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Article

Nematicidal Activity of Alkyloxyalkanols Against Bursaphelenchus xylophilus

by
Joon Oh Park
1,2,†,
Sujin Lee
1,3,†,
Min-Jung Kim
1 and
Junheon Kim
1,*
1
Forest Entomology and Pathology Division, National Institute of Forest Science, Seoul 02455, Republic of Korea
2
Urban Forest Clinic, Yangpyeong 12501, Republic of Korea
3
Department of Biochemistry, Nutrition and Health Promotion, Mississippi State University, Starkville, MS 39762, USA
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Appl. Sci. 2025, 15(18), 9862; https://doi.org/10.3390/app15189862
Submission received: 28 July 2025 / Revised: 5 September 2025 / Accepted: 6 September 2025 / Published: 9 September 2025
(This article belongs to the Section Agricultural Science and Technology)
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Abstract

Pine wilt disease, caused by the pine wood nematode Bursaphelenchus xylophilus (Steiner & Bührer) Nickle, poses a major threat to pine forests worldwide. While avermectin-based pesticides are currently used for pine wilt disease management, alternative approaches are needed to mitigate the risk of resistance. This study evaluated the nematicidal activity of 24 synthetic alkyloxyalkanols (ROR′OH) against B. xylophilus. The compounds were synthesized by the etherification of diols with 1-bromoalkanes and tested in a microplate bioassay. Mortality was measured after 24 h, and LD50 values were calculated. Several compounds, including 2-(1-decyloxyl)-1-ethanol (C10OC2OH) and 8-(1-hexyloxy)-1-octanol (C6OC8OH), showed potent nematicidal effects, with LD50 values of less than 50 ppm. Structure–activity relationship analysis revealed that compounds with chains containing an even number of carbons in both the alkyl and alkyloxy groups tended to exhibit increased activity. Clustering analysis confirmed that carbon parity significantly affected efficacy (Mann–Whitney U = 15, p < 0.001). Compared with previously reported plant-derived compounds, several of these alkyloxyalkanols demonstrated superior potency. The results suggest that odd–even carbon chain parity, a known physicochemical phenomenon of n-alkanes, may underlie variations in nematicidal activity. These findings provide insight into the design of novel nematicides targeting B. xylophilus.

