Chemical variability in the essential oil of leaves of Araçá (Psidium guineense Sw.), with occurrence in the Amazon.

BACKGROUND: Psidium guineense, known as Araçá, is a Brazilian botanical resource with commercial application perspectives, based on the functional elements of its fruits and due to the use of its leaves as an anti-inflammatory and antibacterial agent. The essential oils of leaves of twelve specimens of Araçá were analyzed by GC and GC-MS to identify their volatile constituents and associate them with the biological activities reputed to the plant.
RESULTS: In a total of 157 identified compounds, limonene, α-pinene, β-caryophyllene, epi-β-bisabolol, caryophyllene oxide, β-bisabolene, α-copaene, myrcene, muurola-4,10(14)-dien-1-β-ol, β-bisabolol, and ar-curcumene were the primary components in descending order up to 5%. Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) displayed three different groups with the following chemical types: limonene/α-pinene, β-bisabolene/epi-β-bisabolol, and β-caryophyllene/caryophyllene oxide. With the previous description of another chemical type rich in spathulenol, it is now understood that at least four different chemotypes for P. guineense should occur.
CONCLUSIONS: In addition to the use of the Araçá fruits, which are rich in minerals and functional elements, it should be borne in mind that the knowledge of the chemical composition of the essential oils of leaves of their different chemical types may contribute to the selection of varieties with more significant biological activity.

Background

Myrtaceae comprises 132 genera and 5671 species of trees and shrubs, which are distributed mainly in tropical and subtropical regions of the world, particularly South America, Australia and Tropical Asia [1]. It is one of the most prominent families in Brazil, represented by 23 genera and 1034 species, with occurrence in all regions of the country [2, 3]. Psidium is a genus with at least 60 to 100 species, occurring from Mexico and Caribbean to Argentina and Uruguay. Therefore, it is naturally an American genus, although P. guajava, P. guineense and P. cattleyanum are subtropical and tropical species in many other parts of the world [4].

Psidium guineense Swartz [syn. Guajava guineensis (Sw.) Kuntze, Myrtus guineensis (Sw.) Kuntze, Psidium araca Raddi, P. guyanense Pers., P. laurifolium O. Berg, P. rotundifolium Standl., P. sprucei O. Berg, among others [5] (www.tropicos.org/Name/22102032) is a native shrub or small tree up to about 6 m high occurring in all Brazilian biomes, commonly known as Araçá. It has a berry-type fruit with yellow, red or purple peel and whitish pulp, rich in minerals and functional elements, such as vitamin C and phenolic compounds [6-9]. The leaves and pulp of Araçá have been used as an anti-inflammatory remedy for wound healing and oral antibacterial agent [10, 11], as well as it presented antibacterial activity against pathogenic microorganisms [11-13]. Some essential oils of Araçá were previously described: Foliar oil from a specimen growing in Arizona, USA, with predominance of β-bisabolene, α-pinene and limonene [14]; foliar oil from a specimen collected in Roraima, Brazil, with β-bisabolol, epi-α-bisabolol and limonene as the main constituents [15]; and another foliar oil from a specimen sampled in Mato Grosso do Sul Brazil, where spathulenol was the primary volatile compound [16].

The present work aimed at investigating the variability of the chemical composition of the essential oils of different specimens of Psidium guineense, occurring in the Amazon region, to contribute to the knowledge of its chemical types.

Experimental

Plant material

The leaf samples of twelve Psidium guineense specimens were collected in Pará state, Brazil. Collection site and voucher number of each specimen are listed in Table 1. The plant vouchers after the identification were deposited in the Herbaria of Embrapa Amazônia Oriental, in Belém (IAN) and Santarém (HSTM), Pará state, Brazil. The leaves were dried for two days in the natural environment and, then, subjected to essential oil distillation.

