Essential oils (EOs), extracted from aromatic plants, are interesting natural products and represent an important part of the traditional pharmacopeia. The use of some EOs as alternative antimicrobial and pharmaceutical agents has attracted considerable interest recently. Most of the EOs and their single constituents have been reported to inhibit several phytopathogens, human pathogens, and insects as well as their effective uses in food and pharmaceutical industries. The current review discussed the chemical composition and bioactivity of some important EOs extracted from some Mediterranean plants and their principal bioactive single constituents. Information has been furnished on the mechanisms, mode of actions, and factors affecting the bioactivity of some single constituents from different Mediterranean plant EOs. The current review gives an insight into some common plant EOs belonging to Lamiaceae, Apiaceae, Rutaceae, and Verbenaceae families commonly growing in Mediterranean region. Further information has been provided about the medical uses of some EOs for several human diseases covering the pharmacological effects (anti-inflammatory, antioxidant, and anticarcinogenic). The antimicrobial effects have been also considered in the current review. Although plant EOs are considered promising natural alternatives for many chemical drugs, they still need more specific research for wide application especially in food and pharmaceutical industries.
Essential oils (EOs) are one of the most important natural products derived from plants for their various biological properties and medicinal uses [
The current review intends to discuss some aspects of plant EOs and their main single constituents ranging from an overview of historical perspective, analytical techniques for chemical analysis (classical and modern methods), bioactivity of single substances (mode of action, factors affecting their bioactivity, and common families of aromatic Mediterranean plants), medical uses for human health and biological characterization including pharmacological aspects (anti-inflammatory, antioxidant, and anticarcinogenic effects), and antimicrobial effects (antibacterial and antifungal activities).
This review gives also an insight into the chemical composition of some important EOs and their principal bioactive single constituents. Detailed information focuses on the mechanism of bioactivity action of the main bioactive single constituents of some important plant EOs such as sage, oregano, thyme, marjoram, and vervain related to different families such as Lamiaceae, Apiaceae, Rutaceae, and Verbenaceae.
EOs have been used by many cultures around the world for centuries for different purposes according to each culture. It is unknown exactly whether the EOs were used as healing agents or for domestic use in the beginning. However, recently great consideration has been given to the effective use of EOs in clinical procedures [
Ancient Egyptians have used aromatic oils as early as 4500 BC in cosmetics and ointments [
In the 18th and 19th centuries, chemists documented the active components of medicinal plants and identified many substances such as caffeine, quinine, morphine, and atropine, which were considered to play an important role in their biological effects [
Some EOs such as lavender, peppermint, and myrrh are still being used pharmaceutically and could be used effectively in the upcoming future as suitable alternatives for many synthetically produced medications [
As widely known, the chemical composition of plant EOs is principally represented by mono- and sesquiterpene hydrocarbons and their oxygenated derivatives, along with aliphatic aldehydes, alcohols, and esters [
According to the characteristics of each plant material, some specific extraction techniques can be applied such as steam distillation, solvent extraction, soxhlet extraction, microwave-assisted hydrodistillation, dynamic headspace, static headspace, solvent flavor evaporation, solid-phase microextraction, and direct thermal desorption [
Generally, the traditional classical techniques for analysis EOs were mainly focused on the quality aspects of oil, concerning mainly two properties, namely, identity and purity [
On the other hand, classical methodologies have been widely applied to assess the chemical properties of EOs [
The use of the above-mentioned traditional analytical techniques for the systematic study of EOs is generally applied for the assessment of pure compounds as well as some major compounds. Classical methods need to be combined with some modern analytical techniques, such as Gas Chromatography-Mass Spectrometry (GC-MS).
Most of the modern analytical techniques of EOs depend on chromatographic procedures. The main objective in any chromatographic separation is always the complete resolution of the compounds in the minimum time; for that, the most appropriate analytical chromatographic column with a specific dimension and stationary phase has to be used under adequate chromatographic conditions.
In particular, the GC analysis can be summarized as the evaporation of the compound and the elution by the mobile gas phase, the carrier gas, through the column. The different substances are separated on the basis of their relative vapor pressures and affinities for the stationary bed. On the other hand, the liquid chromatographic analysis depends on the elution of the compound by a liquid mobile phase consisting of a solvent or a mixture of solvents and the different substances are separated according to their affinities for the stationary bed.