1. Introduction

Pine wilt disease (PWD), caused by the plant-parasitic nematode Bursaphelenchus xylophilus (Steiner & Buhrer 1934) Nickle 1981 (Aphelenchida, Parasitaphelenchidae) pine wood nematode (PWN) (Figure 1), is a major cause of mortality in pine species across East Asia and parts of Europe [1,2,3]. The disease was first documented in Korea in 1988 and has since spread to most of the country’s pine-growing regions, severely affecting dominant species such as red pine (Pinus densiflora), black pine (P. thunbergii), and Korean pine (P. koraiensis) [4]. In Europe, P. nigra and P. radiata are among the most susceptible species [2,5]. Given that pine species dominate Korean forest ecosystems, PWD results in considerable environmental degradation and economic losses [6]. Furthermore, the European forestry sector is projected to experience substantial financial impact from ongoing and future PWN infestations [3,7].
The pathogenicity of B. xylophilus stems from its ability to rapidly migrate through the resin canals of host trees, disrupting water transport and inducing oxidative stress, which leads to needle discoloration, wilting, and eventual tree death. Its life cycle is short, and reproduction is prolific, allowing for swift population expansion under favorable conditions [8,9,10]. The nematode is vectored primarily by Monochamus spp. (Coleoptera, Cerambycidae), which introduce it during maturation feeding, further accelerating its spread across forest ecosystems [11].
Current Korean management programs integrate aerial spraying to reduce populations of the insect vectors (Monochamus alternatus Hope, 1842 and M. saltuarius Gebler, 1830) with systemic trunk injections of avermectin-based nematicides [12,13]. These compounds are valued for their high efficacy and relative environmental safety; however, prolonged reliance on a single chemical class can eventually lead to resistance, as documented in other nematode and insect pests [14,15,16]. Although resistance to avermectins in B. xylophilus has not yet been confirmed [17], adopting alternative chemical classes is advisable to preserve control effectiveness and slow resistance development [18,19,20]. In response, researchers have explored natural products such as plant essential oils, botanical extracts, and microbial metabolites as candidate nematicides [21,22,23,24]. While some of these exhibit promising activity, their efficacy often falls short of commercial standards when tested under field conditions [25,26]. More recently, attention has turned to synthetic compounds with amphiphilic properties that may offer novel modes of action and improved stability.
Among these, alkyloxyalkanols represent a structurally simple yet versatile class of molecules characterized by both hydrophilic hydroxyl groups and hydrophobic alkyl chains. Their amphiphilic nature suggests potential interactions with lipid membranes and disruption of nematode cellular integrity. Moreover, their modular structure allows for systematic modification, making them ideal candidates for structure–activity relationship (SAR) studies. Despite these advantages, their nematicidal potential has received limited attention compared to more established chemical scaffolds.
Interestingly, 2-(1-undecyloxy)-1-ethanol (monochamol), an aggregation pheromone for Monochamus spp. [27,28,29,30], has recently been reported to exhibit nematicidal activity against PWN [31]. Furthermore, structural modifications of phenolic alcohols, such as the conversion of hydroxy (-OH) groups to hydroxyalkyloxy (-OROH) groups, have been shown to enhance nematicidal activity [32]. However, systematic studies evaluating the SARs of such aliphatic compounds, especially with respect to the carbon chain length and its even–odd parity, remain limited.
To address this gap, the present study investigates the nematicidal activity of 24 synthetic alkyloxyalkanols (ROR′OH) against B. xylophilus. We assess their efficacy and analyze how structural features such as the total carbon number and even–odd parity of alkyl (-R′OH) and alkyloxy (RO-) groups influence nematicidal potency. By combining in vitro bioassays with statistical SAR analysis, this work aims to inform the rational design of next-generation nematicides for the sustainable management of pine wilt disease.

2. Materials and Methods

2.1. Pine Wood Nematodes

Wood chips infested with pine wood nematode (Bursaphelenchus xylophilus) were collected from naturally infected trees in the field. The nematodes were separated from the wood material using the Baermann funnel extraction technique and identified by a combination of morphological criteria and restriction fragment length polymorphism (RFLP) analysis, as described in previous studies [33]. Cultures were maintained on potato dextrose agar (PDA) plates overgrown with Botrytis cinerea at 25 ± 1 °C and 40% relative humidity. Several laboratory generations were propagated before their use in bioassays.

2.2. Chemicals

The authentic compounds used for the bioassays are listed in Table 1. Abamectin (98% pure) and Triton X-100 were purchased from Sigma-Aldrich (St. Louis, MO, USA). Dimethyl sulfoxide (DMSO) was obtained from Wako Chemicals (Osaka, Japan).

2.3. Instrumental Analysis

Gas chromatography–Mass spectrometry (GC–MS) analysis was conducted using a 7890A gas chromatograph coupled with a 5975C mass spectrometer (Agilent Technologies, Santa Clara, CA, USA), equipped with an HP-INNOWax capillary column (30 m length × 0.25 mm internal diameter, 0.25 μm film thickness; Agilent Technologies). The oven temperature program began with an initial hold at 40 °C for 1 min, followed by a linear increase at 6 °C/min until reaching 250 °C, which was then sustained for 4 min. Helium served as the carrier gas, maintained at a constant flow rate of 1 mL/min. This analytical setup was employed to confirm the chemical structure and purity of the synthesized compounds. Additionally, nuclear magnetic resonance (NMR) spectroscopy was used to further characterize the compounds. Proton (1H) and carbon (13C) NMR spectra were recorded at 500 MHz and 125 MHz, respectively, using a Varian UI500 spectrometer (Agilent Technologies) at the Korea Basic Science Institute, Seoul, Republic of Korea. All measurements were carried out in deuterated chloroform (CDCl3), with tetramethylsilane (TMS) serving as the internal reference standard.

