Essential Oils from Annonaceae Species from Brazil: A Systematic Review of Their Phytochemistry, and Biological Activities

The present work involves a systematic review of the chemical composition and biological effects of essential oils from the Annonaceae species collected in Brazil from 2011 to 2021. Annonaceae is one of the most important botanical families in Brazil, as some species have economic value in the market as local and international fruit. In addition, the species have useful applications in several areas—for instance, as raw materials for use in cosmetics and perfumery and as medicinal plants. In folk medicine, species such as Annona glabra L. and Xylopia sericea A. St.-Hil. are used to treat diseases such as rheumatism and malaria. The species of Annonaceae are an important source of essential oils and are rich in compounds belonging to the classes of mono and sesquiterpenes; of these compounds, α-pinene, β-pinene, limonene, (E)-caryophyllene, bicyclogermacrene, caryophyllene oxide, germacrene D, spathulenol, and β-elemene are the most abundant. The antimicrobial, anti-inflammatory, antileishmania, antioxidant, antiproliferative, cytotoxic, larvicidal, trypanocidal, and antimalarial activities of essential oils from the Annonaceae species in Brazil have been described in previous research, with the most studies on this topic being related to their antiproliferative or cytotoxic activities. In some studies, it was observed that the biological activity reported for these essential oils was superior to that of drugs available on the market, as is the case of the essential oil of the species Guatteria punctata (Aubl.) R. A. Howard., which showed a trypanocidal effect that was 34 times stronger than that of the reference drug benznidazol.


Introduction
The species of Annonaceae are flowering plants consisting of trees, shrubs, and lianas. These species present a combination of striking characteristics and form one of the most uniform botanical families from both anatomical and structural points of view; they are one of the most primitive families of Angiosperms and belong to the class Magnoliopsida, subclass Magnoliidae, and order Magnoliales [1].
Annonaceae consists of 2106 species and more than 130 genera. The family is concentrated in the tropics, and about 900 species are neotropical, 450 are Afrotropical, and the others are Indomalayan [2]. Annonaceae plays an important ecological role in terms of species diversity, especially in tropical forest ecosystems [3]. In Brazil, the family has confirmed occurrence in all states, with about 380 species being described here, distributed across 32 genera. The Amazon biome contains three quarters of all Annonaceae species, with 268 occurring here. Meanwhile, the Atlantic Forest houses 98 species and the Cerrado has approximately 52 [4].
Some species of Annonaceae are of economic value in the international fresh fruit market, such as Annona cherimola Mill. ("Cherimólia") and Annona squamosa L. ("pinha") [5]. In Brazil, some Annona fruits are highly sought after, such as Annona crassiflora Mart. ("Araticum"), A. squamosa, and Annona muricata L. ("graviola") [3]. In addition, some species are often used as raw materials in the cosmetics and perfumery industries and as medicinal plants [6].
Numerous species of Annonaceae are odoriferous and these fragrances are due to the presence of essential oils (EOs) [7]. In nature, EOs have many important functions, such as attracting insects or allowing allelopathic communication between plants [8]. In addition, they have antibacterial, antiviral, anti-inflammatory, and antifungal properties, among others [9].
According to the review published by Fournier et al. [10], the main volatile constituents of EOs from the Annonaceae species are monoterpene hydrocarbons in fruits and seeds, sesquiterpene hydrocarbons in leaves, and oxygenated sesquiterpenes in bark and roots. After this review (1999), several articles were made available in the literature showing the chemical and biological properties of EOs obtained from Annonaceae species [11][12][13][14]. In this context, the present work aims to carry out a systematic review of the essential oils of the Annonaceae species collected in Brazil in the last ten years, evaluating their chemical compositions and their potential biological activities.

