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Essential oil, dichloromethane extract, and ethanol extract were prepared from fresh Schinus terebinthifolius leaves cultivated in Egypt. The essential oil was analyzed by gas chromatography and gas chromatography/mass spectrometry. The essential oil comprised 4.97% monoterpenes, 56.96% sesquiterpenes, 34.37% oxygenated monoterpenes, and 3.32% oxygenated sesquiterpenes. The major compounds in the essential oil were cis-beta-terpineol (GC peak area%, 17.87%), (E)-caryophyllene (17.56%), beta-cedrene (9.76%), and citronellal (7.03%). The major phenolic compounds identified in the ethanol extract were caffeic acid (5.07 mg/100 mg extract), coumaric acid (1.64 mg), and syringic acid (1.59 mg). The antioxidant activity of ethanol extract, which was comparable with that of butylhydroquinone, was superior to essential oil and dichloromethane extract in 2,2-diphenylpicrylhydrazyl and beta-carotene/bleaching assays. The dichloromethane extract exhibited the greatest antimicrobial activity against 6 strains, followed by the ethanol extract and the essential oil.

The use of natural antimicrobial compounds in food has gained much attention by the consumers and the food industry. This is primarily due to two major factors. First, the misuse and mishandling of antibiotics has resulted in the dramatic rise of a group of microorganisms including foodborne pathogens that are not only antibiotic resistant but also more tolerant to several food processing and preservation methods. In addition, increasing consumers' awareness of the potential negative impact of synthetic preservatives on health versus the benefits of natural additives has generated interest among researchers in the development and use of natural products in foods. Essential oils are volatile, natural, complex compounds characterized by a strong odor and are formed by aromatic plants as secondary metabolites. The bioactivity properties of essential oils are generally determined by the major compounds present in them. They have been widely used for bactericidal, virucidal, fungicidal, antiparasitical, insecticidal, medicinal, and antioxidant applications. The biological activity of the oils can be compared with the activity of synthetically produced pharmacological preparations. Thus, essential oils are promising natural extracts that need further evaluation for possible application as supplement, preservatives, or antioxidants in food or pharmaceutical industries.

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Volatile chemicals in a dichloromethane extract from a steam distillate of juniper berry fruit (Juniperus drupacea L.) and its two column chromatographic fractions (eluted with hexane and ethyl ether) were analyzed by gas chromatography/mass spectrometry. The major compounds in the dichloromethane extract were alpha-pinene (23.73%), thymol methyl ether (17.32%), and camphor (10.12%). A fraction eluted with hexane contained alpha-pinene (44.24%) as the major constituent. A fraction eluted with ethyl ether had thymol methyl ether (22.27%) and camphor (19.65%) as the main components. Three samples prepared from the distillate and two additional samples prepared by petroleum ether and ethanol extraction directly from juniper berry fruits exhibited clear antioxidant activities with dose response in both 1,2-diphenyl picrylhydrazyl and beta-carotene assays. All samples except the hexane fraction showed comparable activities to that of the synthetic antioxidant t-butyl hydroquinone at a level of 200 microg/mL in the two testing systems. The extracts of dichloromethane, petroleum ether, and ethanol exhibited appreciable antimicrobial activities against six microorganisms with minimum inhibitory concentrations ranging from 0.5 mg/mL (volatile extract against Candida albicans ) to 1.2 mg/mL (ethanol extract against Aspergillus niger ). The results of the present study suggest that this fruit could be a natural antioxidant supplement for foods and beverages.

A total of 33 compounds of bell pepper volatile oils were identified by gas chromatography and mass spectrometry (GC-MS) in the volatile dichloromethane extract obtained from Pakistani bell pepper (Capsicum annum L.), locally known as Shimla Mirch. The main constituents of the volatile oils of bell pepper (fresh and dried) were benzaldehyde (20.9-3%), 2-methoxy-3-isobutyl-pyrazine (20.4-9%), Z-β-ocimene (13-3%), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (12.7-2.5%), and β-ionone (12.1-0.9%). Non volatile components of bell pepper 'Twingo' and Bell Pepper No. 1 (fresh and dried) were extracted with n-hexane and methanol. All extracts from solvent extraction and the volatile extract described above exhibited clear antioxidant activities at levels of 10-60 µg/mL in the 2,2-diphenyl-1-picrylhydrazyl/linoleic acid and β-carotene bleaching assays. The dried bell pepper 'Twingo' volatile oil inhibited 2,2-diphenyl-1-picrylhydrazyl activity by 70.95 ± 0.89%, at a concentration of 60 µg/mL. This study indicates that Pakistani bell pepper could be used to produce novel natural antioxidants as well as a flavoring agent in various food products.

A comparative study of volatile constituents, antioxidant activity, and molecular docking was conducted between essential oils from Mentha longifolia L., Mentha spicata L., and Origanum majorana L., widely cultivated in Madinah. The investigation of volatile oils extracted by hydrodistillation was performed using Gas Chromatography-Mass Spectrometry (GC-MS). A total number of 29, 42, and 29 components were identified in M. longifolia, M. spicata, and O. majorana representing, respectively, 95.91, 94.62, and 98.42, of the total oils. Pulegone (38.42%), 1,8-cineole (15.60%), menthone (13.20%), and isopulegone (9.81%) were the dominant compounds in M. longifolia oil; carvone (35.14%), limonene (27.11%), germacrene D (4.73%), and β-caryophyllene (3.02%) were dominant in M. spicata oil; terpin-4-ol (42.47%), trans-sabinene hydrate (8.52%), γ-terpinene (7.90%), α-terpineol (7.38%), linalool (6.35%), α-terpinene (5.42%), and cis-sabinene hydrate (3.14%) were dominant in O. majorana oil. The antioxidant activity, assessed using DPPH free radical–scavenging and ABTS assays, was found to be the highest in O. majorana volatile oil, followed by M. spicata and M. longifolia, which is consistent with the differences in total phenolic content and volatile constituents identified in investigated oils. In the same context, molecular docking of the main identified volatiles on NADPH oxidase showed a higher binding affinity for cis-verbenyl acetate, followed by β-elemene and linalool, compared to the control (dextromethorphan). These results prove significant antioxidant abilities of the investigated oils, which may be considered for further analyses concerning the control of oxidative stress, as well as for their use as possible antioxidant agents in the pharmaceutical industry.

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