Bioactive compounds and functional potential of pequi (Caryocar spp.), a native Brazilian fruit: a review

L.R.O. Torres^a,b,*, F.C. Santana^a, F.B. Shinagawa^a and J. Mancini-Filho^a

^aDepartment of Food Science and Experimental Nutrition, University of São Paulo, Av. Prof. Lineu Prestes, 580, Bloco 14, Cidade UniversitÁria, 05508-900, São Paulo, Brazil.

^bFederal Institute of Education, Science, and Technology of Maranhão, Rodovia MA 349 (Caxias/Aldeias Altas), Km 2, s/n, Gleba Buriti do Paraíso, Povoado Lamego, Zona Rural, 65.600-970, Caixa Postal 77, Caxias, Maranhão, Brazil.

*Corresponding author: lucillia.rabelo@ifma.edu.br

1. INTRODUCTIONTOP

Fruits and vegetables are important components of a diversified and healthy diet due their numerous bioactive components such as carotenoids, polyphenols, fibers, hydrosoluble vitamins, and minerals. Those components are associated with improved overall health and the prevention of several major chronic and neurodegenerative diseases and cancers (Yuan et al., 2015; Kishimoto et al., 2013; Pérez-Jiménez et al., 2010; Dauchet et al., 2009; WHO, 2003).

The mechanisms of action of bioactive compounds are not totally elucidated and vary between cells and organisms, but in general, they are associated with antioxidants as well as anti-inflammatory, antitumor, antigenotoxic, and antimicrobial properties (Li et al., 2016). Since an increased consumption of fruits is one of the strategies to promote a healthy nutrition and beneficial eating habits, it is crucial that information about the dietary composition and specific benefits is available not only for the most frequently consumed foods, but also for those farmed and consumed in small communities scattered around the world, as is the case of the pequi fruit.

The pequi belongs to the Caryocaraceae family, which is widely distributed throughout Central and South America and comprises 25 species divided into two genera (Caryocar and Anthodiscus) (Ascari et al., 2013). According to De Oliveira et al. (2008), several species of the genus Caryocar are known as pequi and other derivatives such as piqui, piquiÁ, and piqui-vinagreiro. However, other authors describe pequi as a popular denomination for the fruits of C. brasiliense, which grows in the Central-West Region of Brazil and the western part of the state Minas Gerais; while “piqui” would be considered the fruits of C. coriaceum, which grows in northeastern Brazil; and “pequiÁ” the fruits of C. villosum, which grows in the Amazon Region (Geocze et al., 2013; Costa et al., 2011; De Oliveira et al., 2010; Lima et al., 2007; Segall et al., 2006; Marx et al., 1997). These three species represent the main source of income for many small communities in Brazil (Leite et al., 2017; Guedes et al., 2017; Figueiredo et al., 2016; Costa et al., 2011; De Morais Cardoso et al., 2013; Marx et al., 1997).

The C. brasiliense is a drupaceous, spherical, and green fruit, presenting one to four segments (pyrenes). Its structure is composed of a green epicarp (very thin peel), an external mesocarp (non-­edible), and an internal mesocarp (edible, light-yellow, pulpy, rich in oil), which includes a layer of thin and rigid endocarp (approximately 2−5 mm) with spines and a white kernel (also called seed, nut, or almond) (Faria-Machado et al., 2015) (Figure 1). Although sparsely described, the fruits from other species are structurally similar to those of C. brasiliense (Marx et al., 1997).

The external mesocarp makes up the largest part of the pequi fruit, but it is usually thrown away since it is non-edible (Ascari et al., 2010). Both the internal mesocarp (pulp) and the almond are an excellent sources of lipids and proteins, appreciated in culinary applications as color and flavoring agents. The pulp can be used in the preparation of juices, ice cream, jelly, jam and liquors, for fresh consumption, or for the preparation of typical meals; the almond is used as a culinary ingredient in a tamale-like cake or in condiments or is consumed fresh (Torres et al., 2016b; Ascari et al., 2013; Ascari et al., 2010; Roesler et al., 2008; Segall et al., 2006). The pulp and the almond are often used as a source of edible oil, generating income for the communities involved (Roesler et al., 2008; Afonso et al., 2015). In this way, both pulp and almond are routinely used for therapeutic purposes by the regional population to treat e.g. tumors, respiratory diseases, wound lesions, gastric and inflammatory diseases, muscle pain, and chronic arthritis (Miranda-Vilela et al., 2014; Costa et al., 2011; Da Silva Quirino et al., 2009; Miranda-Vilela et al., 2008).

Pequi presents some beneficial biological properties, such as wound-healing and anti-inflammatory activities, antimicrobial activity, and protection against genomic and oxidative damage, among others (Colombo et al., 2015; Costa et al., 2011; De Oliveira et al., 2010; Da Silva Quirino et al., 2009; Passos et al., 2002). These biological properties, along with the nutritional and health benefits, are mainly attributed to the presence of monounsaturated fatty acids (MUFA) and phytochemicals (Aguilar et al., 2011; Roesler et al., 2008).

