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. 2022 Dec 16;27(24):8975. doi: 10.3390/molecules27248975

Variability in the Chemical Composition of Myrcia sylvatica (G. Mey) DC. Essential Oils Growing in the Brazilian Amazon

Jamile Silva da Costa 1,2, Jofre Jacob da Silva Freitas 3, William N Setzer 4, Joyce Kelly R da Silva 5, José Guilherme S Maia 1,6, Pablo Luis B Figueiredo 2,7,*
Editor: Laura De Martino
PMCID: PMC9783174  PMID: 36558108

Abstract

Myrcia sylvatica (G. Mey) DC. is known as “insulin plant” because local communities use the infusions of various organs empirically to treat diabetes. The leaves of seven specimens of Myrcia sylvatica (Msy-01 to Msy-07) were collected in the Brazilian Amazon. Furthermore, the essential oils were extracted by hydrodistillation and analyzed by gas chromatography coupled to mass spectrometry, and their chemical compositions were submitted to multivariate analysis (Principal Component Analysis and Hierarchical Cluster Analysis). The multivariate analysis displayed the formation of four chemical profiles (chemotypes), described for the first time as follows: chemotype I (specimen Msy-01) was characterized by germacrene B (24.5%), γ-elemene (12.5%), and β-caryophyllene (10.0%); chemotype II (specimens Msy-03, -06 and -07) by spathulenol (11.1–16.0%), germacrene B (7.8–20.7%), and γ-elemene (2.9–7.6%); chemotype III (Msy-04 and -05) by spathulenol (9.8–10.1%), β-caryophyllene (2.5–10.1%), and δ-cadinene (4.8-5.6%); and chemotype IV, (Msy-02) by spathulenol (13.4%), caryophyllene oxide (15.0%), and α-cadinol (8.9%). There is a chemical variability in the essential oils of Myrcia sylvatica occurring in the Amazon region.

Keywords: chemical variability, sesquiterpenes, multivariate analyses

1. Introduction

The Myrcia genus has about 800 species distributed from Central to Tropical America [1]. In addition, it is considered one of the most taxonomically and morphologically complex homogeneous genera of the Myrtaceae family [2], including in the Myrtales order, Rosideas clade, and Malvideas sub-clade [3]. The Amazon rainforest, despite comprising a low diversity of Myrcia spp., was an important region in the biogeographic history of this genus because evidence indicates that it participated in the diversification of ancestral lineages [4].

Myrcia species have great ecological relevance, as their fruits are a food source for ants, birds, and mammals, and their flowers are attractive to pollinators, such as bees. These ecological relationships are responsible for promoting the conservation of the diversity of this genus [5]. In addition, Myrcia species have economic, nutritional [6], and medicinal importance [7].

Myrcia species can be recognized in the field by the sweet aroma emanating from the leaves, flowers, and fruits, in addition to generally appearing as shrubs with leaves elliptical-co-lanceolate; apex long-acuminate to caudate; inflorescences in panicles; and flowers with deltoid sepals and petals white—rarely yellow—connective with glands of blackish color and stigma hairy at the base [8].

Several species of the Myrcia genus are popularly known as “pedra-ume-caá” or “pedra-hume-caá”, among them Myrcia punicifolia (Kunth) DC., M. speciosa (Amsh.) Mc Vaugh, M. amazonica DC., M. citrifolia (Aubl.) Urb., M. guianensis (Aubl.) DC., M. multiflora (Lam.) DC., M. salicifolia DC., M. sylvatica (G. Mey) DC., and M. uniflora DC. These species are also as known “insulin plant” because local communities use the infusions of various organs of these plants empirically to treat diabetes [9].

Myrcia sylvatica (G. Mey) DC. is also known as “kumate-folha-miúda” or “murtinha”. It is native and non-endemic to Brazil, widely distributed in South America, where it is found from Guyana to Brazil [10]. However, in Brazil, its occurrence is restricted to the phytogeographic domains of the Amazon, Caatinga, and Cerrado [11].