Table 1

Identification data and collection site of the specimens of Psidium guineense

Samples	Collection site	Herbarium Nº	Local coordinates
PG-01	Curuçá, PA, Brazil	IAN-195396	0°72’65” S/47°84’07” W
PG-02	Curuçá, PA, Brazil	IAN-195397	0°43’40” S/47°50’58” W
PG-03	Curuçá, PA, Brazil	IAN-195398	0°72’67” S/47°85’13” W
PG-04	Curuçá, PA, Brazil	IAN-195399	0°72’57” S/47°84’84” W
PG-05	Curuçá, PA, Brazil	IAN-195400	0°72’57” S/47°84’07” W
PG-06	Santarém, PA, Brazil	HSTM-3611	2°27’48.7” S/54°44’04” W
PG-07	Monte Alegre, PA, Brazil	HSTM-6763	1°57’24.9” S/54°07’07.8” W
PG-08	Monte Alegre, PA, Brazil	HSTM-6763	1°57’24.9” S/54°07’07.8” W
PG-09	Santarém, PA, Brazil	HSTM-6775	2°25’14.6” S/54°44’25.8” W
PG-10	Santarém, PA, Brazil	HSTM-3603	2°25’08.4” S/54°44’28.3” W
PG-11	Santarém, PA, Brazil	HSTM-6769	2°29’16.8” S/54°42’07.9” W
PG-12	Ponta de Pedras, PA, Brazil	HSTM-6759	2°31’08.3” S/54°52’25.8” W

Isolation and analysis of the composition of oils

The leaves were ground and submitted to hydrodistillation using a Clevenger-type apparatus (3 h). The oils were dried over anhydrous sodium sulfate, and their yields were calculated by the plant dry weight. The moisture content of the samples was calculated using an Infrared Moisture Balance for water loss measurement. The procedure was performed in duplicate.

The oils were analyzed on a GCMS-QP2010 Ultra system (Shimadzu Corporation, Tokyo, Japan), equipped with an AOC-20i auto-injector and the GCMS-Solution software containing the NIST (Nist, 2011) and FFNSC 2 (Mondello, 2011) libraries [17, 18]. A Rxi-5ms (30 m x 0.25 mm; 0.25 μm film thickness) silica capillary column (Restek Corporation, Bellefonte, PA, USA) was used. The conditions of analysis were: injector temperature of 250 °C; Oven temperature programming of 60-240 °C (3 °C/min); Helium as carrier gas, adjusted to a linear velocity of 36.5 cm/s (1.0 mL/min); split mode injection for 1 μL of sample (oil 5 μL : hexane 500 μL); split ratio 1:20; ionization by electronic impact at 70 eV; ionization source and transfer line temperatures of 200 and 250 °C, respectively. The mass spectra were obtained by automatic scanning every 0.3 s, with mass fragments in the range of 35-400 m/z. The retention index was calculated for all volatile components using a homologous series of C8-C20 n-alkanes (Sigma-Aldrich, USA), according to the linear equation of Van den Dool and Kratz (1963) [19]. The quantitative data regarding the volatile constituents were obtained by peak-area normalization using a GC 6890 Plus Series, coupled to FID Detector, operated under similar conditions of the GC-MS system. The components of oils were identified by comparing their retention indices and mass spectra (molecular mass and fragmentation pattern) with data stored in the GCMS-Solution system libraries, including the Adams library (2007) [20].

Statistical analysis

The multivariate analysis was performed using as variables the constituents with content above than 5%. For the multivariate analysis, the data matrix was standardized by subtracting the mean and then dividing it by the standard deviation. For hierarchical cluster analysis, the complete linkage method and the Euclidean distance were used. Minitab software (free 390 version, Minitab Inc., State College, PA, USA), was used for these analyzes.

Results and discussion

Yield and composition of the oils

Psidium guineense is a botanical resource that presents commercial application perspectives, based on its fruits and functional elements, as well as due to the use of its leaves as anti-inflammatory and antibacterial agent [6-14]. For this study were selected twelve Araçá specimens, with occurrence in various localities of Pará state (PA), Brazil (see Table 1), and which showed different composition for the leaf oils. The yields of the oils from these twelve Araçá samples ranged from 0.1 to 0.9%, where the higher yields were from specimens sampled in the Northeast of Pará, Brazil (0.4-0.9%), and the lower yields were from plants collected in the West of Pará, Brazil (0.1-0.3%). The identification of the constituents of the oils by GC and GC-MS was 92.5% on average, with a total of 157 compounds, where limonene (0.3-47.4%), α-pinene (0.1-35.6%), β-caryophyllene (0.1-24.0%), epi-β-bisabolol (6.5-18.1%), caryophyllene oxide (0.3-14.1%), β-bisabolene (0.1-8.9%), α-copaene (0.3-8.1%), myrcene (0.1-7.3%), muurola-4,10(14)-dien-1-β-ol (1.6-5.8%), β-bisabolol (2.9-5.6%), and ar-curcumene (0.1-5.0%) were the primary components, in descending order up to 5% (see Figure 1 and Table 2). In general, the constituents identified in oils belong to the terpenoids class, with the following predominance: monoterpene hydrocarbons (0.9-76.9%), oxygenated sesquiterpenes (5.2-63.5%), sesquiterpene hydrocarbons (5.6-46.7%), and oxygenated monoterpenes (1.9-8.8%).

