Chemical composition and antimicrobial activity of essential oils from Scabiosa arenaria Forssk: growing wild in Tunisia

The essential oils isolated from three organs, i.e., fruits, stems and leaves, and flowers, of the endemic North African plant Scabiosa arenaria Forssk. were screened for their chemical composition, as well as their possible antibacterial, anticandidal, and antifungal properties. According to the GC-FID and GC/MS analyses, 61 (99.26% of the total oil composition), 79 (98.43%), and 51 compounds (99.9%) were identified in the three oils, respectively. While α-thujone (34.39%), camphor (17.48%), and β-thujone (15.29%) constituted the major compounds of the fruit oil, chrysanthenone (23.43%), together with camphor (12.98%) and α-thujone (10.7%), were the main constituents of the stem and leaf oil. In the case of the flower oil, also chrysanthenone (38.52%), camphor (11.75%), and α-thujone (9.5%) were identified as the major compounds. Furthermore, the isolated oils were tested against 16 Gram-positive and Gram-negative bacteria, four Candida species, and nine phytopathogenic fungal strains. It was found that the oils exhibited interesting antibacterial and anticandidal activities, comparable to those of thymol, which was used as positive control, but no activity against the phytopathogenic fungal strains was observed.     

Chemotype Diversity of Indigenous Dalmatian Sage (Salvia officinalis L.) Populations in Montenegro

To identify how many chemotypes of Salvia officinalis exist in Montenegro, the chemical composition of the essential oils of 12 wild‐growing populations was determined by GC‐FID and GC/MS analyses. Among the 40 identified constituents, the most abundant were cis‐thujone (16.98–40.35%), camphor (12.75–35.37%), 1,8‐cineol (6.40–12.06%), trans‐thujone (1.5–10.35%), camphene (2.26–9.97%), borneol (0.97–8.81%), viridiflorol (3.46–7.8%), limonene (1.8–6.47%), α‐pinene (1.59–5.46%), and α‐humulene (1.77–5.02%). The composition of the essential oils under study did not meet the ISO 9909 requirements, while the oils of populations P02–P04, P09, and P10 complied with the German Drug Codex. A few of the main essential‐oil constituents appeared to be highly intercorrelated. Strong positive correlations were observed between α‐pinene and camphene, camphene and camphor, as well as between cis‐thujone and trans‐thujone. Strong negative correlations were evidenced between cis‐thujone and α‐pinene, cis‐thujone and champhene, cis‐thujone and camphor, as well as between trans‐thujone and camphene. Multivariate analyses allowed the grouping of the populations into three distinct chemotypes, i.e., Chemotype A, rich in total thujones, Chemotype B, with intermediate contents of thujones, α‐pinene, camphene, and camphor and high borneol contents, and Chemotype C, rich in camphor, camphene, and α‐pinene. The chemotypes did not significantly differ in the total essential‐oil content and the cis/trans‐thujone ratio.     

Chemical Composition and Biological Activities of the Essential Oil from Leaves and Flowers of Pulicaria incisa sub. candolleana (Family Asteraceae)

The composition of the essential oil isolated from leaves and flowers of Pulicaria incisa sub. candolleana E. Gamal ‐Eldin , growing in Egypt, was analysed by GC and GC‐MS. Forty‐nine and 68 compounds were identified from the oils of the leaves and flowers accounting for 86.69 and 84.29%, respectively of the total detected constituents. Both leaves and flowers oils were characterized by the high content of carvotanacetone with 66.01, 50.87 and chrysanthenone 13.26, 24.3%, respectively. The cytotoxic activity of both essential oils was evaluated against hepatocellular carcinoma cell line HEPG‐2, using MTT assay and vinblastine as a reference drug. Leaf oil showed higher activity with IC₅₀ 11.4 μg/ml compared with 37.4 μg/ml for flower oil. The antimicrobial activity of both oils was evaluated using agar well diffusion method towards two representatives for each of Gram positive and Gram negative bacteria as well as four representatives for fungi. The minimum inhibitory concentration of both essential oils against bacterial and fungal strains was obtained in the range of 0.49 – 15.63 μg/ml.     

