Chemometrics of Seasonal Variation on Essential Oil Chemical Composition of Myrciaria tenella (DC.) O. Berg

Abstract

Myrciaria tenella (DC.) O. Berg is a native and non-endemic fruit tree from Brazil, popularly known as cambuí, and widely used to treat skin rashes, diarrhea, herpes, and colic. The present study aimed to evaluate the influence of climatic parameters on the yield and chemical composition of the essential oil of this species. M. tenella leaves were collected in Salvaterra, in Marajó Island, Pará, Brazil. Essential oils were extracted by hydrodistillation and analyzed by gas chromatography coupled to mass spectrometry. The correlations between yields and climatic parameters were verified using chemometrics tools. M. tenella essential oils showed an average yield of 1.44 ± 0.46% and the highest yield in October (2.6%). There was no significant difference in yield throughout the year. A total of 105 constituents were identified: (E)-caryophyllene (0 to 31%), caryophyllene oxide (0 to 33.61%), δ-cadinene (0 to 6.9%), 1-epi-cubenol (1.96 to 5.82%), and aromadendrene (1.16 to 5.84%) were the major constituents. Temperature, humidity, and insolation significantly influenced the levels of the classes and the main components. Multivariate analysis showed a homogeneous distribution of the samples with high chemical variability. The M. tenella essential oils show variations throughout the year, indicating independence from climatic conditions.

Keywords:
cambuí; chromatography; chemometrics; sesquiterpenes; volatiles

Introduction

Natural products have been used by humanity since ancient times. The search for relief and cure of diseases through the ingestion of herbs and leaves may have been one of the first forms to use natural products.¹ Essential oils (EOs) are naturally occurring volatile and lipophilic compounds with a strong odor that is typically produced by the secondary metabolism of aromatic plants.² In addition, there are several applications in industries, such as cosmetics, food, perfumery, and as adjuvants in medicines.³ These compounds are valued not only for their fragrances but also for their phytochemical properties that provide antioxidant capabilities, as well as anti-inflammatory, anti-edematogenic, antinociceptive, and analgesic properties.⁴-⁶ In this sense, the extraction of OEs is one of the strategies for the detection of bioactive phytochemical molecules.⁷

Among the taxa of botanical families used in traditional medicine that produce essential oils, Myrtaceae stands out for being considered the ninth largest family of angiosperms (plants with flowers and fruits), which comprises around 140 genera catalogued in 6,000 species of trees and shrubs.⁸ In Brazil, it consists of 29 genera and 1,212 species, which are important in the cosmetic, medicinal and food industries.⁹ Its leaves are opposite, decussate, generally simple, with entire blades. The flowers are predominantly white or cream and may occasionally display pink, magenta or red hues. The fruits, known for being succulent, have the crown formed by the hypanthium tube (structure that connects the parts of the flower) and by the calyx renascents, which remain attached to the fruit.¹⁰

Myrciaria tenella (DC.) O. Berg is a fruit tree with a dense canopy measuring approximately 3 to 6 m in height, with light flowers and red fruits, popularly known as cambuí, “murta-do-campo”, “cambuim” and “cambuinzinho”.¹¹ It is native and not endemic to Brazil, covering the North, Northeast, South and Southeast regions.¹²

M. tenella has been widely used by the indigenous population to treat skin rashes, diarrhea, herpes, and colic due to its astringent action.¹³,¹⁴ Despite the scarcity of reports in the literature on the medicinal applications of this species, some studies¹³-¹⁵ show that extracts from the leaves of M. tenella have antioxidant and antiproliferative potential, and its essential oil has antibacterial and anti-inflammatory activity.

Myrciaria EOs are rich in terpenoids and showed significant variations in the content of secondary metabolites, with emphasis on the genetic aspects of the plant, collection regions and use of different parts of the species.¹⁶ Furthermore, there are several works published in the literature on the chemical composition of M. tenella leaves EOs,¹⁴,¹⁵,¹⁷ although there is no report that describes the seasonal variation on the EO chemical composition of this species.

