laboratory Mill Model 4, Swedesboro, NJ) and passed through a sieve with a pore size of 2 mm. The powders were stored at 4°C until use.
In Thailand, 1-yr-old roots of field-grown vetiver cv. Songkha 3 were collected from plants grown at the Land Development Department, Nakhon Ratchasima province, Thailand. The vetiver plants were cultivated in Pak Chong series, red brown earth loam soil. In addition, because French marigold (
Shoot and root extracts from 2-mon-old and 4-yr-old vetiver plants were prepared from cv. Sierra in the U.S. Since vetiver shoots can be harvested and used as soil mulch (Lim, 2016), studies with shoots focused on water-soluble compounds that might more readily leach into the soil. Research on root extracts was conducted with aqueous extracts, and with ethanol extracts that would provide material for GC-MS investigation of secondary metabolites. Procedures for making extracts were similar to those described in Meyer et al. (2006). To summarize, water-soluble compounds were extracted from dried, powdered shoots and roots (10% dry weight plant material/volume water) on a mechanical rotary shaker (VWR, Advanced Digital Shaker, Radnor, PA) at 100 rpm for 24 hr at room temperature (25°C). The mixture was filtered through eight layers of cheesecloth, centrifuged for 10 min at 3,000
To prepare ethanol extracts, dried root powder was immersed in 95% ethanol (10% dry weight plant material/volume ethanol) and placed on a shaker as described above. The solution was then vacuum filtered through Whatman No. 1 filter paper, and the filtered solution was evaporated in a rotary evaporator at 45°C, 172 bar (Heidolph 2 Rotavac, Schwabach, Germany) to nearly dry. The small amount of remaining ethanol was air dried and the extracts were stored at -20°C.
Haitian vetiver oil (VO), also from
Ethanol root extracts from French marigold and from 1-yr-old vetiver plants (cv. Songkha 3) were prepared in Thailand. Dried powder from vetiver roots or French marigold roots was immersed in 95% ethanol (20% dry weight plant material/volume ethanol) for 7 d in the dark at room temperature (28-30°C) without shaking. The solution was then vacuum filtered through a Whatman No. 1 filter paper and concentrated in a rotary evaporator at 50°C, 200 bar (Heidolph Hei-VAP Value, Schwabach, Germany). The concentrated extract was then transferred to a separatory funnel and partitioned with dichloromethane (Sac Science-Eng, Ltd, Thailand) at a ratio of 1:3. The dichloromethane phase was kept and re-evaporated at 50°C, dried with nitrogen, and finally stored at −20°C (procedure modified from Laksanaphisut, 2010).
Laboratory assays with aqueous and ethanol extracts were conducted in 96-well polystyrene plates, following the procedures in Meyer et al. (2006). Approximately 20 J2 were added to each well in 10 µl SDW, and then 190 µl of extract, or of vetiver oil, was added to each well. The microwell plates were covered by a plastic adhesive sealing film (Excel Scientific, Inc., Victorville CA) and the lids were sealed with Parafilm (Bemis, Neenah, WI). The plates were incubated at 26°C.
For microwell assays of vetiver shoot aqueous (VSA) extracts and vetiver root aqueous (VRA) extracts from 2-mon-old plants, 100 µl of a 50.0 mg/ml streptomycin sulfate (Sigma-Aldrich, St. Louis, MO) stock solution was added to 9.9 ml of 100% vetiver aqueous extract (100% was the undiluted extract, and was filtered through a 0.2 µm syringe filter prior to addition of the antibiotic). The streptomycin sulfate was used to eliminate the growth of microbes that sometimes occurred in the aqueous extract assays despite sterile filtering. The extract solutions were then diluted to 75%, 50%, and 25% with SDW, and 190 µl of each extract was added to 10 µl J2 in SDW in each well. There were eight aqueous extract treatments: VSA and VRA at final concentrations in the wells of 94%, 71%, 47%, and 24%. Control treatments were SDW and the highest concentration of the antibiotic, equivalent to that in the 94% treatment: 0.5 mg/ml streptomycin sulfate, also diluted with 10 µl J2 in SDW in each well for a final streptomycin sulfate concentration of 0.48 mg/ml. Treatments were replicated in eight wells in each of the two trials, for a total of 16 wells. Active J2 (those exhibiting any movement within 5 seconds) and inactive J2 (no movement after 5 sec) were counted after 1 and 2 d (Days 1 and 2) incubation in the treatments. Following the Day 2 count, the J2 were rinsed two times with SDW and incubated in the second SDW rinse. Active vs. inactive J2 (those exhibiting body movements and those that were not) were counted on Day 3. J2 not active after the water rinse were considered dead.