Fig. 1

Main constituents identified in the oils of P. guineense: (1) α-pinene, (2) myrcene, (3) limonene, (4) β-caryophyllene, (5) caryophyllene oxide, (6) α-copaene, (7) ar-curcumene, (8) β-bisabolene, (9) muurola-4,10(14)-dien-1-β-ol, (10) epi-β-bisabolol, (11) β-bisabolol

Table 2

Yield and volatile composition of twelve essential oil samples of P. guineense

RI(C)	RI(L)	Constituents (%)	PG-01	PG-02	PG-03	PG-04	PG-05	PG-06	PG-07	PG-08	PG-09	PG-10	PG-11	PG-12
848	846a	(2E)-Hexenal					0.3	0.1
850	850a	(3Z)-Hexenol					0.2	0.1		0.1	0.1
933	932a	α-Pinene	35.6	26.1	17.7	13.4	34.0	26.4	2.0	0.8	1.0	1.3	0.1	0.6
946	948a	α-Fenchene	0.1		0.1		0.1
957	952a	Benzaldehyde	0.3	0.5	1.1	0.8	0.9	0.6	0.1	0.4	0.3	0.3	0.5	0.1
977	974a	β-Pinene	2.1	1.8	1.4	1.3	1.7	3.9	0.1					0.3
985	981a	6-methyl-5-Hepten-2-one			0.2		0.1		0.1	0.4	0.1		0.1	0.1
990	988a	Myrcene	0.2	1.4	1.2	1.4	1.3	1.6	0.1	0.1	0.6	0.7	0.1	7.3
1005	1003a	p-Mentha-1(7),8-diene		0.5	0.9	1.0	0.7	0.3	0.1	0.2	0.7	1.2		0.1
1016	1014a	α-Terpinene		0.1		0.1		0.1
1023	1020a	p-Cymene	0.3	0.5	1.0	0.7	1.4	0.5	0.2	0.3	0.4	0.3	0.1	0.6
1028	1024a	Limonene	3.7	30.7	30.4	26.5	37.2	14.0	4.3	9.6	23.4	47.4	0.3	5.4
1031	1032b	1,8-Cineole	0.3	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.1		1.7	0.8
1035	1032a	(Z)-β-Ocimene	0.1		0.1	0.1			0.1				0.1	0.1
1046	1044a	(E)-β-Ocimene	0.1		0.2	0.1		0.1	0.8				0.1	0.1
1057	1054a	γ-Terpinene	0.6	0.4	0.7	0.6	0.3	0.9			0.2	0.2	0.1	0.1
1088	1086a	Terpinolene	0.1	0.1	0.2	0.1	0.1	0.3			0.1			0.1
1100	1095a	Linalool	0.1		0.1	0.1		0.1		0.2	0.1		0.1	0.1
1114	1114a	endo-Fenchol	0.1	0.1	0.1		0.1	0.1
1116	1113b	4,8-dimethyl-(E)-Nona-1,3,7-triene	0.1		0.1
1120	1122b	trans-p-Mentha-2,8-dien-1-ol			0.1	0.1	0.1
1125	1122a	α-Campholenal	0.1		0.1		0.1	0.1
1130	1131b	Limona ketone								1.6
1134	1133a	cis-p-Mentha-2,8-dien-1-ol					0.1			0.1	0.1			0.1
1138	1136a	trans-p-Menth-2-en-1ol												0.1
1139	1135a	trans-Pinocarveol	0.4	0.1	0.4	0.1	0.4	0.4	0.2
1148	1145a	Camphene hydrate	0.1	0.1	0.1	0.1	0.1	0.2
1161	1165b	Hydrocinnamaldehyde			0.9	1.5	0.5
1166	1165a	Borneol	0.2	0.1	0.2	0.1	0.2	0.3
1177	1174a	Terpinen-4-ol	0.1	0.1	0.2	0.1	0.2	0.3			0.1
1186	1187a	trans-p-Mentha-1(7),8-dien-2-ol		0.1				0.1		0.4	0.2
1187	1189a	trans-Isocarveol			0.4		0.2