Thus, considering the economic, botanical and pharmacological relevance of Myrciaria species, in addition to the absence of scientific reports on the effects of seasonality on the essential oil of M. tenella, the present study aimed to evaluate the influence of climatic factors on the yield and chemical composition of the essential oil of this species.

Experimental

Plant material and climate data

M. tenella leaves from a single specimen were collected in Salvaterra, in Marajó Island, Pará, Brazil (0°46’14.10”S/48°30’55.8”W). Collections were done on the first day of the month, from May 2022 to May 2023. The collected material was transported in aired plastic bags and stored in a shaded and ventilated place. Botanical identification was performed by comparison with authentic samples from the “João Murça Pires” Herbarium of the Museu Paraense Emílio Goeldi, located in the municipality of Belém, Pará, Brazil, by botanist Carlos Alberto Santos da Silva. The access to the genetic heritage was registered in SisGen under number AD9E191.

The climatic parameters (relative humidity, precipitation, average temperature and solar radiation) were obtained monthly from the National Institute of Meteorology (INMET),¹⁸ of the Brazilian Government. Meteorological data were recorded at the automatic station A-201 (Belém-PA), equipped with a Vaisala system, model MAWS 301 (Vaisala Corporation, Helsinki, Finland).

Essential oil extraction and yield calculation

The leaves were separated and dried at room temperature (25 °C) in an air-conditioned room for 5 (five) days. After drying, the botanical material was crushed with the aid of a mixer. The essential oils (EOs) were extracted by hydrodistillation with a modified Clevenger-type extractor for 3 h. Then, the EOs were centrifuged for 5 min to separate the aqueous phase from the essential oil, dried with anhydrous sodium sulfate (Na₂SO₄) and centrifuged again under the same conditions. The EOs were stored in amber vials and kept refrigerated. The residual moisture of the botanical material was obtained by drying in an oven at 110 °C until constant weight. Oil yields were calculated in % m/v (mL per 100 g) from moisture-free biomass, related plant mass, oil and residual moisture.

Chemical composition analysis

The chemical composition was analyzed by gas chromatography coupled to mass spectrometry (GC-MS) in a Shimadzu QP 2010 ultra-system with Auto-injector: AOC-20i equipped with a Rtx-5MS silica capillary column (30 m × 0.25 mm; 0.25 μm film thickness) under the following operating conditions: temperature program: 60-240 °C (3 °C min^-1) followed by an isotherm by 10 min; injector temperature: 250 °C; carrier gas: helium (1 mL min^-1); injection: split type 1:20 (5 μL essential oil solution: 500 μL hexane); mass spectra were obtained by electron impact at 70 eV; ion source temperature: 200 °C. Individual components were identified by comparing their retention indices and mass spectra (molecular mass and fragmentation pattern) with those existing in the Adams¹⁹ and FFNSC 2 libraries.²⁰

Statistical analysis

The chemical composition was subjected to multivariate analysis: hierarchical cluster analysis (HCA) and principal component analysis (PCA) in Minitab^® software version 18.²¹ Essential oil yields were analyzed by t-test (p < 0.05) in GraphPad Prism 5.0 software.²² Pearson’s correlation coefficients (r) were calculated to determine the relationship between the analyzed climatic parameters (insolation, relative humidity, temperature and precipitation) using GraphPad Prism software, version 5.0.²²

Results and Discussion

Yield and climate parameters

The climatic parameters (precipitation, temperature, humidity, and insolation) were evaluated during the months of May 2022 to May 2023 to assess the influence of seasonality on the composition and yields of M. tenella essential oil. The insolation values ranged from 88.2 h (March) to 253.4 h (September), the monthly precipitation from 103.9 mm (September) to 482.5 mm (May 2022), the temperature from 26.1 °C (March) to 27.7 °C (November) and the relative humidity from 77.9% (October) to 92.9% (March) (Figure 1).

