Many essential oils (EOs) of different plant species possess interesting antimicrobial effects on buccal microorganisms and cytotoxic properties. EOs of
The plants are part of our daily life and their essential oils (EOs) have been extracted from 3000 different sources, of which 200 to 300 have domestic, industrial, and medicinal use [
The Brazilian cerrado (savannah) biome is a great source of medicinal plants, with several pharmacologically active species used in folk medicine, contributing to significant knowledge of bioactive compounds. The plants of the genus
The species
The aim of the present study is to evaluate the antimicrobial activity of essential oils from different parts of
The plant material was collected in Monte Alegre de Minas, Minas Gerais state, Brazil, (Latitude: 18°34′56.85′′S; Longitude: 49°2′52.61′′O) in July 2012 (dry season). A specialist identified the plant and a voucher specimen (57181) was deposited in the herbarium of the Federal University of Uberlândia, Brazil.
The fresh material of
The compounds in the EO were identified by a GC-17A/QP-5000 gas chromatograph coupled to a mass spectrometer (Shimadzu, Kyoto, Japan) equipped with a 30-m DB-5 capillary column (5% phenyl, 95% polydimethylsiloxane, J&W, USA, 30 m × 0.25 mm × 0.25
The tested strains were obtained from the American Type Culture Collection (ATCC, Rockville MD, USA). The following microorganisms were used in the evaluation of the antibacterial activity of the essential oils:
The minimum inhibitory concentration (MIC) values of the essential oils were determined in triplicate by the microdilution broth method in 96-well microplates (TPP, EUA) [
Samples of the essential oils were dissolved in methanol and diluted in DMEM (Dulbecco’s modified Eagle’s medium) culture medium supplemented to form a stock solution of 640
A relationship between cytotoxicity and antimicrobial activity was determined through the selectivity index (SI), which was calculated by the logarithm of the ratio of the cytotoxic concentration (CC50) and the MIC value for microorganisms
Experimental results of essential oils yields were expressed as Mean ± SD for analysis performed in triplicate. Statistical analysis of the data was performed by Student’s
The yields of the essential oils from leaves, inner bark, outer bark, and wood were
Chemical constituents of the essential oils from
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Composition % | |||||||||
Compound | Leaves | Inner bark | Outer bark | Wood | AI reference | AIc | Mode of |
Reference | |
1 | ( |
0.5 | — | — | — | 846 | 847 | a, c, d | e, g |
2 | ( |
2.1 | — | — | 1.3 | 850 | 851 | a, c, d | e, g |
3 | Linalool | 0.4 | — | — | — | 1095 | 1093 | a, c | e |
4 |
|
0.6 | — | — | — | 1335 | 1327 | a, c | e |
5 |
|
0.6 | — | — | — | 1345 | 1341 | a, c, d | e, g |
6 |
|
— | 1.2 | — | — | 1350 | 1349 | a, c | e |