1191	1186a	α-Terpineol	1.0	0.6	1.3	0.4	1.0	1.7	0.2	0.2	0.1		0.1	0.1
1218	1215a	trans-Carveol			0.2		0.1	0.1		0.1	0.1
1221	1218a	endo-Fenchyl acetate	0.7	0.2	0.4	0.3	0.4	0.7
1226	1227a	cis-p-Mentha-1(7),8-dien-2-ol			0.4		0.2	0.1		0.3	0.1
1243	1239a	Carvone			0.1					0.1	0.1
1267	1261a	cis-Chrysanthenyl acetate		0.1	0.1	0.1	0.1	0.4						0.1
1286	1287a	Bornyl acetate	1.5	0.6	0.7	0.5	0.9	1.5	0.1					0.1
1300	1298a	trans-Pinocarvyl acetate	1.5	0.3	0.3	0.2	0.8	1.6
1324	1322a	Methyl geranate		0.2	0.6	0.6	0.4		0.3	0.3	0.9	2.0	0.3
1326	1324a	Myrtenyl acetate	0.1					0.2
1336	1335a	δ-Elemene	0.2	0.1			0.1	0.1		0.1		2.3
1338	1339a	trans-Carvyl acetate			0.1	0.1	0.2	0.1
1364	1359a	Neryl acetate	0.1	0.1	0.1			0.1
1367	1369a	Cyclosativene	0.1		0.1	0.1
1378	1374a	α-Copaene	8.1	6.2	8.1	7.2	3.0	3.7	4.2	4.7	2.5		1.1	0.3
1383	1379a	Geranyl acetate	0.1	1.1	1.0	1.7	0.6	0.8	0.2	0.2	1.9	0.5	0.8
1401	1401a	iso-Italicene							0.5	0.6	0.6	0.2	0.1
1406	1405a	Sesquithujene							0.1		0.1		0.1
1412	1410a	α-Cedrene							0.8	0.8	1.0	0.4	0.5
1416	1407a	Acora-3,7(14)-diene							0.9	0.6	1.0	0.5
1423	1417a	β-Caryophyllene	6.1	2.8	0.1	0.1	0.8	5.2	1.4		1.0	0.9	1.1	24.0
1426	1419a	β-Cedrene							0.1	0.3	0.1		0.1
1431	1430a	β-Copaene							0.2	0.2	0.2		0.1	0.1
1435	1434a	γ-Elemene												0.2
1436	1432a	trans-α-Bergamotene							0.3	0.3	0.3		0.2
1436	1435b	Perillyl acetate	0.1	0.1	0.1	0.2	0.1	0.1			0.2	0.4
1440	1439a	Aromadendrene	0.2	0.1		0.2		0.2	0.2	0.2
1441	1439a	Phenyl ethyl but-2-anoate												0.4
1444	1440a	(Z)-β-Farnesene							0.2
1444	1442a	Guaia-6,9-diene								0.3
1447	1445a	epi-β-Santalene							0.1		0.1		0.1
1452	1449a	Amorpha-4,11-diene							0.3		0.3
1452	1453a	Geranyl acetone			0.1								0.2
1455	1452a	α-Humulene	0.9	0.7	0.3	0.5	0.1	0.9	0.4		0.1		0.2	2.8
1458	1454a	(E)-β-Farnesene							1.0	0.1	0.5	0.2	0.3	0.1
1460	1457a	β-Santalene							1.2		1.1	0.5	0.5
1461	1460a	allo-Aromadendrene	0.2	0.2	0.3	0.3	0.1	0.1
1464	1464a	α-Acoradiene							1.3	1.1	1.3	0.6	0.7
1467	1469a	β-Acoradiene							0.4	0.3	0.4	0.2	0.2
1471	1471a	4,5-di-epi-Aristolochene				0.1		0.1	0.1	0.1				0.1
1474	1474a	10-epi-β-Acoradiene							0.4	0.3	0.4		0.2
1477	1475a	γ-Gurjunene		0.3				0.3
1477	1476a	β-Chamigrene												1.0
1479	1478a	γ-Muurolene			0.4	0.8	0.1		0.3	0.5	0.2		0.1
