Chemical composition of the essential oil
The steam distillation of 2000
g of dried plant material yielded 7.2 mL (0.36%, v/w) of a light- yellow oil with a distinct smell. The GC–MS analysis of
Zanthoxylum acanthopodium essential oil revealed 63 components representing 99.32% of the oil (Table
1). The composition was 13.98% monoterpene hydrocarbon fraction, 24.24% oxygenated monoterpene fraction, 16.60% sesquiterpene hydrocarbon fraction, 13.75% oxygenated sesquiterpenoid fraction, 21.57% phenylpropanoids and 9.18% others. The main components of the oil were estragole (15.46%), eucalyptol (10.94%), β-caryophyllene (5.52%),
cis-linalool oxide (3.76%),
cis-limonene oxide (3.06%).
Table 1
Chemical composition of essential oil of Zanthoxylum acanthopodium
| | Monoterpene hydrocarbons | 13.98 | |
1 | 930 | α-Thujene | 0.62 | MS, RI |
2 | 936 | α-Pinene | 1.28 | MS, RI |
3 | 973 | Sabinene | 2.63 | MS, RI |
4 | 986 | β-Myrcene | 0.41 | MS, RI |
5 | 1012 | 3-Carene | 2.76 | MS, RI |
6 | 1024 | β-Phellandrene | 1.36 | MS, RI |
7 | 1030 | Limonene | 2.47 | MS, RI |
8 | 1040 | (Z)-β-Ocimene | 1.22 | MS, RI |
9 | 1059 | γ-Terpinene | 1.23 | MS, RI |
| | Oxygenated monoterpenes | 24.24 | |
10 | 1036 | Eucalyptol | 10.94 | MS, RI, Co |
11 | 1078 | cis-Linalool oxide | 3.76 | MS, RI |
12 | 1099 | Linalool | 5.10 | MS, RI, Co |
13 | 1120 | cis-4-Isopropyl-1-methyl-2-cyclohexen-1-ol | 0.25 | MS, RI |
14 | 1143 | Camphor C10H16O | 1.91 | MS, RI |
15 | 1196 | Citronellol | 0.60 | MS, RI |
16 | 1255 | Piperitone | 0.28 | MS, RI |
17 | 1257 | Geraniol | 0.73 | MS, RI |
18 | 1270 | Perillaaldehyde | 0.67 | MS, RI |
| | Sesquiterpene hydrocarbons | 16.60 | |
19 | 1335 | δ-Elemene | 0.79 | MS, RI |
20 | 1351 | a-Cubebene | 0.28 | MS, RI |
21 | 1375 | Isoledene | 0.46 | MS, RI |
22 | 1384 | β-Bourbonene | 0.92 | MS, RI |
23 | 1388 | β-Cubebene | 0.63 | MS, RI |
24 | 1390 | β-Elemene | 0.47 | MS, RI |
25 | 1418 | β-Caryophyllene | 5.52 | MS, RI, Co |
26 | 1431 | 2-Norpinene | 0.66 | MS, RI |
27 | 1438 | E-α-Bergamotene | 0.67 | MS, RI |
28 | 1458 | Seychellene | 0.28 | MS, RI |
29 | 1458 | (E)-b-Farnesene | 0.38 | MS, RI |
30 | 1474 | γ-Muurolene | 0.40 | MS, RI |
31 | 1486 | Germacrene D | 2.81 | MS, RI |
32 | 1493 | Zingiberenol | 0.63 | MS, RI |
33 | 1498 | Bicyclogermacrene | 0.34 | MS, RI |
34 | 1514 | trans-γ-cadinene | 0.73 | MS, RI |
35 | 1525 | β -Sesquiphellandrene | 0.63 | MS, RI |
| | Oxygenated sesquiterpenes | 13.75 | |
36 | 1130 | cis-Limonene oxide | 3.06 | MS, RI |
37 | 1549 | Elemol | 1.65 | MS, RI |
38 | 1562 | (trans)-Nerolidol | 0.19 | MS, RI |
39 | 1575 | Spathulenol | 1.33 | MS, RI |
40 | 1578 | Caryophyllene oxide | 2.27 | MS, RI |
41 | 1587 | Viridiflorol | 0.83 | MS, RI |
42 | 1606 | α-Humulene epoxide II | 0.75 | MS, RI, Co |
43 | 1639 | Isospathulenol | 0.56 | MS, RI, Co |
44 | 1648 | β-Eudesmol | 2.46 | MS, RI |
45 | 1654 | α-Eudesmol | 0.27 | MS, RI |
46 | 1666 | Bulnesol | 0.38 | MS, RI |
| | Phenylpropanoids | 21.57 | |
47 | 1045 | Benzene acetaldehyde | 0.85 | MS, RI |
48 | 1229 | Estragole | 15.46 | MS, RI, Co |
49 | 1286 | Bornyl ester | 0.7 | MS, RI |
50 | 1308 | Carvacrol | 0.68 | MS, RI |
51 | 1315 | 2-Methoxy-4-vinylphenol | 0.32 | MS, RI |
52 | 1357 | Eugenol | 1.32 | MS, RI |
