**1. Introduction**

Taxa belonging to *Pulicaria* (Asteraceae Family) are widely distributed in Asia, Africa, and Europe. These plants are considered very important medicinal plants due to their traditional applications around the world, in addition to the presence of interesting metabolites comprising mono-, sesqui-, and diterpenoids, as well as phenolic and flavonoids [1–4].

The Egyptian widespread desert plant, *Pulicaria undulata* (L.) (syn. *Pulicaria crispa* (Forssk.) Benth et Hook), was documented as a very important traditional plant for the

**Citation:** Abd-ELGawad, A.M.; Al-Rowaily, S.L.; Assaeed, A.M.; EI-Amier, Y.A.; El Gendy, A.E.-N.G.; Omer, E.; Al-Dosari, D.H.; Bonanomi, G.; Kassem, H.S.; Elshamy, A.I. Comparative Chemical Profiles and Phytotoxic Activity of Essential Oils of Two Ecospecies of *Pulicaria undulata* (L.) C.A.Mey. *Plants* **2021**, *10*, 2366. https://doi.org/ 10.3390/plants10112366

Academic Editors: Hazem Salaheldin Elshafie, Laura De Martino and Adriano Sofo

Received: 11 October 2021 Accepted: 28 October 2021 Published: 3 November 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

treatment of diabetes, abscesses, cardiac and skin diseases, and chills [5]. In Egypt, this plant was used as a herbal tea for inflammation treatment, in addition to insect repellent [4].

Numerous pharmaceutical activities were described for different extracts and ingredients of this plant such as antioxidant [6–8], neuroprotective [9], antiulcer [10], antiacetylcholinesterase [8], anticancer [11], and *α*-glucosidase inhibitory activity [12]. These biological activities of *P. undulata* were ascribed to different classes of identified chemical compounds such as terpenes [4,12–15], flavonoids [7,16], and sterols [11]. The essential oil (EO) of *P. undulata* exhibited various potent biological activities such as antiproliferative, antioxidant [6,15], anticancer [8], antibacterial [13], and cytotoxic [12].

Many documents have been published concerning the chemical characterization EOs of different ecospecies of *P. undulata* from different countries such as Sudan [6,17], Iran [15,18,19], Algeria [14], Yemen [13], and Egypt [8,16,20]. However, by comparing all these ecospecies, there was evidence that their EOs were different either in quality or quantity. This deduced that the biosynthesis of the natural metabolites including EOs in the plant kingdom is correlated with environmental and climatic conditions, in addition to genetic variability [21–23]. The present study aimed to analyze and compare the EO profiles of two ecospecies of *P. undulata* growing in Saudi Arabia and Egypt, assess phytotoxicity against the noxious weeds *Dactyloctenium aegyptium* and *Bidens pilosa,* as well as holistically categorize their EOs with other reported ecospecies using chemometric tools.