Mass Spectrometry (MS) can be defined as the study of systems through the formation of gaseous ions, with or without fragmentation, which are then characterized by their mass-to-charge ratios (
Applications of GC-MS include drug detection, fire investigation, environmental analysis, explosives investigation, and identification of unknown samples. GC-MS is composed of two major building blocks: the gas chromatograph and the mass spectrometer. The gas chromatograph utilizes a capillary column which depends on the column’s dimensions and the phase properties. The difference of the chemical properties between different molecules in a mixture and their relative affinity for the stationary phase of the column will promote their separation. Different molecules are retained by the column and then are eluted from the column at different retention times [
List of some single constituents existing in common aromatic Mediterranean plants.
Number | Main single constituent | Common aromatic plants |
---|---|---|
(1) |
|
Dill, balm, caraway, lavender, marjoram, oregano, sage |
(2) | Camphene | Mint, hyssop, lavender, marjoram, oregano, sage, thyme |
(3) | Sabinene | Dill, parsley, basil, caraway, marjoram, sage |
(4) | Myrcene | Dill, parsley, mint, balm, basil, caraway, fennel, hyssop, lavender, marjoram, oregano, sage |
(5) |
|
Dill, parsley, balm, basil, caraway, fennel, marjoram, oregano, sage |
(6) |
|
Parsley, coriande, mint |
(7) |
|
Mint, balm, hyssop, marjoram, oregano, thyme |
(8) |
|
Dill, parsley, mint, balm, caraway, fennel, lavender, marjoram, oregano, sage, thyme |
(9) |
|
Dill, parsley, balm, basil, caraway, fennel, hyssop, lavender, marjoram, oregano, sage, thyme, vervain |
(10) |
|
Dill, parsley, mint, basil, caraway, hyssop, lavender, marjoram, vervain |
(11) |
|
Parsley, mint, balm, fennel, hyssop, lavender, marjoram, oregano, sage, thyme, vervain |
(12) | Terpinolene | Balm, basil, hyssop, marjoram, oregano, thyme |
(13) | Linalool | Mint, balm, basil, caraway, hyssop, lavender, marjoram, oregano, sage, thyme, vervain |
(14) | Nonanal | Coriander, mint |
(15) | Limonene | Mint, balm, basil, caraway, hyssop, lavender, marjoram, oregano, sage, thyme, vervain |
(16) |
|
Mint |
(17) |
|
Parsley |
(18) | Carvomenthyl acetate | Mint |
(19) | Bornyl acetate | Mint, caraway, lavender, marjoram, sage |
(20) |
|
Coriander |
(21) | 1-Undecanol | Coriander |
(22) |
|
Mint, basil |
(23) |
|
Dill, mint, balm, basil, marjoram, oregano, sage, thyme, vervain |
(24) |
|
Mint, hyssop, sage |
(25) | Carvone | Dill, coriander, |
(26) |
|
Dill, parsley, fennel, lavender, marjoram, oregano |
(27) |
|
Mint, balm, basil, caraway, hyssop, lavender, marjoram, oregano, sage, thyme, vervain |
(28) | Dodecanal | Coriander |
(29) |
|
Parsley, mint, balm, basil, caraway, hyssop, lavender, marjoram, oregano, sage, thyme, vervain |
(30) |
|
Mint |
(31) |
|
Basil, caraway, lavender, oregano |
(32) | D3-Carene | Fennel, lavender, marjoram, oregano |
(33) | a-Terpinene | Balm, hyssop, marjoram, oregano |
(34) |
|
Anise, balm, basil, caraway, hyssop, lavender, marjoram, oregano, sage, thyme, vervain |
(35) |
|
Caraway, fennel, lavender, marjoram, oregano, sage, thyme |
(36) | 1,8-Cineole | Balm, basil, hyssop, marjoram, oregano, sage, vervain |
(37) |
|
Anise, basil, fennel |
(38) | (-)-Citronellal | Balm, sage, thyme |
(39) |
|
Balm, marjoram, thyme |
