Analysis of the volatile oils from three species of the gender Syzygium Análise dos óleos voláteis de três espécies do gênero Syzygium Análisis de los aceites volátiles de tres especies del género Syzygium

The species Syzygium cumini, Syzygium malaccense and Syzygium jambos, belong to the family Myrtaceae and are popularly known, respectively, by jambolan, red jambo and yellow jambo. These species are used in traditional medicine to treat diabetes mellitus, asthma, bronchitis, diuresis, gastrointestinal and respiratory infections, properties antipyretic, anti-inflammatory, antirheumatic and several other uses. The objective of this work is to identify and quantify the volatile compounds in the leaves of S. cumini, S. malaccense and S. jambos. The volatile oils were obtained by hydrodistillation using Clevenger apparatus and analyzed by Gas Chromatography Coupled to Mass Spectrometry (GC-MS). It was possible to identify 44 compounds present in the volatile oils of the leaves, being 20 compounds of S. cumini, 9 compounds of S. malaccense and 15 compounds of S. jambos. The major compounds present in the species S. cumini were α-terpineol, β-caryophyllene and α-humulene; for the species S. malaccense were aristolochene, γ-himachalene and δ-amorphene; and for S. jambos species were β-cariophyllene, (E,E)-αfarnesene and cariophyllene alcohol. The species S. cumini, S. malaccense and S. jambos showed considerable differences in terms of volatile compounds, it is important to know their constituents in order to promote further studies focused on their medicinal potential.


Introduction
Medicinal plants have global importance, in their fresh and processed form, in addition to being widely used in traditional medicine due to the bioactive molecules present in their composition (Hajimehdipoor et al., 2014). These plants play a vital role in the prevention and treatment of diseases, being used by more than 80% of the world population to meet primary health needs (WHO, 2013). In addition, more than 50% of new drugs developed and approved for commercialization are derived from modified products of medicinal plants or their active constituents (Teng & Shen, 2015).
Active compounds can be classified as volatile and non-volatile, non-volatile include tannins, phenols, flavonoids, coumarins, chromones, xanthones, lignans, neolignans, quinones, saponins, alkaloids, methylxanthines and volatile compounds, also called volatile oils, are defined as a product resulting from distillation by steam vapor and have as a starting point some part of the plant in question. They are generally pleasant in aroma, acid and spicy taste, generally colorless, lipophilic, oily-looking, volatile and soluble in an organic solvent. Its composition includes terpenic hydrocarbons, ethers, oxides, peroxides, ketones, phenols, simple and terpenic alcohols, aldehydes, organic acids, furans, lactones, coumarins, varying their concentrations (Simões et al., 2007).
Volatile oils have commercial and industrial importance, being used by the food, pharmaceutical, perfumery and cosmetic industries and are part of the healing action of medicinal plants (Trancoso, 2013). Volatile oils are not restricted to specific taxonomic groups, as they occur widely in the plant kingdom (Sangwan et al., 2001), so it is important to know and identify the chemical compounds present in these oils, as they confer pharmacological properties, requiring identification and quantification of these chemical compounds (Santos et al. 2021).
Among the species of plants producing volatile oils with greater prominence, is the family Myrtaceae, also known as family Myrtle, which has about 145 genera and more than 5,970 species (The plant list, 2021), being the genus Syzygium one of the genera that stand out for their phytochemical composition and various therapeutic properties, such as antimicrobial, antiseptic, antiviral, antidiabetic, anti-inflammatory action, in addition to its use for the treatment of respiratory disorders and stomach problems (Cock & Cheesman, 2018). Syzygium cumini (L.) is commonly known as black jambo, black plum, jambolana, among other popular names, originating in India and regions in southern Africa (Ayyanar & Subash-Babu, 2012) and is distributed in several regions of Brazil such as, North, Northeast and Southeast (Migliato et al., 2007). S. cumini has anti-cancer, hypoglycemic, antimicrobial properties, among others (Ruan, Zhang & Lin, 2008;Ahmed et al., 2019). Syzygium malaccense (LO), also known as red apple and mountain apple, is originally from Malaysia, but has spread to several tropical regions, such as Brazil (Augusta et al., 2010), has reports of hypoglycemic activities (Bairy, Sharma & Shalini, 2005) and antioxidants (Batista et al., 2017). Syzygium jambos (L.), also called yellow jambo, is originally from Southeast Asia, but is currently distributed in all tropics. It has antipyretic and anti-inflammatory properties is traditionally used to treat hemorrhages, syphilis, leprosy, wounds, ulcers and lung diseases (Kuiate et al., 2007;Nawwar et al., 2016).
The objective of the present work was to carry out the identification and quantification of the volatile compounds present in the species S. cumini, S. malaccense and S. jambos collected in the region of Rio Vermelho -Goiás (GO), Brazil.

Collect botanical material and obtaining of volatile oil
The collect of botanical material (leaves) of Syzygium malaccense and Syzygium cumini were carried out in November 2020, in Itapuranga-Goiás, whereas the sample of Syzygium jambos was collected in October 2020 in Guaraíta-Goiás. All samples were collected in the morning before 10 AM. Syzygium cumini at the time of collection had ripe and green fruits, while Syzygium malaccense had flowers and Syzygium jambos had fruits.