Essential‐Oil Diversity of Salvia tomentosa Mill. in Greece

Salvia tomentosa essential oils from Greece were studied for the first time here. The oils from five populations growing in Mediterranean pine forests on the island of Thassos (northern Aegean Sea) and from 14 populations situated in deciduous forests in Thrace (northeastern Greek mainland) were investigated. Their essential‐oil contents ranged from 1.1 to 3.3% (v/w, based on the dry weight of the plant material). The populations from Thassos had high contents of α‐pinene (18.0±2.9%), 1,8‐cineole (14.7±3.0%), cis‐thujone (14.0±6.9%), and borneol (12.8±2.2%) and smaller amounts of camphene, camphor, and β‐pinene, whereas the populations from Thrace showed high α‐pinene (16.7±4.0%), β‐pinene (22.8±4.5%), camphor (18.3±4.3%), and camphene (10.3±2.4%) contents, much lower 1,8‐cineole and borneol amounts, while cis‐thujone was completely lacking. The comparison of the present results with published data showed that oils having cis‐thujone as one of the main compounds were reported for the first time here. Multivariate statistical analyses indicate that the observed essential‐oil variation was related to geographical and environmental factors.     

Essential Oils and Chemical Diversity of Southeast European Populations of Salvia officinalis L.

The essential oils of 25 populations of Dalmatian sage (Salvia officinalis L.) from nine Balkan countries, including 17 indigenous populations (representing almost the entire native distribution area) and eight non‐indigenous (cultivated or naturalized) populations were analyzed. Their essential‐oil yield ranged from 0.25 to 3.48%. Within the total of 80 detected compounds, ten (β‐pinene, 1,8‐cineole, cis‐thujone, trans‐thujone, camphor, borneol, trans‐caryophyllene, α‐humulene, viridiflorol, and manool) represented 42.60 to 85.70% of the components in the analyzed essential oils. Strong positive correlations were observed between the contents of trans‐caryophyllene and α‐humulene, α‐humulene and viridiflorol, and viridiflorol and manool. Principal component analysis (PCA) on the basis of the contents of the ten main compounds showed that four principal components had an eigenvalue greater than 1 and explained 79.87% of the total variation. Performing cluster analysis (CA), the sage populations could be grouped into four distinct chemotypes (A–D). The essential oils of 14 out of the 25 populations of Dalmatian sage belonged to Chemotype A and were rich in cis‐thujone and camphor, with low contents of trans‐thujone. The correlation between the essential‐oil composition and geographic variables of the indigenous populations was not significant; hence, the similarities in the essential‐oil profile among populations could not be explained by the physical proximity of the populations. Additionally, the southeastern populations tended to have higher EO yields than the northwestern ones.     

High Diversity of Indigenous Populations of Dalmatian Sage (Salvia officinalis L.) in Essential‐Oil Composition

Essential oils of 25 indigenous populations of Dalmatian sage (Salvia officinalis L.) that represent nearly half of native distribution area of the species were analyzed. Plantlets collected from wild populations were grown in the same field under the same environmental conditions and then sampled for essential‐oil analysis. The yield of essential oil ranged from 1.93 to 3.70% with average of 2.83%. Among the 62 compounds detected, eight (cis‐thujone, camphor, trans‐thujone, 1,8‐cineole, β‐pinene, camphene, borneol, and bornyl acetate) formed 78.13–87.33% of essential oils of individual populations. Strong positive correlations were observed between camphor and β‐pinene, β‐pinene and borneol, as well as between borneol and bornyl acetate. The strongest negative correlation was detected between camphor and trans‐thujone. Principal component analysis (PCA) on the basis of eight main compounds showed that first main component separated populations with high thujone content, from those rich in camphor, while the second component separated populations rich in cis‐thujone from those rich in trans‐thujone. Cluster analysis (CA) led to the identification of three chemotypes of S. officinalis populations: cis‐thujone; trans‐tujone, and camphor/β‐pinene/borneol/bornyl acetate. We propose that differences in essential oils of 25 populations are mostly genetically controlled, since potential environmental factors were controlled in this study.     

Volatile Compounds in Fruits of Peucedanum cervaria (Lap.) L.

The volatile compounds from Peucedanum cervaria (Lap. ) L. were obtained by hydrodistillation (HD) and headspace solid‐phase microextraction techniques (HS‐SPME), and then analyzed by GC/MS methods. The composition of samples from a botanical garden was compared with plants collected in the wild. The main compounds of the essential oils of P. cervaria were identified as α‐pinene, sabinene, and β‐pinene (more than 80% of oil). The content of β‐myrcene, limonene+β‐phellandrene, and germacrene D was higher than 1%. The in vitro antibacterial activity of the essential oil was evaluated by the agar dilution method against ten reference strains of Gram‐positive and Gram‐negative bacteria.     

