Volatile Compounds and Antioxidant and Antimicrobial Activities of Selected Citrus Essential Oils Originated from Nepal

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.

The Chemical Composition and Antibacterial and Antioxidant Activities of Five Citrus Essential Oils

“…EOs or most single components of EOs showed high efficacy against Salmonella typhimurium , E. coli O157: H7 and E. coli K88 , but had little inhibitory effect on Lactobacillus and Bifidobacterium . Bhandari et al [ 16 ] found that citrus EOs showed selective antibacterial activity in vitro. In agreement with those studies, the present study showed that the citrus EOs had selective antibacterial activity and inhibitory activity against pathogenic E. coli and Salmonella , but their activity varied with type of EO and the concentration added.…”

Evaluation of the Pathogenic-Mixed Biofilm Formation of Pseudomonas aeruginosa/Staphylococcus aureus and Treatment with Limonene on Three Different Materials by a Dynamic Model

“…Many studies have shown the antibacterial activity of limonene, one of the major ingredients of essential oils in various plants and seeds [ 34 , 35 , 36 ].…”

Impact of Storage Condition on Chemical Composition and Antifungal Activity of Pomelo Extract against Colletotrichum gloeosporioides and Anthracnose in Post-harvest Mango

“…The major constituents of essential oil isolated from pomelo in Taiwan were 0.8% α -pinene, 2.7% β -pinene, 3.1% myrcene, 0.1% α -phellandrene, 0.4% β -ocimene, 87.5% limonene, and 0.4% linalool [ 17 ]. The constituents of essential oil isolated from peel of 3 pomelo cultivars in Nepal were 0.2–0.58% α -pinene, 0.77–2.17% sabinene, 0.15–6.09% β -pinene, 0.74–1.75 myrcene, 63.76–89.15% limonene, 0.35% β -phellandrene, 0.13–0.43% β -ocimene, and 0.35–2.65% linalool [ 20 ]. The constituents of essential oil of pomelo from Tunisia was 0.15% ± 0.06% α -pinene, 0.19% ± 0.01% sabinene,1.52% ± 0.06% β -pinene, 0.03% ± 0.00% β -myrcene, 95.4% ± 3.91% limonene, 0.26% ± 0.09% β -ocimene, and 0.09 ± 0.02 [ 21 ].…”