(40) | Camphor | Balm, basil, lavender, marjoram, sage |
(41) |
|
Basil, hyssop, lavender, marjoram, oregano, sage |
(42) |
|
Balm, caraway, hyssop, sage |
(43) | Terpinen-4-ol | Balm, basil, hyssop, lavender, marjoram, oregano, sage, vervain |
(44) | Myrtenol | Basil, hyssop, lavender, marjoram, sage, thyme |
(45) | ( |
Vervain, oregano |
(46) | Isobornyl acetate | Caraway, lavender, marjoram, sage |
(47) | Bornyl acetate | Caraway, lavender, marjoram, sage |
(48) | Thymol | Balm, marjoram, oregano, thyme |
(49) | a-Copaene | Basil, hyssop, marjoram, oregano, vervain |
(50) | b-Elemene | Balm, basil, caraway, vervain |
(51) | b-Caryophyllene | Balm, basil, caraway, hyssop, lavender, marjoram, oregano, sage, thyme, vervain |
(52) | b-Cedrene | Balm, basil, hyssop, lavender, marjoram, oregano, sage, vervain |
(53) | a-Humulene | Balm, basil, hyssop, lavender, marjoram, oregano, sage, vervain |
(54) | Caryophyllene oxide | Balm, lavender, oregano, sage |
The bioactivity of EOs is the sum of its constituents which act either in a synergistic or in an antagonistic way [
The following part of the current review covers the following points: (i) mode of action of single components; (ii) factors affecting the single components bioactivity.
Most antimicrobial activities of several plant EOs depend mainly on their bioactive single components which are able to inhibit the growth of microorganisms and/or completely suppress the pathogens [
The synergism between the aromatic plant components often plays an essential role in the effectiveness and reduction of the developing resistance of any pathogenic microorganism. Therefore, some constituents such as carvacrol,
The composition of each EO can vary depending on certain conditions such as plant variety, plant part, growth area, climatic changes, harvesting time, storage conditions, and the chemotype of each component [
For improving the antimicrobial outfindings of many plant EOs, several factors either biological and experimental should be taken into consideration such as (i) appropriate and exact standardized microbiological test; (ii) available standard strains from different collections; (iii) assays including a variety of microorganisms either gram-positive and gram-negative bacteria, phytopathogens and human pathogens and yeasts; (iv) exact botanical identification of the plant EOs origin; (v) biochemical characterization of the extracted EOs as well as their production, storage conditions, and age. In addition, the distinctive water solubility and volatility of many EOs enable them to reveal a broadband spectrum of activity in various
Several plant EOs demonstrated different antimicrobial activities according to the tests carried out, examiners themselves, or any other factors. For example, lemon EO showed to some extent a clear inhibition effect against
Möse and Lukas (1957) [
On the other hand, Pellecuer et al. (1976) [
Many common Mediterranean aromatic plants are belonging to Lamiaceae, Apiaceae, Rutaceae, and Verbenaceae families. The selected discussed aromatic plants in the current review are considered as the most important Mediterranean officinal plants.
The EO extracted from lavender (
Furthermore, lavender EO was well documented for the treatment of abrasions, burns, stress, headaches, skin problems, muscular pain, and boosting the immune system [
Chemical composition of some common Mediterranean plant essential oils.
