Original Article Larvicidal Activity of Essential Oil of Syzygium Aromaticum (Clove) in Com- Parison with Its Major Constituent, Eugenol, Against Anopheles Stephensi
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J Arthropod-Borne Dis, December 2018, 12(4): 361–369 M Osanloo et al.: Larvicidal Activity of … Original Article Larvicidal Activity of Essential Oil of Syzygium aromaticum (Clove) in Com- parison with Its Major Constituent, Eugenol, against Anopheles stephensi Mahmoud Osanloo 1, 2, Mohammad Mehdi Sedaghat 3, Fariba Esmaeili 1, *Amir Amani 1, 4 1Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran 2Students’ Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran 3Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran 4Natural Products and Medicinal Plants Research Center, North Khorasan University of Medical Sciences, Bojnurd, Iran (Received 22 May 2017; accepted 31 June 2018) Abstract Background: In this study, larvicidal activity of clove essential oil (EO), as a green and relatively potent larvicide, was compared with its main constituent, Eugenol, against Anopheles stephensi. Methods: High-performance liquid chromatography (HPLC) was used to determine the amount of eugenol, major constituent of clove EO. In addition, larvicidal activity of clove EO and eugenol was evaluated against An. stephensi. Results: The amount of eugenol in clove EO was determined as 67% using HPLC analysis. LC50 and LC90 of clove EO (57.49 and 93.14ppm, respectively) were significantly lower than those of eugenol (86.96 and 128.18 ppm, re- spectively). Conclusion: EO showed more effective than its major component. Considering the lower cost of the essential oil and lower risk in occurrence of resistance in larvae, use of clove EO is preferred as larvicide in comparison with eugenol, against An. stephensi. Keywords: Larvicidal activity, HPLC, Syzigium aromaticum, Eugenol, Essential oil, Anopheles stephensi Introduction More than 17% of all infectious diseases vantages such as biodegradability and negli- around the world are vector-borne diseases, gible effects on non-target specious and en- such as dengue fever, yellow fever, and ma- vironment (7, 8). laria (1). The number of death for such dis- Recently, comparisons of larvicidal activ- eases is more than 1 million annually e.g. ma- ity of EOs with their major components have laria caused 429000 death just in 2015 (1, 2). been reported (9, 10). However, there is no con- In order to control malaria, WHO recommends clusion so fare, EOs are better or their major control of larva which now used in 55 coun- constituent(s) in terms of larvicidal activity. tries (2). Unfortunately, due to frequent use Syzygium aromaticum (Clove) belongs to of synthetic larvicides (such as Temephos), not the Myrtaceae family which considers as an only environmental pollution have appeared, important medicinal plant with wide range of but also many cases of resistance has oc- biological activities such as anti-bacterial or curred in mosquitoes around the world (3-6). anti-oxidant activities (11, 12). Clove EO has Essential oils (EOs) have been suggested as al- also shown larvicidal activity against field col- ternative sources for insect control as repellents, lected larva of Ae. Aegypti with LC50 of 92.56 insecticides or larvicides and they offer ad- and 62.3ppm in two different reports (13, 14). 361 *Corresponding author: Dr Amir Amani, E-mail: http://jad.tums.ac.ir [email protected] Published Online: December 25, 2018 J Arthropod-Borne Dis, December 2018, 12(4): 361–369 M Osanloo et al.: Larvicidal Activity of … Eugenol, as the major constituent of clove EO, tion. By comparing peak areas of eugenol with has also indicated larvicidal activity against solution of clove EO, its amount in clove EO laboratory reared and field collected of Ae. was determined. aegypti (LC50: 33 and 93.3ppm, respectively) (14, 15). Its larvicidal activity against other pop- Evaluation of larvicidal activity ulation of mosquito has been documented, with Third and fourth instar larvae of An. ste- LC50 of 25.4, 28.14 and 30.8ppm against An. phensi were used, they obtained from insec- subpictus, Ae. albopictus and Cx. tritaeniorhyn- tarium of Tehran University of Medical Sci- chus (16). ences. They reared in special condition: 28± Anopheles stephensi is an important ma- 2 °C, 12:12 dark and light periods and rela- laria vector with wide distribution in the Ara- tive humidity of 65±5%. Larvicidal bioassay bian Peninsula, the Indian subcontinent, Af- was performed in line with WHO recommen- ghanistan and Iran (17-19). In this research, dation test in lab, with some modifications (20). for the first time, larvicidal activity of clove Standard solutions were prepared by dissolv- EO and eugenol against An. stephensi was ing