2.4. Synthesis of the Alkyloxyalkanols

2-(1-Alkyloxy)-1-ethanol (ROC2OH) was synthesized following the method of Kim et al. [31], and the spectral data were consistent with previous reports. 4-(1-Alkyloxy)-1-butanol (ROC4OH) was synthesized following the method of Loffredo et al. [34] (Scheme A in Figure 2), and the other alkyloxyalkanols (ROCR′OH, R′ = C3, C5, C6, C7, C8, and C9) were synthesized following the methods of Pajares et al. [30] (Scheme B in Figure 2). The yields and 1H and 13C NMR spectral data of the synthesized compounds are presented in the Supplementary Materials.

2.4.1. 4-(1-Alkyloxyl)-1-butanol

The general procedure was as follows. First, 80 mmol of 1,4-butanediol (Daejung, Hwaseong, Republic of Korea) was added to a 3-necked round-bottom flask equipped with a dropping funnel, a reflux condenser, and an inlet for nitrogen. Sodium (23 mmol, Alfa Aesar, Waltham, MA, USA) was carefully added to the 1,4-butanediol mixture in small portions with vigorous magnetic stirring, and the mixture was heated to 60 °C until the sodium had dissolved completely. The appropriate 1-bromoalkane (20 mmol, Alfa Aesar or Sigma-Aldrich) was added, and the solution was then heated at 60 °C for 4–6 h. After cooling and adding water, the solution was extracted with diethyl ether three times. The combined organic layer was washed with 2 N HCl and brine and dried over MgSO4. After the solvent was removed, the residue was subjected to silica gel column chromatography (35% diethyl ether in hexane) to obtain the desired compound.

2.4.2. 3-(1-Alkyloxy)-1-propanol, 5-(1-Alkyloxy)-1-pentanol, 6-(1-Alkyloxy)-1-hexanol, 7-(1-Alkyloxy)-1-heptanol, 8-(1-Alkyloxy)-1-octanol, and 9-(1-Alkyloxy)-1-nonanol

To a 3-necked round-bottom flask equipped with a dropping funnel, a reflux condenser, and inlet for nitrogen containing sodium hydride (65 mmol; Alfa Aesar, 65% in mineral oil) suspended in 100 mL of dry N,N-dimethylformamide (DMF) was added 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, or 1,9-nonanediol (65 mmol, Alfa Aesar or Sigma-Aldrich) in dry DMF (50 mL) dropwise, and the mixture was heated to 50 °C for 1 h. After cooling, the appropriate 1-bromoalkane (40 mmol, Alfa Aesar or Sigma-Aldrich) was added, and the solution was then heated at 60 °C and allowed to stand overnight. After cooling, the work-up and purification described above were performed.

2.5. Nematicidal Activity

Stock solutions of each alkyloxyalkanol compound and abamectin were initially prepared in dimethyl sulfoxide (DMSO) at a concentration of 10,000 ppm. These solutions were subsequently diluted using distilled water containing Triton X-100, with serial dilutions performed to evaluate nematicidal efficacy. If a particular concentration demonstrated notable activity against pinewood nematodes (PWNs), further dilutions were made accordingly. The final working solutions contained 1% DMSO and 0.2 ppm Triton X-100. For comparative purposes, alkyloxyethanol derivatives previously reported to exhibit nematicidal properties were also included in the assay [31].
Approximately 1000 PWNs, comprising a mixed population of males, females, and juveniles in a ratio of 1:1.2:9.5, were suspended in 90 µL of distilled water and dispensed into individual wells of a 96-well microplate (Corning, Glendale, AZ, USA). Each well then received 10 µL of the test solution. Control wells were treated with solutions containing only DMSO and Triton X-100 at the same final concentrations. The plates were incubated under conditions identical to those used for routine nematode culture maintenance.
After 24 h of incubation, nematode mortality was assessed using a stereoscopic microscope. Nematodes were classified as dead if they exhibited a straight body posture and failed to respond to mechanical stimulation, even after transfer to fresh water. The experiment was repeated over three to four independent trials, each consisting of three replicates, conducted on separate days. All data collected across trials were combined for statistical analysis.

