1. Introduction
The Annonaceae family is widely distributed in subtropical and tropical regions. This family comprises a great diversity
[1], with 180 genera and more than 3000 species. It stands out as the most prominent family in the Magnoliales order. The presence of many primitive morphological features and the ability to survive mass extinctions have characterized Annonaceae species as “living fossils”
[2].
The botanical characteristics of the Annonaceae family may differ from species to species, depending on the origin, climate, and topography. This diversity can range from trees to shrubs to perennial vines, with elongated cylindrical intracellular resin channels and a broad and well-developed septate pith in the stems. The aromatic flowers bloom before they are fully developed. They are axillary, singular or grouped, hermaphroditic, and regular in shape. The fruits are made up of bunches of berries and are widely consumed due to their high nutritional value
[2][3].
Annonaceae are very famous due to their wide use in traditional medicine. Several pharmacological studies have been conducted related to the medicinal use of the Annonaceae family, such as its use against pain, arthritis, rheumatism, and neuralgia, and in weight loss
[4], anthelmintic and malaria
[5], and antiplatelet
[6] treatments.
This family also stands out for its wide variety of chemical constituents belonging to various phytochemical groups. Studies report the presence of cyclopeptides
[7], flavonoids
[8][9], terpenoids
[10][11], lignans
[12][13], steroids
[14], tannins
[8], volatile oils, resins
[12], many alkaloids
[15][16], and acetogenins
[17]. Commercially, the most important Annonaceae are the species of the genus
Annona [18]. Among the species of this genus,
wresearche
rs can highlight plants such as pinha, marolo, graviola
[19], araticum
[20], marolinho
[21], and bananinha
[22].
2. Flavonoids are Mostly Found in Plant Parts Belonging to the Annona Genus
Araticunzeiro plants are heterogeneous in terms of stem diameter (10.4 cm), plant height (3.7 m), and production (average of six fruits per plant), with production being the most variable characteristic
[23]. The tree produces fruits with acceptable sensory characteristics, as well as significant nutritional and functional potentials
[24], and their fruit is the most studied part of this plant. In this vein, the Araticum (
Annona crassiflora Mart.) (
Figure 1) is a fruit-bearing species native to the Brazilian Cerrado biome. When ripe, the araticum fruit has a flattened circular shape, rigid epicarp, and brown coloration
[25]. The fruit has an oval or rounded shape, weighing from 0.5 to 4.5 kg, and its seeds are dark brown with a flat oval shape
[26]. The harvest of this fruit takes place between September and April
[27][28] and provides a great nutritional richness and a wide diversity of phytochemicals, such as carotenoids, folate, flavonoids, ascorbic acid, and vitamins A and E
[29][30]. The fruit has reduced total titratable acidity (0.51 g citric acid/100 g) and pH (4.64) and high levels of total soluble solids (13 Brix) and moisture (74.30%), allowing its use in desserts such as sweets, jams, and yogurts. The fruit pulp contains high levels of carbohydrates (18.65%), lipids (3.78%), and energy value (113.65 kcal/100 g), and relatively low amounts of proteins (1.27%)
[24].
Figure 1.
Araticum (
Annona crassiflora
Mart.). Source: Illustration by Ribeiro, L.V., 2022.
The fruit and parts of the tree (leaves, stem, and peel) are the subjects of numerous research works due to their content of potentially bioactive compounds
[31]. The biological activities of infusions, decoctions, or extracts of
A. muricata leaves are related to their content of bioactive compounds, and these leaves are considered a rich source of bioactive compounds with potential uses in the formulation of therapeutic drugs or nutraceutical foods
[32]. The fruit of the gravioleira tree, graviola (
Annona muricata) also known as soursop (
Figure 2), is a native fruit of North and South America and is currently distributed in subtropical and tropical regions. Its fruits are large and green in color
[33]. The fruiting period of graviola generally occurs throughout the year; however, depending on the altitude, there are more defined seasons
[34]. This species has a high concentration of secondary metabolites, such as flavonoids, terpenoids, alkaloids, and some lactones, in addition to minerals such as potassium, calcium, sodium, iron, and magnesium
[35]. According to Fuentes (2021), in a bibliographic survey, the nutritional composition of soursop ranges from 55.4 to 81.83 (kcal) for total energy, 80.48–83.2% for moisture content, 0.69–1.10% for protein, 0.20–0.97% for lipid content, 12.50–18.23% for soluble carbohydrates, and 4.83–5.76% for dietary fiber content
[36].
Figure 2.
Graviola (
Annona muricata
). Source: Illustration by Ribeiro, L.V., 2022.
The atemoya tree a hybrid plant resulting from the cross between cherimoya (
A. cherimola Mill.) and pinha (
A. squamosa L.)
[37] maintains the good qualities of both plants. The atemoya fruit (
Annona cherimola Mill. ×
Annona squamosa L.) (
Figure 3) has a small number of seeds, better conservation after harvest, absence of cracks and resistance to weeds, and improved biological control
[38]. When pollinated, its shape is heart-shaped, ovate, or conical. The surface of the atemoya is smooth or may present prominence, and the pulp of this fruit has a white color. Regarding its phytochemicals, reports in the literature place the greatest emphasis on the class of acetogenins
[39]. This fruit has approximately 65.18% moisture, 0.55% lipids, 1.24% proteins, 2.04% ash, 31.99% carbohydrates, and 1.55% total fiber
[38]. Its leaves and stems stand out for their total phenol and flavonoid levels, as well as their antioxidant and antimicrobial activities
[40].
Figure 3.