Overall, there is a lack of published and detailed information about the phytochemical composition and the potential for the use of the fruits of the genus Caryocar, especially concerning the species C. coriaceum and C. villosum with negative repercussions for the improvement of the current system of exploitation (Barreto et al., 2009; De Oliveira et al., 2008). Thus, the objective of this review is to highlight the potential of pequi (pulp and almond), more specifically the oil produced from these parts, as a source of functional compounds by presenting the differences found amongst the three more commercially-important species from the genus Caryocar. In addition, an attempt was made to evaluate new findings on biological activities. In each of the following sections, the information was ordered first in terms of species: C. brasiliense, C. coriaceum, and C. villosum, and then for data from the pulp and almond, when available.

2. NUTRITIONAL COMPOSITIONTOP

Caryocar spp. is a good source of MUFA, fiber, minerals, and bioactive compounds (Ramos and Souza, 2011; Lima et al., 2007; Marx et al., 1997), although there is a lack of information in the literature about the macronutrient contents and minor compounds, mainly from the almonds of the species C. coriaceum and C. villosum. The contents of these components vary according to the species, environmental conditions, and type of analysis, as shown in Table 1.

Both edible parts of C. brasiliense, the pulp and the almond, are primarily a source of vegetable oils (Ascari et al., 2013; Aguilar et al., 2011). The C. brasiliense pulp contains lipids, water, carbohydrates, proteins, and minerals, along with a high fiber content (Table 1) (Macedo et al., 2011; Vera et al., 2007; Lima et al., 2007). Additionally, C. brasiliense pulp is a potential source of potassium (K) (560 mg/100 g), magnesium (Mg) (174 mg/100 g), copper (Cu) (0.9 mg/100 g), and manganese (Mn) (1.4 mg/100 g) and contains zinc (Zn) (2.5 mg/100 g), calcium (Ca) (161 mg/100 g), phosphorus (P) (162 mg/100 g), iron (Fe) (1679 mg/100 g), and nitrogen (N) (1148 mg/100 g) (data expressed on dry basis) (db) (Mariano-da-Silva et al., 2009).

The lipid content in the almond of C. brasiliense is higher (30–40%) compared to that in the pulp. In addition, the almond seems to contain more protein (80%) and minerals (80%) (Table 1) (Macedo et al., 2011; Lima et al., 2007) and is rich in Mg (452.1 mg/100 g), selenium (Se) (0.0014 mg/100 g), and Zn (7.4 mg/100 g) (db). The amount of Zn present in the roasted C. brasiliense almond is higher than that of any other almond or nut reported in the literature, reaching 67% of the dietary reference intake for adults (De Oliveira Sousa et al., 2011).

The pulp of C. coriaceum contains water, ­lipids, ­carbohydrates, protein, fiber, and minerals (Table 1) including K (140.3–460.4 mg/100 g), Mg (36.1–124.6 mg/100 g), Cu (0.2–7.2 mg/100 g), Mn (1.1–2.5 mg/100 g), Zn (0.7–2.2 mg/100 g), Ca (30.8–102.0 mg/100 g), P (17.3–83.5 mg/100 g), Fe (0.4–3.1 mg/100 g), and Na (1.2–4.7 mg/100 g) (data expressed on a wet basis) (wb) (Ramos and Souza, 2011; Oliveira et al., 2010). Furthermore, the C. coriaceum almond contains more protein (90%), minerals (30%) and lipids (30%) compared to the pulp (Table 1). The mineral contents of the almond are as follows: Ca (51.7–163.6 mg/100 g), K (374.1–965.7 mg/100 g), Mg (301.1–560.0 mg/100 g), Cu (0.5–2.9 mg/100 g), Mn (2.0–4.8 mg/100 g), Fe (0.9–3.7 mg/100 g), P (391.2–1008.4 mg/100 g), and Zn (2.3–6.0 mg/100 g) (wb) (Ramos and Souza, 2011; Oliveira et al., 2010).

According to Chisté and Mercadante (2012), C. ­villosum pulp contains water, lipids, carbohydrates, proteins, and ashes (Table 1). Marx et al. (1997) found the minerals Ca (83.0 mg/100 g), Mg (52.0 mg/100 g), P (41.0 mg/100 g), Se (0.7 mg/100 g), Fe (0.6 mg/100 g), Zn (0.5 mg/100 g), and Mn (0.3 mg/100 g) (db). No detailed descriptions were found regarding the nutritional composition of C. villosum almond.

Comparing the average values of the pulps of the different species presented in Table 1, C. coriaceum pulp has higher amounts of minerals (70%), carbohydrates (70%), and linoleic acid (30%), while C. brasiliense pulp appears to present more fiber (20%) and protein (18%). The C. coriaceum almond appears to be richer in ­moisture (50%), carbohydrates (50%), fiber (40%), and protein (20%) than the C. brasiliense almond, which appears to contain more minerals (18%) and linoleic acid (40%).