Figure 1
Climatic parameters and yield of Myrciaria tenella essential oil.

According to the precipitation parameter, the dry period occurred during the months of August to November and the rainy period in the months of May to July 2022 and from December 2022 to May 2023. During the dry period, precipitation had an average of 128.28 ± 21.83 mm. In contrast, in the months that comprise the rainy period, the average precipitation was 362 ± 88.83 mm.

The Amazon region has two seasons: rainy and dry. The rainy period is called the Amazonian winter, while the dry period is called the Amazonian summer. These cycles cover the entire year. Thus, precipitation stands out as the most heterogeneous parameter, presenting significant variations in both times and locations.²³

The yield of Myrciaria tenella EO averaged 1.44 ± 0.46%, reaching its highest value in October with 2.6% and the lowest in May 2023, with a 1.0% yield. Comparing the yield during each period (dry and rainy), there was no differentiation in the contents throughout the year, according to the statistical hypothesis test (Student’s t-test, p > 0.05), as shown in Figure 2. Furthermore, no significant correlation (p > 0.05) was observed between yield and sunlight (r = 0.48), precipitation (r = -0.31), temperature (r = 0.39) and relative humidity (r = -0.49), indicating that yield variations are independent of climatic conditions and its variation may be related to biotic, genetic and other factors that interfere with plant secondary metabolism.

Figure 2
Yield of Myrciaria tenella essential oil during the seasons.

According to Antonelo et al.²⁴ samples belonging to the Myrtaceae family collected in the Paraná state (Brazil) have yields of 0.043% (M. gigantea), 0.274% (M. tenella) and 0.817% (M. oblongata). The leaves of M. eximia were collected in the city of Magalhães Barata (Pará state) and presented yields ranging from 0.01 to 0.36% with the highest yield demonstrated in the dry period.²⁵ Thus, in this study, the yields varied from 1 to 2.6% higher than reported yields.

Eugenia uniflora essential oil yield from Paraná state varied from 0.22 to 1.68% with an average yield of 0.62%.²⁵ On the other hand, another specimen from Belém (Pará state) presented a yield of 2.6%.²⁶

Seasonal variability of Myrciaria tenella essential oil chemical composition

Using the GC-MS technique, it was possible to identify 105 constituents in the EOs of M. tenella leaves. The total amounts of identified compounds ranged from 82.67% (November) to 94.69% (March 2023). The compounds classes identified were monoterpene hydrocarbons, present only in October to December 2022 and January 2023, with an average of 0.13 ± 0.25%; sesquiterpene hydrocarbons, present in all months with an average of 56.99 ± 14.86%, and oxygenated sesquiterpenes with an average of 33.85 ± 11.44%, also present throughout the analyzed period. The constituents are arranged in increasing order of the retention index (Table 1).

Table 1
Chemical composition of Myrciaria tenella essential oils during the seasonal study