7 |
|
3.6 | 14.9 | 2.1 | — | 1374 | 1375 | a, c | e |
8 |
|
1.6 | — | — | — | 1387 | 1384 | a, c | e |
9 |
|
1.3 | — | — | — | 1389 | 1387 | a, c | e |
10 | Sesquithujene <7- |
— | 1.7 | — | — | 1390 | 1389 | a, c | e |
11 |
|
— | 5.2 | 0.9 | — | 1419 | 1418 | a, c | e |
12 | n.i. ( |
— | 3.6 | — | — | — | 1419 | — | — |
13 | ( |
15.5 | — | — | — | 1417 | 1422 | a, c | e |
14 |
|
— | 4.2 | 0.8 | — | 1429 | 1429 | a, c, d | e, g |
15 |
|
— | 13.0 | 0.8 | — | 1432 | 1434 | a, c | e |
16 | Aromadendrene | 0.9 | — | — | — | 1439 | 1442 | a, c | e |
17 | n.i. ( |
— | 2.4 | 0.7 | — | — | 1450 | — | — |
18 | ( |
— | 8.6 | — | — | 1454 | 1454 | a, c | e |
19 |
|
3.0 | — | — | — | 1452 | 1456 | a, c | e |
20 |
|
— | 1.3 | — | — | 1469 | 1464 | a, c | e |
21 |
|
0.5 | — | — | — | 1461 | 1465 | a, c | e |
22 |
|
— | 1.3 | 1.0 | — | 1477 | 1475 | a, c | e |
23 |
|
— | 7.4 | 0.7 | — | 1479 | 1479 | a, b | e |
24 | Germacrene-D | 24.2 | — | — | — | 1484 | 1483 | a, c | e |
25 |
|
0.4 | — | 0.5 | — | 1489 | 1490 | a, c | e |
26 | Pentadecane | — | — | 0.5 | — | 1500 | 1493 | a, b | e |
27 |
|
— | 0.6 | 1.1 | — | 1500 | 1497 | a, d | e, f |
28 | Bicyclogermacrene | 11.6 | — | — | — | 1500 | 1500 | a, c | e |
29 |
|
— | 1.7 | 0.3 | — | 1503 | 1500 | a, c | e |
30 | n.i. | — | — | 2.3 | — | — | 1502 | — | — |
31 |
|
— | 9.5 | — | — | 1505 | 1504 | a, c | e |
32 |
|
— | 0.5 | — | — | 1514 | 1507 | a, b | e |
33 |
|
1.1 | — | — | — | 1513 | 1511 | a, c | e |
34 | ( |
— | 1.6 | — | — | 1514 | 1511 | a, b | e |
35 |
|
4.8 | 2.2 | — | — | 1522 | 1520 | a, c | e |
36 | Spathulenol | 1.1 | — | — | — | 1577 | 1576 | a, c | e |
37 | Caryophyllene oxide | 3.3 | — | — | — | 1582 | 1581 | a, c, d | e, g |
38 | Viridiflorol | 3.1 | — | — | — | 1592 | 1592 | a, c | e |
39 | Widdrol | — | — | 0.8 | — | 1599 | 1599 | a, c | e |
40 |
|
— | — | 3.8 | — | 1607 | 1602 | a, b | e |
41 | Oxygenated sesquiterpene | 2.2 | — | — | — | — | 1623 | — | — |
42 | Oxygenated sesquiterpene. ( |
— | — | 2.4 | — | — | 1624 | — | — |
43 |
|
— | — | 0.8 | — | 1630 | 1631 | a, b | e |
44 |
|
4.3 | — | — | — | 1640 | 1639 | a, b | e |
45 |
|
4.5 | — | — | — | 1652 | 1651 | a, c | e |
46 |
|
— | — | 4.2 | — | 1652 | 1653 | a, c | e |
47 | Dioctyl eter | — | — | — | 1.2 | — | 1656 | c, d | f |
48 |
|
— | 1.4 | — | — | 1674 | 1668 | a, c | e |
49 | Cadalene | — | — | 1.8 | — | 1675 | 1670 | a, c, d | e, g |
50 |
|
— | 1.8 | — | — | 1683 | 1680 | a, b | e |
51 |
|
— | 1.9 | — | — | 1685 | 1682 | a, c, d | e, f |
52 | Oxygenated sesquiterpene | — | — | 2.7 | — | — | 1709 | — | — |
53 | Oxygenated sesquiterpene | — | — | 2.3 | — | — | 1722 | — | — |
54 | Oxygenated sesquiterpene | — | — | 6.4 | — | — | 1731 | — | — |
55 | Oxygenated sesquiterpene | — | — | 6.3 | — | — | 1740 | — | — |
56 | Oxygenated sesquiterpene | — | — | 1.6 | — | — | 1758 | — | — |
57 | Cyclocolorenone | — | — | 1.6 | — | 1759 | 1759 | c | e |
