**1. Introduction**

Worldwide, the Annonaceae family comprises more than 128 genera and approximately 2106 species and they are mainly distributed in tropical and subtropical regions [1]. For Ecuador, 25 genera, 106 species and 20 endemic species are reported [2]. In a review of the antimalarial properties of the Annonaceae family, 11 species from *Annona* and *Xilopia* genus were recognized for their antiparasitic potential. Annonaceae species used in traditional medicine, over the tropical regions, are well documented for having potential for the treatment of parasitic diseases such as Malaria, Chagas and Leishmaniasis as well as other illnesses [3]. Indeed, *Annona muricata* was one of the most cited species with a variety of medicinal properties including the treatment for the symptoms of malarial infection, fever, liver ailments and headaches [4].

*Annona cherimola*, *A. crassiflora*, *A. muricata*, *A. squamosa* and *A. reticulata* are the commercial species, highly valued by their exotic edible fruit. Furthermore, different parts of the tree from these species have been used in folk medicine to treat several conditions including gastrointestinal diseases, diabetes and hypertension [5]. Many secondary metabolites have

**Citation:** Valarezo, E.; Ludeña, J.; Echeverria-Coronel, E.; Cartuche, L.; Meneses, M.A.; Calva, J.; Morocho, V. Enantiomeric Composition, Antioxidant Capacity and Anticholinesterase Activity of Essential Oil from Leaves of Chirimoya (*Annona cherimola* Mill.). *Plants* **2022**, *11*, 367. https://doi.org/ 10.3390/plants11030367

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

Received: 20 December 2021 Accepted: 26 January 2022 Published: 28 January 2022

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**Copyright:** © 2022 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/).

been reported such as phenols and other bioactive compounds but, the main chemical marker of the genus is a diverse group of polyketides called acetogenins, compounds closely associated to their antiproliferative effect on cancer cell lines [5,6].

In a related study, nine species from *Annona* genus, including *A. cherimola*, where reviewed in relation to their phytochemical composition and biological activity and found that mainly polar extracts obtained from these plants, induce a reduction in blood sugar levels in chemically induced type-2 diabetic rats which demonstrate the antidiabetic potential of species from this genus. Likewise, seven out of nine of the studied species reported a good antioxidant capacity profile in different in vitro assays. *A. cherimola* was only tested trough the oxygen radical absorbance capacity (ORAC) assay [7].

*Annona cherimola* Mill. is a native shrub, widely distributed in the Andean, Coastal, Amazon and Insular regions of Ecuador, between 0–3000 m a.s.l [2]. Currently, this species is cultivated in the subtropical and tropical regions worldwide, especially for its fruit, which is considered exotic. The *A. cherimola* species is commonly known as "chirimoya" or "chirimoyo" (Spanish language) and "custard-apple" (English language) [8]. The vernacular name "chirimoya" is derived from the Quechua (indigenous language) word "chirimuya", "chiri" that means cold and "muya" seeds. The fruit of this species is considered one the most appreciated inside the genus. The plant has been used in traditional medicine for the treatment of boils and others skin diseases [9].

Anthropological evidence suggests that the species *A. cherimola* was cultivated since the times of the Incan Empire and its fruit was considered as an active ingredient in the their diet [10]. Some important compounds have been isolated from this species such as alkaloids as cherimoline, annocherine A, annocherine B, cherianoine and rumocosine H [11], and some amides as cherinonaine, cheritamide, (N-trans-feruloyltyramine, N-trans-caffeoyltyramine, N-*cis*-caeoyltyramine, dihydro feruloyltyramine, N-transferuloylmethoxytyramine, N-*cis*-feruloylmethoxytyramine, and N-*p*-coumaroyltyramine [12]. Recent studies have shown that custard apple leaves contain flavonoids and other phenolic compounds with biological properties [13,14] and that alcoholic extracts from the leaves have proapoptotic and antidepressant activities [15].

Several studies on the species of the *Annona* genus have reported the occurrence of compounds with potential application for pharmaceuticals, food, agrochemicals products and cosmetics [3,5,6,16]. Extracts from these species are used for a wide range of beneficial purposes, however, the research have been focused mainly on the non-volatile fraction of the fruits, meanwhile, the enantiomeric distribution and biological properties of the EOof *Annona cherimola* have not been reported previously. This fact stimulated our interest in studying the chemical composition, enantiomeric distribution and antimicrobial, antioxidant and anticholinesterase activities of the essential oil of custard apple leaves.