RIC	RIL	Constituent / %
			May	June	July	August	September	October	November	December	January	February	March	April	May
		Oil yield / %	1.2	2.1	1.2	1.3	1.8	2.6	1.3	1.4	1.4	1.2	1.2	1.1	1.0
974	969a	sabinene						0.32	0.79	0.46	0.12
1351	1345a	α-cubebene	0.02	0.07	0.04	0.03	0.11	0.12		0.02	0.04	0.15	0.22	0.03	0.19
1369	1369a	cyclosativene	0.05	0.03	0.03	0.02	0.04	0.08	0.07	0.05	0.02	0.05	0.06		0.05
1373	1373a	α-ylangene	0.82	0.47	0.59	0.47	0.58	0.78	0.40	0.43	0.46	0.51	0.49	0.26	0.43
1377	1374a	α-copaene	1.94	1.22	1.55	1.25	1.43	1.67	0.92	1.08	1.23	1.75	1.42	1.15	1.44
1380	1374a	isoledene	0.03	0.01	0.02	0.02	0.02					0.13	0.09		0.09
1386	1387a	β-bourbonene	0.02				0.02					0.03	0.05		0.03
1387	1387ª	β-cubebene					0.02					0.02	0.03		0.03
1391	1390ª	sativene	0.06	0.04	0.04	0.03	0.07	0.12	0.12	0.09	0.05	0.05	0.05		0.05
1393	1389ª	β-elemene		0.05	0.03					0.02	0.03
1408	1407ª	longifolene							0.08	0.04			0.05
1408	1417ª	β-longipinene	0.06			0.11	0.08	0.04	0.08	0.09	0.10
1411	1409ª	α-gurjunene	0.13	0.08	0.10	0.09	0.08			0.22	0.44	0.59	0.46	0.26	0.64
1412	1415b	β-maaliene						0.07				0.13	0.06
1420	1419ª	β-ylangene							0.30	0.15
1422	1417ª	(E)-caryophyllene	26.75	23.88	31.50	27.28	21.67	17.91		6.47	12.93	17.30	23.52	18.99	23.82
1425	1430b	γ-maaliene	0.05		0.03		0.06
1430	1430ª	β-copaene	1.25	1.33	1.35	1.35	2.05	1.91	1.06	1.25	1.43	1.60	1.81	1.12	1.84
1434	1431ª	β-gurjunene							0.07	0.12	0.16	0.20	0.15	0.13
1435	1434ª	γ-elemene		0.10			0.10
1436	1438b	α-maaliene	0.07	0.04	0.06	0.06	0.07	0.08	0.13	0.18	0.23	0.32	0.25	0.22	0.28
1439	1439ª	aromadendrene	1.37	1.16	1.35	1.34	1.63	1.66	5.84	4.90	3.96	5.23	3.89	4.72	4.80
1444	1442ª	6,9-guaiadiene	0.34	0.25	0.30	0.29	0.37
1445	1445b	selina-5.11-diene						0.15	0.08	0.42	0.76	0.92	0.69	0.70	0.82
1448	1448ª	(Z)-muurola-3,5-diene	0.04	0.07	0.06	0.04									0.03
1452	1451ª	(E)-muurola-3,5-diene		0.04					0.02	0.01		0.37	0.44	0.06	0.21
1454	1452ª	α-humulene	3.63	3.47	3.94	3.86	2.96	2.44		1.28	2.56	2.13	2.78	1.82	2.71
1458	1458ª	allo-aromadendrene	0.06	0.06	0.06	0.39	0.07	0.05		0.04	0.07
1462	1464ª	9-epi-(E)-caryophyllene	0.39	0.31	0.32		0.26	0.29	0.27	0.62	0.96	1.07	0.73	0.70	0.82
1463	1465ª	(Z)-muurola-4(14),5-diene			0.09	0.11	0.16	0.04					0.21		0.18
1471	1471ª	4.5-di-epi-Aristolochene						0.06	0.05	0.03		0.04	0.07	0.02	0.07
1475	1475ª	(E)-cadina-1(6),4-diene	0.49	0.55	0.53	0.51	0.10					0.80	0.63	0.49	0.52
