1. INTRODUCTION
The preservation of wood using synthetic chemicals has long been used to protect wood from destructive organisms. However, the toxicity and risks to human health as well as the environmental impact of the use of synthetic chemicals have limited their use in many countries (Coles et al., 2014). Grewal et al. (2018) suggested that natural products from bio-renewable resources need to be developed as alternative protective agents. Chemicals, such as wood vinegar, liquid smoke, and bio-oil, are produced as the result of wood or other biomass burning at a high temperature. In addition, burning wood in the absence of oxygen produces by-products like charcoal, tar, and other gaseous chemical components. Due to their complex chemical compounds, wood vinegar is hypothesized to protect wood from fungal and termite attacks. There are numerous studies that have tested their effectiveness against termites (Adfa et al., 2020; Arsyad et al., 2020; Kadir et al., 2022; Subekti and Yoshimura, 2020), other insects (Urrutia et al., 2021), fungi (Adfa et al., 2020; Oramahi et al., 2020a; Sharip et al., 2016), and bacterial attack (Misuri and Marri, 2021; Suresh et al., 2019).
Sharip et al. (2016) reported that condensates from superheated steam pre-treatment of oil palm mesocarp fiber at 190°C–240°C showed antifungal activities. Antifungal tests against Aspergillus fumigatus and Trichoderma asperellum using the agar dilution method at 10% (10 mL wood vinegar: 90 mL Potato Dextrose Agar /PDA solution), and against Ganoderma boninense using the spore germination method at a 1:1 ratio (spore suspensions of 106 with PDA solution) showed promising results. Wood vinegars from a mixture of softwoods exhibited antibacterial activity against Escherichia coli, Enterobacter aerogenes, Pseudomonas aeruginosa, Listeria monocytogenes, and Esterococcus faecalis. The principal antibacterial compounds of these wood vinegars were acetic acid, vanillin, and furfural (Suresh et al., 2019). Wood vinegar from sunflower seed hull waste demonstrated insecticidal activity against Sitophilus orizae, Lasioderma serricorne, and Tribolium castaneum (Urrutia et al., 2021).
Temiz et al. (2013) revealed that giant cane (Arundo donax L.) contains acids, ketones, furans, benzene, phenols, sugars, and guaiacols, which all exhibited antitermitic activity against Reticultermes flavipes.Adfa et al. (2020) reported the antifungal and antitermitic activities of wood vinegar from Cinnamomum parthenoxylon stem wood against Schizophyllum commune, Fomitopsis palustris, and Coptotermes curvignathus. Recently, Kadir et al. (2022) reported that wood vinegar from Dyera costulata produced at 500°C showed antitermitic activity. Termites are important bio-deterioration agents of wood and wood products. Therefore, the development of alternative bio-renewables is needed to protect wood and wood products from termites, C. curvignathus.
To the best of our knowledge, there are no reports on the chemical characterization of wood vinegar from shells or a mixture of shells and nipah fruit fiber, in terms of antitermitic activity. The aim of this study was to evaluate the termicidal activity and chemical components of wood vinegars from shells and a mixture of shells and nipah fruit coir fiber against the subterranean termite, C. curvignathus.
2. MATERIALS and METHODS
The preparation of nipah palm shells (NFS) and a mixture of shells and fiber (MSF) was carried out at the Wood Workshop Laboratory of the Faculty of Forestry, Tanjungpura University, Pontianak. The raw materials (NFS and MSF) were obtained from Kubu Raya Regency, West Kalimantan, Indonesia. NFS and MSF were ground into particles using a 425 micrometer sieve and retained 250 micrometer. The no-choice bioassay procedure was carried out at the Wood Technology Laboratory, Faculty of Forestry, Tanjungpura University. The wood vinegar was made using the pyrolysis method, according to methods outlined in previous studies (Darmadji and Triyudiana, 2006; Oramahi et al., 2021), which was carried out at the Engineering Laboratory, Faculty of Agricultural Technology, Gadjah Mada University, Yogyakarta. This included pouring approximately 5 kg NFS and MSF particles into an aluminum reactor, setting the aluminum condenser circuit, and heating the furnace to 420°C for 150 min.
The chemical components of NFS and MSF wood vinegar were analyzed using gas chromatography with mass spectrometry (GC-MS; QP-210S, Shimadzu Manufacturing, Kyoto, Japan). The GC-MS conditions were as follows: Stabilwax-DA Capillary Column (silica fusion) 30 m × 0.25 mm; injection temperature, 250°C; column temperature, 60°C–200°C, increasing by 10°C/min; and helium flow rate, 40.0 mL/min. The GC-MS was utilized in the electron ionization mode at 70 eV with an interface temperature of 200°C. Eleven samples were injected into the column and maintained at 60°C–200°C with an increase of 5°C per min. Compound identification was carried out by comparing MS spectral data with standard library data (Mun and Ku, 2010) and quantified using the integrated peak areas.