Essential Oils
EOs are present in various aromatic plants, usually found in tropical and subtropical countries. They are obtained from various parts of aromatic plants, including leaves, flowers, fruits, seeds, buds, rhizomes, roots, and bark [9]. Chemically, EOs are mixtures of 20-60 components in varying concentrations, with some compounds found in high concentrations (20-70%) and others in only small amounts. Most of the components of EOs are designated as lipophilic terpenoids, phenylpropanoids, or derivatives of short-chain aliphatic hydrocarbons of low molecular weight, with the first being the most frequent and characteristic constituents. Among these, acyclic mono-and sesquiterpenoids and mono-, bi-, or tricyclics of different chemical classes constitute the majority of EOs, such as hydrocarbons, ketones, alcohols, oxides, aldehydes, phenols, and esters [15].
Several techniques have been used to obtain EOs. These techniques depend on the part of the plants from which the oil will be extracted, the stability of the oil when faced with heat, and the susceptibility of the oil's constituents to undergoing chemical reactions. Some of the techniques commonly used for EO extraction are hydrodistillation, hydrodiffusion, enfleurage, cold pressing, steam distillation, solvent extraction, microwave-assisted process, and carbon dioxide extraction [16][17][18][19][20][21].
Essential oils play an important role in plants and act as antibacterials, antivirals, antifungals, and insecticides and protect plants from herbivores. It is possible to list about 3000 EOs, but only 300 are used in perfumes, and makeup products, sanitary products, dentistry, and agriculture; as preservatives and flavor additives for food; as fragrances for household cleaning products; as industrial solvents; and as natural remedies [22].
In recent years, EOs have gained great popularity in the food, cosmetic, and pharmaceutical industries. Consumers have developed increasing interest in the use of natural products as alternatives to artificial additives or pharmacologically relevant agents.
Medical professionals are more interested in the medicinal properties of EOs, as research has shown the antibacterial, fungicidal, relaxant, stimulant, and antidepressant effects of these volatile substances. Furthermore, EOs are known for their therapeutic properties and are therefore used in the treatment of various infections caused by pathogenic and non-pathogenic diseases [16].
Consumer concerns about chemical preservatives have driven the growing interest in some natural antimicrobials, such as EOs [23]. In the food industry, the current trend to reduce the use of food preservatives in favor of natural alternatives makes EOs and their components viable alternatives for this application [24].
In the food industry, limonene monoterpene, a component of many EOs, is used as a flavoring in the production of desserts, ice cream, and non-alcoholic beverages. Thymol, a crystalline substance with an intense odor that is part of the chemical composition of the EO of thyme (Thymus vulgaris L. and T. zygis L.) and whose content varies between 22% and 50%, is used as a flavoring agent in food products, such as sweets, syrups, and seasoning mixtures [25]. The monoterpene eucalyptol (or cineole) is a colorless liquid with a camphor odor; one of the most abundant sources of 1,8-cineole is Eucalyptus globulus Labill. leaves. The EO of this species is used as a flavoring additive in various food products (such as in meat) as well as in beverages. Due to the fresh odor of cineole, this substance is applied in large quantities in oral care products [25].
In the cosmetics industry, EOs are vital assets, as in addition to providing pleasant aromas for various products they are also able to act as preservatives and active agents and, simultaneously, offer several benefits to the skin. EOs with a high added value include are citrus, lavender, eucalyptus, tea tree, and other floral oils, which are used as fragrances, while linalool, geraniol, limonene, citronellol, and citral are very popular fragrance components used in different cosmetics [26].