1479	1481a	γ-Curcumene							0.4		1.1	0.8	0.7
1482	1479a	ar -Curcumene							5.0	4.6	2.5	0.6	1.6	0.1
1486	1481a	γ-Himachalene	1.0	0.9									0.4
1488	1488a	β-Selinene	0.7	0.8	1.0	3.8	0.5	3.2	3.0	3.7	0.1			3.2
1495	1493a	α-Zingiberene									0.4	0.3	0.7
1497	1498a	α-Selinene			0.9	3.7	0.3	2.7	4.3	2.4				3.2
1502	1500a	α-Muurolene	0.4	0.3	0.5	0.5	0.1	0.2	0.3	0.4	0.2		0.1	0.2
1502	1506a	(Z)-α-Bisabolene	0.1						0.8	0.3	1.0	0.7	0.6	0.1
1509	1505a	(E,E)-α-Farnesene												2.6
1509	1511a	δ-Amorphene				0.4
1510	1508b	β-Bisabolene	0.1						8.9	4.0	6.4	5.2	4.0
1512	1514a	β-Curcumene							2.0	0.1	3.6	2.9	2.5
1516	1513a	γ-Cadinene	0.3	0.3	0.3	0.4	0.1	0.2	2.9	0.5				0.2
1516	1514a	(Z)-γ-Bisabolene							0.9		1.1	1.0	1.0
1519	1520a	7-epi-α-Selinene				0.1		0.1						0.1
1522	1524a	δ-Cadinene	1.0	1.9	1.7	2.6	0.3	0.7		0.8	2.7	1.9		0.7
1525	1521a	β-Sesquiphellandrene											1.8
1532	1529a	(E)-γ-Bisabolene							2.7		2.3	2.0	1.4	0.1
1534	1533a	trans-Cadina-1,4-diene	0.1	0.1	0.1	0.1		0.1
1534	1536a	Italicene ether							0.2	0.5	0.2		0.5
1539	1540a	10-epi-cis-Dracunculifoliol							0.1	0.4	0.1
1543	1540b	(E)-α-Bisabolene							0.8		0.6	0.4	0.4
1543	1545a	Selina-3,7(11)-diene												0.8
1544	1544a	α-Calacorene			0.2	0.3	0.1	0.3		0.7
1559	1559a	Germacrene B						0.1			1.1			0.4
1565	1561a	E-Nerolidol	0.3	0.1	0.4	0.2		0.1	1.0	1.3		0.9	2.2	0.2
1570	1571a	Caryolan-8-ol												0.4
1572	1570a	Caryophyllenyl alcohol	0.3					0.2
1579	1578b	ar-Tumerol							0.3	0.6	0.1
1580	1577a	Spathulenol	0.7						0.4	0.6
1584	1590a	Globulol		0.1		0.4
1585	1586a	Gleenol			0.3
1586	1582a	Caryophyllene oxide	2.5	0.7			0.6	2.7	1.0		0.3		1.2	14.1
1589	1590a	β-Copaen-4-α-ol			0.5	0.1	0.2	0.3	0.2	0.8
1594	1592a	Viridiflorol	0.2	0.9	0.2	0.1	0.1	0.1	0.2	0.3			0.2	0.3
1596	1595a	Cubeban-11-ol							0.1	0.2
1599	1600a	Guaiol												0.5
1601	1600a	Cedrol							0.4	0.4	0.5		0.8
1609	1619a	(Z)-8-hydroxy-Linalool							0.9	0.7	0.1
1611	1613b	Humulene Epoxide	0.4	0.1	0.1		0.1							1.0
1615	1613b	Copaborneol					0.4
1617	1618a	1,10-di-epi-Cubenol					0.2							1.7
1625	1622a	10-epi-γ-Eudesmol							1.3	1.0	1.7	0.7	2.1
1630	1627a	epi-Cubenol							1.5	3.4	0.7	0.5
1631	1632a	α-Acorenol							1.5	1.1	1.8	1.2	4.3
1632	1630a	Muurola-4,10(14)-dien-1-β-ol	5.8	2.4	3.6	2.3	1.6	2.6