Vetiver root ethanol (VRE) extracts and French marigold root ethanol (FMRE) extracts were prepared at 0.1 and 0.01 mg/ml concentrations in a solvent (referred to as CTD) of equal parts castor oil (BASF, Ludwigshafen, Germany), Tween 80 (Sigma, St. Louis, MO), and dimethyl sulfoxide (DMSO: Fisher, Fairlawn, NJ). To dissolve the extracts, a stock solution was prepared of 10 mg of crude ethanol extract in 1.0 ml of 100% CTD. To prepare the extract concentration of 0.1 mg/ml, 100 µl of this solution was then added to 9.9 ml SDW and was sequentially filtered through 1.0 µm, 0.45 µm, and 0.2 µm sterile filters. To prepare the 0.01 mg/ml extract, 1 ml of the 0.1 mg/ml filtered solution was added to 9.0 ml SDW. After addition of 190 µl extract to 10 µl J2 in SDW, the final extract concentrations in the wells were 0.095 mg/ml and 0.0095 mg/ml, respectively. The treatments at each of the two concentrations were (1) 2-mon VRE, (2) 1-yr VRE, (3) 4-yr VRE, (4) VO (vetiver oil), and (5) FMRE; these comprised treatments 1 through 10. Control treatments were: (11) SDW; (12) 1% CTD (which was 0.95% after dilution in the wells); and 13) 0.1% CTD (0.095% after dilution in the wells). Treatments were each replicated in eight wells for each of the two trials, for a total of 16 wells per treatment. Counts were performed as described above.
Chemotaxis assays were conducted with methods modified from Laznik and Trdan (2013). For our studies, 1.4% water agar (Noble agar, Difco, Leeuwarden, The Netherlands) was poured into plastic plates that were sold as lid sizes of 100- and 60-mm diam. The corresponding plate bases were 85-mm diam. (used for ethanol extracts; 25 ml agar added per plate), and 53-mm diam. (used for aqueous extracts, 10 ml agar per plate). Dried aqueous extracts were dissolved in SDW to obtain 0.1 g/ml. The treatments tested with aqueous extracts were: (1) 2-mon VRA and (2) 2-mon VSA. SDW was the control. Dried ethanol extracts were dissolved in 95% ethanol to obtain 0.1 g/ml. The treatments tested with ethanol extracts were: (1) 2-mon VRE, (2) 1-yr VRE, (3) 4-yr VRE, (4) VO, (5) FMRE, and (6) 95% ethanol. SDW was the control. Each plate was divided into three areas (Figure 1): the starting area, the treatment area, and the control area. Extract treatments (10 µl) were gently pipetted onto the agar at the treatment point, 10 µl of live J2 (ca. 20 J2) onto the starting point, and 10 µl of water onto the control point. Ethanol-dissolved treatments and the ethanol control were air dried for 10 min to allow ethanol to dissipate. The plates were incubated at 26°C for 24 hr. Each treatment was replicated with 5 plates in each of the two trials, for a total of 10 plates. The J2 were counted in each area and the chemotaxis index was calculated using the formula: CI = (number of nematodes in the treatment area – number of nematodes in the control area)/total number of nematodes in the assay. The interpretations of the CI values for the treatments are summarized as follows (from Laznik and Trdan, 2013): ≥0.2 indicated an attractant; between 0.2 and 0.1, a weak attractant; from 0.1 to -0.1, without effect; between -0.1 and -0.2, a weak repellent; and ≤-0.2, a repellent.
Diagram of a chemotaxis assay. Each plastic plate was divided into three areas: the treatment area (consisting of the treatment point and the surrounding area), the starting area (consisting of the starting point and the surrounding area), and the control area (consisting of the control point and the surrounding area). J2 were placed on the agar at the starting point, treatments were applied to the agar at the treatment point, and sterile distilled water was applied to the agar at the control point. Measurements are given for a plate with an 85-mm-diam. cup (100-mm-diam. lid).