Some of main |
Ki |
Ki |
Percentage |
||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Apiaceae | Lamiaceae | Verbenaceae | Identification |
||||||||
Anise | Caraway | Lavender | Marjoram | Oregano | Sage | Thyme | Vervain | ||||
|
930 | 1,035 | — | 0.2 ± 0.0 | 0.2 ± 0.0 | 0.1 ± 0.0 | 0.5 ± 0.0 | 0.4 ± 0.0 | T | — | 1, 2 |
|
938 | 1,032 | 0.3 ± 0.0 | 0.5 ± 0.2 | — | 9.0 ± 0.1 | 0.4 ± 0.0 | 4.4 ± 0.1 | 2.5 ± 0.1 | 0.2 ± 0.0 | 1, 2, 3 |
(-)-Camphene | 953 | 1,076 | — | — | 0.7 ± 0.0 | 0.3 ± 0.0 | 0.2 ± 0.0 | 4.1 ± 0.0 | 1.0 ± 0.1 | — | 1, 2, 3 |
Sabinene | 973 | 1,132 | T | 1.0 ± 0.1 | T | 1.1 ± 0.1 | T | 0.4 ± 0.0 | T | 0.5 ± 0.0 | 1, 2, 3 |
|
978 | 1,118 | — | 7.4 ± 0.4 | — | 3.8 ± 0.9 | 0.2 ± 0.0 | 2.5 ± 0.1 | — | T | 1, 2, 3 |
|
980 | — | 0.1 ± 0.0 | 0.1 ± 0.0 | — | 0.1 ± 0.0 | — | — | — | 1, 2 | |
Myrcene | 993 | 1,174 | — | 0.7 ± 0.1 | 0.3 ± 0.0 | 0.7 ± 0.3 | 0.5 ± 0.0 | 0.5 ± 0.1 | 0.1 ± 0.0 | — | 1, 2, 3 |
|
995 | 1,176 | 0.1 ± 0.0 | T | 0.2 ± 0.0 | 0.2 ± 0.0 | 0.1 ± 0.0 | T | T | — | 1, 2, 3 |
|
1,020 | 1,187 | 0.1 ± 0.0 | 0.2 ± 0.0 | 0.6 ± 0.1 | 2.6 ± 0.9 | 41.9 ± 0.1 | 2.5 ± 0.2 | 56.2 ± 0.2 | 0.1 ± 0.0 | 1, 2, 3 |
|
1,024 | 1,280 | — | 0.1 ± 0.1 | 0.3 ± 0.0 | 0.4 ± 0.1 | 0.1 ± 0.0 | 1.2 ± 0.1 | 0.1 ± 0.0 | — | 1, 2, 3 |
|
1,029 | 1,218 | T | 0.6 ± 0.2 | 0.1 ± 0.0 | 9.1 ± 0.5 | 0.1 ± 0.0 | 1.0 ± 0.0 | 0.2 ± 0.1 | 0.7 ± 0.2 | 1, 2, 3 |
Limonene | 1,030 | 1,203 | — | 14.3 ± 0.5 | 0.3 ± 0.0 | 6.4 ± 0.5 | 0.3 ± 0.0 | 1.4 ± 0.0 | 0.6 ± 0.0 | 2.3 ± 0.9 | 1, 2, 3 |
1,8-Cineole | 1,034 | 1,213 | — | 0.1 ± 0.0 | T | 33.5 ± 0.3 | 0.6 ± 0.1 | 4.2 ± 0.3 | T | 0.4 ± 0.1 | 1, 2 |
( |
1,038 | 1,246 | T | 0.1 ± 0.0 | 1.7 ± 0.3 | 0.1 ± 0.0 | T | T | T | T | 1, 2, 3 |
( |
1,049 | 1,280 | — | 0.3 ± 0.1 | 0.6 ± 0.1 | 0.2 ± 0.1 | T | T | T | 0.3 ± 0.1 | 1, 2, 3 |
|
1,057 | 1,255 | T | T | T | 0.8 ± 0.3 | 2.8 ± 0.2 | 0.1 ± 0.0 | 0.4 ± 0.0 | 0.1 ± 0.0 | 1, 2, 3 |
Linalool | 1,097 | 1,553 | 0.4 ± 0.1 | 0.5 ± 0.1 | 23.1 ± 0.2 | 9.8 ± 0.7 | 0.7 ± 0.3 | 1.1 ± 0.06 | 0.4 ± 0.1 | 0.1 ± 0.0 | 1, 2, 3 |
|
1,115 | 1,449 | — | 0.1 ± 0.0 | — | T | — | 37.9 ± 0.1 | — | — | 1, 2, 3 |
|
1,138 | 1,654 | — | T | T | 0.1 ± 0.0 | T | 0.2 ± 0.0 | T | T | 1, 2 |
(-)-Citronellal | 1,143 | 1,491 | — | — | — | — | — | 0.2 ± 0.0 | 0.5 ± 0.1 | — | 1, 2, 3 |
|
1,144 | 1,633 | — | — | — | 0.1 ± 0.0 | — | — | 0.1 ± 0.0 | — | 1, 2, 3 |
Camphor | 1,145 | 1,532 | — | T | 0.9 ± 0.0 | 0.2 ± 0.0 | T | 13.9 ± 0.7 | T | — | 1, 2, 3 |
|
1,153 | 1,566 | — | T | 0.1 ± 0.0 | 0.2 ± 0.0 | 0.1 ± 0.0 | 0.1 ± 0.0 | T | 0.2 ± 0.0 | 1, 2 |
|
1,159 | — | 4.3 ± 0.9 | — | T | T | 0.3 ± 0.0 | T | T | 1, 2 | |
Borneol | 1,167 | 1,719 | — | — | 6.3 ± 0.9 | 2.0 ± 0.5 | 0.3 ± 0.0 | 7.6 ± 0.4 | 0.2 ± 0.0 | 0.1 ± 0.0 | 1, 2, 3 |