53 | 1408 | Methyl eugenol | 0.61 | MS, RI |
54 | 1534 | α-Calacorene | 0.38 | MS, RI |
55 | 1620 | Dill apiole | 1.25 | MS, RI |
| | Others | 9.18 | |
56 | 852 | trans-2-Hexenal | 2.73 | MS, RI |
57 | 982 | 1-Octen-3-ol | 1.24 | MS, RI |
58 | 1062 | trans-2-Octenal | 0.48 | MS, RI |
59 | 1368 | α-Terpinyl acetate | 0.57 | MS, RI |
60 | 1385 | Geranyl acetate | 1.34 | MS, RI |
61 | 1396 | cis-Jasmone | 0.85 | MS, RI |
62 | 1702 | 2-Hexadecanol | 1.34 | MS, RI |
63 | 1971 | n-Hexadecanoic acid | 0.63 | MS, RI |
| | Total identified (%) | 99.32 | |
In the
Zanthoxylum acanthopodium essential oil, main compounds were estragole, eucalyptol and β-caryophyllene. They were often reported in the essential oil extracted from different kinds of
Zanthoxylum plants. Estragole is a component isolated from various trees and plants and its extraction from
Zanthoxylum plants has been described but is relatively rare. Wang et al. [
17] showed that in the essential oil of fresh fruits of
Zanthoxylum schinifolium, estragole was the major compound (69.52%). Eucalyptol was common in many plants including
Zanthoxylum plants in related literature. Liu et al. [
18] showed that the essential oil of
Zanthoxylum avicennae leaves and stems had high content of monoterpenoids including 53.05% eucalyptol. Prieto et al. [
19] determined the major constituents of
Zanthoxylum monophyllum oil were eucalyptol (9.19%); Eiter et al. [
20] analysed the essential oil from
Zanthoxylum clava-
herculis and found the content of eucalyptol ranged from 16 to 43%. Similar research was also carried out on the essential oil from the fruits of
Zanthoxylum bungeanum [
21];
Zanthoxylum rhetsoides and
Zanthoxylum myriacanthum [
22], the content of eucalyptol is 16.0% 15.7% and 18%, respectively. β-Caryophyllene, is also a common constituent in many
Zanthoxylum essential oils. It reported to be found in the essential oils of
Zanthoxylum newbouldia leaves (36%) [
23];
Zanthoxylum syncarpum (9.2–9.3%) [
24];
Zanthoxylum acanthopodium leaves (3.0%) [
25];
Zanthoxylum rubescens leaf (22.1%) [
26];
Zanthoxylum setulosum (13.7%) [
27];
Zanthoxylum ekmanii (11.5%) [
28];
Zanthoxylum procerum leaves (7.0%) [
29]. The results indicate that the
Z. acanthopodium essential oil shares some similar main constituents with other species of
Zanthoxylum.
Larvicidal assays
Tables
2,
3 displays the results on percent mortality of larvae of
An. sinensis and
An. anthropophagus with increase in essential oil and test compounds concentration. The mortality of
An. sinensis was 17, 54, 68, 83, 94 and 100% when the oil at concentration of 25.0, 50.0, 100.0, 125, and 150 mg/L. The mortality of
An. anthropophagus was 36, 62, 78, 90, 97 and 100% when the oil at concentration of 25.0, 50.0, 100.0, 125, and 150 mg/L. The LC
50 and LC
90 values against
An. sinensis larvae were 49.02 and 125.18 mg/L and for
An. anthropophagus were 36.00 and 101.49 mg/L, respectively. Between two compounds tested for 24 h, estragole exhibited a stronger mosquito larvicidal activity than the oil with LC
50 41.67, 38.56 mg/L and LC
90 107.89, 95.90 mg/L for
An. sinensis and
An. anthropophagus. Eucalyptol had less LC
50 values (45.49 and 42.41 mg/L) and LC
90 values (124.95 and 111.45 mg/L).