2.1. Fatty acidsTOP

The pulp and almond of the Caryocar species are rich in lipids, as seen in the previous section, and have a similar fatty acid (FA) composition, with a predominance of unsaturated fatty acids (UFA) (Aguilar et al., 2011).

The C. brasiliense pulp has a high content of MUFA, with oleic acid (C18:1) as the main component, followed by linoleic acid (C18:2) and palmitoleic acid (C16:1). Saturated fatty acids (SFA) are also present in high amounts, mainly in the form of palmitic acid (C16:0), followed by stearic acid (C18:0) (Mariano et al., 2009; Garcia et al., 2007; Lima et al., 2007; Facioli and Gonçalves, 1998). All values are presented in Table 1.

Therefore, the C. brasiliense almond and pulp are composed primarily of oleic and palmitic acids, with minor amounts of linoleic, stearic, myristic, palmitoleic, and linolenic acids (Torres et al., 2016b; Lima et al., 2007). According to Faria-Machado et al. (2015), despite similarities in the major FA, it is possible to distinguish pequi pulp oil from pequi almond oil based on the content of linoleic acid. This statement could be confirmed by the data stated in Table 1, showing that the average linoleic acid values of the almonds of both C. brasiliense and C. coriaceum are higher (70 and 38%, respectively) when compared to their respective pulps.

The fatty acid profiles of C. coriaceum and C. villosum pulps are similar to those observed for C. brasiliense (Saraiva et al., 2011a; De Oliveira et al., 2010; Da Silva Quirino et al., 2009; Marx et al., 1997; Figueiredo et al., 1989). In addition, C. coriaceum almonds have a similar oleic and palmitic acid-rich composition (Table 1) (De Oliveira et al., 2010; Figueiredo et al., 1989). The chemical structures of the main FAs found in pequi are shown in Figure 2.

The distributions of FAs in terms of triacylglycerol (TAG) molecules have been described previously. Segall et al. (2006) used a mixture of pulp and almond oils (C. brasiliense) for the evaluation of the TAG composition by liquid chromatography-mass spectrometry (LC-MS) and found three major peaks: trioleoyl glycerol (OOO), palmitoyl dioleoyl glycerol (POO), and dipalmitoyl oleoyl glycerol (POP). Other TAGs, such as dioleoyl ­stearoyl glycerol (OOS), were present in small amounts. In addition, the authors report that the composition of pequi oil may have potential application in the food industry (i.e., less expensive chocolate substitute upon fractionation) and can be used without fractionation or hydrogenation for frying and cooking because of its low content of polyunsaturated fatty acids and a high content of oleic acid.

Guedes et al. (2017) reported that pequi oil is a source of POP, a TAG of great interest in the food industry. Its high contents of C18:1 and C16:0 is interesting for the food industry, either for cosmetic or oleochemical uses, and the TAG composition indicates its potential use as cocoa butter substitute.

3. PHYTOCHEMICAL COMPOUNDSTOP

The literature does not provide complete information on the phytochemical composition of fruits of the Caryocar species, specially for the almond, as shown in Table 2. Among the compounds that have been identified in this genus, carotenoids are the most important ones (Torres et al., 2016b; Barreto et al., 2009; Lima et al., 2007; Marx et al., 1997).

3.1. CarotenoidsTOP

Several studies have identified C. brasiliense pulp as a source of carotenoids (Table 2), with amounts being comparable to those in papaya and guava, which are caroteinoid-rich fruits. The carotenoids β-carotene, lycopene, ζ-carotene, cryptoflavin, β-cryptoxanthin, anteraxanthin, zeaxanthin, mutatoxanthin, violaxanthin, lutein, and neoxanthin have already been identified in the fruit pulp (De Morais Cardoso et al., 2013; Machado et al., 2013; Ribeiro et al., 2012; Lima et al., 2007; Oliveira et al., 2006; Azevedo-Meleiro and Rodriguez-Amaya, 2004; Ramos et al., 2001), see Figure 3.

Beta-carotene, the most important pro-vitamin A found in fruits, is the main carotenoid present in C. brasiliense pulp according to Ribeiro et al. (2012) and Oliveira et al. (2006) (25 mg/100 g oil and 6.3 to 11.4 mg/100 g pulp, respectively). The consumption of 100 g of cooked C. brasiliense pulp would supply 57.3 and 66.9% of the recommended dietary allowance (RDA) of vitamin A for adult men and pregnant women, respectively (De Morais Cardoso et al., 2013). However, different findings were observed by Azevedo-Meleiro and Rodriguez Amaya et al. (2004), who reported violaxanthin, lutein, and zeaxanthin as the main carotenoids of C. brasiliense pulp (values not provided). On the other hand, Ramos et al. (2001) reported larger amounts of β–cryptoxanthin (9.4 mg/100 g) and anteraxanthin (7.9 mg/100 g) (wb) and stated that the total pro-vitamin A found in pequi pulp is rather low.

