Skip to main content
PMC home page
Molecules logoLink to Molecules
. 2020 Mar 12;25(6):1303. doi: 10.3390/molecules25061303

Chemical Compositions, Mosquito Larvicidal and Antimicrobial Activities of Essential Oils from Five Species of Cinnamomum Growing Wild in North Central Vietnam

Do N Dai 1,2,*, Nguyen T Chung 1, Le T Huong 3, Nguyen H Hung 4, Dao TM Chau 5, Nguyen T Yen 3, William N Setzer 6,7,*
Editor: Giovanni Benelli
PMCID: PMC7144099  PMID: 32178471

Abstract

Members of the genus Cinnamomum (Lauraceae) have aromatic volatiles in their leaves and bark and some species are commercially important herbs and spices. In this work, the essential oils from five species of Cinnamomum (C. damhaensis, C. longipetiolatum, C. ovatum, C. polyadelphum and C. tonkinense) growing wild in north central Vietnam were obtained by hydrodistillation, analyzed by gas chromatography and screened for antimicrobial and mosquito larvicidal activity. The leaf essential oil of C. tonkinense, rich in β-phellandrene (23.1%) and linalool (32.2%), showed excellent antimicrobial activity (MIC of 32 μg/mL against Enterococcus faecalis and Candida albicans) and larvicidal activity (24 h LC50 of 17.4 μg/mL on Aedes aegypti and 14.1 μg/mL against Culex quinquefasciatus). Cinnamomum polyadelphum leaf essential oil also showed notable antimicrobial activity against Gram-positive bacteria and mosquito larvicidal activity, attributable to relatively high concentrations of neral (11.7%) and geranial (16.6%). Thus, members of the genus Cinnamomum from Vietnam have shown promise as antimicrobial agents and as potential vector control agents for mosquitoes.

Keywords: Lauraceae, Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, antibacterial, antifungal

1. Introduction

The Lauraceae is a large family of tropical and subtropical trees and shrubs [1]. In this family, the genus Cinnamomum is comprised of around 250 species with concentrations in east and southeast Asia [1]. Vietnam is home to 45 species of Cinnamomum [2,3], many of which are used in traditional medicine, for essential oils, as well as for timber [4,5].

We are in the midst of a post-antibiotic era. Numerous pathogenic microorganisms have developed resistance to commonly used antibiotic agents [6,7]. For example, Klebsiella pneumoniae [8], Pseudomonas aeruginosa [9] and Staphylococcus aureus [10], three organisms that are major causes of nosocomial infections, have developed extremely drug resistant (XDR) strains. Likewise, antibiotic resistance is increasing in fungi such as Candida ssp. and Aspergillus spp. [11]. Essential oils have shown promise as complementary or adjuvant therapies for combating antimicrobial resistance [12,13,14,15,16,17,18,19].

Mosquitoes have been and continue to be the deadliest animals on earth. Aedes aegypti (L.) (Diptera: Culicidae) and Ae. albopictus (Skuse) are vectors for the arboviral diseases dengue, Zika, chikungunya and yellow fever and Ae. aegypti is also a vector for the emerging Rift Valley fever virus [20]. Culex quinquefasciatus (Say) is a vector of West Nile virus, Saint Louis encephalitis virus and lymphatic filariasis [21]. Culex quinquefasciatus may also serve as a vector in emerging viral diseases such as Zika virus [22], Sindbis virus [23] and Usutu virus [24]. Unfortunately, insecticidal resistance of these mosquito species is increasing leading to failure of vector control programs in many locations [25]. Furthermore, populations of Ae. aegypti [26], Ae. albopictus [27] and Cx. quinquefasciatus [28] are showing widespread resistance to commonly used larvicidal agents. It has been suggested that essential oils may serve as alternative and more ecologically benign mosquito larvicidal agents [29,30,31].

Because of the biological activities and traditional uses of members of the Cinnamomum genus, we hypothesize that Cinnamomum species from Vietnam may also exhibit potentially useful biological activities. As part of our ongoing investigations into the essential oils of Vietnamese Cinnamomum [32,33,34], we have obtained, analyzed and carried out antimicrobial and larvicidal screening of Cinnamomum ovatum C.K. Allen (syn. Cinnamomum rigidissimum H.T. Chang), Cinnamomum tonkinense (Lecomte) A. Chev. (syn. Cinnamomum albiflorum var. tonkinense Lecomte), Cinnamomum damhaensis Kosterm., Cinnamomum longipetiolatum H.W. Li and Cinnamomum polyadelphum (Lour.) Kosterm. (syn. Laurus polyadelpha Lour., Cinnamomum litseafolium Lecomte, Cinnamomum litseafolium var. denticupulatum Liou, Cinnamomum saigonicum Farw, Camphorina saigonica Farw).

2. Results

2.1. Essential Oil Collection and Analysis

Plant materials were collected from mature Cinnamomum trees from different locations in north central Vietnam. The collection details and essential oil yields of the Cinnamomum species are summarized in Table 1. The essential oils were analyzed by gas-chromatography–mass spectrometry (GC-MS) and gas chromatography–flame ionization detector (GC–FID). The chemical compositions of the Cinnamomum species are presented in Table 2.

Table 1.

Collection details for Cinnamomum species from north central Vietnam.

Cinnamomum Species Vietnamese Name Voucher Numbers Part Yield, % v/w Collection Month/Year Collection Location
Cinnamomum ovatum Re trứng DND-762 Leaf
Stems		 0.60
0.21		 April/2019 Chau Hoan Commune, Pù Huống Nature Reserve
19°28′12″N, 104°56′45″E, elev. 374 m
Cinnamomum tonkinense Re xanh, Re bắc, Quế bắc DND-768 Leaf 0.33 April/2019 Chau Hoan Commune, Pù Huống Nature Reserve
19°28′12″N, 104°56′45″E, elev. 374 m
Cinnamomum damhaensis Re đầm hà DND-786 Leaf 0.30 July/2019 Huong Phu Commune, Nam Đông District, Bach Ma National Park
16°12′47″N, 107°43′33″E, elev. 101 m
Cinnamomum longipetiolatum Re cuống dài DND-800 Leaf 1.35 August/2019 Nam Nhong Commune, Que Phong District, Pù Hoạt Nature Reserve
19°30′24″N, 104°42′52″E, elev. 667 m
Cinnamomum polyadelphum Quế bời lời, Miếng sành, Tà Dúi, Ô dược, Đam dao, Hậu phát DND-813 Leaf 1.20 August/2019 Nam Nhong Commune, Que Phong District, Pù Hoạt Nature Reserve
19°30′24″N, 104°42′52″E, elev. 667 m
Open in a new tab

Table 2.

Chemical compositions (%) of Cinnamomum essential oils from north central Vietnam.