Terpinen-4-ol | 1,176 | 1,611 | — | T | 0.2 ± 0.0 | 0.4 ± 0.1 | 0.4 ± 0.0 | 0.5 ± 0.0 | T | 0.2 ± 0.0 | 1, 2, 3 |
Dihydrocarveol | 1,177 | — | — | 0.4 ± 0.0 | 0.8 ± 0.1 | — | 0.2 ± 0.0 | 0.2 ± 0.0 | — | 1, 2 | |
|
1,185 | 1,864 | — | — | 0.3 ± 0.0 | 0.1 ± 0.0 | 0.2 ± 0.0 | 0.1 ± 0.0 | T | T | 1, 2 |
|
1,189 | 1,706 | T | T | 0.4 ± 0.0 | 0.7 ± 0.1 | T | 0.3 ± 0.0 | 0.3 ± 0.0 | 0.3 ± 0.1 | 1, 2, 3 |
Myrtenal | 1,193 | 1,648 | — | 0.1 ± 0.0 | 0.4 ± 0.1 | 0.7 ± 0.1 | — | 0.2 ± 0.0 | 0.3 ± 0.0 | — | 1, 2 |
Estragole | 1,195 | 1,670 | — | 65.0 ± 0.9 | — | 0.1 ± 0.0 | 0.1 ± 0.0 | T | — | — | 1, 2, 3 |
Myrtenol | 1,196 | 1,804 | — | — | 0.4 ± 0.0 | 0.2 ± 0.1 | — | 0.2 ± 0.0 | 0.3 ± 0.0 | — | 1, 2 |
Isobornyl formate | 1,228 | — | — | — | — | — | — | — | 45.4 ± 0.9 | 1, 2 | |
Linalyl acetate | 1,248 | 1,565 | — | — | 44.4 ± 0.7 | 3.3 ± 0.6 | 0.1 ± 0.0 | 1.5 ± 0.2 | — | — | 1, 2, 3 |
Geraniol | 1,255 | 1,857 | — | — | 9.3 ± 0.3 | 0.6 ± 0.1 | — | 0.3 ± 0.0 | — | — | 1, 2 |
|
1,262 | 97.1 ± 0.4 | T | — | --- | — | — | — | 0.2 ± 0.0 | 1, 2 | |
( |
1,270 | 1,727 | — | — | — | — | — | — | — | 44.5 ± 0.9 | 1, 2, 3 |
Isobornyl acetate | 1,277 | — | 0.1 ± 0.0 | 0.3 ± 0.0 | 0.6 ± 0.1 | T | 0.7 ± 0.0 | T | T | 1, 2 | |
Bornyl acetate | 1,284 | 1,591 | — | 0.1 ± 0.0 | 0.2 ± 0.0 | 1.2 ± 0.5 | T | 0.9 ± 0.0 | T | T | 1, 2 |
Thymol | 1,290 | 2,198 | — | — | — | 0.7 ± 0.1 | 0.7 ± 0.0 | T | 8.7 ± 0.9 | — | 1, 2, 3 |
Carvacrol | 1,297 | 2,239 | — | — | — | 4.1 ± 0.9 | 44.0 ± 0.9 | 0.3 ± 0.0 | 24.4 ± 0.9 | — | 1, 2, 3 |
Terpinyl acetate | 1,333 | — | — | — | 0.5 ± 0.0 | — | — | — | — | 1, 2 | |
|
1,377 | 1,497 | — | T | T | 0.1 ± 0.0 | 0.1 ± 0.0 | T | T | 0.2 ± 0.1 | 1, 2 |
Geranyl acetate | 1,379 | 1,765 | — | — | — | — | — | — | — | — | 1, 2 |
Isoledene | 1,382 | — | T | T | T | 0.1 ± 0.0 | T | T | 0.1 ± 0.0 | 1, 2 | |
|
1,418 | 1,612 | T | 0.1 ± 0.0 | 1.0 ± 0.9 | 0.3 ± 0.1 | 0.2 ± 0.1 | 1.3 ± 0.0 | 0.1 ± 0.0 | 0.1 ± 0.1 | 1, 2 |
|
1,424 | 1,638 | — | — | 1.3 ± 0.1 | 0.5 ± 0.1 | 0.6 ± 0.0 | 1.0 ± 0.0 | — | 0.4 ± 0.1 | 1, 2 |
|
1,455 | 1,689 | — | T | 0.6 ± 0.0 | 0.3 ± 0.1 | 0.1 ± 0.0 | 5.9 ± 0.9 | T | 0.2 ± 0.0 | 1, 2 |
|
1,518 | 1,740 | — | T | — | 0.1 ± 0.0 | 0.1 ± 0.0 | 0.1 ± 0.0 | T | 0.2 ± 0.1 | 1, 2 |
Caryophyllene oxide | 1,580 | 2,008 | — | — | 0.4 ± 0.0 | — | 0.2 ± 0.0 | 0.8 ± 0.0 | — | — | 1, 2 |
|
|||||||||||
Total compounds | 98.3 | 98 | 97.0 | 97 | 98.9 | 98.7 | 99.1 | 97.6 |
Oregano (
Four main groups of oregano commonly used as culinary herbs can be distinguished, that is, Greek oregano (
The most common variety is
The most important species are peppermint (