Atemoya (
Annona cherimola
Mill. ×
Annona squamosa
L.). Source: Illustration by Ribeiro, L.V., 2022.
The pine tree (
Annona squamosa) is characterized by its small size, pivoting roots, and elongated leaves. These features also have several ramifications. The height of this plant varies from three to six meters, its flowers are small and can be isolated or in the form of a bunch, and its fruits are flat, ovoid, or heart-shaped
[41]. The
Annona squamosa L. fruit (
Figure 4), popularly known as “ata”, “pinha”, or “fruta-do-conde”, is widely used for fresh consumption
[42]. The fruit is widely known and consumed according to its medicinal and nutritional properties and its pleasant taste. It stands out for the presence of health-related components such as vitamins (A, B, C, E, and K1), antioxidants, polyunsaturated fatty acids, and the presence of essential minerals. In addition, this plant has a variety of compounds responsible for various activities such as the inhibition of insect attack, antimalarial, cytotoxic, immunosuppressive, and anti-HIV properties, and antiplatelet activity
[43]. This fruit has an average caloric content of 95.3 (kcal), 70% moisture, 1.23% proteins, 0.21% lipids, 22.8% soluble carbohydrates, and 1.02% dietary fiber
[44].
Figure 4.
Pinha (
Annona squamosa
L.). Source: Illustration by Ribeiro, L.V., 2022.
Annona leptopetala is considered an endemic Brazilian tree. It is a woody, deciduous species with a high representation. This species’ reproductive and vegetative development is associated with the availability of water in nature
[45][46]. The fruit (
Figure 5), popularly known as “bananinha”
[47], is the second most abundant species in the Brazilian Cerrado
[46]. This species is unique in the genus, which has red flowers. From 2 to 9 m in height, its tree has elliptical to ovate leaves, with yellow, orange, or red apocarpous fruits, its flowering and fruiting ranges from November to April
[47]. Bananinha is indicated in traditional medicine for the treatment of inflammation and tumors
[48], and for its larvicidal potential
[49], as well as its modulating effect on bacterial resistance to norfloxacin, in addition to a considerable antitumor effect in vivo
[50]. The phytochemical study points to the presence of aporphine and tetrahydro-protoberberine alkaloids, in addition to acetogenins and a xanthone
[51].
Figure 5.
Bananinha (
Annona leptopetala
). Source: Illustration by Ribeiro, L.V., 2022.
Annona coriacea is considered an evergreen shrub or small tree
[21]. Popularly known as “marolinho” and “cabeça-de-negro”, the species
Annona coriacea occurs in some states of northeastern Brazil in an area of caatinga
[52]. The height of this tree species varies from 3 to 18 m, with simple, obovate leaves, glabrous on the ventral surface, the base is often chordate and the margin wavy; the flowers are solitary, terminal, and bushy, with fleshy petals ranging in color from orange to orange-pink
[21][53]. The fruit (
Figure 6) is globular or elongated, white pulp, watery, soft, smooth rind, or fleshy scales. In Brazil, it is popularly used against chronic diarrhea, malaria, helminths, and leishmaniasis
[53]. Many biological activities are described for
A. coriacea, including insecticidal activity
[50][54], antiprotozoal
[55], phytotoxic
[56], cytoprotective
[57], antiproliferative, cytotoxic, and enzymatic inhibitory effects
[58]. Phytochemical studies report the presence of polyphenols
[57], alkaloids
[59], and volatile compounds
[60].
Figure 6.
Marolinho (
Annona coriácea
). Source: Illustration by Ribeiro, L.V., 2022.
Several reports in the literature show that such varieties are correlated with antitumor, antioxidant, and antiparasitic activities, as well as antimicrobial and anti-inflammatory effects
[24][60][61]. Anaya-Esparza and collaborators (2020) show in a bibliographical review that
Annona species are widely used in folk medicine, demonstrating great importance. Their traditional use is associated with treating fever, diarrhea, dysentery, hematuria, urethritis, asthma, and parasitic and hepatic diseases, in addition to exerting antispasmodic, laxative, antiemetic, antisudorific, antitussive, antiflu, and antidepressant effects
[62]. Several of these species are well known due to their pharmacological properties and benefits to human health, mainly attributed to the presence of flavonoids, the main bioactive constituent found within them
[18].
Phenolic compounds belong to a large compound class that includes both simple and complex structures with at least one aromatic ring. WResearchers can highlight several derived classes of phenolic compounds and their basic skeleton: C6 simple phenols, benzoquinones; C6-C1 phenolic acids; C6-C2 acetophenones and phenylacetic acids; C6-C3 phenylpropanoids; C6-C3 coumarins; C6-C4 naphthoquinones; C6-C1-C6 xanthones; C6-C2-C6 stilbenes and anthraquinones; C6-C3-C6 flavonoids and isoflavonoids; (C6-C3)2 lignans; (C6-C3-C6)2 diflavonoids; (C6)n plant melanins; (C6-C3)n lignins; (C6-C1)n atemoya tannins; (C6-C3-C6)n condensed tannins. Figure 7 shows the simplified biosynthetic route of phenolic compounds, highlighting flavonoids.
Figure 7.
Simplified biosynthetic pathway of phenolic compounds. Source: Authors, 2022.
Flavonoids are part of the most relevant and diversified group of phenolic compounds among natural products
[63] and are widely distributed in the plant kingdom
[64][65]. They stand out for having great economic attractiveness due to their various properties beneficial to health
[66]. In the
Annona genus, the most common flavonoid classes are quercetin-3-
O-rhamnoside, luteolin-7-
O-glucoside, kaempferol-3-
O-galactoside, and their derivatives
[67].
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