2.6. Statistical Analyses

Nematode mortality was corrected using Abbott’s formula, and the corrected mortality data were arcsine square root-transformed for analysis via one-way ANOVA [35]. The transformed data were confirmed to be normally distributed via normality tests. The means were analyzed by Tukey’s test. The LD50 and LD90 values were estimated by probit analysis of the dose-response data. Statistical analyses were performed using JMP ver. 9.0.2 (SAS Institute Inc., Cary, NC, USA). The untransformed mean (±SEM) values are reported.
Unsupervised clustering analysis was conducted to evaluate whether the properties of the compounds examined in this study can explain their insecticidal effects. We considered properties such as the number of carbons on the alkyloxy group (RO-), the number of carbons on the alkanol group (-R′OH), whether the number of carbons on the RO- is even (Reven0), whether the -R′OH is even (R′even0), the ratio of R to R′ (R/R′), the total number of carbons (total), LogP, LogS, and the topological index as variables. We performed principal component analysis (PCA) and then used the first three principal components for the analysis. We subsequently performed k-means clustering analysis with two groups (k = 2) using the FactorMineR package in R 4.4.0. The LD50 values of the insecticides, which clustered into two groups, were compared using the Mann-Whitney U test with a 5% error rate in R 4.4.0.

3. Results

3.1. Nematicidal Activity of Alkyloxyalkanols

The nematicidal activity of the tested alkyloxyalkanols and abamectin was quantified using LD50 and LD90 values (Table 2). None of the synthetic alkyloxyalkanol derivatives was superior to abamectin in efficacy. Detailed mortality data for each concentration level are available in Supplementary Materials (Table S1). At a concentration of 100 ppm, most compounds exhibited similar nematicidal effects, with the exception of C5OC9OH, however, which, at 500 ppm, exhibited considerable differences (Table S1).

3.2. Multivariate Analysis of Nematicidal Activity and Alkyloxyalkanol

Unsupervised clustering analysis was conducted to assess whether the structural features of the alkyloxyalkanols could explain their differences in nematicidal efficacy. The three principal components derived from the structural property variables explained 86.4% of the total variance (Figure 3). Furthermore, the alkyloxyalkanols formed two clusters upon k-means clustering, and a significant difference in the LD50 values was observed between the two groups (Mann–Whitney U = 15; p < 0.001). Notably, compounds with chains with an even number of carbons in both the alkyl (-R′OH) and alkyloxy (RO-) groups tended to exhibit stronger nematicidal activity, and the activity generally increased along with the total carbon number (LD50: C14 ≤ C13 < C12).