No Compounds RIa RIb C. ov. c C. ov. c C. to. d C. da. e C. lo. f C. po. g
Leaf Stem Leaf Leaf Leaf Leaf
1 α-Thujene 930 924 - - 0.4 - - 0.3
2 α-Pinene 939 932 2.1 1.6 4 0.3 2.9 4.3
3 α-Fenchene 953 945 - - - 0.1 - 0.2
4 Camphene 955 946 0.7 0.6 0.4 0.2 0.3 1.9
5 Sabinene 978 969 - - 3.4 0.7 0.5 0.4
6 β-Pinene 984 974 0.9 0.6 2.1 0.2 1.7 2.4
7 Myrcene 992 988 0.2 0.1 3.1 0.1 0.2 2.1
8 Dehydroxy-trans-linalool oxide 995 991 - - - - 0.7 -
9 Dehydroxy-cis-linalool oxide 1008 1006 - - - - 0.6 -
10 α-Phellandrene 1010 1002 1.3 0.3 4.8 - - 0.2
11 α-Terpinene 1022 1014 - - 0.4 - 0.2
12 p-Cymene 1030 1020 0.7 0.4 0.5 0.7 0.2 0.7
13 Limonene 1035 1024 0.9 0.8 3.4 0.2 0.3 5.4
14 β-Phellandrene 1036 1025 - - 23.1 - - -
15 1,8-Cineole 1038 1026 0.2 0.6 9.8 1 2.5 0.8
16 (E)-β-Ocimene 1049 1044 0.3 0.2 0.3 - 0.8 -
17 γ-Terpinene 1063 1054 - - 0.5 - 0.3 -
18 Terpinolene 1094 1086 0.2 0.1 0.2 - - -
19 Rosefuran 1098 1091 - - - - - 0.1
20 Perillene 1104 1102 - - - - - 0.2
21 Linalool 1105 1095 5.9 8.3 32.2 44.8 75.7 3.2
22 Hotrienol 1107 1104 - - - - 3.2 -
23 Isocitral 1147 1140 - - - - - 0.2
24 Camphor 1156 1141 - - - - - 32.2
25 Nerol oxide 1158 1154 - - - - 0.2 -
26 Isoneral 1166 1162 - - - - - 0.6
27 cis-Linalool oxide (pyranoid) 1174 1170 - - - - 3.2 -
28 trans-Linalool oxide (pyranoid) 1177 1173 - - - - 2.7 -
29 Borneol 1178 1165 - - 0.2 - - 1.6
30 Isogeranial 1184 1180 - - - - - 0.9
31 Terpinen-4-ol 1187 1174 - - 0.7 0.4 0.5 0.4
32 α-Terpineol 1200 1186 - - 1.7 0.2 0.6 0.6
33 Decanal 1208 1201 - - 0.2 - - 0.2
34 Citronellol 1228 1223 - - - - - 0.4
35 Nerol 1231 1227 - - - - - 0.8
36 Cuminal 1238 1238 - - - 0.1 - -
37 Neral 1245 1235 - - - - - 11.7
38 Geraniol 1255 1249 - - - - 0.2 1.9
39 Geranial 1274 1264 - - - - - 16.6
40 (E)-Cinnamaldehyde 1278 1267 - - - - - 0.2
41 Bornyl acetate 1294 1287 0.5 0.5 0.1 - - 0.1
42 Safrole 1299 1285 - 0.2 - - - -
43 δ-Elemene 1348 1335 - - 0.2 - - -
44 Eugenol 1367 1356 70.5 71.2 0.2 - - 0.4
45 α-Ylangene 1385 1373 0.4 0.3 - - - -
46 α-Copaene 1389 1374 - - 0.4 - - 0.1
47 β-Elemene 1403 1389 - - 0.3 0.7 - -
48 Methyl eugenol 1409 1403 - 0.3 - 0.1 - 0.3
49 β-Caryophyllene 1437 1417 1.9 1 1.8 0.2 - 1.3
50 trans-α-Bergamotene 1445 1432 0.2 0.2 0.1 - - -
51 allo-Aromadendrene 1457 1458 0.1 - - 0.3 - -
52 α-Humulene 1471 1452 0.3 - 0.6 - - 0.2
53 α-Amorphene 1483 1483 - - - 0.3 - -
54 β-Selinene 1489 1489 - - - 19.1 - -
55 trans-β-Bergamotene 1496 1480 - 0.1 - - - -
56 α-Selinene 1498 1498 - - - 0.5 - -
57 Germacrene D 1498 1484 0.3 0.1 2.7 - - -
58 Bicyclogermacrene 1513 1500 0.7 0.6 1 - 0.2 0.2
59 β-Bisabolene 1517 1505 - 0.2 - - - -
60 Eugenyl acetate 1533 1521 9.5 9.3 0.1 - - -
61 δ-Cadinene 1537 1522 0.2 0.3 0.2 - - 0.1
62 (E)-α-Bisabolene 1551 1544 - 0.3 - - - -
63 (E)-Nerolidol 1570 1561 - - 0.3 0.9 - -
64 Germacrene B 1577 1559 - - 0.2 - - -
65 Spathulenol 1598 1577 - 0.6 - 0.4 1.1 0.8
66 Caryophyllene oxide 1605 1582 - 0.5 0.2 1.1 0.5 0.9
67 Intermedeol isomer 1616 - - - - 5.8 - -
68 Selin-11-en-4-one 1626 1626 - - - 1.5 - -
69 Selina-3,11-dien-6α-ol 1644 1642 - - - 0.6 - -
70 α-Cadinol 1652 1652 - - - 0.5 - -
71 Selin-11-en-4α-ol 1660 1658 - - - 7.3 - -
72 Germacra-4(15),5,10(14)-trien-1α-ol 1685 1685 - - - 1 - -
73 Aromadendrane-4,10-diol 1717 - - - - 0.5 - -
74 Oplopanone 1735 1739 - - - 0.3 - -
75 α-Cyperone 1747 - - - - 4 - -
76 Cyclocolorenone 1763 1759 - - - 0.1 - -
Monoterpene hydrocarbons 7.3 4.7 46.6 2.5 7.4 17.9
Oxygenated monoterpenoids 6.6 9.4 44.7 46.5 90.1 72.3
Sesquiterpene hydrocarbons 4.1 3.1 7.5 21.1 0.2 1.9
Oxygenated sesquiterpenoids 0 1.1 0.5 24 1.6 1.7
Phenylpropanoids 80 81 0.3 0.1 0 0.9
Others 0 0 0.2 0 0 0.2
Total identified 98 99.3 99.8 94.2 99.3 94.9
Open in a new tab

a RI = Retention Index determined on an HP-5ms column. b RI from the databases. c C. ov. = Cinnamomum ovatum. d C. to. = Cinnamomum tonkinense. e C. da. = Cinnamomum damhaensis. f C. lo. = Cinnamomum longipetiolatum. g C. po. = Cinnamomum polyadelphum.

2.2. Antimicrobial Screening

The Cinnamomum essential oils were screened for antimicrobial activity against Gram-positive (Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica) bacteria and a yeast (Candida albicans). Minimum inhibitory concentrations and IC50 values were determined using the microbroth dilution assay (Table 3).