Variations in carotenoid contents can be attributed to environmental conditions during fruit production, to the state of ripeness, and to the extraction procedure, among others (De Morais Cardoso et al., 2013). The contradictions regarding the pro-vitamin A content of C. brasiliense pulp indicate that further research is necessary to identify and quantify the amount of the carotenoids present in this fruit from different regions. It is important to mention that additional information, such as sampling methods, fruit origin, and species identification, are factors that must be considered by researchers during the planning and execution of their studies.

With respect to the C. brasiliense almond, Lima et al. (2007) showed a lower total carotenoid content when compared to the pulp (Table 2). This result was in agreement with Torres et al. (2016b) for C. brasiliense almond oil (up to 0.3 mg/100 g).

No descriptions were found regarding the carotenoid composition of the in natura C. coriaceum pulp or almond. However, Souza et al. (2013) found carotenoid values of 0.3 mg/100 g pulp (wb) for C. coriaceum pulp cut into slices and packaged under vacuum.

Several studies have shown the presence of carotenoid in C. villosum pulp, as presented in Table 2. (Almeida et al., 2013; Almeida et al., 2012; Chisté et al., 2012; Chisté and Mercadante, 2012; Barreto et al., 2009). Chisté and Mercadante, (2012) reported that the main identified carotenoids in C. villosum pulp were all-trans-antheraxanthin (3.4 mg/100 g pulp), followed by all-trans-zeaxanthin (2.9 mg/100 g pulp) and the lutein-like carotenoid (2.8 mg/100 g pulp) (db). Antheraxanthin and zeaxanthin were the major carotenoids identified in C. villosum pulp by Almeida et al. (2012), corresponding to 24 and 19% (db) of the total carotenoid content, respectively.

3.2. Phenolics TOP

Regarding the total phenolic compounds in C. brasiliense, the levels were higher in the pulp than in the almond (Lima et al., 2007) (Table 2). Besides that, the almond oil, according to Torres et al. (2016b), contains higher values (up to 392.0 mg ­gallic acid equivalents (GAE) per 100 g of oil).

The phenolic composition of the in natura C. coriaceum pulp and almond is not described in the scientific literature, but Souza et al. (2013) found 69.6 mg/100 g pulp (wb) of phenolic compounds in C. coriaceum pulp cut into slices and packaged in vacuum-sealed bags.

Chisté and Mercadante (2012) and Almeida et al. (2012) found 58.9 and 236.2 mg/100 g pulp (db) of phenolics, respectively, in C. villosum pulp (Table 2). Characterization of the phenolic compounds in C. villosum pulp showed gallic and ellagic acids as the main ones (Figure 4) (Yamaguchi et al., 2017; Almeida et al., 2013; Almeida et al., 2012; Chisté et al., 2012; Chisté and Mercadante, 2012), with values of 73.2 and 40.1 mg/100 g pulp (db), respectively, corresponding to 31 and 17% of the total amount of phenolic acids (Almeida et al., 2012).

3.3. Vitamin ETOP

Studies determining vitamin E levels in Caryocar spp. are scarce. De Morais Cardoso et al. (2013) found vitamin E in cooked C. brasiliense pulp (0.2 mg/100 g pulp) (wb), with values being higher than that found in banana but lower than for kiwi and avocado, which are high in vitamin E. The isomers identified by these authors were α-tocopherol (0.06 mg/100 g), α-tocotrienol (0.05 mg/100 g), γ-tocopherol (0.04 mg/100 g), and γ-tocotrienol (0.02 mg/100 g).

Previous investigations revealed the presence of tocopherols in C. brasiliense almond oil (13.3 to 19.2 mg/100 g oil), with α-tocopherol and γ-tocopherol accounting for 67 and 48% of the total tocopherols, respectively (Torres et al., 2016b) (Figure 5).

According to Almeida et al. (2012), C. villosum pulp contains 1.2 mg tocopherols/100 g pulp (db) (Table 2), with α-tocopherol accounting for 100%.

3.4. Vitamin C and phytosterolsTOP

According to Machado et al. (2013) and Barreto et al. (2009), C. brasiliense and C. villosum pulps have a vitamin C (ascorbic acid or ascorbate) content of 6.6 and 5.9 mg ascorbic acid/100 g (wb), respectively (Table 2). However, cooked C. brasiliense pulp presented a vitamin C content greater than that found in the fresh pulp of pequi (14.3 mg/100 g) (wb) (De Morais Cardoso et al., 2013). The authors suggest that the differences may be related to fruit origin.

Caryocar brasiliense almond oil has up to 96.5 mg phytosterols/100 g (Table 2), which is within the range of most oils (100 to 500 mg/100 g) (Torres et al., 2016b; Gunstone and Padley, 1997). The main phytosterols found in this oil were stigmasterol (48.2–65.3 mg/100 g), β-sitosterol (20.5–27.9 mg/ 100 g), and campesterol (4.8–3.8 mg/100 g) (Torres et al., 2016b) (Figure 5).