Total phenol was determined for each wood vinegar using the Folin-ciocalteu reagent assay (Theapparat et al., 2019). The absorbance was read with a spectrophotometer (UV-1601 UV-VIS Spectrophotometer, Shimadzu Manufacturing) at a wavelength of 750 nm. The total phenol content of the sample solution was calculated based on the standard curve obtained from the pure phenol solution.
The total acidity in NFS and MSF wood vinegar was carried out according to the AOAC (1990). NFS and MSF wood vinegar (1 mL) were diluted with distilled water (total volume 100 mL). The solution was titrated with standard 0.1 N NaOH solution until the pH reached 8. The total acid content is expressed in percentage weight of acetic acid.
Mature workers and soldiers of C. curvignathus Holmgren were collected from infected trees in the Ambawang area, Kubu Raya district, West Kalimantan, Indonesia. An optional test procedure (Ganapaty et al., 2004) was used to evaluate the termicidal qualities of NFS and MSF wood vinegar. Diluted wood vinegar (2.5%, 5.0%, 7.5%, 10.0%, and 12.5%, v/v) was pipetted and dripped onto filter paper (Whatman No. 1, 55 mm diameter). The treated filter paper was placed in a Petri dish and 30 workers and 5 soldiers of C. curvignathus Holmgren were added to each. Filter paper treated with DI alone was used as a control. All destilat water and vinegar mixtures were diluted to 0.3% (v/v) and the test dishes were then covered and placed in an incubator with approximately 70%–85% humidity in the dark at 27 + 2°C. The number of dead termites was calculated every day for 21 days. Termite mortality and filter paper mass loss were calculated on mean and expressed as a percentage (%). Each measurement was replicated three times, and the filter paper mass loss was calculated at the end of the experiment.
3. RESULTS and DISCUSSION
The chemical compounds in NFS and MSF vinegar are shown in Tables 1 and 2, respectively. The most abundant compounds in NFS vinegar were cyclopropanecarbonyl chloride, 2,5-dichlorophenol, 2-propanone, acetic acid, propanoic acid, benzenesulfonic acid, 3,7- dimethyl-6-octenal, and trans-geraniol. Meanwhile, the main compounds in the MSF vinegar were 1,2-ethanediol, formic acid, acetic acid, ethanoic acid, 2-furancarboxaldehyde, 2-methoxy phenol, 4-methyl phenol, and phenol.
Oramahi et al. (2020a) characterized the main components of wood vinegar made from Shorea leavis at 400°C; these were acetic acid, 1-hydroxy-2-propanone, 2-furancarboxaldehyde, 3-pentanone, phenol, 2-methoxy phenol, 2-methoxy-4-methyl phenol, 2,6-dimethoxy phenol, and 1,2,4-trimethoxybenzene. Aguirre et al. (2020) used GC-MS to analyze wood vinegar made from feedstock, such as pine, poplar, forest pine residues, and urban pruning waste; the main constituents were acetaldehyde, acetic acid, 2-propanone, propanoic acid, 1,2- ethanediol monoacetate, 1-hydroxy-2-butanone, succindialdehyde, furfural, 2-cyclopenten-1-one, 2(5H)-furanone, phenol, 2-methoxyphenol, cresol, 2,6-dimethoxy phenol, and levoglucosan. The main compound of wood vinegar from NFS dan MSF were same with Oramahi et al. (2020a) and Aguirre et al. (2020) results ie : acetic acid, 2-methoxy phenol, and phenol.
Maliang et al. (2021) reported on GC-MS analysis of bamboo tar, which found that the main components were 2,6-dimethoxyphenol, 2- or 4-ethylphenol, 2- or 4-methylphenol, phenol, 4-ethylguaiacol, dimethoxyphenol, 4-methylguaiacol, 4-propenyl-2,6-dimethoxyphenol, and 2,4-dimethylphenol. Baharom et al. (2020) carried out GC-MS on wood vinegars made from Cocos nucifera, Averrhoa carambola, and Mangifera indica; these were different in chemical composition and active compounds. The main compounds identified in C. nucifera shells were furfural, phenol, benzofuran, acetic acid, hexanal, ethanone, and formic acid. In A. carambola, the abundant compounds are furfural, imidazole, 3-pyridinecarboxaldehyde, benzaldehyde, phenol, benzofuran, indene, acetic acid, indazole, naphthalene, cyclohexanecarboxylic acid, palmitamide, palmitic acid, heptadecanenitril, and sterylamide. Meanwhile the dominant components in M. indica are toluene, furfural, imidazole, annulene, benzaldehyde, phenol, carbamic acid, acetic acid, naphthalene, heptadecanenitril, and stearylamide. Lu et al. (2019) characterized the main organic components in wood vinegar from Cunninghamia lanceolata (Lamb.) Hook. waste as acid, phenols, alcohols, ketones, aldehydes, and esters. Wood vinegar obtained from Acacia mangium contains acetic acid, methanol, phenol, o-cresol, furfural, and cyclohexane (Nurhayati et al., 2005).