Table 3.

Antimicrobial activities of Cinnamomum essential oils from north central Vietnam.

Gram-Positive Gram-Negative Yeast
Sample Enterococcus faecalis Staphylococcus aureus Bacillus cereus Escherichia coli Pseudomonas aeruginosa Salmonella enterica Candida albicans
MIC (μg/mLa)
C. ovatum leaf 64 64 128 64 128 64 64
C. ovatum stem 64 64 64 64 16 64 32
C. tonkinense 32 128 128 - - - 32
C. damhaensis - - - - - - -
C. longipetiolatum 64 128 128 256 256 128 256
C. polyadelphum 32 64 64 - - 128 256
Streptomycin 32 128 64 32 128 64 -
Nistatin - - - - - - 8
Cyclohexamide - - - - - - 32
IC50 (μg/mLa)
C. ovatum leaf 32.33 32.33 65.45 32.56 65.44 33.22 33.22
C. ovatum stem 32.44 32.78 33.56 32.56 8.77 31.22 15.67
C. tonkinense 5.67 37.78 56.67 - - - 15.67
C. damhaensis - - - - - - -
C. longipetiolatum 17.88 36.78 56.79 100.34 105.67 56.78 112.45
C. polyadelphum 10.67 24.78 30.24 - - 57.45 123.45
Open in a new tab

a Micrograms of essential oil per milliliter of test solution.

2.3. Larvicidal Screening

The Cinnamomum essential oils were screened for mosquito larvicidal activity against Aedes aegypti, Aedes albopictus and Culex quinquefasciatus. The 24 h and 48 h LC50 and LC90 values are summarized in Table 4 and Table 5.

Table 4.

Twenty-four-hour mosquito larvicidal activities (μg/mL) of Cinnamomum essential oils from north central Vietnam.

Sample LC50 (95% Confidence Limits) LC90 (95% Confidence Limits) χ2 p
Aedes aegypti
C. ovatum leaf EO 24.12 (20.92–27.45) 50.61 (45.02–58.65) 48.86 0.000
C. ovatum stem EO 52.51 (48.77–57.69) 71.23 (64.50–82.64) 0.4722 0.790
C. tonkinensis leaf EO 17.44 (15.53–19.58) 31.40 (27.93–36.64) 0.1354 0.987
C. damhaensis leaf EO 21.43 (18.66–24.15) 38.98 (34.75–45.58) 0.5494 0.760
C. longepetiolatum leaf EO 64.20 (55.67–73.61) 127.9 (111.0–156.5) 8.805 0.003
C. polyadelphum leaf EO 23.41 (21.37–25.78) 36.69 (33.27–41.52) 8.277 0.041
Aedes albopictus
C. ovatum leaf EO n.t. n.t. --- ---
C. ovatum stem EO 61.45 (55.66–68.20) 103.3 (93.3–117.1) 34.38 0.000
C. tonkinensis leaf EO 42.89 (39.73–46.59) 61.65 (56.52–69.09) 2.595 0.273
C. damhaensis leaf EO 43.91 (41.25–46.46) 56.16 (52.95–60.79) 0.04480 0.978
C. longepetiolatum leaf EO n.t. n.t. --- ---
C. polyadelphum leaf EO 20.66 (18.02–23.28) 37.21 (33.04–43.97) 2.577 0.276
Culex quinquefasciatus
C. ovatum leaf EO 34.19 (31.18–37.65) 56.01 (50.85–63.12) 10.73 0.013
C. ovatum stem EO 28.79 (22.07–34.79) 78.3 (67.72–94.57 8.295 0.016
C. tonkinensis leaf EO 14.05 (12.28–15.75) 25.70 (23.06–29.59) 16.31 0.001
C. damhaensis leaf EO 46.74 (41.58–52.63) 86.80 (77.37–100.39) 13.53 0.001
C. longepetiolatum leaf EO 126.8 (108.3–151.4) 293.9 (248.2–368.9) 21.47 0.000
C. polyadelphum leaf EO 18.33 (13.26–22.87) 58.95 (50.62–72.05) 5.639 0.131
Open in a new tab

Table 5.

Forty-eight-hour mosquito larvicidal activities (μg/mL) of Cinnamomum essential oils from north central Vietnam.

Sample LC50 (95% Confidence Limits) LC90 (95% Confidence Limits) χ2 p
Aedes aegypti
C. ovatum leaf EO 13.76 (11.42–15.95) 30.17 (26.76–35.17) 46.16 0.000
C. ovatum stem EO 46.74 (43.17–51.21) 67.53 (61.30–77.07) 2.744 0.254
C. tonkinensis leaf EO 15.83 (13.76–17.99) 31.17 (27.53–36.80) 2.196 0.533
C. damhaensis leaf EO 17.36 (13.67–20.36) 37.53 (32.94–45.22) 5.494 0.064
C. longepetiolatum leaf EO 39.50 (29.92–47.24) 95.24 (83.27–114.77) 2.513 0.113
C. polyadelphum leaf EO 17.30 (15.44–19.41) 30.80 (27.43–35.89) 3.650 0.302
Aedes albopictus
C. ovatum leaf EO n.t. n.t. --- ---
C. ovatum stem EO 50.18 (45.07–56.12) 87.98 (78.88–100.81) 35.66 0.000
C. tonkinensis leaf EO 42.74 (39.48–46.59) 62.40 (57.00–70.25) 4.098 0.129
C. damhaensis leaf EO 39.85 (37.05–42.91) 56.02 (51.91–61.70) 0.06006 0.970
C. longepetiolatum leaf EO n.t. n.t. --- ---
C. polyadelphum leaf EO 20.79 (17.84–23.61) 39.45 (34.97–46.59) 6.980 0.031
Culex quinquefasciatus
C. ovatum leaf EO 30.48 (27.00–34.48) 59.19 (52.54–68.81) 1.181 0.757
C. ovatum stem EO 20.54 (11.92–27.10) 72.40 (62.01–89.54) 5.799 0.055
C. tonkinensis leaf EO 8.721 (6.874–10.253) 18.81 (16.70–22.01) 26.83 0.000
C. damhaensis leaf EO 18.63 (9.90–25.06) 67.93 (58.16–84.15) 6.243 0.001
C. longepetiolatum leaf EO 76.88 (52.08–101.93) 314.5 (249.3–447.0) 47.36 0.000
C. polyadelphum leaf EO 11.03 (4.50–15.93) 52.40 (44.35–65.76) 10.30 0.016
Open in a new tab

3. Discussion

3.1. Cinnamomum ovatum

The leaf and stem bark essential oils of C. ovatum demonstrated broad antimicrobial activity against the organisms tested with MIC values ranging from 16 to 128 μg/mL (Table 3). The major components of the leaf and stem essential oils were eugenol (70.5% and 71.2%, respectively), eugenyl acetate (9.5% and 9.3%, respectively) and linalool (5.9% and 8.3%, respectively) (Table 2). The high concentration of eugenol in these two essential oils is likely responsible for the observed antimicrobial effects. Eugenol has shown broad spectrum antibacterial [35,36] and antifungal [37,38,39] activities. Likewise, the mosquito larvicidal activity of C. ovatum leaf essential oil is likely due to eugenol; that compound has shown larvicidal activity against Ae. aegypti [40], Ae. albopictus [41] and Cx. quinquefasciatus [42]. Cinnamomum cambodianum leaf [34] and stem bark [33] essential oils from Vietnam have also shown high concentrations of linalool (27.0% and 33.1%, respectively).