According to Marx et al. (1997), the total phytosterol content in C. villosum pulp is 580 mg/100 g pulp (db) (Table 2), with 7, 25-stigmastadienol (195.7 mg/100 g), β-sitosterol (129.7 mg/100 g), stigmasterol (80.2 mg/100 g), and squalene (63.8 mg/100 g) being the main compounds.

Based on these findings, pequi fruits have considerable amounts of nutrients and bioactive compounds that are associated with protection in many biochemical processes underlying the development of diseases. Therefore, this review also focusses on studies that have shown the main biological effects of these compounds after fruit intake.

4. BIOLOGICAL EFFECTS OF CARYOCAR FRUIT CONSUMPTIONTOP

Scientific evidence for popular knowledge refers to several healthy effects of the consumption of fruits of the Caryocar spp. Commonly, C. brasiliense fruits are used to treat several diseases, including tumors, several respiratory diseases, and ophthalmic problems (Miranda-Vilela et al., 2014; Miranda-Vilela et al., 2008), while fruits of C. coriaceum are popularly used to treat many types of afflictions, such as wound lesions, gastric and inflammatory diseases, respiratory tract infections, muscle pain, and chronic arthritis (Costa et al., 2011; Da Silva Quirino et al., 2009). As stated earlier, most of these effects are attributed to the oil that is extracted from the pulp of the Caryocar spp. due to the fact that it is routinely used for therapeutic purposes, but some studies have also reported positive effects of both the pulp and the almond (Aguilar et al., 2011; Roesler, et al., 2007) (Table 3).

4.1. Anticancer activityTOP

Evidence suggests that cancer cells are under increased oxidative stress compared with normal cells, and this is associated with oncogene-induced transformation, increased metabolic activity, mitochondrial malfunction, and increased generation of reactive oxygen species (ROS) (Miranda-Vilela et al., 2014). Many cancer-chemopreventive agents possess antioxidant potential, and biological antioxidants contain bioactive phytochemicals that may play a vital role in protecting cells from oxidative stress (Miranda-Vilela et al., 2011). Animal studies have demonstrated that the administration of pequi could improve the antioxidant system and consequently decrease the advance of carcinogenesis (Miranda-Vilela et al., 2014; Almeida et al., 2012; Miranda-Vilela et al., 2011).

Previous results for Ehrlich solid tumor-­bearing mice demonstrated that the administrations of C. brasiliense pulp oil before tumor inoculation or in continuous and concurrent administration with doxorubicin (DXR, an antitumor agent) were effective in inhibiting tumor growth and in increasing lymphocyte-dependent immunity, thereby reducing the adverse side effects associated with DXR-induced oxidative damage to normal cells (Table 3). This indicates that at least for DXR, pequi pulp oil instead of the vitamins C and E would be a relevant option to reduce its adverse effects (Miranda-Vilela et al., 2014; Miranda-Vilela et al., 2011).

Miranda-Vilela et al. (2013) stated that the preventive use of C. brasiliense pulp oil could increase the efficiency of magnetic hyperthermia therapies mediated by dextran-coated maghemite nanoparticles in cancer treatment. The authors showed effective action of the oil against the advance of the carcinogenesis process after the second week, acting to control tumor growth and promoting lymphocyte-dependent immunity.

Palmeira et al. (2016) showed that C. brasiliense pulp oil exerts a hepatoprotective effect against the diethylnitrosamine-induced development of preneoplastic lesions and adenoma in BALB/C mice. The total volume of lesions and adenomas was reduced by 51% in the group treated with the carcinogen and pequi oil. In addition, some mice supplemented with the oil did not develop lesions, demonstrating the potential of this oil for the prevention of liver cancer.

In another study, C. brasiliense pulp oil and an ethanolic extract of the pulp affected urethane-induced lung cancer in BALB/C mice and restored urethane-mediated conformational changes of deoxyribonucleic acid (DNA), suggesting that pequi may modify the carcinogenic process either by blocking the development of early lesions or by inhibiting the progression to invasive cancer (Colombo et al., 2015).

Khouri et al. (2007) and Miranda-Vilela et al. (2008) suggested that C. brasiliense pulp, as chloroform or aqueous extract, has anticlastogenic and antimutagenic potentials, being able to inhibit cyclophosphamide (CP)- and bleomycin (BLM)-induced DNA damage in mice. They also demonstrated antiproliferative activity when tested in vitro in hamster cells, possibly due to its antioxidative properties (Khouri et al., 2007). On the other hand, Castro et al. (2008), using somatic mutation and recombination test (SMART) with Drosophila melanogaster, found a genotoxicity attributed to C. brasiliense pulp aqueous extract which was attributed to the higher extract concentrations (1, 5, and 10%), with elevated contents of phytochemicals acting as pro-oxidants on the DNA of exposed larvae.