58 | n.i. | — | — | 2.7 | — | — | 1764 | — | — |
59 | Tetradecanoic acid | — | — | — | 1.6 | 1768 | 1764 | c, d | f, g |
60 | n.i. | — | 2.3 | — | — | — | 1789 | — | — |
61 | Cyclohexadecane | — | — | — | 2.5 | 1880 | 1874 | a, c | g |
62 | Nonadecane | — | — | 1.0 | — | 1900 | 1900 | a, c, d | e, g |
63 | Hexadecenoic acid | — | — | — | 1.2 | 1953 | 1925 | d | f, g |
64 | Palmitic acid | — | 0.7 | 1.0 | 16.2 | 1959 | 1943 | c, d | f, g |
65 | Eicosane | — | — | 1.4 | — | 2000 | 2000 | a, c, d | e, g |
66 |
|
— | — | 1.7 | — | 2009 | 2042 | a, c | e |
67 | Kaurene | — | — | 2.3 | — | 2042 | 2063 | a, d | e, g |
68 | Phytol + n.i. | 3.2 | — | — | — | 2110 | 2078 | d | d, g |
69 | Octadecanol | — | 0.6 | — | 4.0 | 2077 | 2100 | a, b, c | e |
70 | Heneicosane | — | — | 1.1 | — | 2100 | 2100 | a, d | e, g |
71 |
|
— | 0.7 | — | — | — | 2118 | — | e |
72 | Linoleic acid | — | — | — | 1.2 | 2132 | 2149 | c | f, g |
73 | Oleic acid | — | — | — | 1.8 | 2141 | 2152 | c, d | f, g |
74 | ( |
— | — | — | 2.2 | — | 2171 | c, d | f |
75 | Geranyl linalool | — | 0.8 | — | — | — | 2192 | c | f, g |
76 | Unsaturated hydrocarbon | — | — | — | 1.4 | — | 2192 | — | — |
77 | Docosane | — | — | 0.9 | — | 2200 | 2200 | a, c | e, f |
78 | Octadecyl methoxy acetate | — | — | — | 1.4 | — | 2212 | d | — |
79 | Tricosane | — | — | 1.1 | 1.3 | 2300 | 2300 | a, c | e |
80 | ( |
— | — | — | 2.3 | — | 2303 | c, d | f |
81 | Unsaturated hydrocarbon | — | — | — | 1.5 | — | 2306 | — | — |
82 | Oleic acid amide | — | — | — | 2.4 | — | 2328 | c | — |
83 | Tetracosane | — | — | 1.3 | 1.5 | 2400 | 2400 | a, c, d | e, g |
84 | Pentacosane | — | — | 2.7 | 3.2 | 2500 | 2500 | a, b | e, g |
85 | Hexacosane | — | — | 3.0 | 4.8 | 2600 | 2600 | a | g |
86 | Heptacosane | — | — | 3.7 | 7.4 | 2700 | 2700 | a | g |
87 | Octacosane | — | — | 5.0 | 8.4 | 2800 | 2800 | a, d | g |
88 | Squalene | — | — | 1.7 | 1.5 | — | 2851 | d | f, g |
89 | Saturated hydrocarbon | — | — | — | 1.3 | — | 2874 | — | — |
90 | Nonacosane | — | — | 5.8 | 9.7 | 2900 | 2900 | a, c, d | f, g |
91 | Saturated hydrocarbon | — | — | 2.4 | 7.4 | — | 3059 | — | — |
92 | Saturated hydrocarbon | — | — | — | 6.3 | — | 3315 | — | — |
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Total |
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Yield (%w/w ± sd) |
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Oxygenated monoterpenes | 0.4 | — | — | — | |||||
Sesquiterpene hydrocarbons | 69.7 | 74.9 | 8.2 | — | |||||
Oxygenated sesquiterpenes | 18.5 | 5.1 | 32.9 | — | |||||
Oxygenated diterpenes | 1.6 | 0.8 | 1.7 | — | |||||
Long-chain alkanes | — | — | 29.9 | 51.3 | |||||
Fatty acids derivatives | — | 1.4 | 1.0 | 22.0 | |||||
Others | 2.6 | 1.6 | 5.8 | 21.7 | |||||
n.i. | 1.6 | 7.3 | 5.7 | — |
AI: arithmetic index on DB-5 capillary column; AIc: arithmetic index calculated.