3.2. Cinnamomum tonkinense

Cinnamomum tonkinense leaf essential oil showed excellent antimicrobial activity against E. faecalis and C. albicans with MIC of 32 μg/mL and good activity against B. cereus and S. aureus (Table 3). The essential oil is rich in monoterpenes, α-pinene (4.0%), sabinene (3.4%), α-phellandrene (4.8%), β-phellandrene (23.1%), 1,8-cineole (9.8%), linalool (32.2%) (Table 2). Both α-pinene and linalool have shown antibacterial activity against E. faecalis [35] and S. aureus [43]; α-pinene and 1,8-cineole have shown antifungal activity against C. albicans [43]. Sabinene, on the other hand, has shown little [44] or no [45] antimicrobial activity. Likewise, α-phellandrene has shown no activity against C. albicans [46]. The leaf essential oils of C. cordatum and C. scortechini from Pahang, Malaysia, both rich in β-phellandrene (9.0% and 17.3%, respectively) and linalool (17.3% and 16.4%, respectively), have shown antifungal activities against several fungal strains [47].

The leaf essential oil of C. tonkinense is one of the most larvicidal in this study (Table 4 and Table 5). The major components in the essential oil likely account for the observed larvicidal activity. α-Pinene, has been shown to be larvicidal against Ae. aegypti, Ae. albopictus and Cx. quinquefasciatus [48]; sabinene and linalool have both demonstrated larvicidal against Ae. aegypti and Cx. quinquefasciatus [49]; and α-phellandrene has shown activity against Ae. aegypti and Ae. albopictus [50] as well as Culex pipiens molestus [51]. The leaf essential oil of C. scortechinii, rich in β-phellandrene (17.3%) and linalool (16.4%), had shown excellent larvicidal activity against Ae. aegypti and Ae. albopictus (LC50 = 21.5 and 16.7 μg/mL, respectively) [52].

3.3. Cinnamomum damhaensis

The major components of C. damhaensis leaf essential oil were linalool (44.8%) and β-selinene (19.1%) (Table 2). The essential oil also showed pronounced larvicidal activity against Ae. aegypti and Cx. quinquefasciatus with 48 h LC50 values of 17.4 and 18.6 μg/mL, respectively (Table 5), which can be attributed to the high concentration of linalool (see above). Note that Piper gaudichaudianum and Piper humaytanum leaf essential oils, rich in β-selinene (10.5% and 15.8%, respectively), but devoid of linalool, showed only marginal larvicidal activity against Ae. aegypti [53].

3.4. Cinnamomum longipetiolatum

The leaf essential oil of C. longipetiolatum was dominated by linalool (75.7%, Table 2), which likely accounts for the observed antimicrobial (Table 3) activity; linalool has shown broad antibacterial and antifungal activity [35,54]. Although linalool has shown larvicidal activity against Ae. aegypti (LC50 = 38.6 μg/mL) and Cx. quinquefasciatus (LC50 = 42.3 μg/mL) [49], the larvicidal activity of C. longipetiolatum leaf oil was less (24 h LC50 = 64.2 and 126.8 μg/mL against Ae. aegypti and Cx. quinquefasciatus, respectively, Table 4).

3.5. Cinnamomum polyadelphum

The leaf essential oil of C. polyadelphum showed good activity against the Gram-positive organisms tested with MIC values of 32, 64 and 64 μg/mL on E. faecalis, S. aureus and B. cereus, respectively (Table 3). The essential oil also showed notable larvicidal activity against all three mosquito species with 48-h LC50 values of 17.3, 20.8 and 11.0 μg/mL against Ae. aegypti, Ae. albopictus and Cx. quinquefasciatus, respectively (Table 5). The major components in C. polyadelphum leaf essential oil were camphor (32.2%), neral (11.7%) and geranial (16.6%) (Table 2). The antimicrobial properties of camphor are relatively marginal [55,56]. Citral (mixture of neral and geranial), on the other hand, has shown greater antimicrobial activity on Gram-positive bacteria [57,58,59] and fungi [60,61]. Likewise, citral has exhibited mosquito larvicidal activity against Ae. albopictus [62] but camphor is inactive against larvae of Ae. aegypti, Ae. albopictus [52,62] or Cx. pipiens [63].

4. Materials and Methods

4.1. Plant Material

Leaves or stem bark of the Cinnamomum species were collected from locations in north central Vietnam (see Table 1). Plants were identified by Do N. Dai and voucher specimens (Table 1) have been deposited in the plant specimen room, Faculty Agriculture, Forestry and Fishery, Nghe An, College of Economics. The fresh plant materials (2.0 kg each) were shredded and hydrodistilled using a Clevenger apparatus for 4 h to give the essential oils. The essential oil yields are summarized in Table 1.

4.2. Gas Chromatographic Analysis

Gas chromatography (GC) analysis was performed on an Agilent Technologies (Santa Clara, CA, USA) HP 7890A Plus Gas chromatograph equipped with a flame ionization detector (FID) and fitted with HP-5ms column (30 m × 0.25 mm, film thickness 0.25 μm, Agilent Technologies). The analytical conditions were—carrier gas H2 (1 mL/min), injector temperature (PTV) 250 °C, detector temperature 260 °C, column temperature programmed from 60 °C (2 min hold) to 220 °C (10 min hold) at 4 °C/min. Samples were injected by splitting and the split ratio was 10:1. The volume injected was 1.0 μL. Inlet pressure was 6.1 kPa.

An Agilent Technologies (Santa Clara, California, USA) HP 7890A Plus Chromatograph fitted with a fused silica capillary HP-5ms (30 m × 0.25 mm, film thickness 0.25 μm) and interfaced with a mass spectrometer (HP 5973 MSD) was used for the GC-MS analysis, under the same conditions as those used for GC-FID analysis. The conditions were the same as described above with He (1 mL/min) as carrier gas. The MS conditions were as follows—ionization voltage 70 eV; emission current 40 mA; acquisitions scan mass range of 35–350 amu at a sampling rate of 1.0 scan/s.

The identification of constituents was performed on the basis of retention indices (RI) determined with reference to a homologous series of n-alkanes, under identical experimental conditions, co-injection with standards (Sigma-Aldrich, St. Louis, MO, USA) or known essential oil constituents, MS library search (NIST 08 and Wiley 9th Version) and by comparing with MS literature data [64]. The relative amounts of individual components were calculated based on the GC peak area (FID response) without using correction factors.