4. Discussion

In this study, 24 synthetic alkyloxyalkanols (ROR′OH) were evaluated for their nematicidal activity against Bursaphelenchus xylophilus. Among them, C10OC2OH, C12OC2OH, C11OC2OH, C11OC3OH, C10OC4OH and C6OC8OH exhibited relatively strong activities in the term of LD50 values than others. These variations appeared to correlate with the molecular architecture of the carbon chains. In general, compounds featuring alkyl groups (-R′OH) with an odd number of carbon atoms—such as ROC5OH, ROC7OH, and ROC9OH—tended to show reduced nematicidal activity. For instance, at 500 ppm, these compounds induced less than 10% mortality, whereas C9OC5OH achieved 17.1%. Conversely, compounds like ROC2OH, C11OC3OH, C10OC4OH, and C6OC8OH demonstrated LD50 values between 42.6 and 49.2 ppm, indicating stronger activity than many previously studied natural products. For comparison, phenolic compounds such as thymol, and carvacrol have reported LD50 values of 96–119 and 97–125 ppm, respectively, while aliphatic alcohols like geraniol and nerol show much weaker activity (415–540 and 865–979 ppm) [36]. Previously, the nematicidal activity of 2-(1-alkyloxyl)-1-ethanol was reported [31]. The LD50 values of C10OC2OH, C11OC2OH, and C12OC2OH in that study were much lower than those in the present study. A key methodological difference lies in the use of the surfactant BFC30 in that study, which is no longer commercially available. Its absence in the present work may explain the comparatively reduced activity observed.
To control B. xylophilus, extensive screening of naturally derived compounds has been conducted, and more recently, research has focused on structural modification of nematicidal compounds to develop more effective agents. Among such studies, aromatic heterocycles such as coumarins and indoles have received considerable attention. For example, 3-indoleacetonitrile, in which an acetonitrile group is attached to the indole backbone, and 5-iodoindole, bearing an iodine substituent, exhibited stronger nematicidal activity than indole and its simple analogs [22,37]. Pan et al. [38] synthesized coumarin derivatives and demonstrated that targeted modification at the C7 hydroxyl position was more effective than modification at the C4 hydroxyl, and that the length of the coupling chain played a crucial role in nematicidal activity. In the present study, we evaluated the nematicidal activity of alkyloxyalkanols with varying carbon chain lengths in both the alkyloxy and alkanol moieties. Furthermore, it would be valuable to assess the nematicidal activity of derivatives in which the hydroxyalkyl (-ROH) group is replaced by other functional groups, such as α,β-unsaturated alcohol and α,β-unsaturated aldehyde (-R-CH=CH-CH2OH, -R-CH=CH-CHO). In line with this approach, Seo et al. [39] reported that 2-alkenols and 2-alkenals (α,β-unsaturated alcohol and α,β-unsaturated aldehyde) exhibited higher nematicidal activity than saturated compounds, such as hydrocarbons, alkyl acetates, and alkanoic acids.
Toxicological assessment is essential for the development of new pesticides, as potential risks to humans, invertebrates, and vertebrates must be evaluated. Among the 24 compounds tested, only the toxicity of alkyloxyethanols has been reported, in the context of their use as polyethylene glycol (PEG) derivatives in cosmetics [40]. This limited information highlights the need for comprehensive safety evaluation of alkyloxyalkanols before their potential application as nematicides.
To explore the possible mode of action of alkyloxyalkanols in B. xylophilus, we conducted preliminary assays of inhibitory activity against acetylcholinesterase (AChE) and glutathione S-transferase (GST) using C10OC2OH and C11OC2OH. No inhibition was detected at the tested concentrations (Table S2). Consistently, Kim et al. [32] reported that benzyloxyalkanols exhibited nematicidal activity but did not inhibit AChE or GST. In contrast, inhibitory activity against AChE and GST has been described for certain aliphatic compounds with nematicidal properties [41]. Taken together, these results suggest that AChE and GST are unlikely to be involved in the nematicidal effects of alkyloxyalkanols. Therefore, elucidating alternative mechanisms—such as inhibition of monooxygenase and ATPase—would be needed for the safe and effective development of alkyloxyalkanols as nematicides.
SAR analysis highlighted the critical role of specific structural modifications in enhancing insecticidal potency [42]. Previous research has shown that the nematicidal activity of aliphatic compounds is influenced by both the functional group type and the carbon chain length. Compounds such as alkanols and 2E-alkenols are most active with 8–11 carbons, whereas 2E-alkenals and alkanoic acids show maximum activity with 7–10 and 7–11 carbons, respectively [39]. In the case of benzyloxyalkanols, the number of carbons in the hydroxyalkyloxy group is related to nematicidal activity [32].
In the present study, we evaluated compounds with the molecular formulas C12H26O2, C13H28O2, and C14H30O2 as ROR′OH structures. The total chain length appeared to have a limited effect, whereas the specific positioning and structure of the alkyl (-R′OH) and alkyloxy (RO-) groups played more substantial roles. Compounds containing an alkyloxy (RO-) group with an even number of carbons generally tended to have higher nematicidal activity. To our knowledge, there are no prior reports showing that the even–odd parity of the carbon chain length directly influences insecticidal activity in the context of their SAR. The phenomenon known as the odd–even effect describes how certain physical properties of n-alkanes (CnH2n+2)—such as the melting point, density, conformational ordering, and molecular dynamics—alternate depending on whether the carbon number is even or odd [43]. Dhiman et al. [44] reported that this effect persists in the translational dynamics of n-alkanes above their melting points. Although our study did not investigate the physicochemical properties, the observed differences in nematicidal activity between compounds with odd and even numbers of carbons in their alkyl and alkyloxy chains may be attributable to the odd–even effect.