The M. sylvatica essential oil have shown great chemical variability due to intraspecific or seasonal variations [9,12], in addition to antioxidant, anesthetic potential [13] and bactericidal properties [14].

Therefore, in view of the biological potential presented by Myrcia sylvatica, the objective of this work was to investigate the chemical variability of the essential oils of leaves that occur in the Amazon of Pará.

2. Results and Discussion

2.1. Yield and Chemical Composition of the Essential Oils

The seven Myrcia sylvatica wild specimens evaluated in this work showed chemical variability of their essential oils. The oil yield ranged from 0.3 to 0.9%, as shown in Table 1. The quantification and identification of 112 constituents in the analyzed oils represent an average of 81.1% of the total oil content.

Table 1.

Yield and composition of essential oils from Myrcia sylvatica leaves.

RI(C) RI(L) Constituents (%) * Msy-01 Msy-02 Msy-03 Msy-04 Msy-05 Msy-06 Msy-07
1 847 846 a Hex-(2E)-enal 0.1 tr 0.1 0.5 tr tr
2 850 850 a Hex-(3Z)-enol 0.1 tr 0.1 0.4 0.7 0.1 tr
3 858 859 a Hex-(2Z)-enol 0.1 0.2
4 862 863 a n-Hexanol 0.1 0.1 0.2 0.5 tr tr
5 904 907 a Butyl propanoate 0.1
6 934 932 a α-Pinene 0.1 1.2 0.1
7 977 974 a β-Pinene 0.1 0.4 tr
8 991 988 a Myrcene 0.1 0.7 tr
9 1028 1024 a Limonene tr 0.2 0.1 tr
10 1190 1186 a α-Terpineol 0.1 0.1
11 1194 1190 a Methyl salicylate 0.1
12 1195 1195 a Myrtenal 0.1
13 1338 1335 a δ-Elemene 0.4 0.1 0.3 0.8 0.1 0.1
14 1349 1345 a α-Cubebene 0.1 0.2 0.4 tr
15 1352 1350 a Citronellyl acetate 0.1
16 1368 1367 b Cyclosativene 0.1 0.2 0.1
17 1371 1373 a α-Ylangene 0.1 0.3 0.1 tr 0.1
18 1374 1374 a Isoledene tr 0.1
19 1377 1374 a α-Copaene 0.1 0.3 0.1 1.8 2.8 0.3 0.2
20 1381 1378 a Hex-(3Z)-enyl hexenoate 0.1
21 1386 1387 a β-Bourbonene 0.2 0.1 0.3 0.8 0.6 0.2 0.2
22 1390 1387 a β-Cubebene 0.1
23 1392 1389 a β-Elemene 1.3 0.9 1.1 1.8 1.4 1.6 0.9
24 1410 1409 a α-Gurjunene 0.1 tr 0.1 0.3 0.1
25 1422 1417 a β-Caryophyllene 10.0 2.4 4.3 2.5 10.1 1.8 4.7
26 1428 1428 a (E)-α-Ionone 0.2 0.2 0.1
27 1429 1430 a β-Copaene 0.2 0.1 0.3 0.5 0.1 0.1
28 1429 1431 a β-Gurjunene 0.9
29 1434 1434 a γ-Elemene 12.5 0.3 2.9 0.7 7.6 2.9
30 1437 1432 a α-trans-Bergamotene 0.6 0.3 0.3 0.3 1.0