4.3. Antimicrobial Screening

The antimicrobial activity of the essential oils was evaluated using three strains of Gram-positive test bacteria, Enterococcus faecalis (ATCC299212), Staphylococcus aureus (ATCC25923), Bacillus cereus (ATCC14579), three strains of Gram-negative test bacteria, Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC27853), Salmonella enterica (ATCC13076) and one strain of yeast, Candida albicans (ATCC 10231).

Minimum inhibitory concentration (MIC) and median inhibitory concentration (IC50) values were measured by the microdilution broth susceptibility assay [65]. Stock solutions of the oil were prepared in dimethylsulfoxide. Dilution series were prepared from 16,384 to 2 μg/mL (214, 213, 212, 211, 210, 29, 27, 25, 23 and 21 µg/mL) in sterile distilled water in micro-test tubes from where they were transferred to 96-well microtiter plates. Bacteria grown in double-strength Mueller-Hinton broth or double-strength tryptic soy broth and fungi grown in double-strength Sabouraud dextrose broth were standardized to 5 × 105 and 1 × 103 CFU/mL, respectively. The last row, containing only the serial dilutions of sample without microorganisms, was used as a positive (no growth) control. Sterile distilled water and medium served as a negative (no antimicrobial agent) control. Streptomycin was used as the antibacterial standard, nystatin and cycloheximide were used as antifungal standards. After incubation at 37 °C for 24 h, the MIC values were determined to be the well with the lowest concentration of agents completely inhibiting the growth of microorganisms. The IC50 values were determined by the percentage of microorganisms that inhibited growth based on the turbidity measurement data of EPOCH2C spectrophotometer (BioTeK Instruments, Inc Highland Park Winooski, VT, USA) and Rawdata computer software (Brussels, Belgium) according to the following equations:

%inhibition=ODcontrol(−)−ODtest agentODcontrol (−)−ODcontrol(+) (1)
IC50=Highconc−(Highinh%−50%)×(Highconc−Lowconc)(Highinh%−Lowinh%) (2)

where OD is the optical density, control(–) are the cells with medium but without antimicrobial agent, test agent corresponds to a known concentration of antimicrobial agent, control(+) is the culture medium without cells, Highconc/Lowconc is the concentration of test agent at high concentration/low concentration and Highinh%/Lowinh% is the % inhibition at high concentration/% inhibition at low concentration). Each of the antimicrobial screens were carried out in triplicate.

4.4. Larvicidal Screening

Eggs of Aedes aegypti were purchased from Institute of Biotechnology, Vietnam Academy of Science and Technology and maintained at the Laboratory of Department of Pharmacy of Duy Tan University, Da Nang, Vietnam. Adults of Culex quinquefasciatus and Aedes albopictus collected in Hoa Khanh Nam ward, Lien Chieu district, Da Nang city (16°03′14.9″N, 108°09′31.2″E) and were identified by National institute of Malariology, Parasitology and Entomology, Ho Chi Minh City. Adult mosquitoes were maintained in entomological cages (40 × 40 × 40 cm) and fed a 10% sucrose solution and were allowed to blood feed on 1-week-old chicks and mice, respectively. Egg hatchings were induced with tap water. Larvae were reared in plastic trays (24 × 35 × 5 cm). The larvae were fed on Koi fish food. All developmental stages were maintained at 25 ± 2 °C, 65–75% relative humidity and a 12:12 h light:dark cycle at the Laboratory of the Faculty of Environmental and Chemical Engineering of Duy Tan University, Da Nang, Vietnam.

Larvicidal activities of the Cinnamomum essential oils were evaluated according to the protocol Liu and co-workers [66] with slight modifications. For the assay, 150 mL of water that contained 20 larvae (fourth instar) was placed in 250-mL beakers and aliquots of the Cinnamomum essential oils dissolved in EtOH (1% stock solution) were then added. With each experiment, a set of controls using EtOH only (negative control) and permethrin (positive control) were also run for comparison. Mortality was recorded after 24 h and again after 48 h of exposure during which no nutritional supplement was added. The experiments were carried out at 25 ± 2 °C. Each test was conducted with four replicates with five concentrations (100, 50, 25, 12.5 and 6 μg/mL). The data obtained were subjected to log-probit analysis [67] to obtain LC50 values, LC90 values and 95% confidence limits using Minitab® 19 (Minitab, LLC, State College, PA, USA).

5. Conclusions

The essential oils of five species of Cinnamomum were collected from north central Vietnam and screened for antimicrobial and mosquito larvicidal activities. According to Duarte and co-workers [68], essential oils with MIC values between 50 and 500 μg/mL can be considered to have strong antimicrobial activity. Similarly, Dias and Moraes have concluded that essential oils with LC50 < 100 μg/mL are considered to be active [69]. Therefore, all of the Cinnamomum essential oils in this study can be considered to be active and show promise as antimicrobial agents and as alternative insecticidal agents against mosquito larvae.

Acknowledgments

W.N.S. participated in this work as part of the activities of the Aromatic Plant Research Center (APRC, https://aromaticplant.org/).

Author Contributions

Conceptualization, D.N.D. and W.N.S.; methodology, D.N.D., L.T.H., N.H.H., W.N.S.; validation, D.N.D. and W.N.S.; formal analysis, L.T.H., W.N.S.; investigation, N.T.C., L.T.H., N.T.Y., D.T.M.C.; resources, D.N.D.; data curation, W.N.S.; writing—original draft preparation, W.N.S., D.N.D.; writing—review and editing, D.N.D., L.T.H., W.N.S.; supervision, D.N.D.; project administration, D.N.D.; funding acquisition, D.N.D. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number: 106.03-2018.02.

Conflicts of Interest

The authors declare no conflict of interest.

Footnotes

Sample Availability: The Cinnamomum essential oils are no longer available.