1478	1478ª	γ-muurolene	3.80	3.74	4.07	3.83	4.15	4.37	2.32	2.66	3.00	2.35	2.66	2.06	2.70
1482	1483ª	α-amorphene	0.74	0.71	0.69	0.70	0.66	0.56	0.15	0.41	0.67	0.42	0.48	0.33	0.51
1488	1489ª	β-selinene	2.10	2.09	2.04	2.17	2.08	2.20	2.11	2.31	2.51	2.34	2.12	2.12	2.39
1492	1492ª	δ-selinene	0.71	0.74	0.68	0.73	0.33			0.38	0.76	0.74	0.70	0.47	0.72
1495	1498b	α-selinene					3.05	2.42	0.39	2.10	3.80	4.21	3.91	3.56	4.96
1500	1501ª	epi-zonarene	0.70	0.51	0.58					0.06	0.11		0.23
1502	1500ª	α-muurolene	1.49	1.63	1.49	2.36	1.69	1.43	0.59	1.13	1.66	1.36	1.16	1.11	1.35
1502	1502ª	γ-patchoulene	3.52	4.07	3.83	3.56
1509	1511ª	δ-amorphene	1.20	2.45	1.92	1.90	0.16					1.18	1.59	0.53	0.57
1516	1513ª	γ-cadinene	3.25	3.26	3.05	3.33	3.67	3.98	1.93	2.40	2.86	2.22	2.43	1.93	2.58
1519	1520ª	7-epi-α-selinene	0.07	0.07	0.06	0.08	0.11	0.09		2.89	5.78	0.08	0.09		0.09
1525	1521ª	(E)-calamenene						2.76	0.70	0.35
1525	1522ª	δ-cadinene	6.31	5.76	5.75	6.54	5.66	4.00		0.02	0.04	6.09	5.93	5.96	6.90
1527	1528ª	zonarene	0.41		0.35							0.38		0.03
1534	1533ª	(E)-cadina-1,4-diene	0.67	0.54	0.57	0.63	0.15			0.05	0.09	0.63	0.54	0.48	0.44
1539	1537ª	α-cadinene	0.97	0.75	0.77	0.90	0.88	0.82		0.41	0.81	0.58	0.64	0.48	0.67
1539	1540b	selina-4(15),7(11)-diene						0.87	0.15	0.08		0.52	0.53	0.36	0.56
1543	1544ª	α-calacorene	5.32	3.45	3.76	4.09	2.30			0.39	0.78	3.34	2.57	4.10	2.61
1543	1545ª	selina-3,7(11)-diene						1.12
1555	1562ª	epi-longipinanol								1.00	2.00
1558	1559ª	germacrene B		0.23	0.06	0.08	0.15	0.04				0.17	0.38	1.97	0.47
1565	1561ª	(E)-nerolidol						0.14
1565	1564ª	β-calacorene	0.28			0.24	0.16			1.62	3.24	0.38	0.39	0.20	0.23
1567	1570ª	caryophyllenyl alcohol							0.90	0.45
1569	1566ª	maaliol						0.07	0.53	0.58	0.63
1572	1567ª	palustrol							0.87	0.44
1572	1571ª	caryolan-8-ol	0.64	0.41	0.34	0.36	0.30	0.27
1579	1577ª	spathulenol	0.22	0.28	0.16	0.16	0.05		0.54	0.63	0.71	1.48	1.94	1.33	1.09
1584	1582ª	caryophyllene oxide	6.83	7.69	6.49	7.40	14.60	22.30	33.61	21.90	10.19		8.03	12.23	7.92
1589	1590ª	β-copaen-4-α-ol						0.02
1594	1592ª	viridiflorol							1.09	1.16	1.22	10.15
1596	1595ª	cubeban-11-ol							0.86	1.17	1.48	0.84
1603	1600ª	rosifoliol	0.41	0.45	0.39			0.53	1.38	1.86	2.34	1.70	1.62		1.53
1606	1600ª	guaiol	0.09	0.09	0.07	0.08	0.10			0.09	0.18			0.06
1610	1608ª	humulene epoxide II	0.27	0.34	0.28	0.31	1.06	1.62	2.65	1.67	0.68	0.45	0.38		0.34
1615	1613b	copaborneol							0.93	0.47