GC-MS analysis of the volatile constituents of VRE and VO was carried out using an Agilent 6890 N GC instrument coupled with a 5973 mass selective detector. The instrument was equipped with a DB-5 capillary column of length 30 m, internal diam. 0.25 mm, and film thickness 0.25 µm. The carrier gas was helium at a constant flow rate of 2.0 ml/min. The oven temperature was maintained at 50°C for 5 min and ramped to 280°C at 10°C/min and held there for 3 min. Diluted samples (in methanol) of 2 µl were injected in the split mode with a split ratio of 25:1 and the inlet temperature was 280°C. The mass detector scanned from 4.5 min to 30 min at a mass range from 40 to 400 (EI, 70 eV). The MS ion source temperature was 230°C and the quadrupole temperature was 150°C. The components were identified by comparing mass spectra with the NIST mass spectra library in the GC/MS data system.
Data were analyzed with the statistical package JMP Version 12.1.0 (SAS Institute, Inc., 2015). Differences among treatments were determined by analysis of variance (ANOVA) and means were compared using Tukey–Kramer’s adjustment for multiple comparisons (
An initial screening of 2-mon VSA, 2-mon VRA, and 4-yr VRA indicated that aqueous extracts from the younger plants showed greater activity against
Percentage inactive or dead
Percentage inactive J2 | Percentage dead J2 | ||
---|---|---|---|
Treatmenta | Day 1 | Day 2 | Day 3 rinsed |
VSA 94% | 53.4 bAb | 70.4 abA | 68.2 aA |
VRA 94% | 79.6 aAB | 86.7 aA | 71.9 aA |
VSA 71% | 46.2 bB | 63.5 bcA | 71.1 aA |
VRA 71% | 74.4 aA | 72.1 abA | 68.0 aA |
VSA 47% | 39.8 bcB | 49.3 cdB | 67.6 aA |
VRA 47% | 50.3 bA | 49.8 cdA | 53.4 abA |
VSA 24% | 23.7 cdB | 38.3 dAB | 56.3 abA |
VRA 24% | 16.6 deB | 34.3 deA | 43.6 bA |
0.48 mg/ml streptomycin sulfate | 14.7 deA | 18.7 efA | 22.3 cA |
Water | 6.7 eB | 9.8 fAB | 17.5 cA |
aAll extracts were from shoots or roots of greenhouse-grown, 2-mon-old vetiver cv. Sierra. Treatments were prepared from 100% extracts (undiluted extracts) containing streptomycin sulfate, diluted to 75%, 50%, and 25% with water, and then added to J2 suspensions in the wells. Final extract dilutions in the wells are presented in the table.
bValues are means of eight replications in each of the two trials, for a total of
The aqueous extracts used for the microwell assays were not dried to determine weights. However, weights were estimated based on the weights of the dried aqueous extracts used for the chemotaxis assays. For 30 g of dry, powdered plant material, the dry weight of the crude aqueous shoot extract (384 mg) was almost twice the weight of the crude aqueous root extract (207 mg). An estimate of the extract weights used in the microwell assays would be: 94% VSA (9.02 mg/ml), 94% VRA (4.87 mg/ml), 71% VSA (6.82 mg/ml), 71% VRA (3.68 mg/ml), 47% VSA (4.51 mg/ml), 47% VRA (2.43 mg/ml), 24% VSA (2.30 mg/ml), and 24% VRA (1.24 mg/ml). The 24% VRA was likely about half the concentration of the 24% VSA, which might have resulted in this root extract causing significantly lower mortality than the highest root and shoot concentrations.
On Day 1 in the ethanol extracts, J2 activity was similar among the 0.95 mg/ml FMRE and VRE (crude extract) treatments, with more than twice as many inactive J2 than in SDW or the 0.95% CTD control (Table 2). In contrast, 0.95 mg/ml VO treatment resulted in only 20% inactive J2, which was not significantly different from the controls. Unlike the higher concentration of vetiver extracts and FMRE, no treatment at the lower concentration (0.095 mg/ml) was active against J2. Results on Day 2 were similar to those on Day 1, with the 0.95 mg/ml FMRE and VRE all resulting in more than 3 times as many inactive J2 as in 0.95% CTD. The 0.95 mg/ml VO again had no effect on J2 activity. Most of the 0.095 mg/ml treatments, including FMRE, were not effective against J2. At 0.095 mg/ml, only 2-mon VRE was antagonistic to J2, with 2½ times more inactive J2 than in 0.095% CTD. On Day 3, after incubation in a water rinse, the 0.95 mg/ml FMRE and vetiver extract treatments all resulted in greater mortality than the VO or the SDW and 0.95% CTD controls. The 0.95 mg/ml FMRE treatment was the most nematotoxic (Table 2), increasing J2 mortality by more than 6 times compared with mortality in 0.95% CTD. The 0.95 mg/ml VRE treatments increased J2 mortality by more than three times compared with 0.95% CTD. Mortality in FMRE was significantly affected by extract concentration, and was twice as great in the higher concentration of FMRE. However, mortality in 0.095 mg/ml VRE and VO treatments was not significantly lower than in the comparable 0.95 mg/ml VRE and VO treatments. Among the 0.095 mg/ml treatments, all but vetiver oil and extract from 2-mon-old cv. Sierra plants increased mortality compared with the comparable CTD control.