Annonaceae Ethnobotanics
Natural products, especially those derived from plants, have been used to help humanity treat various ailments for many millennia [27]. Plants have played an important role in the survival of many human communities. They have been used in many different ways-e.g., as food, medicines, and ornaments; for mystical and religious purposes; as lumber; and for making handicrafts. Knowledge about the use of plant resources has been transmitted from father to son and from ancient civilizations to the present day.
Brazil is formed from the Amazon Forest biome, the Pantanal, savannah and woodland Cerrado, the semi-arid forest Caatinga, pampas fields, and the Atlantic Forest rainforest. These varied biomes reflect the enormous wealth of flora and the greatest biodiversity on the planet. In addition, there is great cultural diversity in Brazil and the use of medicinal plants results from different knowledge built over time [28].
The Amazon region has approximately 55,000 species of plants, most of which are still little known and many of which are used for medicinal and religious purposes [29]. In this region, indians, caboclos, riverside dwellers, rubber tappers, quilombolas, fishermen, small rural producers, and extractivists hold rich knowledge about plants that is passed from generation to generation through oral tradition. It is also known that the cultural diversity of this country positively influences the ethnobotanical use of medicinal plants and in a way increases its biodiversity, given the inclusion of exotic species in the national flora brought by the different peoples who have come to this country [30].
In this context, ethnobotany is a branch of science that analyzes and studies the knowledge of various peoples about the use of plants. It is through this that the profile of a community and its uses of plants are learned, as each community has its own customs and peculiarities, aiming to extract information that may be beneficial regarding the uses of medicinal plants [30].
Several plants of the Annonaceae family are used in folk medicine due to their pharmacological properties, which are attributed to the presence of secondary metabolites of different classes, such as alkaloids, acetogenins, and flavonoids [31].
The Annona muricata L. species, similar to other Annona species, including A. squamosa L. and A. reticulata L., are widely used in traditional medicine against a variety of diseases, especially cancer and parasitic infections. The fruits of A. muricata are used as a natural remedy for diseases such as neuralgia, arthritis, diarrhea, dysentery, fever, malaria, parasites, rheumatism, skin rashes, and worms. In addition, many women eat the fruit to increase their production of breast milk after giving birth. The leaves of this species are used to treat cystitis, diabetes, headaches, and insomnia. Extract made from the leaves has anti-rheumatic and neurologic effects, while the cooked leaves are used to treat abscesses and rheumatism. Crushed seeds are believed to be anthelmintic [32].
Among the medicinal species of Xylopia, X. frutescens Aubl. is found in Central and South America, Africa, and Asia. In Brazil, the plant is popularly known as "embira", "embira-vermelha", and "pau carne", and its seeds are used in folk medicine as a bladder stimulant; to trigger menstruation; and to combat rheumatism, halitosis, caries, and intestinal diseases [33]. The leaves and flowers of the X. laevigata (Mart.) R.E.Fr. species are used to treat painful diseases, heart disease, and inflammatory conditions [34]. Xylopia sericea A. St.-Hil. is an aromatic plant popularly known as pindaíba, pindaíba vermelha, and/or pimento-de-macaco; it is traditionally used as food and as an antimalarial, similar to other representatives of the Xylopia genus [35].
Some species of Guatteria are used in traditional medicine; in Northern Brazil, the seeds of G. ouregou (Aubl.) Dunal are used to treat dyspepsia, stomach pain, and uterine pain [36].
The species Duguetia furfuracea (A.St.-Hil.) Saff. is known as "araticum-seco". In folk medicine, the powder from its seeds is mixed with water for use in the treatment of pediculosis, while an infusion of its leaves and branches is used to treat rheumatism. [37]. Duguetia lanceolata A.St.-Hil., popularly known as pindaíba, beribá, or pinhão, is a perennial species distributed across several states of Brazil; in popular medicine, this plant has been used as an anti-inflammatory, for healing, and as an antimicrobial agent [38]. Table 1 shows the 19 species of Annonaceae used in traditional Brazilian medicine.

Phytochemistry of Annonaceae Essential Oils
The chemical composition of Annonaceae EOs is varied; in general, mono and sesquiterpenes are the most abundant compounds. In this work, were gathered studies on the chemical composition of EOs from Annonaceae, referring to 38 different species with a geographic distribution in the Brazilian territory. Information regarding the major chemical constituents identified (>5%), yield, collection data, and extraction method used for these EOs is shown in Table 2.    Most studies carried out with EOs of Annonaceae occurring in Brazil, published between the years 2011 and 2021, were conducted with species belonging to the genera Annona, Guatteria, and Xylopia (Figure 1). Collections were mostly carried out in the states of Amazonas and Sergipe (Figure 2). To date, about 100 volatile chemical constituents (>5%) have been obtained from the EOs of Annonaceae species collected in Brazil. Among these compounds, α-pinene, β-pinene, limonene, (E)-caryophyllene, bicyclogermacrene, caryophyllene oxide, germacrene D, spathulenol, and β-elemene are the most abundant ( Figure 3).

Biological Activities
It is generally accepted that chemical composition determines the bioactivities of EOs. Annonaceae species have been widely used in folk medicine. Their EOs have been evaluated for several effects, including anti-inflammatory, antitumor, antibacterial, and antioxidant effects [49,61].
A total of 60 studies involving the biological activities of EOs from Annonaceae species collected in the Brazilian territory between the years 2011 and 2021 are described in this work. The bioactivities reported for Annonaceae EOs are represented in Figure 4. Several EOs presented more than one reported biological activity, with the most frequent studies being related to antiproliferative or cytotoxic activities, representing 28% of the results listed here.