1617	1618ª	1,10-di-epi-cubenol	0.90	0.89	0.82	0.93	2.35	2.18	0.66	1.79	2.91	0.91	2.26	1.89	1.93
1620	1618ª	junenol							0.11	0.06
1627	1624b	epi-γ-eudesmol	0.52	0.67	0.56	0.59	0.53	0.36	0.30	0.15		0.37	0.98	1.31	0.99
1630	1627ª	1-epi-cubenol	4.20	5.06	3.77	4.32	3.72	2.65	2.11	2.04	1.96	4.68	4.14	5.82	3.57
1638	1638ª	epi-α-cadinol	2.78	1.82	2.76	3.00		1.43		0.95	1.90
1638	1639ª	caryophylla-4(12).8(13)-dien-5-β-ol	1.82	2.17	1.44	1.83	1.24	0.45	0.73	0.91	1.09	1.18	1.08
1644	1640ª	epi-α-murrolol		1.69				1.13	1.68	0.84		3.16
1648	1644ª	α-muurolol	0.95	1.25	0.93	1.00	3.93	1.00	0.86	1.31	1.76	1.25	4.24	8.11	6.77
1651	1652ª	α-eudesmol				0.31	0.43
1652	1649ª	β-eudesmol		0.40				0.55	0.60	0.65	0.70	0.49
1654	1652ª	α-cadinol	3.30	4.03	2.41		3.02	2.95	2.13	3.13	4.13	3.42	3.20
1659	1661ª	allo-himachalol	1.30	1.49	0.93		1.07		1.24	0.62		1.66
1668	1668ª	(E)-calamenen-10-ol					0.39	0.72	0.49	0.42	0.35		0.43	0.08	0.41
1672	1668ª	14-hydroxy-9-epi-(E)-caryophyllene		1.42	0.80	1.04	1.51		3.37	2.08	0.79	0.07	1.19	2.22
1676	1675ª	cadalene	0.31	0.43	0.30	0.41	0.77	0.85	1.48	1.00	0.52	0.22	0.21	0.34	0.23
1679	1676ª	mustakone						0.06	0.58	0.29
1680	1679ª	khusinol	0.13	0.25	0.15	0.18	0.10						0.19	0.06	0.12
1688	1688ª	(Z)-14-nor-muurol-5-en-4-one						0.30		0.06	0.12
1696	1700ª	eudesm-7(11)-en-4-ol					0.17						0.23	0.15	0.19
1702	1702ª	10-nor-calamenen-10-one	0.03	0.05	0.02	0.04	0.09	0.18	0.10	0.05		0.05	0.07	0.04	0.05
1705	1709ª	mayurone					0.07		0.13	0.07
1715	1713ª	longifolol							0.06	0.03
1715	1714ª	nootkatol						0.30
1727	1718ª	β-davanone-2-ol							0.76	0.38
1731	1728ª	iso-longifolol							0.15	0.08
1751	1759ª	cyclocolorenone							1.04	0.55	0.06
1762	1762ª	aristolone							0.33	0.17
1765	1765ª	β-costol					0.20	0.27	0.33	0.17
1780	1773ª	α-costol					0.03		0.52	0.26
1786	1783ª	hinesol acetate							0.39	0.20
1798	1793ª	(E)-isovalencenol						0.06
1815	1823ª	khusinol acetate					0.12
1818	1819ª	iso-longifolol acetate							0.34	0.17
1837	1839ª	eudesm-7(11)-en-4-ol acetate						0.07	0.20	0.10
Monoterpene hydrocarbons								0.32	0.79	0.46	0.12
Sesquiterpene hydrocarbons			69.42	63.66	71.96	68.80	57.92	52.98	19.31	35.69	52.06	60.60	64.71	56.70	67.03
Oxygenated sesquiterpenoids			24.39	30.45	22.32	21.55	35.08	39.61	62.57	48.89	35.20	31.86	29.98	33.30	24.91
Total identified			93.81	94.11	94.28	90.35	93.00	92.91	82.67	85.03	87.38	92.46	94.69	90.00	91.94