J2 activity and mortality were also compared among days to determine if the treatments were nematostatic or nematotoxic. No difference in J2 activity was found between Day 1 and Day 2 for any treatment. However, on Day 3, J2 mortality increased compared with inactive J2 on Day 2 in almost all extracts (Table 2). The one exception was 0.095 mg/ml VRE from 2 mon-old plants, in which J2 inactivity on Day 2 was the same as J2 mortality after the rinse on Day 3. There were also no significant differences in percent inactive or dead J2 among Days 1, 2, and 3 in vetiver oil, in CTD, or in the SDW control.
Percentage inactive or dead
Percentage inactive J2 | Percentage dead J2 | ||
---|---|---|---|
Treatmenta | Day 1 | Day 2 | Day 3 rinsed |
FMRE 0.95 mg/ml | 34.9 aBb | 30.7 aB | 69.1 aA |
2-mon VRE 0.95 mg/ml | 24.9 abcB | 28.0 abB | 38.3 bcA |
1-yr VRE 0.95 mg/ml | 27.6 abB | 26.5 abB | 42.4 bA |
4-yr VRE 0.95 mg/ml | 29.7 abB | 30.0 aB | 41.9 bA |
VO 0.95 mg/ml | 20.3 bcdA | 12.6 cdA | 17.1 deA |
0.95% CTD | 12.9 dA | 8.0 dA | 11.3 eA |
FMRE 0.095 mg/ml | 13.7 cdB | 17.0 bcdB | 35.0 bcA |
2-mon VRE 0.095 mg/ml | 16.2 cdA | 20.2 abcA | 24.0 cdeA |
1-yr VRE 0.095 mg/ml | 16.2 cdB | 13.9 cdB | 30.5 bcdA |
4-yr VRE 0.095 mg/ml | 14.2 cdB | 11.0 cdB | 27.8 bcdA |
VO 0.095 mg/ml | 9.7 dA | 8.6 cdA | 9.8 eA |
0.095% CTD | 12.8 dA | 8.0 dA | 11.8 eA |
Sterile distilled water | 11.8 dA | 12.4 cdA | 15.2 deA |
a2-mon VRE = vetiver root ethanol extracts from greenhouse-grown, 2-mon-old cv. Sierra; 1-yr VRE = vetiver root ethanol extracts from field-grown, 1-year-old cv. Songkha 3; 4-yr VRE = vetiver root ethanol extracts from greenhouse-grown, 4-yr-old cv. Sierra; VO = commercial vetiver oil. Treatments were prepared from 1.0 mg/ml and 0.1 mg/ml extracts that were dissolved in a solvent of equal parts castor oil, Tween 80, and dimethyl sulfoxide (CTD) and then added to J2 suspensions in the wells. Final extract dilutions in the wells are presented in the table.
bValues are means of eight replications in each of the two trials, for a total of
The chemotaxis assay used to evaluate the repellent/attractant effects of crude aqueous extracts from vetiver shoots and roots demonstrated that J2 were repelled by 0.1 g/ml VRA and VSA (Table 3). The two aqueous extracts had similar chemotaxis indices. In chemotaxis assays with VO and crude ethanol extracts from French marigold and vetiver roots, the ethanol control did not attract or repel J2 (Table 4). French marigold and vetiver root extract treatments were repellent, although the 1-yr VRE was not significantly different from the water control (Table 4). The root extract from 2-mon VRE (cv. Sierra, greenhouse, U.S.) was twice as repellent as extracts from 1-yr VRE (cv. Songkha 3, field, Thailand) and 4-yr VRE (cv. Sierra, greenhouse, U.S.), but was only significantly greater than the effect of 1-yr VRE. Repellency by French marigold root extracts was similar to repellency with all of the vetiver root extract treatments. VO was not a repellent or an attractant, with a CI that was not significantly different from 1-yr VRE, 4-yr VRE, water, or ethanol in its effects on J2.
