1. Introduction
Leishmaniasis is a major health problem in the tropical region, which is caused by more than 20 species of the genus of protozoa parasite known as
leishmania. Over 90 species of sandflies are the transmitting vectors and more than 70 animal species including humans are used as reservoir hosts [
1]. The involvement of several bio-actors for leishmaniasis, made it too complex for prevention and control of the health problem associated with it. Worldwide, 50,000 to 90,000 and 600,000 to 1 million cases have been reported annually for visceral and cutaneous forms of leishmaniasis, respectively [
1]. Cutaneous leishmaniasis is the most common form in Ethiopia, with an estimated 20,000 to 50,000 cases annually and
Leishmania aethiopica,
Leishmania tropica, and
Leishmania major are the causative agents [
2].
Affordable, safe, and short-course treatment is one of the strategies among leishmaniasis prevention tools by the World Health Organization [
3]. So far, some leishmanicidal drugs such as pentavalent antimonial, paromomycin, amphotericin B, liposomal amphotericin, pentamidine, and miltefosine have been availed, but they have limitations like drug resistance, high cost, least availability, toxicity, and painful route of administration [
4,
5]. Therefore, it is vital to search for leishmanicidal molecules that have efficacy and tolerable safety. Medicinal plants are a good source of secondary metabolites that have diverse biological activities [
6].
Echinops kebericho Mesfin is an endemic and endangered Ethiopian medicinal plant belonging to the genus
Echinops and family Asteraceae. Its root is a potential medicinal part and has been used for treating various ailments such as dispelling nightmares in children, constipation, headache, heart pain, stomachache, typhus, as fumigant after childbirth, intestinal pains, lung TB, leprosy, syphilis, cough, ward off evil eye, toothache, and vomiting [
7,
8,
9,
10,
11,
12,
13]. Besides, it is used as Snake and Mosquito repellant [
14,
15].
The essential oil extracted from roots of
E. kebericho has major constituent of eudesm-7 (11) -en-4-ol, caryophyllene oxide, τ-cadinol, β-cubebene, β-patchoulene, longifolene, cyperene, dehydrocostus lactone, β-phellandrene, germacrene B, α-selinene, isoshyobunone, modephene, α-pinene, and β-pinene [
16,
17]. Moreover, β-sitosterol, stigmasterol, campesterol, β-amyrene, lupeol, and ursolic acid, together with a series of fatty acids were identified from the solvent extract of
E. kebericho roots [
18,
19].
The essential oil, petroleum ether, and chloroform extracts of roots of
E. kebericho have anti-leishmanial activity against
Leishmania species [
20]. Assay for biological activities of the isolated active ingredients from roots of
E. kebericho were obscure. Indeed, this work had the aim to identify the leishmanicidal crude fraction next to the isolated compound against the promastigote stage of
L. major and
L. tropica strains. The in vitro method of screening leishmanicidal compound and crude fraction was determined by 96 well plates assay with microscope detection method [
21].
2. Results and Discussion
Hydro distillation of dried roots of
E. kebericho obtained a 0.16% yield of essential oil. The in vitro antileishmanial activity test of the essential oil showed leishmanicidal activity with an IC50 value of 38.3µg/mL for
L. major and 55.16µg/mL for
L. tropica. A supportive result has been reported as the essential oils of
E. kebericho showed concentration-dependent growth inhibitory effects against promastigote forms of
L. donovani (MIC = 0.0765 µl/ml) and
L. aethiopica (MIC = 0.0097 µl/ml) [
17].
Furthermore, the essential oil profile was characterized, and a total of 43 compounds were identified by GC-MS analysis (
Table 2). Dehydrocostus lactone (24.95%), β-guaiene (11.13%), cis lanceol (5.92%), 1,4-methanoazulen-9-one, decahydro-1,5,5,8a-tetramethyl-, [1R-(1α,3aβ,4α,8aβ)] (4.98%), (±)-cadinene (3.94%) δ-neoclovene (3.68%), aromadendrene oxide (3.29%), and caryophyllene (3.05%) were the major constituents of the essential oil. A comparable result of the major constituents of
E. kebericho essential oil was reported by Tariku et. al., (2011) [
16] which were dehydrocostus lactone (41.83%), β-phellandrene (10.84%), germacrene B (5.38%), α-selinene (4.13%), α-pinene (3.63%), and β-pinene (3.62%).
Dichloromethane-methanol maceration of the dried roots of E. kebericho was achieved with a crude extract yield of 10.38% (92.63g). Different yields of fractions were recovered from liquid-liquid partition, such as hexane (55.61g), dichloromethane (8.53g), ethyl acetate (4 g), n-butanol (11.70g) and water fraction (12.79g). From the in vitro test of fractions, the hexane fraction had an antileishmanial activity with an IC50 value of 33.3 and 36.6 µg/mL for L. major and L. tropica, respectively. All other crude fractions were not active against the tested leishmania strain. The dichloromethane fraction was not tested due to partial solubility by DMSO.