Essential Oil Variability in Natural Populations of Artemisia campestris (L.) and Artemisia herba‐alba (Asso) and Incidence on Antiacetylcholinesterase and Antioxidant Activities

The intraspecific variability of Artemisia herba‐alba and A. campestris essential oils and the evaluation of their antioxidant and antiacetylcholinesterase activities were determined. Artemisia herba‐alba essential oil was found rich in camphor (19.61%), α‐thujone (19.40%), β‐thujone (9.44%), chrysanthenone (9.26%), and trans‐sabinyl acetate (8.43%). The major compounds of A. campestris essential oil were germacrene D (16.38%), β‐pinene (16.33%), and limonene (9.17%). Significant variation in the essential oil composition was observed among populations of each species. The divergence between populations was attributed to the variation of some climatic factors such as altitude, annual rainfall, winter cold stress, summer precipitation, summer drought stress, evapotranspiration, and humidity. Artemisia herba‐alba and A. campestris essential oils exhibited promising antioxidant and antiacetylcholinesterase activities. The level of activity varied significantly according to the species and the essential oil. The highest scavenging activity (IC₅₀ = 0.14 mg/ml) and the uppermost capacity to prevent β‐carotene bleaching (IC₅₀ = 0.10 mg/ml) characterized A. campestris from population 6. A. campestris population 3 possessed the uppermost ability to reduce ferric ions (450.7 μmol Fe²⁺/g EO). The population 2 of A. campestris showed the strongest antiacetylcholinesterase activity (IC₅₀ = 0.02 mg/ml). The variation of these activities between the essential oils was explained by their composition differences.     

Chemical Composition of Hydrodistilled Essential Oil of Artemisia incana (L.) Druce and Antimicrobial Activity against Foodborne Microorganisms

The oil obtained by hydrodistillation from the aerial parts of Artemisia incana (L.) Druce from Turkey was analyzed by GC and GC/MS. Sixty‐three compounds were characterized, representing 97.2% of the total components detected, and camphor (19.0%), borneol (18.9%), 1,8‐cineole (14.5%), bornyl acetate (7.8%), camphene (4.9%), and α‐thujone (4.8%) were identified as predominant components. The essential oil was also tested for its antimicrobial activity against 44 different foodborne microorganisms, including 26 bacteria, 15 fungi, and 3 yeast species. The essential oil of A. incana exhibited considerable inhibitory effects against all bacteria, fungi, and yeast species tested. However, the oil showed lower inhibitory activity against the tested bacteria than the reference antibiotics.     

Myrtus communis Essential Oil: Chemical Composition and Antimicrobial Activities against Food Spoilage Pathogens

Myrtus communis is a typical plant of the Mediterranean area, which is mainly used as animal and human food and, in folk medicine, for treating some disorders. In the present study, we evaluated in vitro antibacterial and antifungal properties of the essential oils of Myrtus communis (McEO), as well as its phytochemical composition. The GC/MS analysis of the essential oil revealed 17 compounds. Myrtenyl acetate (20.75%), 1,8‐cineol (16.55%), α‐pinene (15.59%), linalool (13.30%), limonene (8.94%), linalyl acetate (3.67%), geranyl acetate (2.99%), and α‐terpineol (2.88%) were the major components. The antimicrobial activity of the essential oil was also investigated on several microorganisms. The inhibition zones and minimal inhibitory concentration (MIC) values of bacterial strains were in the range of 16–28 mm and 0.078–2.5 mg/ml, respectively. The inhibitory activity of the McEO against Gram‐positive bacteria was significantly higher than against Gram‐negative. It also exhibited remarkable activity against several fungal strains. The investigation of the mode of action of the McEO by the time‐kill curve against Listeria monocytogenes (food isolate) showed a drastic bactericidal effect after 5 min using a concentration of 312 μg/ml. These results evidence that the McEO possesses antimicrobial properties, and it is, therefore, a potential source for active ingredients for food and pharmaceutical industries.     

