Toxicity and therapeutic applications of citrus essential oils (CEOs): a review

ABSTRACT

Citrus essential oil (CEO) is obtained from the fruit of Genus Citrus, a flowering plant shrub in the family of the Rutaceae (Eremocitrus or Microcitrus) and extensively used in food, chemical industry, and traditional medicinal treatment owing to its pleasant aroma, antioxidant, and antiseptic properties. This review presents a botanical description, distribution, traditional uses, chemical composition, bioactive components, and the therapeutic uses as well as toxicological effects of the CEO. The objective was achieved via a comprehensive literature search of electronic databases such as Science Direct, PubMed, Web of Science, Wiley, ACS, Springer, Taylor and Francis, Google Scholar, SCOPUS, conference proceedings, thesis, and books until 2022 for publications. Citrus essential oils and their constituents are extracted and isolated either from the fruit peels, seeds, leaves, or flowers of the citrus plants. A comparative study of the sources of CEO confirmed its origin, ethnopharmacological and therapeutic uses. Over 2000 secondary metabolites have been isolated, with the main active constituents: being terpenes, monoterpenes, sesquiterpenes, and diterpenes. A comprehensive literature review revealed vast therapeutic benefits of CEO. Incomplete data report on in vitro and in vivo trials especially, on dosage, positive and negative control groups, intervention time, toxicity studies, phytochemical profiling, and clinical trials seem to be a knowledge gap.

KEYWORDS:

• Citrus essential oil
• anti-fungal
• anti-cancer
• histo-protective
• larvicidal
• nephroprotective
• cytotoxicity
• biopesticide

Abbreviations

5-HT- 5-Hydroxytrytamine; 5-MOP- 5-Methoxypsoralen; ABST- 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid); CAT-catalase; CEOs- citrus essential oils; DLA- Dalton’s Lymphoma Ascites; DPB- Dibenzo-α-pyrene; DPPH- 2,2-Diphenyl-1-picrylhydrazl; EOs- Essential oils; HL-60- Human Leukemia cells; H5N1-Hemagglutinin type 5 and Neuraminidase type 1; HD-Hydro distillation; GC-MS- Gas Chromatography-Mass Spectrometry; GSH-Reduced Glutathione; ICR-Institute of Cancer Research; LNCaP- Human prostate adenocarcinoma; LDL- Low-density lipoprotein; MASD-Microwave Assisted Steam Distillation; MIC- Minimum Inhibitory Concentration; PSA- Prostate Specific Antigen; ROS- Reactive Oxygen Species; SC-CO₂- Supercritical carbon dioxide; SD-Steam Distillation; SHSY5Y-Human neuroblastoma cells; SOD-Superoxide dismutase; UAE- Ultrasound-Assisted Extraction; WAT-White Adipose Tissue.

Acknowledgments

The authors thank the University of Cape Coast for its support.

Authors contributions

CKA, FAA, and CO conceptualized the study. CKA, ASB, and SAA reviewed the research proposal and conducted the ethnobotanical survey. ASB, SAA, and CO drafted the manuscript. All the authors participated in writing and giving feedback on the manuscript. All authors have read and approved the final manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).