Antimicrobian Activity
Annonaceae species are an important source of new antimicrobial agents for combating resistant microorganisms; several EOs of this family had their antimicrobial properties evaluated and showed potentially relevant results.
The EOs from the leaves, branches, and bark of the trunk of Onychopetalum amazonicum were evaluated to determine their antimicrobial activity against four bacterial strains and five pathogenic fungi. The EO from the trunk bark exhibited activity against Staphylococcus epidermidis, E. coli, and Kocuria rhizophila, with an MIC value of 62.5 µg·mL −1 . The observed activity may be associated with the presence of the sesquiterpene allo-aromadendreno (21.2%) [69].
The EOs from two specimens of Guatteria elliptica collected in Paranapiacaba and Caraguatatuba (São Paulo), which have high levels of spathulenol (53.9%) and caryophyllene oxide (40.9%), respectively, showed an inhibition of growth of less than 100% at the highest concentration tested (3 mg.mL −1 ), and MIC values > 3 mg.mL −1 against all the microorganisms tested [9].
The antimicrobial activities of EOs from the leaves, branches, and bark of Bocageopsis pleiosperma were evaluated. The EOs obtained from the bark had a moderate effect against Staphylococcus epidermidis (MIC = 250 µg·mL −1 ), while the other EOs did not show antimicrobial activity [58].

Antioxidant Activity
Antioxidants are widely used in the food industry for a variety of reasons, including preventing oxidation; neutralizing free radicals; preserving food; and enhancing flavor, aroma, or color. As some synthetic antioxidants exhibit carcinogenic effects and can be toxic to nature, researchers have intensified the search for natural antioxidants [79]. In several studies with EOs, the antioxidant activity is related to compounds such as thymol, carvacrol, α-terpinene, β-terpinene, β-terpinolene, 1,8-cineol, eugenol, and linalool, which have an antioxidant activity similar to that of α-tocopherol [80].
The EOs from the leaves of two specimens of Guatteria elliptica, which were collected in Paranapiacaba and Caraguatatuba, showed a low antioxidant potential (EC 50 = 7.24 and 28.68 mg.mL −1 using DPPH assays) for the EOs from Paranapiacaba and Caraguatatuba, respectively [9]. The difference in EC 50 values can be attributed, at least in part, to the different contents of the main compounds present in EOs. Natural products such as EOs are formed by a complex mixture of organic compounds that act synergistically, increasing biological or even antagonistic activity and thus reducing the verified activity [80,81].

Antiproliferative and Cytotoxic Activities
The search for new drugs that show activity against different types of cancer has become one of the most interesting subjects to research in the area of natural products. As a result, several EOs from Annonaceae species and their bioactive constituents were evaluated to determine their antiproliferative and cytotoxic properties.
The cytotoxic, mutagenic, and genotoxic profiles of the EO from Xylopia laevigata leaves were investigated. The results showed that the EO, which is rich in germacrene D (43.6%), bicyclogermacrene (14.6%), (E)-caryophyllene (7.9%), and germacrene B (7.3%), has mutagenic and antiproliferative activities, which can be related to the cytotoxic effect of the main components of the EO [76].
The antitumor activity and toxicity of the EO of Annona leptopetala leaves, which are rich in spathulenol (12.5%) and α-limonene (9.0%), were evaluated. The EO showed antitumor activity in vitro and in vivo, mainly in the leukemia cell line, without major changes seen in the toxicity parameters evaluated [42].
The in vitro cytotoxic activity of the EO from fresh fruits of Xylopia laevigata and its main constituents (limonene, α-pinene, and β-pinene) was evaluated against four tumor cell lines (mouse melanoma, human hepatocellular carcinoma, human promyelocytic leukemia, and chronic myelocytic leukemia) and non-tumor cells (human peripheral blood mononuclear cells). Neither the EO nor its major constituents showed cytotoxic activity (IC 50 > 25.0 µg·mL −1 ) [77].
The antitumor activity and toxicity of Xylopia langsdorffiana EO, which is rich in α-pinene (34.5%) and limonene (31.7%), were evaluated. The EO was found to cause in vitro and in vivo growth inhibition in tumor cells, without major changes seen in the toxicity parameters evaluated [12].
The larvicidal activity of the EOs of Guatteria blepharophylla, Guatteria friesiana, and Guatteria hispida was tested against A. aegypti larvae; the lethal concentrations of LC 50