5. Conclusions

Several alkyloxyalkanol derivatives, notably C10OC2OH, C12OC2OH, and C6OC8OH, demonstrated potent nematicidal activity against Bursaphelenchus xylophilus, with LD50 values below 50 ppm. These findings suggest that structural features such as even-numbered carbon chains contribute significantly to efficacy. However, this study was limited to in vitro assays and did not include field validation or comprehensive toxicological profiling. The environmental impact of these compounds remains to be assessed, particularly regarding effects on non-target organisms. Future research should focus on field trials, detailed ecotoxicological evaluations, and mechanistic studies to elucidate how these compounds interact with nematode physiology. Such efforts will be essential to confirm their suitability as sustainable alternatives to existing nematicides.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/app15189862/s1: Table S1. Nematicidal activity of alkyloxyalkanols (ROR′OH) at each concentration; Table S2. Acetylcholinesterase (AChE) and glutathione S-transferase (GST) inhibitory activity of C10OC2OH and C11OC2OH. Figure S1. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 2-(1-decyloxy)-1-ethanol. Figure S2. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 2-(1-undecyloxy)-1-ethanol. Figure S3. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR spectra of 2-(1-dodecyloxy)-1-ethanol. Figure S4. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 3-(1-nonyloxy)-1-propanol. Figure S5. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 3-(1-decyloxy)-1-propanol. Figure S6. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 3-(1-undecyloxy)-1-propanol. Figure S7. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 4-(1-octyloxy)-1-butanol. Figure S8. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 4-(1-nonyloxy)-1-butanol. Figure S9. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 4-(1-decyloxy)-1-butanol. Figure S10. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 5-(1-heptyloxy)-1-pentanol. Figure S11. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 5-(1-octyloxy)-1-pentanol. Figure S12. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 5-(1-nonyloxy)-1-pentanol. Figure S13. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 6-(1-hexyloxy)-1-hexanol. Figure S14. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 6-(1-heptyloxy)-1-hexanol. Figure S15. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 6-(1-octyloxy)-1-hexanol. Figure S16. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 7-(1-pentyloxy)-1-heptanol. Figure S17. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 7-(1-hexyloxy)-1-heptanol. Figure S18. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 7-(1-heptyloxy)-1-heptanol. Figure S19. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 8-(1-butyloxy)-1-octanol. Figure S20. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 8-(1-pentyloxy)-1-octanol. Figure S21. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 8-(1-hexyloxy)-1-octanol. Figure S22. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 9-(1-propyloxy)-1-nonanol. Figure S23. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 9-(1-butyloxy)-1-nonanol. Figure S24. Mass spectrum (upper), 1H-NMR (middle) and 13C-NMR (lower) spectra of 9-(1-pentyloxy)-1-nonanol. References [31,32,34,41,45,46] are cited in the supplementary materials.

Author Contributions

Conceptualization, J.K.; methodology, J.K. and J.O.P.; validation, S.L. and J.O.P.; formal analysis, S.L.; statistical analysis, M.-J.K.; investigation, S.L. and J.O.P.; writing—original draft preparation, J.K. and M.-J.K.; writing—review and editing, J.O.P., S.L., M.-J.K. and J.K.; project administration, J.K.; funding acquisition, J.K. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Institute of Forest Science (FE-0703-2023-01).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Materials. Further inquiries can be directed to the corresponding author.

