**1. Introduction**

*Aerva javanica* (Burm. f.) Juss. ex Schul. (English names: desert cotton, snow bush) (Arabic names: Al ara', twaim, efhe, tirf) [1], a perennial xerophyte belonging to the Amaranthaceae family (common name: cockscomb). This shrub grows up to 100 cm. It has a woody base, erect and branched stems, covered with fine hairs. The leaves are alternate with greyish-green color on very short stalks, lance-shaped to oblong (1–1.5 × 4–5 cm) with clear veins and midrib on the underside covered with hairs. The flowers are aromatic, soft like cotton and generally available throughout the year [2]. It has five petals on a long spike (5–10 cm) from the leaf nodes. The open flowers are white and the buds are pinkish. The bracts (leaf-like structure) just below the flowers are covered with long woolly white hairs that become more intense as the season progresses. The inside of the fruits have a woolly covering, including one small black or brown shiny seed (0.1 × 0.15 cm) [1].

The genus *Aerva* is well-known as an important medicinal genus, including many species with proven biological activities, such as, antioxidant, hypoglycemic, analgesic, antivenin, antimalarial, and anthelmintic activities [2,3]. *A. javanica* is an important medicinal and commercial plant. It is recommended by Ayurvedic medicine as one of the best sources of natural remedies (e.g., to treat the bladder and kidney stones) [3]. *A. javanica* is an essential oil-bearing shrub (or small tree), common in tropical and subtropical dry

**Citation:** Shahin, S.M.; Jaleel, A.; Alyafei, M.A.M. Yield and In Vitro Antioxidant Potential of Essential Oil from *Aerva javanica* (Burm. f.) Juss. ex Schul. Flower with Special Emphasis on Seasonal Changes. *Plants* **2021**, *10*, 2618. https://doi.org/10.3390/ plants10122618

Academic Editors: Hazem Salaheldin Elshafie and Laura De Martino

Received: 24 September 2021 Accepted: 21 October 2021 Published: 29 November 2021

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areas, with various folk applications related to its flowers in traditional herbal practices. For example, the flowers were mixed with water as a paste to stop wounds bleeding, and to pack suppurating wounds after cleaning. Furthermore, flowers were used for curing kidney and rheumatism problems [1,2].

Consequently, it is of great interest to investigate the flowers' EO yield, which is the first objective of this work, in order to recommend the best harvesting season with the highest yield. Furthermore, for the sake of testing the quality, the antioxidant activity of *A. javanica* flowers' EO will be tested for the first time (in vitro) and during the four seasons, which is the second objective of this research, seeking for a scientific justification for the rich ethnomedicinal applications of this plant's flowers. Besides, the volatiles of flowers' EO will be identified, to the best of our knowledge, for the first time in the literature. The same would be identified for the best flowers' EO yield obtained. In addition, the microscopic photos under scanning electron microscope are included in this study; providing a better understanding of the finer morphology of the trichomes of the flower epidermis.

## **2. Materials and Methods**