1635	1636a	β-Acorenol							0.4	0.5	0.3		0.8
1637	1636a	Gossonorol							1.0	1.6	0.5	0.3	1.1
1639	1638a	Caryophylla-4(12),8(13)-dien-5β-ol	1.3	0.3			0.3	2.1						1.5
1639	1642b	Caryophylla -4(12),8(13)-dien-5α-ol	3.1
1641	1638a	epi-α-Cadinol	1.9	1.8	1.7	1.7	0.6	1.3	1.1	1.6	0.4	0.8	1.4
1645	1640a	epi-α-Murrolol	1.1	0.9					1.2		0.3			2.6
1646	1640a	Hinesol							0.6	1.8	0.7	0.4	1.1
1649	1644a	α-Muurolol			1.2	1.1	0.4	0.8			1.1	1.0	1.6	3.1
1653	1649a	β-Eudesmol				0.1		0.1	0.2	0.1				0.7
1654	1652a	α-Cadinol	1.8	2.0	1.8						0.5	0.4	2.4
1655	1651a	Pogostol							3.8	4.8		0.1
1659	1658a	Selin-11-en-4α-ol				4.2		3.7						4.4
1659	1668b	Intermedeol				0.2								0.5
1660	1656a	α-Bisabolol Oxide B											2.3
1671	1670a	epi -β-Bisabolol							8.1	6.5	9.5	8.2	18.1
1674	1674a	β-Bisabolol							2.9	1.9	3.6	3.9	5.6
1675	1671a	14-hydroxy-9-epi-β-Caryophyllene	1.4					0.7						1.3
1677	1675a	Cadalene						0.1		0.6
1678	1674a	Helifolenol A								0.6	0.2
1680	1679a	Khusinol			0.3	0.2
1685	1683a	epi-α-Bisabolol							1.0	0.8	1.3	1.2	2.5
1687	1685a	α-Bisabolol							2.8	4.0	2.6	2.2	3.4
1692	1692a	Acorenone												0.2
1696	1696b	Juniper camphor												0.8
1698	1700a	Eudesm-7(11)-en-4-ol							0.1					0.1
1714	1713a	(2E,6Z)-Farnesal	0.2	1.3	1.5	2.7	0.2				1.0	0.4	2.8
1721	1722a	(2Z,6E)-Farnesol			3.7	4.6	0.2							0.1
1722	1724a	(2E,6E)-Farnesol	0.4	2.2				1.1		0.2	0.9	0.3	4.9
1741	1740a	(2E,6E)-Farnesal	0.3	1.9	2.1	3.6	0.4			0.7	1.4	0.6	3.8
1751	1751a	Xanthorrhizol							0.1	0.1
1757	1753a	Isobaeckeol								0.2
1767	1768a	β-Bisabolenal		0.1	0.2	0.2							0.1
1841	1832b	Farnesyl acetate	0.1	0.3	0.2				0.1
1843	1845a	(2E,6E)-Farnesyl acetate				0.7		0.1	0.1		0.1		0.1
1962	1958a	Geranyl benzoate		0.1	0.1	0.2					0.2		0.1
Monoterpenes hydrocarbons			42.9	61.6	54.0	45.5	76.9	48.1	7.8	11.0	26.4	51.1	0.9	14.6
Oxygenated monoterpenes			6.6	3.9	7.5	4.7	6.5	8.8	1.9	4.5	3.9	2.8	3.2	1.4
Sesquiterpene hydrocarbons			19.5	14.6	14.0	21.1	5.6	18.6	46.7	28.0	34.3	21.3	20.7	40.1
Oxygenated sesquiterpenes			21.8	15.1	17.8	22.5	5.2	15.9	31.2	36.5	30.2	23.0	63.5	33.6
Others			0.3	1.8	2.1	2.4	1.9	0.8	0.4	0.9	0.5	0.8	0.6	0.8
Total (%)			91.1	97.0	95.4	96.2	96.1	92.2	88.0	80.9	95.3	99.0	88.9	90.5
Yield of oil (%)			0.6	0.6	0.6	0.9	0.4	0.3	0.2	0.1	0.1	0.2	0.2	0.2