Variation of the Chemical Composition and Antimicrobial Activity of the Essential Oils of Natural Populations of Tunisian Daucus carota L. (Apiaceae)

The essential oils of Daucus carota L. (Apiaceae) seeds sampled from ten wild populations spread over northern Tunisia were characterized by GC‐FID and GC/MS analyses. In total, 36 compounds were identified in the D. carota seed essential oils, with a predominance of sesquiterpene hydrocarbons in most samples (22.63–89.93% of the total oil composition). The main volatile compounds identified were β‐bisabolene (mean content of 39.33%), sabinene (8.53%), geranyl acetate (7.12%), and elemicin (6.26%). The volatile composition varied significantly across the populations, even for oils of populations harvested in similar areas. The chemometric principal component analysis and the hierarchical clustering identified four groups, each corresponding to a composition‐specific chemotype. The in vitro antimicrobial activity of the isolated essential oils was preliminarily evaluated, using the disk‐diffusion method, against one Gram‐positive (Staphylococcus aureus) and two Gram‐negative bacteria (Escherichia coli and Salmonella typhimurium), as well as against a pathogenic yeast (Candida albicans). All tested essential oils exhibited interesting antibacterial and antifungal activities against the assayed microorganisms.     

Chemical Composition of the Essential Oils of Three Endemic Species of Anthemis Sect. Hiorthia (DC.) R.Fern. Growing Wild in Sicily and Chemotaxonomic Volatile Markers of the Genus Anthemis L.: An Update

The chemical composition of the essential oils isolated from the aerial parts of Anthemis pignattiorum Guarino, Raimondo & Domina and A. ismelia Lojac . and the aerial parts and flowers of Anthemis cupaniana Tod . ex Nyman , three endemic Sicilian species belonging to the section Hiorthia, was determined by GC‐FID and GC/MS analyses. (Z)‐Muurola‐4(14),5‐diene (27.3%) was recognized as the main constituent of the A. pignattiorum essential oil, together with isospathulenol (10.6%), sabinene (7.7%), and artemisyl acetate (6.8%), while in the oil obtained from the aerial parts of A. ismelia, geranyl propionate (8.8%), bornyl acetate (7.9%), β‐thujone (7.8%), neryl propionate (6.5%), and τ‐muurolol (6.5%) prevailed. α‐Pinene was the main compound of both the aerial part and flower oils of A. cupaniana (18.4 and 13.2%, resp.). Also noteworthy are the considerable amounts of artemisyl acetate (12.7%) and β‐thujone (11.8%) found in the oil from the aerial parts and those of tricosane (9.8%) and sabinene (7.6%) evidenced in the flower oil. Furthermore, an update on the main compounds identified in the essential oils of all the Anthemis taxa studied so far was presented, and cluster analyses were carried out, to compare the essential oils of these taxa.     

Genetic and Chemical Diversity in Perovskia abrotanoides Kar. (Lamiaceae) Populations Based on ISSRs Markers and Essential Oils Profile

Genetic and the essential oil composition variability among twelve Perovskia abrotanoides populations (PAbPs) growing wild in Iran were assessed by ISSR markers, GC‐FID and GC/MS, respectively. Nine selected ISSR primers produced 119 discernible bands, of them 96 (80.7%) being polymorphic. Genetic similarity values among populations ranged between 0.07 and 0.79 which indicated a high level of genetic variation. Polymorphic information content, resolving power and marker index generated by ISSR primers were, 0.31, 6.14, and 3.32, respectively. UPGMA grouped PAbPs into four main clusters. Altogether, 38 chemical compounds were identified in the oils, and a relatively high variation in their contents was found. Camphor (11.9 – 27.5%), 1,8‐cineole (11.3 – 21.3%), α‐bisabolol (0.0 – 13.1%), α‐pinene (5.9 – 10.8%), and δ‐3‐carene (0.1 – 10.5%) were the major compounds. Oxygenated monoterpenes (32.1 – 35.8%) and monoterpene hydrocarbons (25.7 – 30.4%) were the main groups of compounds in the oils studied. Cluster analysis and principal‐component analysis were used to characterize the samples according to oil components. Four main chemotypes were found to be Chemotype I (camphor/1,8‐cineol), Chemotype II (1,8‐cineole/camphor), Chemotype III (camphor/1,8‐cineol/α‐bisabolol), and Chemotype IV (camphor/δ‐3‐carene/α‐bisabolol). The information, provided here on P. abrotanoides populations, will be useful to introduce this plant into agricultural systems.     