Mode of identification: (a) Kovat index; (b) Adams mass spectral-retention index library; (c) Wiley library of mass spectral database; (d) Nist mass spectral database.
Reference: (e) Adams [
Up to now, only one phytochemical study on the essential oil composition of
In the essential oil of the inner bark, the sesquiterpenes hydrocarbons were the main constituents, representing about 75% of the essential oil, all of them with recognized antimicrobial properties [
The two major volatile components of the outer bark oil were unidentified oxygenated sesquiterpenes (compounds 54 and 55 in Table
The essential oil of the wood constituted mainly of alkanes and fatty acids. Palmitic acid (16.2%) was the major component, and the main alkanes identified were nonacosane (9.7%), octacosane (8.4%), heptacosane (7.4%), and hexacosane (4.8%). Industry uses palmitic acid to produce a great diversity of everyday goods, such as soap and food additives. The compounds 2-ethylhexyl-3-(4-methoxyphenyl)-2-propenoate (
In order to observe biological activity for the EOs of
Inhibitory effect against aerobic and anaerobic oral bacteria and cytotoxic activity (CC50,
Minimum inhibitory concentration (MIC) – |
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Microorganisms | Samples of essential oils | CHD* | ||||
Leaves | Inner bark | Outer bark | Wood | |||
Anaerobic |
|
>400 | >400 | 400 | >400 | 1.844 |
|
>400 | >400 | 400 | >400 | 1.844 | |
|
200 | 50 | 100 | 200 | 1.844 | |
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Aerobic |
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>400 | 100 | 100 | 100 | 3.688 |
|
>400 | 200 | 100 | 100 | 0.922 | |
|
>400 | 400 | 100 | 100 | 0.922 | |
|
>400 | 100 | 100 | 100 | 0.922 | |
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Cytotoxic activity (CC50, | ||||||
Leaves | Inner bark | Outer bark | Wood | |||
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|
168 ± 10 | 74 ± 3 | 127 ± 1 | >512 | ||
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Selectivity index for Anaerobic microorganisms | −0.38; −0.38; −0.076 | −0.73; −0.73; 0.17 | −0.50; −0.50; 0.10 | 0.11; 0.11; 0.41 | ||
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Selectivity index for Aerobic microorganisms | −0.38 | −0.13, −0.43; −0.73; −0.13 | 0.10 | 0.71 |
From Table
Considering the antimicrobial assays against aerobic bacteria, all the EOs exhibited from good to moderated antimicrobial activity, exception to the leaves EO (weak). This last result may be related to their low concentration of oxygenated mono- and diterpenes.
The outer bark EO (rich in long-chain alkanes) and wood EOs (rich in fatty acids and also in long-chain alkanes) presented same results with regards to anaerobic microorganisms, but not to aerobic. The literature does not present studies about the biological activities of long-chain alkanes separately. Probably, these two classes of compounds with different polarity characteristic act in synergistic effects [
The results observed for wood essential oil against aerobic bacteria (MICs of 100
The CC50 values for cytotoxicity assays of the EOs are shown in Table
More selective results were shown by outer bark EO. In this case, toxicity was observed only for bacteria
The chemical characterization of the volatiles of the specie
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors thank to the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) for research support and the Coordination for the Improvement of Higher Education Personnel (CAPES) for the scholarship. The authors thank too Professor Dr. Glein Monteiro de Araújo (Institute of Biology-UFU) for plant identification and Professor Dr. Ricardo Reis Soares (Engineering Faculty-UFU) for GC/MS equipment (Petrobrás financial support project), and the Chemistry Institute-UFU (Postgraduate Program) for their infrastructure support.