31 1440 1439 a Aromadendrene 0.4 0.4 0.2 0.2 0.9 0.4 0.2
32 1440 1437 a α-Guaiene 0.5
33 1443 1442 a Guaia-6,9-diene 0.6
34 1444 1445 b Selina-5,11-diene 0.1
35 1447 1448 a cis-Muurola-3,5-diene tr 0.5
36 1451 1447 a Isogermacrene D 0.2 0.2
37 1451 1451 a trans-Muurola-3,5-diene 0.1 0.5
38 1454 1452 a α-Humulene 1.4 0.4 1.1 1.6 1.2 1.9 1.4
39 1462 1460 a allo-Aromadendrene 0.6 0.2
40 1461 1464 a 9-epi-(E)-Caryophyllene 0.3 0.9 3.9 0.6 0.3
41 1463 1472 b cis-Cadina-1(6),4-diene 0.2
42 1463 1465 a cis-Muurola-4(14),5-diene 0.1
43 1466 1471 a Dauca-5,8-diene 0.1
44 1474 1475 a trans-Cadina-1(6),4-diene 0.2 0.2
45 1477 1478 a γ-Muurolene 0.6 0.8 0.9 3.0 1.4 0.7
46 1481 1483 a α-Amorphene 0.2
47 1482 1484 a Germacrene D 3.8 3.5 5.0 4.9 0.5 1.1
48 1485 1476 b Selina-4,11-diene 0.7
49 1487 1492 a β-Selinene 0.6 0.8 0.8 2.1 0.4 1.1 0.7
50 1491 1491 a 10,11-epoxy-Calamenene 0.2 0.2
51 1491 1493 a trans-Muurola-4(14),5-diene 0.5
52 1492 1489 a δ-Selinene 0.3
53 1496 1496 a Viridiflorene 2.0 1.1 1.2 3.1 2.3 2.2 1.2
54 1497 1500 a Bicyclogermacrene 5.0 0.8 3.8 1.4 0.8
55 1501 1500 a α-Muurolene 0.5 1.8 0.8 2.7 1.5 0.9 0.5
56 1508 1502 a trans-β-Guaiene 1.0
57 1508 1509 a α-Bulnesene 0.4 0.1
58 1508 1511 a δ-Amorphene 0.4 0.2
59 1509 1505 a β-Bisabolene 0.2 0.9
60 1515 1513 a γ-Cadinene 0.7 0.7 1.0 2.6 0.9 0.4 0.7
61 1519 1514 a Cubebol 0.3 0.2
62 1523 1521 a trans-Calamenene 0.6
63 1524 1522 a δ-Cadinene 1.8 2.7 5.6 4.8 1.1 1.3
64 1531 1532 a γ-Cuprenene 0.1
65 1533 1533 a trans-Cadina-1,4-diene 0.1 tr 0.1 tr
66 1536 1528 a Zonarene 0.3 0.2 0.2
67 1539 1537 a α-Cadinene 0.2 0.7 0.3
68 1539 1540 b Selina-4(15),7(11)-diene 1.6 0.6 1.5 0.7
69 1543 1545 a Selina-3,7(11)-diene 1.9 0.2 1.5 0.6
70 1544 1544 a α-Calacorene 1.4 1.9 0.6 0.5 0.9
71 1558 1559 a Germacrene B 24.5 0.7 7.8 1.3 0.3 20.7 7.9
72 1558 1562 a epi-Longipinanol 0.3
73 1563 1564 a β-Calacorene 0.3 0.2 0.1
74 1568 1567 a Palustrol 0.8 3.3 1.8
75 1578 1577 a Spathulenol 2.9 13.4 11.1 9.8 10.1 15.7 16.0
76 1584 1582 a Caryophyllene oxide 3.3 15.0 9.6 3.7 0.4 0.1 0.6
77 1592 1592 a Viridiflorol 1.5 5.3 1.0 1.2 2.9 0.9 0.8
78 1583 1590 a Globulol 7.4 3.4 5.5
79 1595 1595 a Cubeban-11-ol 0.7 2.9 0.9 1.1 0.6 0.7