The major compound from the hexane fraction was isolated by column chromatography, which collected 30 fractions (F1-F30) (
Figure 1 b). Amongst the fractions, F8 was the major pure compound and coded as Ek-cpd1 with having Rf value of 0.57 (
Figure 1 c) through the solvent system of hexane: ethyl acetate (86, 14) ratio, respectively.
The compound Ek-cpd1 was a colorless crystalline solid and its structure was identified using EI-Mass that gave a molecular mass ion peak ([M]
+) at m/z 230.2 having a molecular formula C
15H
18O
2 (
Figure 2). The
1H NMR (500 MHz, CDCl
3) showed a spectra of δ
1H: 6.19 (1H, d,
J = 3.5 Hz, H-13a), 5.46 (1H, d, J = 3.2 Hz, H-13b), 5.24 (1H, brs, J = 2.4, 1.5 Hz, H-15a), 5.04 (1H, brs, H-15b), 4.87 (1H, brs, H-14a), 4.79 (1H, brs, H-14b), 3.94 (1H, t, J = 9.3 Hz, H-6), 2.93 (1H , m, H-5), 2.89 – 2.79 (2H, m, H-4, 7), 2.59 – 2.41 (3H, m, H-3a, 9a, 3b), 2.22 (1H, m, H-9b ), 2.13 (1H, m, H-2a), 1.97 – 1.79 (2H, m, H-2b,8a), 1.39 (1H, m, H-8b) (
Figure 3). From the spectral analysis and comparisons with the literature [
22,
23], the structure of Ek-cpd1 was characterized as dehydrocostus lactone, which is a sesquiterpene lactone with guaianolides class (
Figure 4).
In vitro, a leishmanicidal test result of Ek-cpd1 (Dehydrocostus lactone) showed an activity with an IC50 value of 15.3 µM/mL for L. major and 14.2 µM/mL for L. tropica. The standard drugs had an IC50 value of 3.39 and 3.41 µM/mL (Amphotericin B), 4.56 µM/mL (Pentamidine), 31.8 and 27.2 µM/mL (Miltefosine) for L. major and L. tropica, respectively.
Antileishmanial activity test of the present finding showed that the essential oil and hexane fraction from roots of E. kebericho had significantly active effects against L. major and L. tropica. Dehydrocostus lactone is the most abundant constituent of the essential oil and hexane fraction from roots of E. kebericho, which showed a potent antileishmanial activity. Specifically, the leishmanicidal test revealed that dehydrocostus lactone had doubled potency of the standard drug miltefosine against the tested leishmania species.
No toxicity test has been done in this study. However, previous studies reported that the essential oil of
E. kebericho showed no mortality in acute oral dose toxicity up to 2000mg/kg body weight and was well tolerated in 200mg/ kg sub-acute toxicity and repeated dose exposure [
17]. Additionally, the decoction of
E. kebericho tuber had LD
50 greater than 5000 mg/kg in acute toxicity and was well tolerated up to the dose of 600mg/kg in sub-acute toxicity [
24]. Moreover, an in vivo cytotoxicity test of dehydrocostus lactone against laryngeal carcinoma showed that inhibition of the growth of the Hep-2 nude mouse xenograft model and had no significant signs of toxicity in the organs of nude mice [
25].
Several researchers reported that dehydrocostus lactone has a range of biological activities such as anticancer activity against different cancer cells [
26,
27,
28,
29], anti-inflammatory activity [
30,
31], anti-allergy activity [
32], and anti-depressant property [
33]. Overall, dehydrocostus lactone could be a potential drug for co-infected patients caused by an association of
leishmania and other pathogens.
Table 1.
In vitro antileishmanial activity test of crude extract, essential oil, and isolated compounds from roots of E. kebericho.
Table 1.
In vitro antileishmanial activity test of crude extract, essential oil, and isolated compounds from roots of E. kebericho.
Tested samples |
Tested Parasites |
|
|
L. major |
L. tropica |
Crude extract |
IC50 (µg/mL)SD |
IC50 (µg/mL) |
Hexane fraction |
33.30.7 |
36.60.5 |
Dichloromethane fraction |
NT |
NT |
Ethyl acetate fraction |
>100 |
>100 |
N-Butanol fraction |
>100 |
>100 |
Water fraction |
>100 |
>100 |
Essential oil |
38.30.8 |
55.160.9 |
Compounds |
IC50 (µM/mL) |
IC50 (µM/mL) |
E.k-cpd1 |
15.30.03 |
14.20.2 |
Amphotericin B |
3.390.03 |
3.410.02 |
Pentamidine |
4.560.01 |
4.560.01 |
Miltefosine |
31.80.2 |
27.20.6 |
Table 2.
Chemical composition analysis of essential oil from roots of E. kebericho.
Table 2.
Chemical composition analysis of essential oil from roots of E. kebericho.