in ethanol at appropriate concentrations evaluated and compared. (i.e. eugenol 60 µL/mL and clove EO 30µL/ mL). By adding 1mL from each sample Materials and Methods (0.5%v/v) to cups containing 199mL of no chlorine water, desired concentrations of sam- Materials ples were prepared. Using separated nets, 25 High-performance liquid chromatography larvae of An. stephensi were added slowly to (HPLC) grade methanol, pure eugenol (99%) all containers. Dead and moribund larvae (un- and Ethanol were supplied by Merck (Ger- able to respond to stimulating agent) were many). Clove EO was purchased from Green counted after 24h of exposing in all cups. Plants of Life Co (Iran). Larvicidal bioassays were performed in 16 repetitions at 4 different replicates at concen- Determining of eugenol contents in clove EO trations (ppm) of 12.5, 25, 50, 75, 100, 150 oil by HPLC for clove EO and 12.5, 25, 50, 100, 150, 200 HPLC analysis was used to determine the and 300 for eugenol. In each replicate, two amount of eugenol in clove EO. The apparatus control groups were considered having etha- consisted of a 30cm× 3.9mm reverse phase nol (0.5%v/v) with similar treatments. Lethal C18 column (Waters, Milford, USA), a pres- concentrations of each sample (i.e. LC50 and sure less injection pump (Model L-6200, Hi- LC90), were determined using a probit re- tachi, Japan) to drive solvent and loading of gression model in SPSS ver. 19 (Chicago, samples, a UV visible detector (Model L- IL, USA). 4000, at 280nm, Hitachi, Japan) for detection, a chromato-integrator (Model D-2500, Hita- Comparison of larvicidal activity of clove chi, Japan) for analyses. A mixture of metha- EO with eugenol nol and distilled water was used as mobile Evaluation of overlaps between confidence phase with flow-rate of 1mL/min. Analytical intervals (CI) of two groups is an easy and procedure was started with dissolving 50µL common approach to compare various LC of eugenol or 0.5mL of clove EO in 10mL of values. If no overlap is observed, the differ- methanol, then, 20µL of this solution was in- ence is considered as significant (21). LC50 jected into system at a flow-rate of 0.7mL/ and LC90 of clove EO and eugenol were cal- min. The optimum mobile phase with a meth- culated and compared using independent anol: water ratio of 80:20 was used for elu- sample test by SPSS. 362 http://jad.tums.ac.ir Published Online: December 25, 2018 J Arthropod-Borne Dis, December 2018, 12(4): 361–369 M Osanloo et al.: Larvicidal Activity of … Results in Fig. 2. Calculated LC50 and LC90 values were 57.49 and 86.96ppm for clove EO and 93.14 Determining content of eugenol in clove EO and 158.2ppm for eugenol, respectively (Table Results of HPLC analysis of eugenol and 1). clove EO samples are shown in Fig. 1. Com- Larvicidal activity in both samples (i.e. paring the graphs, the peak related to euge- clove EO and eugenol) appeared at 25ppm and nol is observed at retention time of 6.43 and enhanced with increasing the concentration of 6.41min, for eugenol and clove EO, respec- those. Nevertheless, perfect larvicidal activi- tively. By comparing peak areas of eugenol ties were achieved at 100 and 200ppm for and clove EO, percentage of eugenol in clove clove EO and eugenol, respectively. Further- EO was calculated as 67%, considered rela- more, no overlap in CI of LC50 and LC90 for tively high. clove EO and eugenol are observed, thus, lar- vicidal activity of clove EO is significantly Evaluation of larvicidal activity of clove EO better than eugenol (Table 1). Moreover, Probit and eugenol regression line of the both clove EO and eu- Results of larvicidal activities of clove EO genol are illustrated in Fig. 3. and eugenol against An. stephensi are shown Table 1. Calculated parameters by probit analysis LC50 (ppm) LC90 (ppm) Specimen A B±SE χ2 (df) Sig CI: (LCL- UCL) CI: (LCL–UCL) 57.49 86.96 Clove EO -2.50 0.04±0.002 47.96 (3) 0.15 > sig* (43.28–74.24) (71.19–128.18) 93.14 158.2 Eugenol -1.83 0.02±0.001 39.13 (4) 0.15 > sig* (75.60–113.33) (133.85–201.20) A= intercept; B±SE= slope and standard error of the line; CI= confidence interval (0.05), UCL= Upper Confidence Limit, LCL= Lower Confidence Limit, χ2 (df)= Chi 2 and degree of freedom. *Since the sig- nificance level is less than 0.15, a heterogeneity factor is used in the calculation of confidence limits. Fig. 1. HPLC profile of solution of eugenol and clove EO, related peak for eugenol appeared at retention time of 6.43 and 6.41min, respectively 363 http://jad.tums.ac.ir Published Online: December 25, 2018 J Arthropod-Borne Dis, December 2018, 12(4): 361–369 M Osanloo et al.: Larvicidal Activity of … Discussion Determining content of eugenol in clove EO In this study, amount of eugenol in clove EO was found as 67%, which is comparable with other reports.