80 1602 1600 a Rosifoliol 0.9 3.0 0.7 0.9 1.5 0.8 0.9
81 1609 1608 a Humulene epoxide 0.9 1.0 0.5 0.4 0.2 0.3
82 1615 1618 a 1,10-di-epi-Cubenol 0.3 0.4 0.4 1.2 1.0
83 1618 1618 a Junenol 1.3 0.9 1.1 0.6
84 1629 1627 a 1-epi-Cubenol 1.7 2.6 2.6 1.8
85 1629 1630 a Muurola-4,10(14)-dien-1β-ol 5.8
86 1629 1632 a α-Acorenol 0.8
87 1633 1630 a γ-Eudesmol 0.3 0.6 1.0
88 1637 1639 a Caryophylla-4(12),8(13)-dien-5β-ol 0.7 0.6
89 1643 1645 a Cubenol 0.3 0.7
90 1643 1640 a epi-α-Murrolol 4.8 3.2 2.2 1.2 2.3
91 1643 1640 b epi-α-Cadinol 1.6 1.4 5.1 1.2
92 1647 1644 a α-Muurolol 0.4 2.3 1.1 2.0 1.2
93 1649 1648 a cis-Guaia-3,9-dien-11-ol 0.9
94 1655 1652 a α-Cadinol 1.9 8.9 3.3 5.5 2.5 1.7 3.1
95 1666 1668 b Intermedeol 0.9 0.7 0.8 0.8 1.0
96 1668 1668 a trans-Calamenen-10-ol 0.1 0.1
97 1671 1668 a 14-hydroxy-9-epi-(E)-Caryophyllene 1.9
98 1675 1675 a Cadalene 0.5 0.6 0.8
99 1677 1676 a Mustakone 0.7
100 1685 1679 a Kusinol 0.7
101 1686 1664 a Longiborneol acetate 0.1
102 1690 1685 a Germacra-4(15),5,10(14)-trien-1α-ol 0.2 0.1 0.2
103 1696 1696 b Juniper camphor 1.5 1.6 2.0 0.2 2.1 3.3
104 1701 1702 a 10-nor-Calamenen-10-one 0.2
105 1739 1733 a Isobicyclogermacrenal 0.2 0.1
106 1762 1766 a Drimenol 0.2
107 1771 1767 a 14-oxy-α-Muurolene 0.2
108 1780 1779 a 14-hydroxy-α-Muurolene 0.1 0.1 tr 0.2
109 1798 1792 a β-Eudesmol acetate 0.2
110 1801 1803 a 14-hydroxy-δ-Cadinene tr 0.1 0.1
111 1836 1845 a (2E,6E)-Farnesyl acetate 0.1
112 2113 2106 b Phytol 0.1 0.1 0.3
Monoterpene hydrocarbons - - - 0.3 2.5 0.2 tr
Oxygenated monoterpenoids - - tr 0.3 0.1 0.1 -
Sesquiterpene hydrocarbons 71.8 12.5 33.1 43.5 47.7 48.0 29.0
Oxygenated sesquiterpenoids 17.4 71.5 39.7 36.0 36.7 29.9 40.4
Others 0.4 0.7 1.3 2.5 2.1 0.2 0.2
Total 89.6 84.7 74.1 82.5 89.2 78.4 69.6
Oil yield (%) * 0.7 0.9 0.6 0.3 0.3 0.3 0.5
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RI(C) = calculated retention index using an n-alkane standard solution (C8–C40) in Rtx-5MS column; RI(L) = literature retention index. * Main constituents in bold, n = 2 (standard deviation was less than 2.0% in chemical composition and <0.1% in oil yield); tr = traces (% < 0.1); Msy = Myrcia sylvatica; a = Adams library [15]; b = FFNCS library [16].