The findings from Almeida et al. (2012) suggest that C. villosum pulp has protective effects against DXR-induced DNA damage in rats. The results demonstrated that the pulp was not genotoxic and inhibited the genotoxicity induced by DXR.

Although the exact mechanism of the anti-carcinogenic action of pequi has not been thoroughly elucidated, it is suggested that the effects are caused by the presence of bioactive compounds. When combined, these compounds can act as preventive agents in cancer, scavenging free radicals, improving the antioxidant defense system, and increasing the activities and expression of antioxidant enzymes at the protein and genomic level, thus reducing oxidative stress and its consequences. Therefore, further investigations are required to elucidate the role of each active constituent of pequi to determine the molecular mechanisms involved and to develop targeted therapies for cancer treatment (Colombo et al., 2015; Miranda-Vilela et al., 2014; Almeida et al., 2012; Miranda-Vilela et al., 2011; Khouri et al., 2007).

4.2. Anti-inflammatory activityTOP

Inflammation is a key component of the immune response to certain tissue injuries. This response occurs as an attempt to neutralize and/or eliminate the source of this injury, restoring tissue function. A change in the magnitude, control or duration of the inflammatory response can cause major tissue damage and contribute to the emergence of diseases (Shinagawa et al., 2015).

Miranda-Vilela et al. (2009b) reported that C. brasiliense pulp oil produced anti-inflammatory effects in athlete runners who were supplemented with 400 mg of oil after races for 14 days, which led to a higher reduction in the values of high-sensitivity C-reactive protein (hs-CRP), an acute-phase reactant and a sign of inflammation, implying that inflammation decreased. These findings are in agreement with those found using C. brasiliense almond oil, in which there was a decrease in inflammation in the serum and hepatic tissue of rats induced by carbon tetrachloride (CCl₄) (Torres et al., 2016a).

Currently, most studies on C. coriaceum deal with its anti-inflammatory activity, gastro-­protective effects, and topical wound-healing ­properties (Saraiva et al., 2011b; Batista et al., 2010; De Oliveira et al., 2010; Da Silva Quirino et al., 2009; Saraiva et al., 2008). Saraiva et al. (2011b), for example, demonstrated the topical anti-edematous effects of C. coriaceum pulp oil in mouse ear edema induced by different agents (croton oil, arachidonic acid (AA), and phenol). This oil exhibited a similar profile of topical anti-inflammatory activity as the drugs that classically modulate the production of AA metabolites and significantly reduced or inhibited the edema when compared to the control group. Consistent with these results, De Oliveira et al. (2015) found that C. coriaceum pulp oil had anti-nociceptive and anti-inflammatory effects in a model of acute arthritis induced by zymosan in rat knees, suggesting its possible application in the treatment of inflammatory joint diseases.

Da Silva Quirino et al. (2009) showed that C. coriaceum pulp oil reduced gastric damage induced by ethanol, at least in part, by mechanisms that involve α2-receptors, endogenous prostaglandins, nitric oxide (NO^•), and ATP-sensitive potassium (K⁺-ATP) channels.

Similarly, C. villosum pulp oil was also related to both the observed topical anti-inflammatory activity and a reduction in granulomatous tissue formation (Xavier et al., 2011). In another study, the anti-inflammatory activity observed by the inhibition of NO^• production, cytotoxicity in tumor strains, and antioxidant activity (ABTS: 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid), DPPH: 2,2-diphenyl-1-picrylhydrazyl and ROS assays) were also observed for shell, pulp, and seed extracts of C. villosum (Yamaguchi et al., 2017).

The exact mechanism of anti-inflammatory action is still subject of debate; however, these effects may correlate with the properties of carotenoids and FA, such as oleic acid, present in the Caryocar spp., probably by reducing the concentration and expression of inflammatory mediators at protein and genomic levels via the production of anti-inflammatory eicosanoids, inhibition of cyclooxygenase (COX) and lipoxygenase (LOX) enzymes, or by the improvement of the antioxidant defense system (Yamaguchi et al., 2017; Torres et al., 2016a; De Oliveira et al., 2015; Saraiva et al., 2011b; De Oliveira et al., 2010; Miranda-Vilela et al., 2009b; Da Silva Quirino et al., 2009).

4.3. Effects on lipid profile and cardiovascular diseasesTOP

The oleic acid-rich FA composition of the Caryocar spp. provides nutritional value, since oleic acid consumption is related to a decrease in low density lipoprotein (LDL) and the maintenance of HDL cholesterol (high-density lipoprotein) levels in humans and animals and, consequently, a reduction in coronary disease risk (Ramadan et al., 2012; Katan et al., 1994). However, palmitic acid, a SFA, is also found in large amounts in Caryocar spp., whose pro-atherogenic and cytotoxic effects are well known (Moreno et al., 2016; Aguilar et al., 2012). Because of this, the challenge of researchers is to evaluate whether the proportion of the cardiovascular protection compounds present in pequi is adequate to neutralize the effects of SFA on blood lipids.

