BackgroundCupressus macrocarpa Hartw and Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson, widely grown in many subtropical areas, are used for commercial purposes, such as in perfumery, cosmetics, and room fresheners. Their potential as a source of antimicrobial compounds may be useful in different applications.MethodsThe chemical composition of essential oils (EOs) from C. macrocarpa branchlets and C. citriodora leaves was analyzed by using gas chromatography–mass spectrometry (GC/MS). Antibacterial and antifungal activities were assessed by the micro-dilution method to determine the minimum inhibitory concentrations (MICs), and minimum fungicidal concentrations (MFCs), and minimum bactericidal concentrations (MBCs). Further, the antioxidant capacity of the EOs was determined via 2,2′-diphenypicrylhydrazyl (DPPH) and β-carotene-linoleic acid assays.ResultsTerpinen-4-ol (23.7%), α-phellandrene (19.2%), α-citronellol (17.3%), and citronellal were the major constituents of EO from C. macrocarpa branchlets, and α-citronellal (56%), α-citronellol (14.7%), citronellol acetate (12.3%), isopulegol, and eucalyptol were the primary constituents of EO from C. citriodora leaves. Antibacterial activity with MIC values of EO from C. citriodora leaves was ranged from 0.06 mg/mL to 0.20 mg/mL, and MBC from 0.12 mg/mL against E. coli to 0.41 mg/mL. EO from C. macrocarpa branchlets showed less activity against bacterial strains. The MIC values against tested fungi of the EO from C. citriodora ranged from 0.11 to 0.52 mg/mL while for EO from C. macrocarpa from 0.29 to 3.21 mg/mL. The MIC and MFC values of EOs against P. funiculosum were lower than those obtained from Ketoconazole (KTZ) (0.20; 0.45; 0.29 and 0.53 mg/mL, respectively, vs 0.21 and 0.41 mg/mL. Antioxidant activity of the EO from C. citriodora was higher than that of the positive control but lower than that of the standard butylhydroxytoluene (BHT) (IC50 = 5.1 ± 0.1 μg/mL).ConclusionThe results indicate that the EO from Egyptian trees such as C. citriodora leaves may possesses strong bactericidal and fungicidal activities and can be used as an agrochemical for controlling plant pathogens and in human disease management which will add crop additive value.

The crude methanolic extracts from leaves of Eucalyptus camaldulensis L., E. camaldulensis var obtusa and E. gomphocephala grown in Egypt were investigated to explore their chemical composition as well as their antibacterial, antifungal and antioxidant activities. Major phenolics found were ellagic acid, quercetin 3-O-rhamnoside, quercetin 3-O-b-D-glucuronide, caffeic acid and chlorogenic acid. The antioxidant activities were examined by the 2,2'-diphenypicrylhydrazyl (DPPH) and β-Carotene-linoleic acid assays. E. camaldulensis extracts showed the highest phenolic content, antioxidant and antimicrobial activities compared to other cultivars. MIC values reported for antibacterial activity of E. camaldulensis ranged from 0.08 μg/mL (Bacillus cereus) to 0.22 μg/mL (Staphylococcus aureus), while MBC values ranged from 0.16 μg/mL (Dickeya solani and B. cereus) to 0.40 μg/mL (S. aureus). The inhibitory activities against growth of bacteria and fungi used is an indication that E. camaldulensis a might be useful resource for the development and formulation of antibacterial and antifungal drugs.

The chemical composition of the essential oil from the leaves of Eucalyptus camaldulensis, Eucalyptus camaldulensis var. obtusa and Eucalyptus gomphocephala grown in northern Egypt was analysed by using GC-FID and GC-MS techniques. The antibacterial (agar disc diffusion and minimum inhibitory concentration methods) and antioxidant activities (2,2'-diphenypicrylhydrazyl) were examined. The main oils constituents were 1,8-cineole (21.75%), β-pinene (20.51%) and methyleugenol (6.10%) in E. camaldulensis; spathulenol (37.46%), p-cymene (17.20%) and crypton (8.88%) in E. gomphocephala; spathulenol (18.37%), p-cymene (19.38%) and crypton (16.91%) in E. camaldulensis var. obtusa. The essential oils from the leaves of Eucalyptus spp. exhibited considerable antibacterial activity against Gram-positive and Gram-negative bacteria. The values of total antioxidant activity were 70 ± 3.13%, 50 ± 3.34% and 84 ± 4.64% for E. camaldulensis, E. camaldulensis var. obtusa and E. gomphocephala, respectively. The highest antioxidant activity value of 84 ± 4.64% could be attributed to the high amount of spathulenol (37.46%).

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The aim of this work is to identify the chemical constituents and the bioactivity of essential oil (EO), acetone extract (ACE) and n-hexane extract (HexE) of S. terebinthifolius ripened fruits using GC-MS. Total phenolic content and antioxidant activity of extracts were determined using the Folin-Ciocalteu and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assays, respectively. The toxicity against the growth of Acinetobacter baumannii, Bacillus subtilis, Escherichia coli, Micrococcus flavus, Pseudomonas aeruginosa, Sarcina lutea, and Staphylococcus aureus was determined with measuring the inhibition zones (IZs) using the disc diffusion method at the concentrations from 125 to 2000 μg/mL, also, the minimum inhibitory concentrations (MICs) using 96-well micro-plates and ranged from 4 to 2000 μg/mL. The major components in EO were α-pinene (36.9%), and α-phellandrene (32.8%). The major components in ACE were oleic acid (38.7%), α-phellandrene (13.33%), and δ-cadinene (11.1%), while the major methyl esters of fatty acids detected in HexE were oleic (12.8%), and palmitic (10.9%). The EO showed good activity against the growth of Staph. aureus and P. aeruginosa with MIC values of 16 μg/mL and 32 μg/mL, the ACE showed broad activity against the studied bacterial pathogens with MIC values ranged from of 4-128 μg/mL against the studied bacterial isolates, while HexE, however, showed weak antibacterial activity. The IC values of EO, ACE and HexE were 15.11 ± 0.99, 118.16 ± 1.7 and 324.26 ± 2.45 μg/mL, respectively, compared to IC of Tannic acid (23.83 ± 1.9 μg/mL) and butylated hydroxytoluene (BHT, 2.9 ± 0.1 μg/mL). Data suggested that the ripened fruits of S. terebinthifolius have potent antioxidant and antibacterial activities.