Italic: main constituents above 5%

RI(C) retention time calculated; RI(L) retention time of literature

a Adams [20]

b Mondello [18]

Comparing these results with the composition of other essential oils described for the same plant, a specimen of P. guineense sampled in Arizona, USA, has also been found to contain β-bisabolene, α-pinene, and limonene as its primary constituents [14]. In addition, the oil from another specimen collected in Roraima, Brazil, presented β-bisabolol as the main component, followed by limonene and epi-α-bisabolol [15]. On the other hand, a specimen sampled in Mato Grosso do Sul, Brazil, presented an essential oil with a very high value of spathulenol [16]. Therefore, it is possible that there is a significant variation in the essential oils of different types of Araçá.

Variability in oils composition

The multivariate analysis of PCA (Principal Component Analysis) (Fig. 2) and HCA (Hierarchical Cluster Analysis) (Fig. 3) were applied to the primary constituents present in oils (content ≥ 5.0%), for the evaluation of chemical variability among the P. guineense specimens.

Fig. 2

Dendrogram representing the similarity relation in the oils composition of P. guineense

Fig. 3

Biplot (PCA) resulting from the analysis of the oils of P. guineense

The HCA analysis performed with complete binding and Euclidean distance showed the formation of three different groups. These were confirmed by the PCA analysis, which accounted for 79.5% of the data variance. The three groups were classified as:

Group I Characterized by the presence of the monoterpenes α-pinene (13.4-35.6%) and limonene (3,7-37,2%), composed by the specimens PG-01 to PG-06, collected in Curuçá (PG -01 to PG-05) and Santarém (PG-06), Pará state, Brazil, with 49.2% similarity between the samples.

Group II Characterized by the presence of the sesquiterpenes β-bisabolene (4.0-8.9%) and epi-β-bisabolol (6.5-18.1%), consisting by PG-07 to PG-10 specimens collected in Monte Alegre (PG-07 and PG-08) and Santarém (PG-09 and PG-10), Pará State, Brazil, with 50.3% similarity between samples.

Group III Characterized by the presence of a significant content of β-caryophyllene (24.0%) and caryophyllene oxide (14.1%), constituted by the PG-12 specimen, collected in the city of Ponta de Pedras, Pará state, Brazil, which presented zero% similarity with the other groups.

Thus, based on the study of these essential oils, the multivariate analysis (PCA and HCA) has suggested the existence of three chemical types among the twelve specimens of P. guineense collected in different locations of the Brazilian Amazon. It would then be the chemical types α-pinene/limonene (Group I), β-bisabolene/epi-β-bisabolol (Group II) and β-caryophyllene/caryophyllene oxide (Group III). Taking into account that two essential oils with a predominance of α-pinene/limonene and β-bisabolene/epi-β-bisabolol, respectively, were previously described [14, 15], it is understood that adding these two chemical types to that one rich in β-caryophyllene + caryophyllene oxide, which was a product of this study, besides the other chemical type with a high value of spathulenol, before reported by Nascimento and colleagues (2018) [16], will be now, at least, four chemical types known for the P. guineense essential oils.

Several studies have demonstrated the anti-inflammatory activities of limonene, α-pinene and β-caryophyllene, the primary constituents found in the oils of P. guineense presented in this paper. Limonene showed significant anti-inflammatory effects both in vivo and in vitro, suggesting a beneficial role as a diet supplement in reducing inflammation [21]; limonene decreased the infiltration of peritoneal exudate leukocytes and reduced the number of polymorphonuclear leukocytes, in the induced peritonitis [22]. α-Pinene presented anti-inflammatory effects in human chondrocytes, exhibiting potential anti-osteoarthritic activity [23], and in mouse peritoneal macrophages induced by lipopolysaccharides [24], being, therefore, a potential source for the pharmaceutical industry. The anti-arthritic and the in vivo anti-inflammatory activities of β-caryophyllene was evaluated by molecular imaging [25].

Conclusion

In addition to the great use of the fruits of P. guineense, which are rich in minerals and functional elements, it is understood that the knowledge of the chemical composition of the essential oils of leaves of their different chemical types may contribute to the selection of varieties with more significant biological activity. The study intended to address this gap.