Sesquiterpene hydrocarbons (12.5–71.8%) and oxygenated sesquiterpenoids (17.4–71.5%) were predominant in the essential oils. The main compounds (>5%) identified in the oils were the sesquiterpenes with germacrane (germacrene B, 0.3-24.5%; γ-elemene, 0.3–12.5%), aromadendrane (spathulenol, 2.9–16.0%; globulol, 0.0–7.4%; and viridiflorol, 0.8–5.3%), and caryophyllane skeletons (caryophyllene oxide, 0.1–15.0%; and β-caryophyllene, 1.8–10.1%), followed by sesquiterpenes with cadinane skeletons (α-cadinol, 1.7–8.9%; muurola-4,10(14)-dien-1-β-ol, 0.0–5.8%; δ-cadinene, 1.1–5.6%; and epi-α-cadinol, 0.0–5.1%), as shown in Figure 1.

Figure 1.

Figure 1

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Biosynthetic pathway of the main constituents from Myrcia sylvatica essential oil.

The seasonal and circadian study of essential oil from leaves and fruits of M. sylvatica collected in the municipality of Santarém, state of Pará, indicated that the yield varied from 0.9 to 1.7% [12], values higher than this work. In contrast, the yield of leaf essential oil from this species collected in Carolina, state of Maranhão, was 0.5% [17], the same content presented by the specimen Msy-07.

In the Myrtaceae species essential oils, the predominance of hydrocarbon and oxygenated sesquiterpenes has been evidenced, some of them with biological properties [18,19]. The presence of the sesquiterpene hydrocarbon β-caryophyllene (45.0%) as the major constituent was identified in a M. sylvatica sample collected in Maranhão [17]. Other compounds were also reported as the main compound in oils from Tocantins, among them the oxygenated sesquiterpenes spathulenol (13.8–40.2%) and caryophyllene oxide (5.0–16.6%) [10]. Germacrene B (6.7%) and γ-elemene (10.5%) were identified as the highest content in M. splendens [20].

2.2. Chemical Variability in the Specimens

The Hierarchical Cluster Analysis (HCA, Figure 2) and the Principal Components Analysis (PCA, Figure 3), carried out with the compounds in the highest abundance (> 4.0%) in the essential oils of M. sylvatica, displayed the formation of four groups (chemotypes).

Figure 2.

Figure 2

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Dendrogram representing the similarity relation of the oil composition of Myrcia sylvatica.

Figure 3.

Figure 3

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Principal components analysis of the oils of Myrcia sylvatica.

The Principal Components Analysis elucidated 81.5% of the data variability. PC1 explained 42.3% and showed positive correlations with the constituents spathulenol (r = 0.22), caryophyllene oxide (r = 0.33), viridiflorol (r = 0.29), muurola-4,10(14)-dien-1β-ol (r = 0.36), epi-α-murrolol (r = 0.34), and α-cadinol (r = 0.36). The second component explained 22.3% and presented a positive correlation with the compounds β-caryophyllene (r = 0.07), germacrene D (r = 0.43), δ-cadinene (r = 0.48), caryophyllene oxide (r = 0.05), viridiflorol (r = 0.08), α-cadinol (r = 0.19), and epi-α-cadinol (r = 0.47). The third component, PC3, explained 17.0% of the data and explained a positive correlation with the variables β-caryophyllene (r = 0.18), γ-elemene (r = 0.33), germacrene D (r = 0.05), bicyclogermacrene (r = 0.25), germacrene B (r = 0.23), caryophyllene oxide (r = 0.33), viridiflorol (r = 0.23), muurola-4,10(14)-dien-1β-ol (r = 0.25), epi-α-cadinol (r = 0.13), and α-cadinol (r = 0.16).

From this, the oil samples were classified into four chemotypes (chromatogram displayed in Figure A1). Group I (specimen Msy-01) was characterized by germacrene B (24.5%), γ-elemene (12.5%), and β-caryophyllene (10.0%). Group II (Msy-03, -06 and -07 specimens) was characterized by the contents of spathulenol (11.1–16.0%), germacrene B (7.8–20.7%), and γ -elemene (2.9–7.6%). Group III (Msy-04 and -05) showed spathulenol (9.8–10.1%), β-caryophyllene (2.5–10.1%), and δ-cadinene (4.8–5, 6%). Group IV (Msy-02) was characterized by spathulenol (13.4%), caryophyllene oxide (15.0%), and α-cadinol (8.9%).

Three chemical profiles of M. sylvatica samples collected in Tocantins were reported, the first one exhibiting selin-11-en-4α-ol (24.7%), caryophyllene oxide (16.6%), and spathulenol (13.8%) as the main constituents. The second was characterized by cis-calamenene (30.1%), spathulenol (18.7%), and α-calacorene (11.5%), and the third by spathulenol (40.2%) and β-bisabolene (14.7%) [10]. The oxygenated sesquiterpene spathulenol was present in all samples of this work. Saccol et al., analyzing the chemical composition and the anesthetic and antioxidant effects of M. sylvatica essential oil, identified β-selinene (9.96%), cadalene (9.36%), α-calacorene (9.17%), and (Z)-calamene (8.17%) as major compounds [13], which is different from the chemical profiles of this study.