Table 2
Larvicidal activity of Zanthoxylum acanthopodium essential oil, estragole and eucalyptol against fourth instar Anopheles sinensis larvae
Essential oil | 25 | 17 | 49.02 (44.15–49.41) | 125.18 (105.90–141.74) | 3.29 ± 0.28 | 2.835 (3)a |
50 | 54 |
75 | 68 |
100 | 83 |
125 | 94 |
150 | 100 |
Estragole | 25 | 28 | 41.67 (29.48–52.07) | 107.89 (82.90–178.83) | 3.10 ± 0.28 | 5.994 (3)a |
50 | 57 |
75 | 72 |
100 | 89 |
125 | 97 |
150 | 100 |
Eucalyptol | 25 | 26 | 45.49 (33.24–56.33) | 124.95 (94.78–213.84) | 2.92 ± 0.27 | 5.329 (3)a |
50 | 51 |
75 | 69 |
100 | 83 |
125 | 95 |
150 | 100 |
DMSO | | 1 ± 0.45 | | | | |
Table 3
Larvicidal activity of Zanthoxylum acanthopodium essential oil, estragole and eucalyptol against fourth instar Anopheles anthropophagus larvae
Essential oil | 25 | 36 | 36.00 (30.90–40.61) | 101.49 (88.49–121.70) | 2.85 ± 0.27 | 3.885a |
50 | 62 |
75 | 78 |
100 | 90 |
125 | 97 |
150 | 100 |
Estragole | 25 | 31 | 38.56 (26.73–48.40) | 95.90 (74.43–153.82) | 3.24 ± 0.29 | 6.248 (3)a |
50 | 60 |
75 | 78 |
100 | 91 |
125 | 99 |
150 | 100 |
Eucalyptol | 25 | 28 | 42.41 (37.49–47.01) | 111.45 (97.62–132.64) | 3.05 ± 0.27 | 4.749 (3)a |
50 | 54 |
75 | 73 |
100 | 88 |
125 | 96 |
150 | 100 |
DMSO | | 2 ± 0.55 | | | | |
Mosquitoes, including
An. sinensis and
An. anthropophagus used in these experiments, act as vectors for many disease-causing viruses and cause serious health problems worldwide in both humans and animals. Although
Zanthoxylum is a known potential source of anthelmintic agents for traditional Chinese medicine, only a few studies have assessed the anti-mosquito activity of
Zanthoxylum species. Trongtokit et al. [
30,
31] showed that the essential oil from
Zanthoxylum limonella had repellent effect against
Aedes aegypti,
Culex quinquefasciatus, and
Anopheles dirus. Effects of
Zanthoxylum armatum essential oil against
Aedes aegypti (LC
50 = 54 ppm),
Anopheles stephensi (LC
50 = 58 ppm) and
Culex quinquefasciatus (LC
50 = 49 ppm) was analysed by Tiwary et al. [
32]. The essential oil from leaves of
Zanthoxylum articulatum was examined with respect to its larvicidal properties against the larvae of
Aedes aegypti and showed that LC
50 was 77.62 ppm [
33]. Essential oil of
Zanthoxylum piperitum had insecticidal effect against
Aedes gardnerii,
Anopheles barbirostris,
Armigeres subalbatus,
Culex tritaeniorhynchus,
Culex gelidus,
Culex vishnui group, and
Mansonia uniformis [
34]. The related activity of
Zanthoxylum beecheyanum was also reported, 24 h LC
50 was 6.895 mg/mL against
Culex pipiens adults and 119.020 mg/mL against 4 instar larvae [
35].
When comes to the larvicidal mechanism of the
Zanthoxylum essential oil, it can be attributed to some compounds in the oil that can lead to alteration in the membrane structure of larval cells [
36,
37], especially estragole, eucalyptol, β-caryophyllene and limonene, whose separated insecticidal effect have been revealed in a series of reports. Zhang et al. [
38] showed estragole had strong contact toxicity against
Lasioderma serricorne adults with 24 h LD
50 value of 15.58 mg/adult, and in the fumigant toxicity test, the 24 h LD
50 was 5.18 mg/L air. When against
Maize weevils, 24 h LC
50 values of estragole was 14.10 ppm [
39]. Kimbaris et al. [
40] showed that 24 h LC
50 of eucalyptol was inactive at concentrations even as high as 100 mg/L against early fourth instar mosquito larvae of
Culex pipiens. Against the 3rd instars of the
Culex pipiens 24 h LC
50 values of eucalyptol was 91.45 mg/L [
41]. The current study proved that estragole and eucalyptol played important role as insecticidal compounds in
Zanthoxylum acanthopodium essential oil against two anopheline mosquito species. Yang et al. [
42] showed that eugenol was the most significant compounds of
Clove Bud oils with reference to repellent activity against the bean bugs
Riptortus clavatus. You et al. [
43] showed that β-caryophyllene, exhibited strong insecticidal and repellent activities against
Lasioderma serricorne. Wang et al. [
39] showed the limonene LC
50 = 6.21 mg/L for
Tribolium castaneum and 14.07 mg/L air
for L. serricorne.
To sum up, a series of investigations for chemical compounds from natural products have revealed that some essential oil with adequate active ingredients is essential to the development of new insecticidal drugs, especially in view of the vast worldwide flora. There is also some evidence indicating that essential oils often prove to be more effective than their components, indicating synergy [
44].