Abstract
Citrus species of plants are among the most commercially cultivated crops, mainly for their fruit. Besides, the generally consumed flesh inside the fruit, the peel is quite important too. Essential oils extracted from the peel have a history of being used by humankind for centuries. These essential oils are rich in antioxidants and antimicrobial agents. Comparative investigation of volatile constituents, and antioxidant and antimicrobial activities were undertaken. The essential oils were evaluated through gas chromatography-mass spectrometry (GC–MS), and enantiomeric composition by chiral GC–MS. Similarly, the antioxidant properties were evaluated by 2,2-diphenyl-1-picrylhydrazyl scavenging assay, and antimicrobial activities were assayed using the disk diffusion method. The highest extraction yield of 1.83% was observed in Citrus sinensis Osbeck. GC–MS analysis showed limonene (63.76–89.15%), γ-terpinene (0.24–6.43%), β-pinene (0.15–6.09%), linalool (0.35–3.5%), sabinene (0.77–2.17%), myrcene (0.74–1.75%), α-terpineol (0.28–1.15%), and α-pinene (0.2–0.58%) as the major constituents of the essential oil of the Citrus species studied. For the first time, through our study, chiral terpenoids have been observed from Citrus grandis Osbeck essential oil. The order of antioxidant activity is as follows: Citrus grandis Osbeck red flesh > Citrus reticulata Blanco > Citrus sinensis Osbeck > Citrus grandis Osbeck white flesh. Except for Citrus grandis Osbeck white flesh (52.34 µL/mL), all samples demonstrated stronger antioxidant activities than those of the positive control, quercetin (5.60 µL/mL). Therefore, these essential oils can be used as a safe natural antioxidant to prevent product oxidation. Likewise, citrus peel essential oil showed antimicrobial activity against tested bacterial strains, albeit marginal.
Highlights
Citrus species belong to the family Rutaceae and are among the most commercially significant crops cultivated in tropical and subtropical climate regions [1]
Citrus essential oils (CEOs) are fascinating among essential oils since they can be used as antioxidants because of their ability to protect organisms and tissues from damage inflicted by reactive oxygen species, and as flavoring agents [6,7]
Tran et al using the hydrodistillation to extract the essential oil from Vietnamese powdered mandarin (Citrus reticulata Blanco) at a temperature of 110–120 ◦ C, reported the greatest yield of 5%, with a peel-to-solvent ratio of 1:4 (g/mL), and an extraction duration of 150 min indicating the size of the peel, the water-to-peel ratio, the temperature extraction, and the time extraction affecting extraction by hydrodistillation [23]
Summary
Citrus species belong to the family Rutaceae and are among the most commercially significant crops cultivated in tropical and subtropical climate regions [1]. The peel of citrus fruit is a valuable raw material for the production of essential oils Such oils have a history dating to very ancient times of being used in human society. Citrus essential oils (CEOs) are fascinating among essential oils since they can be used as antioxidants because of their ability to protect organisms and tissues from damage inflicted by reactive oxygen species, and as flavoring agents [6,7] These essential oils can be used as an alternative to synthetic preservatives since they are observed to display their antimicrobial and antioxidant activities with a broad spectrum of biological activities [8,9]. It has been found that the emission of volatile components such as limonene, α/β-pinene, and camphene from citrus orchards contribute to ozone formation [10] in the troposphere and the deposition of ozone in the environment, contributing to the greenhouse effect [11]
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