Acknowledgments

The authors thank Kyungjae Yoon, Chungbuk National University, for conducting the AChE and GST inhibition assay, and Yeong-Jeong Lim, National Institute of Forest Science, for providing the picture of male and female B. xylophilus.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Applsci 15 09862 g001
Figure 1. Morphology of Bursaphelenchus xylophilus. (A) Live adults and juvenile of B. xylophilus in the control group. (B) Dead B. xylophilus after treatment with compounds. (C) Female adult. (D) Male adult.
Figure 1. Morphology of Bursaphelenchus xylophilus. (A) Live adults and juvenile of B. xylophilus in the control group. (B) Dead B. xylophilus after treatment with compounds. (C) Female adult. (D) Male adult.
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Figure 2. Representative synthetic scheme. Scheme A: 4-(1-octyloxy)-1-butanol; Scheme B: 3-(1-nonyloxy)-1-propanol.
Figure 2. Representative synthetic scheme. Scheme A: 4-(1-octyloxy)-1-butanol; Scheme B: 3-(1-nonyloxy)-1-propanol.
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Figure 3. Results of the multivariate analysis classification of the alkyloxyalkanol property variables. Principal component (PC) 1 and PC 2 explain 40.5% and 30.4% of the variance in the data, respectively. The colors of the circles indicate the different groups, and the size represents the LD50 value. There was a significant difference in the LD50 values between the two groups (Mann-Whitney U = 15; p < 0.001).
Figure 3. Results of the multivariate analysis classification of the alkyloxyalkanol property variables. Principal component (PC) 1 and PC 2 explain 40.5% and 30.4% of the variance in the data, respectively. The colors of the circles indicate the different groups, and the size represents the LD50 value. There was a significant difference in the LD50 values between the two groups (Mann-Whitney U = 15; p < 0.001).
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Table 1. The 24 synthetic compounds subjected to nematicidal activity testing and purity.
Table 1. The 24 synthetic compounds subjected to nematicidal activity testing and purity.
IUPAC NameAbbreviationPurity
2-(1-Decyloxy)-1-ethanolC10OC2OH98.6
2-(1-Undecyloxy)-1-ethanolC11OC2OH98.3
2-(1-Dodecyloxy)-1-ethanolC12OC2OH97.2
3-(1-Nonyloxy)-1-propanolC9OC3OH96.2
3-(1-Decyloxy)-1-propanolC10C3OH98.9
3-(1-Undecyloxy)-1-propanolC11OC3OH96.1
4-(1-Octyloxy)-1-butanolC8OC4OH97.3
4-(1-Nonyloxy)-1-butanolC9OC4OH98.3
4-(1-Decyloxy)-1-butanolC10OC4OH97.2
5-(1-Heptyloxy)-1-pentanolC7OC5OH98.2
5-(1-Octyloxy)-1-pentanolC8OC5OH96.5
5-(1-Nonyloxy)-1-pentanolC9OC5OH98.0
6-(1-Hexyloxy)-1-hexanolC6OC6OH95.5
6-(1-Heptyloxy)-1-hexanolC7OC6OH99.0
6-(1-Octyloxy)-1-hexanolC8OC6OH98.9
7-(1-Pentyloxy)-1-heptanolC5OC7OH96.5
7-(1-Hexyloxy)-1-heptanolC6OC7OH95.8
7-(1-Heptyloxy)-1-heptanolC7OC7OH98.4
8-(1-Butyloxy)-1-octanolC4OC8OH99.5
8-(1-Pentyloxy)-1-octanolC5OC8OH99.3
8-(1-Hexyloxy)-1-octanolC6OC8OH99.5
9-(1-Propyloxy)-1-nonanolC3OC9OH97.8
9-(1-Butyloxy)-1-nonanolC4OC9OH98.3
9-(1-Pentyloxy)-1-nonanolC5OC9OH95.7
Table 2. Nematicidal activity and LD50 and LD90 values of the alkyloxyalkanols and abamectin against the pine wood nematode Bursaphelenchus xylophilus.