Analysis of the chemical composition of volatile oil in leaves of the genus Syzygium
Experimental research was based on the technique described in the Farmacopeia Brasileira (2010), for the extraction of volatile oils, 110g of the dried leaves of S. jambos, 90g of the dried leaves of S. cumini and 117g of the dried leaves of S. malaccense were used. These leaves were crushed through an industrial blender and immediately subjected to hydrodistillation by steam dragging in a Clevenger type apparatus for 2 hours. The volatile oil was desiccated using anhydrous sodium sulfate (Na2SO4) and subsequently stored in amber flasks, hermetically sealed, free of impurities and stored in a freezer for later use.
The volatile oils obtained from the leaves of the three species of the Syzygium genus were subjected to gas phase chromatographic analysis coupled with mass spectrometry (GC-MS) on the QP2010A apparatus. A fused silica capillary column of the DB5 type was used, with a flow rate of 1 mL/min of helium, this being the gas used in the entrainment, the programmed temperature for heating was 60°C/2 min; 3°C min -1/240°C; 10°C min -1/280° C; 280°C/10min, the ionization energy was 70 eV. The injection volume of 1 μL was used in each sample diluted in hexane (C6H14) in a proportion of 1mg: 20 ml. The identification of the chemical components was carried out by comparing the mass spectra and sample retention indices and with the findings in the literature according to Adams (2017) and in comparison, with the QP2010A device library, which uses the Nist reference (1999), for those not found through Adams (2017).

Results and Discussion
The yield of volatile oils from S. cumini, S. malaccense collected in Itapuranga-GO and S. jambos collected in Guaraíta-GO, were 0.76%, 0.05% and 0.24%, respectively.
Leaf yield of S. cumini was reported to be 0.56% in Cairo-Egypt (Mohamed, Ali & El-Baz 2013), 0.05% in Rio de Janeiro (Siani et al., 2013), in Maranhão (Brazil) 0.52% and in Pakistan 0.03% (Hanif et al., 2020). As for the leaves of S. malaccense, a yield of 0.15% was reported in Ifé in Nigeria (Karioti, Skaltsa & Gbolade 2007), 0.0297% in the city of Kuala Selagor (Malaysia) (Ismail, Ismail & Lajis et al., 2010) and 0.03% in Paraná (Brazil) (Feltrin et al., 2020). And for the leaves of S. jambos, information on their yield was not found in the literature. The variation in the yield values of these 3 species of Syzygium is due to the fact that volatile oils are intrinsically related to regional, biotic and abiotic factors. Atmospheric parameters such as climate, temperature and precipitation are related to the chemical diversity of volatile compounds, as well as seasonal aspects (Cruz et al., 2014;Verma, Padalia & Chauhan 2014).
Through the analysis of volatile oils of the 3 species of Syzygium by GC-MS it was possible to identify a total of 44 (100%) compounds (Table 1). In the volatile oil, of S. cumini 20 compounds were identified, of S. malaccense 9 compounds and S. jambos, 15 compounds ( Figure 1). Research, Society and Development, v. 10, n. 7, e13510716375, 2021 (CC BY 4.   Regarding the classes that make up the volatile oil of S. jambos, there are few reports in the literature, but a study by Ghaareb et al. (2017), analyzed the leaves of this species and found that most of the compounds identified belonged to the class of sesquiterpene hydrocarbons, which corroborates with the compounds found in this work.
According to the literature cited above, the majority class common in the species of S. cumini and S. malaccense were mainly monoterpene hydrocarbons, which differs from the present study, in which the majority class common in all species (S. cumini, S. malaccense and S. jambos) were the sesquiterpene hydrocarbons and only the species S. cumini presented compounds belonging to the monoterpene class (8.69%).
However, the samples collected in the Rio Vermelho region shared common compounds with the samples collected in Rio de Janeiro and São Luís, the compounds (Z)-β-ocinene and β-karyophylene, and the compounds trans-β-ocimene, α -terpineol and α-humulene in samples from Rio de Janeiro.
The variability of the chemical composition of the volatile oils of the different Syzygium species, as well as others, are linked to regional, genetic, physiological aspects such as periods of fruiting, flowering and reproductive rest, water stress and ecological factors such as the herbivore, biome, type of soil and available nutrients, in addition to the difference in temperature, solar irradiation, climate and rainfall (Cruz et al., 2014, Domingos et al., 2020. The volatile constituents found in this study corroborate the constituents that are commonly found in several plants of the Myrtaceae family and belonging to the Syzygium genus, such as Syzygium aromaticum (Raina et al., 2001), Guinea-Bissau (Noudogbessi et al., 2008), Syzygium densiflorum (Saranya et al., 2012), Syzygium calophyllifolium (Vignesh et al., 2013) and Syzygium benthamianum (Deepika et al., 2013).

Conclusion
The present study promoted the complete identification of the volatile compounds of the studied species and identified their major compounds, which allows future studies of the biological and pharmacological activities of these components. It can be concluded that the three species of jambo (S. cumini, S. malaccense and S. jambos) present significant differences regarding the chemical constitution of volatile compounds and their major components. It was observed that viridiflorol is the only component that appears in the three species studied. It is important to know the chemical composition of the plants to demonstrate that there is a foundation in the use of these plants in traditional and popular medicine, since their chemical components are what give these plants the various medicinal properties and so that they can be used in the production of pharmaceutical inputs.
It is possible, therefore, in future studies to assess whether inferences in the rainfall regime can influence the concentration of some components and not others. If the variations observed in the results obtained for each sample are indicative that a complex network of environmental factors and/or conditions, such as temperature, humidity, duration and intensity of solar irradiations, interactions with pollinators and predators, are influencing the composition of the oil and not just the rain regime.