Peppermint EO has been intensively studied for its anti-inflammatory, anti-infectious, antimicrobial, and fungicidal effect as well as antiseptic and digestive properties. It is observed that the single constituents of peppermint EO can relieve many bacterial, fungal, and viral infections when inhaled or applied in the form of vapor balm. On the other hand, Ali et al. (2015) [
Sage is considered to be the main genus among the Lamiaceae family, which consists of about 900 species widely distributed in the temperate, subtropical, and tropical regions all over the world but especially in the Mediterranean region, central Asia, central and South America, and southern Africa [
Globally, the best known species of the family used in both traditional and modern medicine are
Anise is a food plant for the larvae of some Lepidoptera species such as butterflies and moths. Anise was first cultivated in Egypt and the Middle East and was brought to Europe for its medicinal value [
The plant characterized by finely divided, feathery leaves with thread-like divisions. The fruits of caraway are usually used as a whole and have a pungent, anise-like flavor and aroma that comes from its EO such as carvone, limonene, and anethole. The main single constituents of caraway EO have been listed in Table
Lemon,
Lemon EO is able to accelerate the production of white blood cells, strengthen the immune system, and help in the digestion processes [
Several researches reported the antimicrobial activity of vervain EO and investigated that this activity could be related to the high amounts of monoterpenes and phenolic compounds. In fact, the major constituents of this EO were
Many of the plant EOs are being widely utilized in the pharmaceutical industry, aromatherapy, and other related medical uses. Many plant EOs have been used as medicine for centuries and have demonstrated several health benefits, including effects on infectious, chronic, and acute diseases [
The medical preparations made with plant EOs as well as their single constituents applied in the therapy of human infectious diseases are well documented. However, the selection of the suitable safe oil and the determination of the best efficient dose should be taken into consideration to avoid any side effects when they are applied for children presupposes. In particular, many EOs have been used for healing purposes and have been highly recommended especially in the treatment of some catarrhal diseases [
A number of medical trials have investigated the effective use of some EOs in treating methicillin-resistant
The detailed pharmacological effects of many plant EOs such as anti-inflammatory, antioxidant, and anticarcinogenic were also discussed in the following section.