The main compounds found in liquid smoke from Dyera costula were benzyl alcohol, guaiacol, cresol, 2,6-dimethyl phenol, cathechol, vanillin, aceto vanillone, and syringaldehyde. The most abundant chemical components were phenols, followed by ketones and acetic acid (Kadir et al., 2022). Desvita et al. (2021) stated that the primary compounds in wood vinegar from cacao pod shells (Theobroma cacao L.) are phenol and its derivatives, such as phenol; 2-methyl-p-cresol; phenol; 3-methyl-; 1-propanol; 2-amino-1-octadecanamine; n- methyl-2-amino-1-propanol; and 4-ethyl-phenol; 4- ethyl. Recently, Aly et al. (2022) reported that the main components of wood vinegar from Ficus benjamina were syringol (48.98%); 4,5 dimethoxy-2-methyl phenol (4.16%); guaiacol-4-ethyl (3.05%); mequinol (2.61%); estragole (33.09%); benzene; 1,2,5-trimethoxy-3-methyl (2.65%); and butylated hydroxytoluene (1.69%). In addition, Oramahi et al. (2022) reported that the dominant components of vinegar made from mabang wood (Shorea panchyphylla) were 1,2-ethanediol, fluoromethane, formic acid, 2-propanone, acetic acid, acetol, furfural, 2,4-hexadecanoic acid, and guaiacol.
In this study, the performance of NFS and MSF exhibited several significant differences. Total phenol and total acid of NFS and MSF wood vinegar are shown in Table 3.
| Wood vinegar source | Components | |
|---|---|---|
| Phenol (%)* | Acid (%)* | |
| NFS | 1.09 | 11.78 |
| MSF | 1.84 | 9.18 |
Total phenol and total acid contents in the NFS wood vinegar were 1.09% and 11.78%, respectively, while the total phenol and acid contents in the MSF wood vinegar were 1.84% and 9.18%, respectively. The total acid content of NFS was greater than that of MSF, resulting in higher antitermitic activity and lower loss of filter paper mass.
The maximum total phenol and total acid contents of wood vinegar from oil palm empty bunches were 2.98% and 10.04%, respectively (Oramahi et al., 2019). The abundant chemical components of vinegar are strongly influenced by the chemical nature of the biomass of origin, including cellulose, hemicellulose, lignin, and temperature of pyrolysis (Abnisa et al., 2013; Demiral and Ayan, 2011). In this research, we focus only on two kinds of wood vinegar.
In this study, the daily termite mortality C. curvignathus treated with NFS and MSF wood vinegar was determined for 21 days using a no-choice feeding test; the results are presented in Table 4. Increasing concentrations of wood vinegar were associated with significantly increased mortality of C. curvignathus and decreased mass loss of the filter paper (Table 4); the highest termite mortality was at the highest concentration (12.5%) of wood vinegar. Statistically significant differences in filter paper consumption were observed for diluted wood vinegar between the control and treated samples. This trend is similar to Oramahi et al. (2020b) wherein Coptotermes formosanus died after 21 days of exposure.
Termicidal activity was consistent with the total concentration of acid in the wood vinegars (Table 1), which is in agreement with previous results. For example, Oramahi and Yoshimura (2013) examined wood vinegar from Vitex pubescens Vahl and found that it exhibited termicidal activity against C. formosanus and Reticulitermes speratus. The largest component of vinegar that contributed to high termicidal activity was total acid.
Overall, wood vinegar contributed significantly to termite mortality and the effectiveness of wood vinegar against C. curvignathus increased with the concentration of the wood vinegar. Wood vinegar made from the shells of the nipah fruit lost more filter paper mass than wood vinegar made from a mixture of shells and nipah fruit coir fiber at a concentration of 12.5%. We hypothesize that the chemical compounds found in the nipah fruit coir fiber vinegar, including acetic acid, propanoic acid, benzenesulfonic acid, and octadecanoic acid, together with its characteristic phenol derivatives may cause this antitermitic activity. Similarly, Kadir et al. (2022) concluded that wood vinegar from D. costulata was effective against C. curvignathus Holmgren. Furthermore, Sunarta et al. (2011) stated that wood vinegars from oil palm fruit had the potential to be an environmentally low-impact wood preservative for preventing attacks by Criptotermes spp.
4. CONCLUSIONS
Wood vinegars made from the shells of the nipah fruit shells (NSF) and with mixture of shells and fiber (MSF) have anti-termite potential, especially NFS vinegar against C. curvignathus. The main compounds found in the NFS vinegar were cyclopropanecarbonyl chloride, 2,5-dichlorophenol, 2-propanone, acetic acid, propanoic acid, benzenesulfonic acid, 3,7-dimethyl- 6-octenal, and trans-geraniol. Meanwhile, in the MSF vinegar, the abundant compounds were 1,2-ethanediol, formic acid, acetic acid, ethanoic, 2-furancarboxaldehyde, phenol, 2-methoxy phenol, and 4-methyl phenol.