Repellent activity of aqueous
Treatmenta | CIb |
---|---|
2-mon VRA 0.1 g/ml | −0.5 bc |
2-mon VSA 0.1 g/ml | −0.6 b |
Control sterile distilled water | 0.0 a |
aVRA = vetiver root aqueous extracts from greenhouse-grown, 2-mon-old cv. Sierra; VSA = vetiver shoot aqueous extracts from greenhouse-grown, 2-mon-old cv. Sierra.
bChemotaxis index (CI): ⩾0.2 indicated an attractant; between 0.2 and 0.1, a weak attractant; 0.1 to −0.1, without effect; between −0.1 and −0.2, a weak repellent; and ⩽−0.2, a repellent.
cValues are means of five replications in each of the two trials, for a total of
Repellent activity of
Treatmenta | CIb |
---|---|
FMRE 0.1 g/ml | −0.4 dec |
2-mon VRE 0.1 g/ml | −0.6 e |
1-yr VRE 0.1 g/ml | −0.3 bcd |
4-yr VRE 0.1 g/ml | −0.3 cde |
VO 0.1 g/ml | −0.1 abc |
Ethanol | 0.1 a |
Sterile distilled water | 0.0 ab |
a2-mon VRE = vetiver root ethanol extracts from greenhouse-grown, 2-mon-old cv. Sierra; 1-yr VRE = vetiver root ethanol extracts from field-grown, 1-yr-old cv. Songkha 3; 4-yr VRE = vetiver root ethanol extracts from greenhouse-grown, 4-yr-old cv. Sierra; VO = commercial vetiver oil.
bChemotaxis Index (CI): ≥0.2 indicated an attractant; between 0.2 and 0.1, a weak attractant; 0.1 to −0.1, without effect; between −0.1 and −0.2, a weak repellent; and ⩽−0.2, a repellent.
cValues are means of five replications in each of the two trials, for a total of
The major component peaks of the three VRE extracts and the vetiver oil (VO) were detected and identified by GC/MS analysis including MS library matching (Table 5, Figs. 2 and 3). The VRE extracts, which represented different vetiver cultivars, growing conditions, and ages, contained similar constituents that differed mainly in their concentrations. Two of the major components in all three extracts and the VO were the sesquiterpene acid 3,3,8,8-tetramethyltricyclo[5.1.0.0(2,4)]oct-5-ene-5-propanoic acid and the sesquiterpene alcohol 6-isopropenyl-4,8a-dimethyl-1,2,3,5,6,7,8,8a-octahydronaphthalen-2-ol (Fig. 2A-D; 3 A,B and Table 5). Among the extracts, the percentage area of 3,3,8,8-tetramethyltricyclo[5.1.0.0(2,4)]oct-5-ene-5-propanoic acid was lowest in the extract from 4-yr, greenhouse-grown vetiver. However, it was even lower in the VO, with the percentage areas in the extracts being 20 to 60 times greater than in the VO. Unlike the extracts from the greenhouse-grown cv. Sierra, the extract from 1-yr, field-grown vetiver cv. Songkha 3 had two other major components, which are esters of fatty acids: ethyl hexadecanoate (ethyl palmitate) and ethyl 9,12-octadecadienoate (ethyl linoleate) (Figs. 2B; 3C,D and Table 5). Vetiver oil had a major component that differed from those found in the extracts: the sesquiterpene alcohol γ-costol (2-(4a,8-dimethyl-1,2,3,4,4a,5,6,7-octahydro-naphthalen-2-yl)-prop-2-en-1-ol) (Fig. 3E, Table 5).
