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Characterization of Oxygenated Heterocyclic Compounds and in vitro Antioxidant Activity of Pomelo Essential Oil

Authors Li G, Cheng Y, Zhang T, Li Y, Han L, Liang G

Received 1 January 2021

Accepted for publication 18 February 2021

Published 2 March 2021 Volume 2021:15 Pages 937—947


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 3

Editor who approved publication: Dr Anastasios Lymperopoulos

Guijie Li,1,* Yujiao Cheng,1,* Tenghui Zhang,2 Yingzhuo Li,3 Leng Han,1 Guolu Liang4

1Citrus Research Institute, Southwest University, Chongqing, People’s Republic of China; 2Chengdu Centre Testing International Group Co., Ltd., Chengdu, People’s Republic of China; 3Chongqing Beibei Agricultural and Rural Committee, Chongqing, People’s Republic of China; 4College of Horticulture and Landscape Architecture, Southwest University, Chongqing, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Leng Han
Citrus Research Institute, Southwest University, No. 15 Ganjucun, Xiema, Beibei District, Chongqing, 400712, People’s Republic of China
Email [email protected]
Guolu Liang
College of Horticulture and Landscape Architecture, Southwest University, No. 2 Tiansheng Road, Beibei District, Chongqing, 400715, People’s Republic of China
Email [email protected]

Purpose: Citrus essential oils are widely used for aromatherapy and the alternative treatment of chronic diseases. Beyond the aroma substances, they are known to contain bioactive nonvolatile components; however, little knowledge has been gained about nonvolatiles in the essential oil of pomelo (Citrus grandis Osbeck), the largest citrus fruit. The purpose of this study was to analyze the nonvolatile oxygenated heterocyclic compounds (OHCs) of pomelo essential oils and evaluate their in vitro antioxidant activities for further development.
Methods: Cold-pressed essential oil (CPEO) and distilled essential oil (DEO) were obtained from the peel of the Liangping pomelo cultivar. High-performance liquid chromatography (HPLC) coupled with a photodiode array and fluorescence detection method was developed to identify and quantify the OHCs of the two essential oils. Ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2-phenyl-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide (PTIO) radical scavenging assays were used to determine the antioxidative capabilities.
Results: Thirteen OHCs were identified in CPEO. Coumarins such as meranzin (2.0 mmol L− 1) and furanocoumarins such as isoimperatorin (1.3 mmol L− 1) composed the majority of nonvolatiles in CPEO. These OHCs were characterized by high proportion (58%) of side chain epoxides. Five OHCs, namely, auraptenol, 6ʹ,7ʹ-dihydroxybergamottin (6ʹ,7ʹ-DHB), imperatorin, isoimperatorin and 8-geranyloxypsoralen were first identified in pomelo CPEO. Eight OHCs were detected at trace amounts in pomelo DEO. Antioxidant assays showed that CPEO was multiple times more potent than DEO regarding the total reducing power and radical scavenging capacity. Clearance of PTIO, a stable reactive oxygen species, followed slow kinetics.
Conclusion: Coumarins and furanocoumarins, two families of OHCs, constituted most of the nonvolatile components in CPEO. The nonvolatiles contributed significantly to the in vitro antioxidant activity of CPEO. Pomelo CPEO showed good prospects as a potential long-lasting natural antioxidant.

Keywords: volatile oil, cold expression, hydrodistillation, psoralen, epoxides, fluorescence, radical scavenging, pummelo, Citrus maxima

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