Furthermore, the seasonal and circadian study of a specimen of M. sylvatica from Santarém, Pará, revealed the influence of climatic factors on the chemical composition of the oils of this species, whose main constituents during the collection period were β-selinene (6.2–10.5%), 1-epi-cubenol (5.9–9.8%), cadalene (1.5–6.5%), mustakone (2.7–6.2%), α-calacorene (1.5–6.2%), δ-cadinene (0.7–6.0%), cubenol (2.4–4.6%), trans-calamenene (3.5–6.5%), and caryophyllene oxide (2.5–4.0%) [12]. All these compounds were also present in the oils of the studied M. sylvatica specimens.

In another study, carried out by Silva et al. [14], the chemical composition of fresh and dried leaves of M. sylvatica, also collected in Santarém, exhibited the compounds 1-epi-cubenol (6.9–9.9%), ar-curcumene (1.9–7.6%), cadalene (5.8–7.2%), β-selinene (6.0–7.0%), β-calacorene (5.4–5.5%), cis-calamenene (4.8–5.2%), ar-turmerol (0.0–4.9%), muskatone (3.4–4.4%), δ-cadinene (4.2%), and cubenol (4.2%). Only the constituents ar-curcumene and cis-calamenene were not identified in the samples of this work.

Another specimen collected in Bujaru, Pará state, was rich in (Z)-trans-α-bergamotene (24.6%), followed by α-sinensal (13.4%), (Z)-α-bisabolene (8.3%), trans-α-bisabolene (7.1%), and trans-β-bisabolene (5.1%). These constituents were not identified in the collected specimens [21]. The oil extracted from a specimen collected in the state of Maranhão showed β-caryophyllene (45.9%), hydroxy-(Z)-caryophyllene (10.2%), β-selenene (5.9%), and seline-3,11-diene (5.4%) in higher content [17]. The sesquiterpenes β-caryophyllene and β-selenene were also identified in the oils of the M. sylvatica described in this work.

Essential oils from Myrtaceae species have shown chemical variability, which may be influenced by seasonality, collection site, extraction method, genetics, and plant part [18,22,23]. This variability affects their biological properties and applications; for example, the existence of four Eugenia uniflora chemotypes was reported, and the samples presented different biological potentials related to their chemical profiles [24].

Therefore, among the collected samples, all chemical profiles were described for the first time: Profile I (germacrene B, γ-elemene, and β-caryophyllene), Profile II (spathulenol, germacrene B, and γ-elemene), Profile III (spathulenol, β-caryophyllene, and δ-cadinene), and Profile IV (spathulenol, caryophyllene oxide, and α-cadinol). Thus, added to the eight chemotypes described in the literature, it is possible that there are at least twelve Myrcia sylvatica chemotypes. The occurrence of different chemical profiles can be attributed to the genetic variability of this species [9].

3. Materials and Methods

3.1. Plant Material

The leaves of the seven Myrcia sylvatica wild-growing specimens were collected on Caratateua Island, Belém, Pará state, Brazil, during the rainy season. The collection site, herbarium voucher number, and geographic coordinates are listed in Table 2. After identification, the plant specimens were deposited in the Herbarium of Museu Paraense Emílio Goeldi (MG) in the city of Belém, Brazil. The leaves were dried for three days at room temperature, ground, and then submitted to essential oil hydrodistillation in duplicate using a Clevenger-type apparatus. The oils obtained were dried over anhydrous sodium sulfate, and total oil yields were expressed as mL/100 g of the dried material [25,26]. The specimens were collected in agreement with the Brazilian laws concerning the protection of biodiversity (SISGEN A78F864).

Table 2.

Collection site, herbarium voucher number, and geographic coordinates for the Myrcia sylvatica specimens.