In a recent study on rats, Oliveira et al. (2017) indicated that C. brasiliense oil (type undefined) was able to reduce hepatic TAG by activating catabolic pathways and increasing fat oxidation. In addition, there was an increase in the ex vivo cardiac function via increasing cardiac relaxation and contractility. The reduced heart rate and the increased SERCA2a/PLB (cardiac sarcoplasmic reticulum Ca₂ + −ATPase isoform 2/ phospholanban) ratio in the pequi oil group were important changes that can explain this effect.

Teixeira et al. (2013) found a higher concentration of serum HDL and lower contents of total lipids in the livers of rats fed with a high-fat diet supplemented with C. brasiliense pulp. Moreno et al. (2016) indicated that pequi pulp intake (15 weeks) by rats minimized liver fat deposition by increasing fecal outputs and improving the intestinal structure, which could account for a reduction in the cardiometabolic risk in rats. Other in vivo studies carried out in human athletes (runners) detected a general tendency for total cholesterol (TC) and LDL to decrease over age, mainly for men, after C. brasiliense pulp oil intake (Miranda-Vilela et al., 2009a).

Aguilar et al. (2012) found that risk factors for atherosclerosis, such as oxidized LDL (oxLDL), oxidative stress, and macrophage liberation of free radicals, were reduced in mice receiving a cholesterol-rich diet supplemented with 7% C. brasiliense (undefined) oil, suggesting that pequi oil confers an important antioxidant effect, thereby reducing oxidative stress, including oxLDL antibodies. Moreover, pequi oil reduced atherosclerotic lesions in the aorta, which is a more relevant atherosclerotic site for humans than the aortic valve. However, these authors paradoxically found a poorer serum lipid profile (increase in total and non-HDL cholesterol), lesions in the aortic root, and higher concentrations of total lipids in the animals’ livers.

Aguilar et al. (2011) evaluated the effects of a diet containing either C. brasiliense pulp or almond on the lipid profile and hepatic histology of healthy mice. The results demonstrated that the consumption of a pequi pulp- or almond-supplemented diet could increase serum HDL without changing the serum atherogenic fraction. However, accumulation of TAG in the liver was also caused by the higher fat intake associated with the pequi diets. The results reported by Aguilar et al. (2011; 2012) showed that the contradictory effects of Caryocar spp. on the lipid profile might be due to an experimental bias; i.e., the amount consumed was not sufficient to evaluate the outcome.

Figueiredo et al. (2016) evaluated the effects of C. coriaceum pulp oil on the lipid profile of healthy mice, on dyslipidemia induced by tyloxapol, and on its anti-inflammatory effects both in vivo and in vitro. The results revealed significant reductions in TC and TAG and an increase in HDL levels. In addition, the authors noted that paw edema (induced by carrageenan) and myeloperoxidase activity (in polymorphonuclear culture cells from human blood) were reduced at all dose levels.

In general, the majority of Caryocar spp. effects were related to improvements in the lipid profile and in cardiovascular risk factors in rats and humans, such as the reductions in hepatic and serum lipids and in oxidative stress, a key factor in the genesis of atherosclerosis. The researchers proposed that MUFA and/or carotenoids would increase fat oxidation rates by increasing fecal outputs and improving the intestinal structure, by inhibiting the 3-hydroxy-3-methyl-glutaryl (HMG)-CoA reductase, a cholesterol biosynthesis limiting enzyme, or by activating the LPL (lipoprotein lipase), an enzyme related to very low-density lipoprotein (VLDL) triglyceride hydrolysis (Figueiredo et al., 2016; Moreno et al., 2016; Aguilar et al., 2012; Aguilar et al., 2011). Taken together, these findings suggest that further studies should be conducted on the cardiovascular effects of Caryocar spp.

4.4. Antibacterial and antifungal effects TOP

Bacteriostatic effects of pequi oil have been reported in some studies. The C. brasiliense pulp oil displayed antibacterial activity against Pseudomonas aeruginosa (Ferreira et al., 2011), while C. coriaceum pulp oil showed, in vitro assays, activity such as a growth inhibitor for Salmonella choleraesuis, Staphylococcus aureus, and Escherichia coli (Costa et al., 2011; Saraiva et al., 2011a). Saraiva et al. (2011a) showed a significant synergistic antibiotic effect of pequi oil when combined with aminoglycosides (class of clinically important antibiotics).

An antifungal activity of the essential and fixed oil of C. brasiliense almonds has been reported by Passos et al. (2003) and Passos et al. (2002), respectively, against Cryptococcus neoformans and Paracoccidioides brasiliensis.

Alabdul Magid et al. (2006) evaluated the methanolic extract of the pulp of the C. villosum fruit for toxicity in a brine shrimp (Artemia salina) assay. The samples showed good larvicidal activity, and the results suggested that the toxicity of the C. villosum fruit was due to the presence of saponins; this study revealed the potential pesticidal and antitumor actions of the fruit.