Recently, great interest was given to the curative effect of many plant EOs especially for wound treatment since the EOs have demonstrated interesting medication against some wound types, which cannot occur with pharmaceuticals [
For centuries, plant EOs have been used for curing many diseases such as melaleuca EO which is considered an effective factor for speeding up the healing process of wounds. Lavender EO was commonly used to heal wounds, cuts, burns, and sunburns by improving the formation of scar tissues [
Inflammatory disorders are associated with pain, redness, and swelling, leading to loss of vital functions. EOs have been used for several decades to relieve pain and inflammation. Usually, EOs have more effective and pain-relieving properties than many pharmaceutical analgesics. The use of EOs has many benefits in the treatment of inflammation because it has fewer side effects than many synthetic and traditional drugs.
A review of the medicinal properties of chamomile documented that plants contain more flavonoids with anti-inflammatory properties than others do. These inflammation-reducing compounds can penetrate the skin easily and reduce inflammation. Tea tree oil has been shown to increase monocytic differentiation
The possible mechanism of the anti-inflammatory property of EOs was suggested to compete with arachidonic acid for its incorporation into the membrane. Hence, arachidonic acid generates slightly modified prostaglandins and eicosanoids, which induces a lesser extent of inflammation via reduced induction of COX-2 [
Antioxidant activity can be defined as the molecules able to react with radicals or having a reducing power to counteract the oxidative stress caused by radicals. Antioxidant properties play an essential role in some of EOs’ biological activities, which is justified by the involvement of oxidative stress in pathology. In addition, the botanical source of aromatic plants and the environmental factors such as climate may affect the actual composition of extracted EOs and thus reflect different antioxidant activities. Oregano EO is able to protect extra virgin olive oil from oxidation during storage and is able to extend the shelf life of sea bream and to reduce the formation of volatile amines and of TBAR compounds [
The antioxidant effect of many EOs is due to the inherent ability of some of their components, particularly phenols, to stop or delay the aerobic oxidation of organic matter [
Anticarcinogenic activity is the ability of a specific substance to counteract or completely inhibit the development of carcinogen. The traditional anticancer therapy, such as multichemotherapeutic drugs, is often compromised of the development of drug resistance and the serious irreversible side effects [
In the current review, some revealing examples of plant EOs and their constituents that have been used effectively as antitumour agents have been discussed. The detailed discussion will also be reported regarding the possible mechanisms and the multiple pathways involving apoptosis, DNA repair modulation, cell cycle arrest, and antiproliferative activity through the increase of reactive oxygen and nitrogen levels (ROS/RNS) in cancer cells [
Some EOs showed a potential anticancer activity against liver, lung, colon, and prostate cancer such as
Further studies demonstrated that some single constituents like carvacrol [
Effect of oregano EO on the cell morphology of hepatocarcinoma cell line (HepG2) and health renal cells (HEK293). The photographs were taken at a magnification ×40. Images are representative of three independent experiments. (a) HepG2 (control); (b) HepG2 cells treated with oregano EO (236
The general mechanism of cytotoxic effect of plant EOs is mostly due to the presence of phenols, aldehydes, and alcohols. In particular, the toxicity towards mammalians decreases significantly with the increase of average lipophilicity of EO components [
Elshafie et al. (2016) [
El-Massrry et al. (2009) [
Numerous plant EOs and their single constituents have been reported to inhibit postharvest fungi
Elshafie et al. (2015) [
Other studies also concluded the presence of significant potential fungicidal effects of some plant EOs such as thyme and vervain higher than chemical preparations in postharvest treatments against
Elshafie et al. (2015) [
In the same study, Elshafie et al. (2015) [
A great many research articles investigating the biochemical properties of plant EOs have obtained interesting results in agricultural, clinical, and pharmaceutical fields. In conclusion, the use of EOs in pharmaceutical and agrochemical industries as natural alternatives for synthetic microbicide drugs is a field of growing interest. Plant EOs mentioned in the current review are considered promising natural alternatives to conventional pharmaceutical drugs. Moreover, there is still a need for more specific and rational research that deals with the method of application of those efficient EOs and their single constituents in agriculture and food industry for manufacturing new health-oriented products as well as novel natural pharmaceutical drugs.
The authors declare that they have no conflicts of interest.
The authors contributed equally to manuscript.