GC-MS spectra of crude
Chemical structures of the major constituents in vetiver root crude extracts and commercial vetiver oil from
Chemical composition of major constituents in three
Sourcea | Compound nameb | Retention time | Component percentage under peakc | Molecular formula | Molecular weight |
---|---|---|---|---|---|
2-mon VRE | 3,3,8,8-Tetramethyltricyclo[5.1.0.0(2,4)]oct-5-ene-5-propanoic acid (a sesquiterpene acid) | 20.11 | 42.8 | C15H22O2 | 234 |
6-Isopropenyl-4,8a-dimethyl-1,2,3,5,6,7,8,8a-octahydronaphthalen-2-ol (a sesquiterpene alcohol) | 19.46 | 11.2 | C15H24O | 220 | |
1-yr VRE | 3,3,8,8-Tetramethyltricyclo[5.1.0.0(2,4)]oct-5-ene-5-propanoic acid | 20.12 | 26.1 | C15H22O2 | 234 |
6-Isopropenyl-4,8a-dimethyl-1,2,3,5,6,7,8,8a-octahydronaphthalen-2-ol | 19.47 | 3.0 | C15H24O | 220 | |
Ethyl hexadecanoate (ethyl palmitate) | 21.86 | 32.3 | C18H36O2 | 284 | |
Ethyl 9,12-Octadecadienoate (ethyl linoleate) | 23.42 | 18.9 | C20H36O2 | 308 | |
4-yr VRE | 3,3,8,8-Tetramethyltricyclo[5.1.0.0(2,4)]oct-5-ene-5-propanoic acid | 20.17 | 14.1 | C15H22O2 | 234 |
6-Isopropenyl-4,8a-dimethyl-1,2,3,5,6,7,8,8a-octahydronaphthalen-2-ol | 19.46 | 9.9 | C15H24O | 220 | |
VO | 3,3,8,8-Tetramethyltricyclo[5.1.0.0(2,4)]oct-5-ene-5-propanoic acid | 20.15 | 0.7 | C15H22O2 | 234 |
6-Isopropenyl-4,8a-dimethyl-1,2,3,5,6,7,8,8a-octahydronaphthalen-2-ol | 19.47 | 17.1 | C15H24O | 220 | |
2-(4a,8-Dimethyl-1,2,3,4,4a,5,6,7-octahydro-naphthalen-2-yl)-prop-2-en-1-ol(the sesquiterpene alcohol γ-costol) | 19.95 | 10.5 | C15H24O | 220 |
a2-mon VRE = vetiver root ethanol extracts from greenhouse-grown, 2-mon-old cv. Sierra; 1-yr VRE = vetiver root ethanol extracts from field-grown, 1-yr-old cv. Songkha 3; 4-yr VRE = vetiver root ethanol extracts from greenhouse-grown, 4-yr-old cv. Sierra; VO = commercial vetiver oil.
bThe components were identified based on the NIST mass spectra library.cRepresents highest area peak of a given compound, and does not include any further isomers.
This study demonstrated that vetiver produces compounds that are repellent and lethal to
In a previous study with vetiver and
Our results with ethanol extracts differ from those reported by Wiratno et al. (2009), who tested the nematotoxicity of ethanol vetiver root extracts prepared from plants grown in an experimental garden in Indonesia. In that investigation, the plant parts were dried in the sun prior to ethanol extraction, and the vetiver extracts were dissolved in a solvent of DMSO:Tween 80:acetone. After 24 hr in 5 mg extract/ml medium,
This premise was supported by the GC-MS analysis of the major compounds from the three ethanol root extracts and one vetiver oil. Although oil production and extraction with ethanol are different processes, there were similarities among all the root-derived samples. Ethyl palmitate, ethyl linoleate, and
It is possible that this difference in plant chemistry played a role in the nematotoxicity of the vetiver extracts vs. the vetiver oil in our study. The higher amounts of the acid in the root extracts than in the root oil may have resulted in repellency and death of the
Vetiver oil was not nematotoxic or repellent to
Other monoterpenes reported from essential oils, including vetiver oil, have been tested against
Vetiver shoot extracts were also active against nematodes in our study. These extracts were aqueous, so the major components were not identified by GC-MS, and the identities of potential nematicidal compounds present in aqueous extracts are unknown at this time. However, some compounds in the aerial parts of vetiver plants were extracted with other solvents and identified in earlier studies. Examples of such constituents include cholesterol, 1,2-bis(4-hydroxy-3-methoxyphenyl)-propane-1,3-diol, 1-
French marigold is well known for activity against plant-parasitic nematodes, and is planted for suppression of multiple taxa, including
In conclusion, the nematicidal and nematode-repellent activity of vetiver root and shoot extracts indicate that the plant chemistry may contribute to the resistance of roots to