4.5. Other biological effects of pequi TOP

The pulp of C. brasiliense contributes to the improvement of both exercise-induced anisocytosis in athletes (runners) and the oxygen-carrying capacity of the blood. The best results with pequi pulp oil were achieved in subjects carrying the manganese superoxide dismutase (MnSOD) Val/Val genotype, catalase (CAT) AA, or CAT AT genotypes and Glutathione peroxidase (GPX)1 proalelle (Miranda-Vilela et al., 2010). The oil was also efficient in reducing tissue injuries evaluated for aspartate aminotransferase (AST) and alanine aminotransferase (ALT) and in reducing lipid peroxidation and DNA damage in athletes (runners), suggesting protective effects of pequi pulp oil against exercise-induced oxidative stress and damage (Miranda-Vilela et al., 2009a). Miranda-Vilela et al. (2009b) also suggested that pequi pulp oil can have a possible hypotensive effect in athletes (runners); however, this presumption requires further investigation.

Roesler et al. (2007) demonstrated the scavenging activity of aqueous and ethanolic extracts of C. brasiliense against the free radical DPPH, and Roesler et al. (2008) reported an antioxidant activity of the ethanolic extract (pulp plus almond), using an in vitro model of lipid peroxidation in rat liver microsomes. Ferreira et al. (2011) demonstrated an antioxidant activity for C. brasiliense pulp oil by the DPPH assay (half maximal inhibitory concentration - IC₅₀ -15.5 mg/mL). However, the same authors found cytotoxicity for pequi oil, with an oral lethal dose (LD₅₀) of 827.6 µg/mL, in comparison to oils of buriti (Mauritia flexuosa), babaçu (Attalea spp.), and passion fruit, suggesting that pequi oil should be used carefully.

Traesel et al. (2016) showed low toxicity in acute and sub-chronic tests with C. brasiliense pulp oil in rats that received, orally and respectively, a single dose of 2,000 mg/kg/body weight (bw) of oil (14 days) or repeated doses of 125, 250, 500, or 1,000 mg/kg/bw of the oil (28 days). The LD₅₀ was established as greater than 2,000 mg/kg/bw. In addition, the oil did not elicit systemic toxicity after sub-chronic exposure; nevertheless, some hematological abnormalities were found. Although these values are within the normal range for the species, a more detailed study is necessary to investigate whether the pequi can affect the circulation or production of blood cells.

In another study, C. villosum pulp showed high antioxidant activity, as measured in a trolox equivalent antioxidant capacity (TEAC) assay, and a high in vitro scavenging capacity against ROS and reactive nitrogen species (RNS), which were closely related to the phenolic compound content (Chisté et al., 2012; Barreto et al., 2009).

5. CONCLUSIONSTOP

The pequi fruit, regardless of the species, is high in nutrients and extremely important to the population groups that consume it as food or for therapeutic purposes. The edible parts of Caryocar spp. fruits (pulp and almond) are good sources of oleic acid, minerals, and bioactive compounds such as carotenoids and polyphenolic compounds, which present significant health-promoting properties.

The fruits show anticancer and antimicrobial activity, effects against inflammatory diseases, and positive impacts on the cardiovascular system, amongst others; the health-promoting benefits are mainly attributed to the oil. The exact mechanisms of action are still under debate and need further studies; however, these effects of pequi may be explained by the presence of MUFA, mainly oleic acid, and of bioactive compounds, which are capable, for example, of stimulating angiogenesis for the production of anti-inflammatory eicosanoids, inhibiting COX and LOX enzymes. They also increase fat oxidation and fecal output and inhibit HMG-CoA reductase or activate LPL, contributing to the improvement of the lipid and the cardiovascular profiles. Its effects also cover an improvement in the antioxidant defense system due to the phytochemicals present in the fruit, increasing the activities and expression of antioxidant enzymes and reducing oxidative stress (Yamaguchi et al., 2017; De Oliveira et al., 2015; Miranda-Vilela et al., 2014; Almeida et al., 2012; Miranda-Vilela et al., 2011; Saraiva et al., 2011b; De Oliveira et al., 2010; Da Silva Quirino et al., 2009).

The pequi fruit has relevance in nutritional applications and could be a promising source of effective ingredients for nutraceutical and pharmaceutical manufacturers, expanding the commercialization of these underrated fruits. Further investigations are required to expand our knowledge on the nutritional characterization and to elucidate the role of each active phytochemical constituent of pequi, including molecular analysis to determine the exact mechanisms responsible for these beneficial activities.

ACKNOWLEDGMENTSTOP

The corresponding author is grateful to the Coordination for the Improvement of Higher Education Personnel (CAPES) and to the National Council for Scientific and Technological Development (CNPq) for financial support at the University of São Paulo. We are also grateful to The Brazilian Agricultural Research Corporation (EMBRAPA), to Federal Institute of Education, Science and Technology of Maranhão (IFMA) for release to attend the doctoral program and to John Harris for assistance with the English review.

REFERENCESTOP