• Main constituents in bold; standard deviation was less than 2.0 (n = 3).
• ^a
  Adams;¹⁹
• ^b
  FFNCS.²⁰ RI_C: calculated retention index; RI_L: literature retention index.

The sesquiterpene hydrocarbon (E)-caryophyllene was the compound with the highest average content in the essential oils throughout the seasonal study (see Figure 3). The concentration ranged from 0% (November 2022) to 31.5% (July 2022), with an annual average of 19.39 ± 8.74%. Moreover, caryophyllene oxide, which ranged from 0% (February 2023) to 33.61% (November 2022), with an average of 12.25 ± 8.91%.

Figure 3
Chemical structures of the main compounds identified in Myrciaria tenella essential oils leaves.

Other compounds were identified in smaller quantities, such as the sesquiterpene hydrocarbon δ-cadinene, which ranged from 0% (November 2022) to 6.90% (May 2023), with an average of 4.54 ± 2.66%; the oxygenated sesquiterpene 1-epi-cubenol, which ranged from 1.96% (January 2023) to 5.82% (April 2023), with an average of 3.70 ± 1.21%, and the hydrocarbon sesquiterpene aromadendrene from 1.16% (June 2022) to 5.84% (November 2022), with an average of 3.22 ± 1.81%.

According to Andrade et al.²⁷ (E)-caryophyllene was the highest constituent (32.0%) in M. tenella essential oil collected in the municipality of Acará, Pará state. Apel et al.¹⁴ also identified (E)-caryophyllene (25.1%) and spathulenol (9.7%) as the highest content in M. tenella oil, corroborating with the results of this study.

(E)-Caryophyllene is a sesquiterpene hydrocarbon present in the EOs of several Myrtaceae species. It is a volatile substance released by corn to minimize damage caused by herbivores or pathogens, in addition to having a “woody” and spicy odor.²⁸,²⁹ On the other hand, caryophyllene oxide is an oxygenated sesquiterpene that the epoxidation of (E)-caryophyllene can obtain, the main constituent of clove and copaiba oils.³⁰,³¹

Seasonal environmental changes can cause changes in the secondary metabolism of plants and, consequently, in the chemical composition, yield and biological activity of essential oils.³² In the case of M. tenella essential oil, the chemical composition presents significant differences depending on the month of collection.

Climatic parameters and chemical composition

The compounds classes and the major constituents amounts with an average content equal to or greater than 3% were analyzed using the Person correlation coefficient to obtain data on the influence of climatic parameters on the concentrations. Among the major compounds, (E)-caryophyllene and aromandrene did not present a significant correlation with any climatic aspect. Caryophyllene oxide indicated a strong positive correlation with temperature (r = 0.72) and a moderate negative correlation with humidity (r = -0.67). The compound 1-epi-cubenol revealed a strong negative correlation with temperature (r = -0.72) and a moderate positive correlation with humidity (r = 0.60). Futhermore, δ-cadinene showed a moderate and negative correlation with temperature (r = -0.53). Moreover, γ-muurolene demonstrated a moderate and positive correlation with insolation (r = 0.64) (Figure 4).

Figure 4
Correlation of the classes of the compounds, and major constituents present in Myrciaria tenella in relation to climatic parameters.

In Figure 4, all classes displayed moderate correlations with temperature, being positive in monoterpenes hydrocarbons (r = 0.67) and oxygenated sesquiterpenes (r = 0.55); and negative for sesquiterpines hydrocarbons (r = -0.57). Moreover, monoterpenes hydrocarbons exhibited a moderate and negative correlation with humidity (r = -0.58).

This demonstrates that temperature, humidity, and insolation were preponderant factors that may influence the amounts of certain constituents and classes of constituents present in the EO of M. tenella. The precipitation parameter, although closely related to other parameters, did not show any correlation in the levels analyzed here.

Regarding (E)-caryophyllene, it presented high levels in most months and was absent only in November. Although weak, its correlation with temperature and the correlation of its class (sesquiterpene hydrocarbon) presented negative values, indicating that its level (and the level of this class) possibly decreased as the temperature increased in each month, and November was the hottest month during the study, with an average monthly temperature of 27.7 °C.