References

  • 1.Mabberley D.J. Mabberley’s Plant-Book. 3rd ed. Cambridge University Press; Cambridge, UK: 2008. [Google Scholar]
  • 2.Ho P.-H. An Illustrated Flora of Vietnam, Vol. 3. Youth Publishing House; Ho Chi Minh City, Vietnam: 2000. [Google Scholar]
  • 3.Dao N.K. Flora of Vietnam, Lauraceae Juss, Vol. 17. Publishing House for Science & Technology; Hanoi, Vietnam: 2017. [Google Scholar]
  • 4.Chi V.V. Dictionary of Vietnamese Medicinal Plants, Vol. I–II. Medical Publishing House; Hanoi, Vietnam: 2012. [Google Scholar]
  • 5.Moi L.D., Cu L.D., Hoi T.M., Thuy N.T., Thao N.T., Thai T.H., Ban N.K. The Essential Oil Resources in Vietnam, Vol. 1. Agriculture Publishing House; Hanoi, Vietnam: 2001. [Google Scholar]
  • 6.Zaman S.B., Hussain M.A., Nye R., Mehta V., Mamun K.T., Hossain N. A review on antibiotic resistance: Alarm bells are ringing. Cureus. 2017;9:e1403. doi: 10.7759/cureus.1403. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7.Banin E., Hughes D., Kuipers O.P. Bacterial pathogens, antibiotics and antibiotic resistance. FEMS Microbiol. Rev. 2017;41:450–452. doi: 10.1093/femsre/fux016. [DOI] [PubMed] [Google Scholar]
  • 8.Navon-Venezia S., Kondratyeva K., Carattoli A. Klebsiella pneumoniae: A major worldwide source and shuttle for antibiotic resistance. FEMS Microbiol. Rev. 2017;41:252–275. doi: 10.1093/femsre/fux013. [DOI] [PubMed] [Google Scholar]
  • 9.Pierce G.E. Pseudomonas aeruginosa, Candida albicans and device-related nosocomial infections: Implications, trends and potential approaches for control. J. Ind. Microbiol. Biotechnol. 2005;32:309–318. doi: 10.1007/s10295-005-0225-2. [DOI] [PubMed] [Google Scholar]
  • 10.Sakoulas G., Moellering R.C., Jr. Increasing antibiotic resistance among methicillin-resistant Staphylococcus aureus strains. Clin. Infect. Dis. 2008;46:S360–S367. doi: 10.1086/533592. [DOI] [PubMed] [Google Scholar]
  • 11.Sweileh W.M., Sawalha A.F., Al-Jabi S., Zyoud S.H. Bibliometric analysis of literature on antifungal triazole resistance: 1980–2015. Germs. 2017;7:19–27. doi: 10.18683/germs.2017.1104. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12.Rajkowska K., Kunicka-Styczyńska A., Maroszyńska M. Selected essential oils as antifungal agents against antibiotic-resistant Candida spp.: In vitro study on clinical and food-borne isolates. Microb. Drug Resist. 2017;23:18–24. doi: 10.1089/mdr.2016.0001. [DOI] [PubMed] [Google Scholar]
  • 13.Orchard A., van Vuuren S. Commercial essential oils as potential antimicrobials to treat skin diseases. Evid. Based Complement. Altern. Med. 2017;2017:4517971. doi: 10.1155/2017/4517971. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14.Orchard A., Viljoen A., van Vuuren S. Wound pathogens: Investigating antimicrobial activity of commercial essential oil combinations against reference strains. Chem. Biodivers. 2018;15:e1800405. doi: 10.1002/cbdv.201800405. [DOI] [PubMed] [Google Scholar]
  • 15.Serra E., Hidalgo-Bastida L.A., Verran J., Williams D., Malic S. Antifungal activity of commercial essential oils and biocides against Candida albicans. Pathogens. 2018;7:15. doi: 10.3390/pathogens7010015. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 16.Powers C.N., Osier J.L., McFeeters R.L., Brazell C.B., Olsen E.L., Moriarity D.M., Satyal P., Setzer W.N. Antifungal and cytotoxic activities of sixty commercially-available essential oils. Molecules. 2018;23:1549. doi: 10.3390/molecules23071549. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17.Wińska K., Mączka W., Łyczko J., Grabarczyk M., Czubaszek A., Szumny A. Essential oils as antimicrobial agents—Myth or real alternative? Molecules. 2019;24:2130. doi: 10.3390/molecules24112130. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.D’agostino M., Tesse N., Frippiat J.P., Machouart M., Debourgogne A. Essential oils and their natural active compounds presenting antifungal properties. Molecules. 2019;24:3713. doi: 10.3390/molecules24203713. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19.Kozics K., Bučková M., Puškárová A., Kalászová V., Cabicarová T., Pangallo D. The Effect of ten essential oils on several cutaneous drug-resistant microorganisms and their cyto/genotoxic and antioxidant properties. Molecules. 2019;24:4570. doi: 10.3390/molecules24244570. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Leta S., Beyene T.J., De Clercq E.M., Amenu K., Kraemer M.U.G., Revie C.W. Global risk mapping for major diseases transmitted by Aedes aegypti and Aedes albopictus. Int. J. Infect. Dis. 2018;67:25–35. doi: 10.1016/j.ijid.2017.11.026. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21.Samy A.M., Elaagip A.H., Kenawy M.A., Ayres C.F.J., Peterson A.T., Soliman D.E. Climate change influences on the global potential distribution of the mosquito Culex quinquefasciatus, vector of West Nile virus and lymphatic filariasis. PLoS ONE. 2016;11:e0163863. doi: 10.1371/journal.pone.0163863. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 22.Song S., Li Y., Fu S., Liu H., Li X., Gao X., Xu Z., Liu G., Wang D., Tian Z., et al. Could Zika virus emerge in Mainland China? Virus isolation from nature in Culex quinquefasciatus, 2016. Emerg. Microbes Infect. 2017;6:e93. doi: 10.1038/emi.2017.80. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23.Bhattacharya S., Basu P. The southern house mosquito, Culex quinquefasciatus: Profile of a smart vector. J. Entomol. Zool. Stud. 2016;4:73–81. [Google Scholar]
  • 24.Cook C.L., Huang Y.-J.S., Lyons A.C., Alto B.W., Unlu I., Higgs S., Vanlandingham D.L. North American Culex pipiens and Culex quinquefasciatus are competent vectors for Usutu virus. PLoS Negl. Trop. Dis. 2018;12:e0006732. doi: 10.1371/journal.pntd.0006732. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25.Naqqash M.N., Gökçe A., Bakhsh A., Salim M. Insecticide resistance and its molecular basis in urban insect pests. Parasitol. Res. 2016;115:1363–1373. doi: 10.1007/s00436-015-4898-9. [DOI] [PubMed] [Google Scholar]