Trypanocidal and Antimalarial Activities
Chagas disease, also known as American trypanosomiasis, is caused by the protozoan parasite Trypanosoma cruzi. With a complex pathophysiology and dynamic epidemiological profile, this disease remains an important public health concern and is an emerging disease in non-endemic countries. For its etiological treatment in both the acute and chronic phase, there are two main drugs for the treatment of the disease: benznidazole and nifurtimox [83].
The EOs of Bocageopsis multiflora, Duguetia quitarensis, Fusaea longifolia, and Guatteria punctata were evaluated to determine their trypanocidal activity. The results showed that these EOs were active at the concentrations tested. The EO of G. punctata was the most active, with an IC 50 = 0.029 µg·mL −1 , being 34 times more active than the reference drug benznidazole. The authors reported that the strong activity observed for this species can be attributed to the presence of germacrene D (19.8%) and (E)-caryophyllene (8.4%) in the composition of the EO of G. punctata [57].
The insecticidal, antifungal, and antiaflatoxigenic activities of Duguetia lanceolata EO were evaluated in stored grain spoilage agents. The main constituents of this EO were β-bisabolene (56.2%) and 2,4,5-trimethoxystyrene (19.1%). The results suggested that the EO has promising grain protection properties against Sitophilus zeamais and Zabrotes subfasciatus, showing a comparable activity to that of a deltamethrin-based insecticide (positive control) [62].

Methodology
In this work, a systematic review was carried out to show studies published between the years 2011 and 2021 on the chemical composition and biological properties of EOs of Annonaceae species collected in Brazil, which can serve as a reference for the future research and use of these species. In addition, a section on the ethnobotanical use of these species was also inserted in order to express their importance in traditional Brazilian medicine.
Pubmed, WOS, Scopus, and Scielo were used as virtual databases to search for the peer-reviewed articles that were used to compose the present work. The keywords used for the research were: "Annonaceae", "óleos essenciais", "essential oils", "atividades biológicas", "biological activities", "ethnobotany", and "medicinal use".
The selection of manuscripts to compose this review was based on studies published in peer-reviewed journals; in addition, a careful review was carried out to confirm whether the species studied in the published articles were of Brazilian origin, as reported at www.floradobrasil.jbrj.gov.br (accessed on 29 September 2021). The quality of the reviewed studies is well known-only peer-reviewed articles were included, and we considered only papers in the English language for gathering data regarding the chemical composition and biological properties of EOs of Annonaceae species. However, for the section on the ethnobotanical use of these species, data published in the Portuguese language were also considered. Theses, Ph.D. dissertations, and unpublished articles were not included in this review. Therefore, we focused on phytochemical and/or in vitro, in vivo, and in animal studies, with the aim of providing up-to-date information on the biological properties of EOs from Annonaceae species collected in Brazil.
In the science direct database, a total of 1888 papers were published, including review and research articles, chapters, and books. The main periodicals were Journal of Ethnopharmacology (270); Biochemical Systematics and Ecology (49) (15); and Food Chemistry (14). By analyzing the numbers of papers published in the two databases, we were able to identify the importance of the topic for the scientific community. Furthermore, this is the first report on a literature review of the Annonaceae species found in Brazil.

Conclusions
Studies relating to natural products are important, as they can be sources of new chemically active molecules with potential applications in diverse human activities. In the present review, we note that Brazilian Annonaceae species can be sources of bioactive compounds such as α-pinene, β-pinene, limonene, (E)-caryophyllene, bicyclogermacrene, caryophyllene oxide, germacrene D, spathulenol, and β-elemene, which are present in the essential oils of the plants. Furthermore, the potential use of these EOs in terms of their antimicrobial, antiproliferative, cytotoxic, larvicidal, antioxidant, anti-inflammatory activities, etc., was also described. In some cases, it was possible to observe that the biological activity reported for the essential oil (EO) was superior to that of drugs available on the market, such as the EO of the species Guatteria punctata, which showed a trypanocidal effect that was 34 times more active than that of the reference drug benznidazole. This and other studies demonstrate that it is necessary to expand research to the EOs of Annonaceae, especially species occurring in Brazil, since studies on these are still scarce and there is a considerable number of Annonaceae species that are unexplored in terms of their content, chemical composition, and the biological activities of their EOs. In addition, the ethnobotanical use of some plants of this family was demonstrated, and it was found that the most cited species in folk medicine belong to the Annona genus.