Code Voucher Number Coordinates Latitude/Longitude
Msyl-1 MG-228738 1°15′52.65″S, 48°28′12.85″W
Msyl-2 MG-229217 1°14′52.69″S, 48°26′30.20″W
Msyl-3 MG-229955 1°15′52.42″S, 48°28′12.58″W
Msyl-4 MG-229956 1°15′52.41″S, 48°28′12.69″W
Msyl-5 MG-229954 1°15′42.54″S, 48°28′1.78″W
Msyl-6 MG-233283 1°14′51.71″S, 48°26′29.66″W
Msyl-7 MG-233284 1°14′20.79″S, 48°26′9.94″W
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3.2. Analysis of Essential Oil Composition

The oil composition analysis was performed by GC-MS, using a Shimadzu instrument Model QP-2010 ultra (Shimadzu, Tokyo, Japan) equipped with a Rtx-5MS (30 m × 0.25 mm; 0.25 μm film thickness) fused silica capillary column (Restek, Bellefonte, PA, USA). Helium was used as carrier gas, adjusted to 1.0 mL/min at 57.5 KPa; split injection (split ratio 1:20) of 1 μL of n-hexane solution (oil 5 μL: n-hexane 500 μL); injector and interface temperature were 250 °C; oven programmed temperature was 60 to 240 °C (3 °C/min), followed by an isotherm of 10 min. EIMS (electron impact mass spectrometry): electron energy, 70 eV; ion source temperature was 200 °C. The mass spectra were obtained by automatically scanning every 0.3 s, with mass fragments in the range of 35–400 m/z. The compounds present in the samples were identified by comparison of their mass spectrum and retention index, calculated for all volatile components using a linear equation by Van den Dool and Kratz [27], with the data present in the commercial libraries FFNSC-2 [16] and Adams [15]. The retention index was calculated using n-alkane standard solutions (C8–C40, Sigma-Aldrich, St. Louis, MO, USA) under the same chromatographic conditions. The GC-FID analysis was carried out on a Shimadzu QP-2010 instrument, equipped with an FID detector, in the same conditions, except that hydrogen was used as the carrier gas. The percentage composition of the oil samples was computed from the GC-FID peak areas. The analyses were carried out in triplicate.

3.3. Multivariate Statistical Analyses

The data matrix was standardized for the multivariate analysis by subtracting the mean and then dividing it by the standard deviation. The hierarchical grouping analysis (HCA), considering the Euclidean distance and complete linkage, was used to verify the similarity of the oil samples based on the distribution of the constituents selected. The principal component analysis (PCA) was applied to verify the interrelation among the oils’ components (>4%) (OriginPro trial version, OriginLab Corporation, Northampton, MA, USA).

4. Conclusions

The intraspecific chemical variability among the Myrcia sylvatica specimens studied was evidenced by the occurrence of four chemotypes, described here for the first time, with a predominance of the sesquiterpenes class in all samples. In addition to the chemotypes already described in the literature (8 chemotypes), it is possible that at least 10 Myrcia sylvatica chemotypes occur. Considering the potential of M. sylvatica, the knowledge of this variability can contribute to chemotaxonomy, economical use, and future studies that evaluate the biological properties of this species.

Acknowledgments

The authors are grateful to the Fundação Amazônia de Amparo a Estudos e Pesquisas (FAPESPA, PA, Brazil) for providing scholarships to J.S.d.C. Additionally, we are grateful to the Aromatic Plant Research Center (APRC, https://aromaticplant.org/, accessed on 25 March 2022).

Appendix A

Figure A1.

Figure A1

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Gas chromatography chromatogram chemotypes of Myrcia sylvatica.

Author Contributions

Formal analysis, J.S.d.C., J.J.d.S.F., W.N.S., P.L.B.F., J.K.R.d.S. and J.G.S.M.; writing, proofreading and editing, P.L.B.F. and J.G.S.M.; conception, P.L.B.F. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

Funding Statement

This research was funded by the PAPQ (Programa de Apoio à Publicação Qualificada), Propesp, UFPa.

Footnotes

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

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