Table 2. Nematicidal activity and LD50 and LD90 values of the alkyloxyalkanols and abamectin against the pine wood nematode Bursaphelenchus xylophilus.
CompoundLD50
(95% CI; ppm)		LD90
(95% CI; ppm)		Slope ± SEGoodness of Fit
χ2df
C10OC2OH42.8 (39.6–45.4)69.8 (65.7–75.9)2.62 ± 0.289.414
C9OC3OH96.8 (86.4–110.2)227.6 (184.9–310.2)3.45 ± 0.37445.446
C8OC4OH276.5 (215.9–370.8)2534.0 (1548.0–5033.0)1.33 ± 0.12548.551
C7OC5OH560.5 (363.5–861.8)1603.0 (993.4–6602.0)2.81 ± 0.761804.128
C6OC6OH390.2 (288.5–552.0)1932.0 (1170.0–4629.0)1.84 ± 0.281842.650
C5OC7OH800.9 (746.2–851.0)1057.5 (990.3–1151.5)10.62 ± 1.15249.522
C4OC8OH239.2 (190.7–301.4)1272.0 (891.5–2099.0)1.77 ± 0.18760.446
C3OC9OH802.3 (706.4–879.1)1042.2 (949.6–1196.9)11.28 ± 1.99591.422
C11OC2OH46.1 (40.9–51.3)120.7 (104.4–145.7)3.07 ± 0.261343.699
C10C3OH73.4 (67.5–79.9)150.2 (128.6–189.9)4.11 ± 0.46328.546
C9OC4OH65.5 (53.5–80.5)236.6 (176.6–357.3)2.30 ± 0.24933.551
C8OC5OH576.8 (353.2–920.8)1440.0 (907.5–7557)3.22 ± 1.002405.928
C7OC6OH131.2 (87.3–194.8)1176.0 (648.1–3240.0)1.35 ± 0.203478.874
C6OC7OH565.8 (n.a.)626.6 (n.a.)28.90 ± 32.8961.322
C5OC8OH107.9 (85.9–132.5)487.3 (368.1–715.0)1.96 ± 0.19691.346
C4OC9OH734.7 (689.4–779.7)936.1 (879.1–1008.6)12.18 ± 1.05212.722
C12OC2OH42.6 (36.1–49.0)231.6 (201.2–273.8)0.76 ± 0.22233.314
C11OC3OH49.2 (43.4–54.4)145.8 (127.1–175.9)2.72 ± 0.25164.546
C10OC4OH43.1 (32.4–56.4)188.4 (130.3–328.4)2.00 ± 0.251357.251
C9OC5OH514.4 (347.0–725.9)1420.0 (939.7–4014.0)2.91 ± 0.711480.228
C8OC6OH55.1 (46.2–64.7)184.0 (147.4–248.4)2.45 ± 0.241291.274
C7OC7OH627.2 (601.3–664.6)766.2 (714.0–849.1)14.70 ± 1.4068.422
C6OC8OH48.0 (35.2–64.0)152.6 (106.8–275.1)2.55 ± 0.40228.558
C5OC9OH871.7 (847.2–896.3)1222.0 (1174–1283)8.73 ± 0.4646.822
Abamectin2.2 (1.87–2.55)13.1 (11.4–15.9)1.66 ± 0.091008.1154
LD50 and LD90 values: The concentrations (ppm) required to kill 50% and 90% of nematodes, respectively, with 95% confidence intervals (CI) shown in parentheses. Slope ± SE: the regression slope of the dose–response relationship and its standard error. χ2 and df: the chi-square statistic and degrees of freedom, which are indicators for evaluating the goodness of fit of the probit model.
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Park, J.O.; Lee, S.; Kim, M.-J.; Kim, J. Nematicidal Activity of Alkyloxyalkanols Against Bursaphelenchus xylophilus. Appl. Sci. 2025, 15, 9862. https://doi.org/10.3390/app15189862

AMA Style

Park JO, Lee S, Kim M-J, Kim J. Nematicidal Activity of Alkyloxyalkanols Against Bursaphelenchus xylophilus. Applied Sciences. 2025; 15(18):9862. https://doi.org/10.3390/app15189862

Chicago/Turabian Style

Park, Joon Oh, Sujin Lee, Min-Jung Kim, and Junheon Kim. 2025. "Nematicidal Activity of Alkyloxyalkanols Against Bursaphelenchus xylophilus" Applied Sciences 15, no. 18: 9862. https://doi.org/10.3390/app15189862

APA Style

Park, J. O., Lee, S., Kim, M.-J., & Kim, J. (2025). Nematicidal Activity of Alkyloxyalkanols Against Bursaphelenchus xylophilus. Applied Sciences, 15(18), 9862. https://doi.org/10.3390/app15189862

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