In the seasonal study of Eugenia patrisii EO, different results were found, (E)-caryophyllene displayed a moderate positive correlation with temperature (r = 0.65), caryophyllene oxide showed significant correlation with temperature (r = -0.85), humidity (r = 0.73), and insolation (r = -0.74).³³

The production of secondary metabolites, especially volatile terpenes, is closely linked to factors external to the plant. Terpenes are of utmost importance in the interaction of the plant with biotic factors, such as fighting predators, communicating with other plants and responding to environmental stress, directly influencing the biosynthesis of compounds, and providing a wide variety of constituents in the essential oil.³⁴

Multivariate analysis

The chemical variability was analyzed by principal component analysis (PCA), using as a data matrix the constituents with content greater than or equal to 3.5%. PCA explained 79.28% of the available data, with PC1 accounting for 43.18% and showing positive correlations with (E)-caryophyllene (r = 0.37), α-humulene (r = 0.36), γ-muurolene (r = 0.27), γ-patchoulene (r = 0.31), γ-cadinene (r = 0.24), δ-cadinene (r = 0.32), α-calacorene (r = 0.31), and 1-epi-cubenol (r = 0.24). PC2 explained 24.63% of the data, demonstrating positive correlations with α-humulene (r = 0.04), γ-muurolene (r = 0.33), γ-patchoulene (r = 0.15), γ-cadinene (r = 0.31), 7-epi-α-selinene (r = 0.18), caryophyllene oxide (r = 0.23), and α-cadinol (r = 0.29). PC3 represents 11.47% of the data, with positive correlation with (E)-caryophyllene (r = 0.03), aromadendrene (r = 0.06), α-humulene (r = 0.13), α-selinene (r = 0.14), γ-patchoulene (r = 0.01), 7-epi-α-selinene (r = 0.30), α-calacorene (r = 0.09), viridiflorol (r = 0.58), 1-epi-cubenol (r = 0.02), and α-cadinol (r = 0.49) (Figure 5).

Figure 5
Principal components analysis of Myrciaria tenella essential oil during the seasonal study.

As displayed in Figure 5, the samples presented a homogeneous distribution throughout the rainy and dry months without the evident formation of similarity groups. This pattern suggests that the essential oil may undergo metabolic variations throughout the year, regardless of the season.

According to Defaveri et al.,³⁵ leaves of Eugenia neonitida and E. rotundifolia (Myrtaceae) collected quarterly in the city of Rio de Janeiro displayed as major compounds bicyclogermacrene (15.2-21.0%), germacrene D (5.7 18.7%), and (E) caryophyllene (6.7 11.0%) in E. neonitida EOs; and α-pinene (19.7 34.4%), β-pinene (20.6-34.1%), and (E)-caryophyllene (3.6-11.7%) in E. rotundifolia EOs. Considering that there were quantitative and qualitative variations in the EOs of these species, the seasonality did not interfere with the chemical composition. So, different results of this work, mainly in the levels of (E)-caryophyllene and caryophyllene oxide were found.

Conclusions

This study showed that the yield of Myrciaria tenella essential oil showed variations throughout the year; however, this change was not significant, indicating that the yield is not directly related to climatic conditions.

There were variations in the compounds in higher content, which were shown to be sensitive to climatic parameters such as temperature, humidity, and insolation. The multivariate analysis, in turn, did not group the dried and rainy season samples, evidencing a high chemical variability among the samples throughout the year.

These results indicate that the essential oil of M. tenella, although presenting stability in yield, may impact variations in the therapeutic properties of the species and should be considered in future therapeutic and industrial applications.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Acknowledgments

The authors thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for financial support (process 443973/2024-5). L.S.P.B. thanks CAPES for the scholarship. R. M. V. thanks the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for scholarship.

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Edited by

• Editor handled this article:
  Hector Henrique F. Koolen (Associate)

Publication Dates

• Publication in this collection
  08 Sept 2025
• Date of issue
  2025

History

• Received
  19 June 2025
• Accepted
  30 July 2025