Insecticidal Activity and Chemical Composition of the Essential Oils of Artemisia lavandulaefolia and Artemisia sieversiana from China

In our screening program for new agrochemicals from local wild plants, Artemisia lavandulaefolia and A. sieversiana were found to possess insecticidal activity against the maize weevil Sitophilus zeamais. The essential oils of the aerial parts of the two plants were obtained by hydrodistillation and analyzed by GC and GC/MS. The main components of A. lavandulaefolia oil were caryophyllene (15.5%), β‐thujone (13.8%), eucalyptol (13.1%), and β‐farnesene (12.3%), and the principal compounds identified in A. sieversiana oil were eucalyptol (9.2%), geranyl butyrate (9.2%), borneol (7.9%), and camphor (7.9%). The essential oils of A. lavandulaefolia and A. sieversiana possessed fumigant toxicity against S. zeamais adults with LC₅₀ values of 11.2 and 15.0 mg/l air, respectively. Both essential oils also showed contact toxicity against S. zeamais adults with LD₅₀ values of 55.2 and 112.7 μg/adult, respectively.     

Dittrichia graveolens (L.) Greuter Essential Oil: Chemical Composition,Multivariate Analysis,and Antimicrobial Activity

The chemical composition and in vitro antimicrobial activities of Dittrichia graveolens (L.) Greuter essential oil was studied. Moreover, using agglomerative hierarchical cluster (AHC) and principal component analyses (PCA), the interrelationships of the D. graveolens essential‐oil profiles characterized so far (including the sample from this study) were investigated. To evaluate the chemical composition of the essential oil, GC‐FID and GC/MS analyses were performed. Altogether, 54 compounds were identified, accounting for 92.9% of the total oil composition. The D. graveolens oil belongs to the monoterpenoid chemotype, with monoterpenoids comprising 87.4% of the totally identified compounds. The major components were borneol (43.6%) and bornyl acetate (38.3%). Multivariate analysis showed that the compounds borneol and bornyl acetate exerted the greatest influence on the spatial differences in the composition of the reported oils. The antimicrobial activity against five bacterial and one fungal strain was determined using a disk‐diffusion assay. The studied essential oil was active only against Gram‐positive bacteria.     

Composition and Antimicrobial Activity of the Essential Oils of Laserpitium latifolium L. and L. ochridanum Micevski (Apiaceae)

The chemical composition and antimicrobial activity of essential oils of Laserpitium latifolium and L. ochridanum were investigated. The essential oils were isolated by steam distillation and characterized by GC‐FID and GC/MS analyses. All essential oils were distinguished by high contents of monoterpenes, and α‐pinene was the most abundant compound in the essential oils of L. latifolium underground parts and fruits (contents of 44.4 and 44.0%, resp.). The fruit essential oil was also rich in sabinene (26.8%). Regarding the L. ochridanum essential oils, the main constituents were limonene in the fruit oil (57.7%) and sabinene in the herb oil (25.9%). The antimicrobial activity of these essential oils as well as that of L. ochridanum underground parts, whose composition was reported previously, was tested by the broth‐microdilution method against four Gram‐positive and three Gram‐negative bacteria and two Candida albicans strains. Except the L. latifolium underground‐parts essential oil, the other investigated oils showed a high antimicrobial potential against Staphylococcus aureus, S. epidermidis, Micrococcus luteus, or Candida albicans (minimal inhibitory concentrations of 13.0–73.0 μg/ml), comparable to or even higher than that of thymol, which was used as reference compound.     

