Phenolic Contents and Antioxidant Activity of Citrullus colocynthis Fruits, Growing in the Hot Arid Desert of the UAE, Influenced by the Fruit Parts, Accessions, and Seasons of Fruit Collection

Shaimaa Al-Nablsi; Ali El-Keblawy; Muna A Ali; Kareem A Mosa; Alshaimaa M Hamoda; Abdallah Shanableh; Ahmed M Almehdi; Sameh S M Soliman

doi:10.3390/antiox11040656

Phenolic Contents and Antioxidant Activity of Citrullus colocynthis Fruits, Growing in the Hot Arid Desert of the UAE, Influenced by the Fruit Parts, Accessions, and Seasons of Fruit Collection

Antioxidants (Basel). 2022 Mar 29;11(4):656. doi: 10.3390/antiox11040656.

Authors

Shaimaa Al-Nablsi^{1

2}, Ali El-Keblawy^{1

2

3}, Muna A Ali^{1

2

4}, Kareem A Mosa^{1

2

5}, Alshaimaa M Hamoda^{4

6

7}, Abdallah Shanableh², Ahmed M Almehdi^{2

8}, Sameh S M Soliman^{6

9}

Affiliations

¹ Department of Applied Biology, College of Sciences, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates.
² Research Institute of Science and Engineering (RISE), University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates.
³ Department of Biology, Faculty of Science, Al-Arish University, Al-Arish 45511, Egypt.
⁴ College of Medicine, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates.
⁵ Department of Biotechnology, Faculty of Agriculture, Al-Azhar University, Cairo 11751, Egypt.
⁶ Research Institute for Medical and Health Sciences, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates.
⁷ Department of Pharmacognosy, Faculty of Pharmacy, Assiut University, Assiut 71515, Egypt.
⁸ Department of Chemistry, College of Sciences, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates.
⁹ Department of Medicinal Chemistry, College of Pharmacy, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates.

Abstract

Citrullus colocynthis (Cucurbitaceae) is an important medicinal plant traditionally used in the United Arab Emirates (UAE). In a recent study, it has been reported that different individuals of the same population of C. colocynthis, growing in the hot arid desert of the UAE, exhibited variations in their fruit size, color, and stripe pattern. In addition, these plants differed genetically, and their seeds showed variation in size, color, and germination behavior (hereinafter, these individuals are referred to as accessions). In the present study, the total phenolic content (TPC) and antioxidant activity of different fruit parts (rinds, pulps, and seeds) of three different accessions with significant genetic variations, from a single C. colocynthis population, were assessed in response to different seasonal environments. Green fruits were collected in summer and winter from three accessions growing in the botanic garden of the University of Sharjah, UAE. Methanolic extracts from different fruit parts were prepared. The TPC was qualitatively determined by a Folin-Ciocalteu assay, while the antioxidant capacity was analyzed using the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical scavenging ability. The metabolic profiling of the antioxidant metabolites was determined using a gas chromatograph coupled to mass spectrometry (GC-MS), associated with a literature search. The results showed that the TPC and the DPPH free radical scavenging activity varied between seasons, accessions, and fruit parts. The highest phenolics were in rinds, but the highest antioxidant activities were in seeds during the summer, reflecting the role of these compounds in protecting the developed seeds from harsh environmental conditions. The metabolomic analysis revealed the presence of 28 metabolites with significant antioxidant activities relevant to fruit parts and season. Collectively, the formation of phenolics and antioxidant activity in different fruit parts is environmentally and genetically dependent.

Keywords: Citrullus colocynthis; antioxidant activity; fruit parts; metabolomics; season; total phenolic contents.