  • 26.Grisales N., Poupardin R., Gomez S., Fonseca-Gonzalez I., Ranson H., Lenhart A. Temephos resistance in Aedes aegypti in Colombia compromises dengue vector control. PLoS Negl. Trop. Dis. 2013;7:e2438. doi: 10.1371/journal.pntd.0002438. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27.Elia-Amira N.M.R., Chen C.D., Lau K.W., Lee H.L., Low V.L., Norma-Rashid Y., Sofian-Azirun M. Organophosphate and organochlorine resistance in larval stage of Aedes albopictus (Diptera: Culicidae) in Sabah, Malaysia. J. Econ. Entomol. 2018;111:2488–2492. doi: 10.1093/jee/toy184. [DOI] [PubMed] [Google Scholar]
  • 28.Delisi N., Ottea J., Healy K. Susceptibility of Culex quinquefasciatus (Diptera: Culicidae) in southern Louisiana to larval insecticides. J. Econ. Entomol. 2017;110:2562–2567. doi: 10.1093/jee/tox244. [DOI] [PubMed] [Google Scholar]
  • 29.Pitasawat B., Champakaew D., Choochote W., Jitpakdi A., Chaithong U., Kanjanapothi D., Rattanachanpichai E., Tippawangkosol P., Riyong D., Tuetun B., et al. Aromatic plant-derived essential oil: An alternative larvicide for mosquito control. Fitoterapia. 2007;78:205–210. doi: 10.1016/j.fitote.2007.01.003. [DOI] [PubMed] [Google Scholar]
  • 30.Silva W.J., Dória G.A.A., Maia R.T., Nunes R.S., Carvalho G.A., Blank A.F., Alves P.B., Marçal R.M., Cavalcanti S.C.H. Effects of essential oils on Aedes aegypti larvae: Alternatives to environmentally safe insecticides. Bioresour. Technol. 2008;99:3251–3255. doi: 10.1016/j.biortech.2007.05.064. [DOI] [PubMed] [Google Scholar]
  • 31.Pavela R. Essential oils for the development of eco-friendly mosquito larvicides: A review. Ind. Crop. Prod. 2015;76:174–187. doi: 10.1016/j.indcrop.2015.06.050. [DOI] [Google Scholar]
  • 32.Son L.C., Dai D.N., Thai T.H., Huyen D.D., Thang T.D., Ogunwande I.A. The leaf essential oils of four Vietnamese species of Cinnamomum (Lauraceae) J. Essent. Oil Res. 2013;25:267–271. doi: 10.1080/10412905.2013.775673. [DOI] [Google Scholar]
  • 33.Son L.C., Dai D.N., Thang T.D., Huyen D.D., Olayiwola T.O., Ogunmoye A.R., Ogunwande I.A. Chemical composition of essential oils from the stem barks of three Cinnamomum species. Br. J. Appl. Sci. Technol. 2015;11:20442. doi: 10.9734/BJAST/2015/20442. [DOI] [Google Scholar]
  • 34.Son L.C., Dai D.N., Thang T.D., Huyen D.D., Ogunwande I.A. Study on Cinnamomum oils: Compositional pattern of seven species grown in Vietnam. J. Oleo Sci. 2014;63:1035–1043. doi: 10.5650/jos.ess14078. [DOI] [PubMed] [Google Scholar]
  • 35.Dorman H.J.D., Deans S.G. Antimicrobial agents from plants: Antibacterial activity of plant volatile oils. J. Appl. Microbiol. 2000;88:308–316. doi: 10.1046/j.1365-2672.2000.00969.x. [DOI] [PubMed] [Google Scholar]
  • 36.Gallucci M.N., Oliva M., Casero C., Dambolena J., Luna A., Zygadlo J., Demo M. Antimicrobial combined action of terpenes against the food-borne microorganisms Escherichia coli, Staphylococcus aureus and Bacillus cereus. Flavour Fragr. J. 2009;24:348–354. doi: 10.1002/ffj.1948. [DOI] [Google Scholar]
  • 37.Boonchird C., Flegel T.W. In vitro antifungal activity of eugenol and vanillin against Candida albicans and Cryptococcus neoformans. Can. J. Microbiol. 1982;28:1235–1241. doi: 10.1139/m82-184. [DOI] [PubMed] [Google Scholar]
  • 38.Cheng S.-S., Liu J.-Y., Chang E.-H., Chang S.-T. Antifungal activity of cinnamaldehyde and eugenol congeners against wood-rot fungi. Bioresour. Technol. 2008;99:5145–5149. doi: 10.1016/j.biortech.2007.09.013. [DOI] [PubMed] [Google Scholar]
  • 39.Abbaszadeh S., Sharifzadeh A., Shokri H., Khosravi A.R., Abbaszadeh A. Antifungal efficacy of thymol, carvacrol, eugenol and menthol as alternative agents to control the growth of food-relevant fungi. J. Mycol. Med. 2014;24:51–56. doi: 10.1016/j.mycmed.2014.01.063. [DOI] [PubMed] [Google Scholar]
  • 40.Cheng S.-S., Liu J.-Y., Tsai K.-H., Chen W.-J., Chang S.-T. Chemical composition and mosquito larvicidal activity of essential oils from leaves of different Cinnamomum osmophloeum provenances. J. Agric. Food Chem. 2004;52:4395–4400. doi: 10.1021/jf0497152. [DOI] [PubMed] [Google Scholar]
  • 41.Govindarajan M., Rajeswary M., Hoti S.L., Bhattacharyya A., Benelli G. Eugenol, α-pinene and β-caryophyllene from Plectranthus barbatus essential oil as eco-friendly larvicides against malaria, dengue and Japanese encephalitis mosquito vectors. Parasitol. Res. 2016;115:807–815. doi: 10.1007/s00436-015-4809-0. [DOI] [PubMed] [Google Scholar]
  • 42.Pavela R. Insecticidal properties of phenols on Culex quinquefasciatus Say and Musca domestica L. Parasitol. Res. 2011;109:1547–1553. doi: 10.1007/s00436-011-2395-3. [DOI] [PubMed] [Google Scholar]
  • 43.Schmidt J.M., Noletto J.A., Vogler B., Setzer W.N. Abaco bush medicine: Chemical composition of the essential oils of four aromatic medicinal plants from Abaco Island, Bahamas. J. Herbs. Spices Med. Plants. 2006;12:43–65. doi: 10.1300/J044v12n03_04. [DOI] [Google Scholar]
  • 44.Wanner J., Schmidt E., Bail S., Jirovetz L., Buchbauer G., Gochev V., Girova T., Atanasova T., Stoyanova A. Chemical composition and antibacterial activity of selected essential oils and some of their main compounds. Nat. Prod. Commun. 2010;5:1359–1364. doi: 10.1177/1934578X1000500905. [DOI] [PubMed] [Google Scholar]
  • 45.Filipowicz N., Kaminski M., Kurlenda J., Asztemborska M., Ochocka J.R. Antibacterial and antifungal activity of juniper berry oil and its selected components. Phyther. Res. 2003;17:227–231. doi: 10.1002/ptr.1110. [DOI] [PubMed] [Google Scholar]
  • 46.Hammer K.A., Carson C.F., Riley T. V Antifungal activity of the components of Melaleuca alternifolia (tea tree) oil. J. Appl. Microbiol. 2003;95:853–860. doi: 10.1046/j.1365-2672.2003.02059.x. [DOI] [PubMed] [Google Scholar]
  • 47.Jantan I., Moharam B.A.K., Santhanam J., Jamal J.A. Correlation between chemical composition and antifungal activity of the essential oils of eight Cinnamomum species. Pharm. Biol. 2008;46:406–412. doi: 10.1080/13880200802055859. [DOI] [Google Scholar]