Salvia officinalis L. Essential Oils from Spain: Determination of Composition,Antioxidant Capacity,Antienzymatic, and Antimicrobial Bioactivities

Four essential oils (EO s) from Salvia officinalis L. cultivated in Spain (Murcia Province) were analyzed by gas chromatography coupled with mass spectrometry (GC /MS ) to determine their relative and absolute compositions. The main components were α ‐thujone (22.8 – 41.7%), camphor (10.7 – 19.8%), 1,8‐cineole (4.7 – 15.6%), and β ‐thujone (6.1 – 15.6%). Enantioselective gas chromatography identified (?)‐α ‐thujone and (+)‐camphor as the main enantiomers in all the analyzed EO s. Furthermore, when the EO s were tested to determine their antioxidant activity against free radicals and as ferric reducing and ferrous chelating agents, all were seen to have moderate activity due to the compounds they contained, such as linalool or terpinene. Because of their known relation with inflammatory illnesses and Alzheimer 's disease, respectively, the inhibition of lipoxygenase and acetylcholinesterase was studied using the EO s. Some individual compounds also inhibited these enzymes. In addition, the studied EO s were able to inhibit the growth of Escherichia coli , Staphylococcus aureus , and Candida albicans . The characterization carried out increases our awareness of the possible uses of S . officinalis EO as natural additives in food, cosmetics, and pharmaceuticals.     

Volatile Oils from the Aerial Parts of Eremophila maculata and Their Antimicrobial Activity

The essential oils isolated from the fresh flowers, fresh leaves, and both fresh and air‐dried stems of Eremophila maculata (Scrophulariaceae) were characterized by GC‐FID and GC/MS analyses. Sabinene was the major component in most of the oils, followed by limonene, α‐pinene, benzaldehyde, (Z)‐β‐ocimene, and spathulenol. The leaf and flower essential oils showed antibacterial and antifungal activity against five Gram‐positive and four Gram‐negative bacterial strains, multi‐resistant clinical isolates from patients, i.e., methicillin‐resistant Staphylococcus aureus (MRSA), as well as two yeasts. Minimum inhibitory concentrations (MICs) and minimum microbicidal concentrations (MMCs) were between 0.25 and 4 mg/ml.     

Chemical Composition and Antipathogenic Activity of Artemisia annua Essential Oil from Romania

The essential oil extracted by hydrodistillation from Romanian Artemisia annua aerial parts was characterized by GC/MS analysis, which allowed the identification of 94.64% of the total oil composition. The main components were camphor (17.74%), α‐pinene (9.66%), germacrene D (7.55%), 1,8‐cineole (7.24%), trans‐β‐caryophyllene (7.02%), and artemisia ketone (6.26%). The antimicrobial activity of this essential oil was evaluated by determining the following parameters: minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), minimal fungicidal concentration (MFC), and minimal biofilm eradication concentration (MBEC). Moreover, the soluble virulence factors were quantified with different biochemical substrates incorporated in the culture media. The reference and resistant, clinical strains proved to be susceptible to the A. annua oil, with MICs ranging from 0.51 to 16.33 mg/ml. The tested essential oil also showed good antibiofilm activity, inhibiting both the initial stage of the microbial cell adhesion to the inert substratum and the preformed mature biofilm. When used at subinhibitory concentrations, the essential oil proved to inhibit the phenotypic expression of five soluble virulence factors (hemolysins, gelatinase, DNase, lipases, and lecithinases). Briefly, the present results showed that the A. annua essential oil contained antimicrobial compounds with selective activity on Gram‐positive and Gram‐negative bacterial strains as well as on yeast strains and which also interfere with the expression of cell‐associated and soluble virulence factors.     

Chemical characterization and antimicrobial activity of rhizome essential oils of very closely allied Zingiberaceae species endemic to Borneo: Alpinia ligulata K. Schum. and Alpinia nieuwenhuizii Val

Two poorly studied, morphologically allied Alpinia species endemic to Borneo, viz., A. ligulata and A. nieuwenhuizii, were investigated here for their rhizome essential oil. The oil compositions and antimicrobial activities were compared with those of A. galanga, a better known plant. A fair number of compounds were identified in the oils by GC‐FID and GC/MS analyses, with large differences in the oil composition between the three species. The rhizome oil of A. galanga was rich in 1,8‐cineole (29.8%), while those of A. ligulata and A. nieuwenhuizii were both found to be extremely rich in (E)‐methyl cinnamate (36.4 and 67.8%, resp.). The three oils were screened for their antimicrobial activity against three Gram‐positive and three Gram‐negative bacteria and two fungal species. The efficiency of growth inhibition of Staphylococcus aureus var. aureus was found to decline in the order of A. nieuwenhuizii>A. ligulata ～ A. galanga, while that of Escherichia coli decreased in the order of A. galanga>A. nieuwenhuzii ～ A. ligulata. Only the A. galanga oil inhibited the other bacteria and the fungi tested.