No. |
RT (minute) |
MW (g/mole) |
MF |
Name of Compounds |
Relative Concentration (%) |
1 |
18.1 |
152 |
C10H16O |
(S)-cis-Verbenol |
0.21 |
2 |
19.1 |
154 |
C10H18O |
Borneol |
0.18 |
3 |
23.5 |
154 |
C10H18O |
p-Menth-2-en-7-ol, trans- |
0.28 |
4 |
24.4 |
196 |
C12H20O2
|
Borneol, acetate |
2.08 |
5 |
26.7 |
204 |
C15H24
|
(±)-Cadinene |
3.94 |
6 |
27.1 |
204 |
C15H24
|
δ-Neoclovene |
3.68 |
7 |
27.5 |
204 |
C15H24
|
β-Elemene |
2.67 |
8 |
28.4 |
204 |
C15H24
|
α-Guaiene |
2.36 |
9 |
28.7 |
204 |
C15H24
|
Caryophyllene |
3.05 |
10 |
30.5 |
204 |
C15H24
|
α-Humulene/α-Caryophyllene |
1.36 |
11 |
30.8 |
204 |
C15H24
|
(-)-Alloaromadendrene |
1.07 |
12 |
31.7 |
204 |
C15H24
|
γ-Muurolene |
0.15 |
13 |
32.1 |
204 |
C15H24
|
β-Eudesmene/β-Selinene |
0.11 |
14 |
32.4 |
204 |
C15H24
|
α-Selinene |
0.43 |
15 |
33.5 |
204 |
C15H24
|
γ-Cadinene |
2.19 |
16 |
33.7 |
204 |
C15H24
|
δ-Cadinene |
0.33 |
17 |
34.1 |
204 |
C15H24
|
β-Guaiene |
11.13 |
18 |
35.6 |
222 |
C15H26O |
±-trans-Nerolidol |
0.48 |
19 |
37.7 |
220 |
C15H24O |
Caryophyllene oxide |
2.33 |
20 |
37.8 |
220 |
C15H24O |
Aromadendrene oxide-(2) |
0.74 |
21 |
38.2 |
220 |
C15H24O |
1,4-Methanoazulen-9-one, decahydro-1,5,5,8a-tetramethyl-, [1R-(1α,3aβ,4α,8aβ)]- |
4.98 |
22 |
38.7 |
220 |
C15H24O |
Diepi-α-cedrene epoxide |
0.37 |
23 |
38.9 |
222 |
C15H26O |
Germacrene D-4-ol |
1.84 |
24 |
39.1 |
222 |
C15H26O |
Cubenol |
0.18 |
25 |
39.8 |
222 |
C15H26O |
τ-Cadinol |
0.33 |
26 |
39.9 |
222 |
C15H26O |
τ-Muurolol |
1.32 |
27 |
40.1 |
222 |
C15H26O |
δ-Cadinol, (-)- |
0.08 |
28 |
40.3 |
222 |
C15H26O |
α-Cadinol |
1.10 |
29 |
40.5 |
220 |
C15H24O |
γ-Gurjunenepoxide-(2) |
0.90 |
30 |
40.8 |
204 |
C15H24
|
Globulol |
0.33 |
31 |
41.0 |
220 |
C15H24O |
Aromadendrene oxide-(1) |
3.29 |
32 |
42.0 |
232 |
C16H24O |
9-Methoxycalamenene |
1.43 |
33 |
42.6 |
220 |
C15H24O |
Cedren-13-ol, 8- |
0.09 |
34 |
42.8 |
220 |
C15H24O |
Ledene oxide-(II) |
0.43 |
35 |
44.0 |
220 |
C15H24O |
Lanceol, cis |
5.92 |
36 |
44.6 |
220 |
C15H24O |
Santalol, cis, α- |
0.80 |
37 |
45.5 |
220 |
C15H24O |
2-(4a,8-Dimethyl-1,2,3,4,4a,5,6,7-octahydro-naphthalen-2-yl)-prop-2-en-1-ol |
1.95 |
38 |
46.2 |
236 |
C15H24O2
|
Bicyclo[4.4.0]dec-5-ene, 1,5-dimethyl-3-hydroxy-8-(1-methylene-2-hydroxyethyl-1)- |
0.39 |
39 |
46.6 |
220 |
C15H24O |
α-Copaen-11-ol |
0.08 |
40 |
47.5 |
236 |
C15H24 O2
|
Bicyclo[4.4.0]dec-2-ene-4-ol, 2-methyl-9-(prop-1-en-3-ol-2-yl)- |
0.18 |
41 |
49.0 |
230 |
C16H22O |
Cycloisolongifolene, 8,9-dehydro-9-formyl- |
0.20 |
42 |
50.5 |
202 |
C15H22
|
Aromadendrene, dehydro- |
0.19 |
43 |
56.9 |
230 |
C15H18O2
|
Dehydrocostus lactone |
24.95 |