  • 48.Hung N.H., Satyal P., Hieu H.V., Chuong N.T.H., Dai D.N., Huong L.T., Tai T.A., Setzer W.N. Mosquito larvicidal activity of the essential oils of Erechtites species growing wild in Vietnam. Insects. 2019;10:47. doi: 10.3390/insects10020047. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 49.Govindarajan M. Chemical composition and larvicidal activity of leaf essential oil from Clausena anisata (Willd.) Hook. f. ex Benth (Rutaceae) against three mosquito species. Asian Pac. J. Trop. Med. 2010;3:874–877. doi: 10.1016/S1995-7645(10)60210-6. [DOI] [Google Scholar]
  • 50.Cheng S.-S., Huang C.-G., Chen Y.-J., Yu J.-J., Chen W.-J., Chang S.-T. Chemical compositions and larvicidal activities of leaf essential oils from two eucalyptus species. Bioresour. Technol. 2009;100:452–456. doi: 10.1016/j.biortech.2008.02.038. [DOI] [PubMed] [Google Scholar]
  • 51.Evergetis E., Michaelakis A., Haroutounian S.A. Exploitation of Apiaceae family essential oils as potent biopesticides and rich source of phellandrenes. Ind. Crops Prod. 2013;41:365–370. doi: 10.1016/j.indcrop.2012.04.058. [DOI] [Google Scholar]
  • 52.bin Jantan I., Yalvema M.F., Ahmad N.W., Jamal J.A. Insecticidal activities of the leaf oils of eight Cinnamomum species against Aedes aegypti and Aedes albopictus. Pharm. Biol. 2005;43:526–532. doi: 10.1080/13880200500220771. [DOI] [Google Scholar]
  • 53.de Morais S.M., Facundo V.A., Bertini L.M., Cavalcanti E.S.B., dos Anjos Júnior J.F., Ferreira S.A., de Brito E.S., de S Neto M.A. Chemical composition and larvicidal activity of essential oils from Piper species. Biochem. Syst. Ecol. 2007;35:670–675. doi: 10.1016/j.bse.2007.05.002. [DOI] [Google Scholar]
  • 54.Pattnaik S., Subramanyam V.R., Bapaji M., Kole C.R. Antibacterial and antifungal activity of aromatic constituents of essential oils. Microbios. 1997;89:39–46. [PubMed] [Google Scholar]
  • 55.Setzer W.N., Vogler B., Schmidt J.M., Leahy J.G., Rives R. Antimicrobial activity of Artemisia douglasiana leaf essential oil. Fitoterapia. 2004;75 doi: 10.1016/j.fitote.2003.12.019. [DOI] [PubMed] [Google Scholar]
  • 56.Satyal P., Paudel P., Poudel A., Dosoky N.S., Pokharel K.K., Setzer W.N. Bioactivities and compositional analyses of Cinnamomum essential oils from Nepal: C. camphora, C. tamala and C. glaucescens. Nat. Prod. Commun. 2013;8:1777–1784. doi: 10.1177/1934578X1300801232. [DOI] [PubMed] [Google Scholar]
  • 57.Setzer W.N., Schmidt J.M., Eiter L.C., Haber W.A. The leaf oil composition of Zanthoxylum fagara (L.) Sarg. from Monteverde, Costa Rica and its biological activities. J. Essent. Oil Res. 2005;17:333–335. doi: 10.1080/10412905.2005.9698923. [DOI] [Google Scholar]
  • 58.Reichling J., Suschke U., Schneele J., Geiss H.K. Antibacterial activity and irritation potential of selected essential oil components—Structure-activity relationship. Nat. Prod. Commun. 2006;1:1003–1012. doi: 10.1177/1934578X0600101116. [DOI] [Google Scholar]
  • 59.Fisher K., Phillips C.A. The effect of lemon, orange and bergamot essential oils and their components on the survival of Campylobacter jejuni, Escherichia coli O157, Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus in vitro and in food systems. J. Appl. Microbiol. 2006;101:1232–1240. doi: 10.1111/j.1365-2672.2006.03035.x. [DOI] [PubMed] [Google Scholar]
  • 60.Mesa-Arango A.C., Montiel-Ramos J., Zapata B., Durán C., Betancur-Galvis L., Stashenko E. Citral and carvone chemotypes from the essential oils of Colombian Lippia alba (Mill.) N.E. Brown: Composition, cytotoxicity and antifungal activity. Mem. Inst. Oswaldo Cruz. 2009;104:878–884. doi: 10.1590/S0074-02762009000600010. [DOI] [PubMed] [Google Scholar]
  • 61.Silva C.D.B.D., Guterres S.S., Weisheimer V., Schapoval E.E. Antifungal activity of the lemongrass oil and citral against Candida spp. Braz. J. Infect. Dis. 2008;12:63–66. doi: 10.1590/S1413-86702008000100014. [DOI] [PubMed] [Google Scholar]
  • 62.Cheng S.-S., Liu J.-Y., Huang C.-G., Hsui Y.-R., Chen W.-J., Chang S.-T. Insecticidal activities of leaf essential oils from Cinnamomum osmophloeum against three mosquito species. Bioresour. Technol. 2009;100:457–464. doi: 10.1016/j.biortech.2008.02.030. [DOI] [PubMed] [Google Scholar]
  • 63.Radwan M.A., El-Zemity S.R., Mohamed S.A., Sherby S.M. Larvicidal activity of some essential oils, monoterpenoids and their corresponding N-methyl carbamate derivatives against Culex pipiens (Diptera: Culicidae) Int. J. Trop. Insect Sci. 2008;28:61–68. doi: 10.1017/S1742758408962366. [DOI] [Google Scholar]
  • 64.Adams R.P. Identification of Essential Oil Components by Gas Chromatography/Mass Spectrometry. 4th ed. Allured Publishing; Carol Stream, IL, USA: 2007. [Google Scholar]
  • 65.Sahm D.H., Washington J.A. Antibacterial susceptibility tests: Dilution methods. In: Balows A., Hausler W.J., Herrmann K.L., Isenberg H.D., Shamody H.J., editors. Manual of Clinical Microbiology. American Society for Microbiology; Washington, DC, USA: 1991. [Google Scholar]
  • 66.Liu Z.L., He Q., Chu S.S., Wang C.F., Du S.S., Deng Z.W. Essential oil composition and larvicidal activity of Saussurea lappa roots against the mosquito Aedes albopictus (Diptera: Culicidae) Parasitol. Res. 2012;110:2125–2130. doi: 10.1007/s00436-011-2738-0. [DOI] [PubMed] [Google Scholar]
  • 67.Finney D. In: Probit Analysis. Vincent K., editor. Cambridge University Press; Cambridge, UK: 2009. [Google Scholar]
  • 68.Duarte M.C.T., Leme E.E., Delarmelina C., Soares A.A., Figueira G.M., Sartoratto A. Activity of essential oils from Brazilian medicinal plants on Escherichia coli. J. Ethnopharmacol. 2007;111:197–201. doi: 10.1016/j.jep.2006.11.034. [DOI] [PubMed] [Google Scholar]
  • 69.Dias C.N., Moraes D.F.C. Essential oils and their compounds as Aedes aegypti L. (Diptera: Culicidae) larvicide: Review. Parasitol. Res. 2014;113:565–592. doi: 10.1007/s00436-013-3687-6. [DOI] [PubMed] [Google Scholar]

Articles from Molecules are provided here courtesy of Multidisciplinary Digital Publishing Institute (MDPI)

RESOURCES