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. 2021 Nov 30;26(23):7283. doi: 10.3390/molecules26237283

Volatolomics of Three South African Helichrysum Species Grown in Pot under Protected Environment

Basma Najar 1, Ylenia Pieracci 1,*, Claudio Cervelli 2, Guido Flamini 1,3,*, Luisa Pistelli 1,3
Editors: Henryk H Jeleń, Antoni Szumny
PMCID: PMC8659169  PMID: 34885854

Abstract

Helichrysum decorum DC, Helichrysum lepidissimum S. Moore, and Helichrysum umbraculigerum are three species traditionally used in the South African medicine. The present work deals with the investigation of the spontaneous emission and the essential oils obtained from these plants cultivated in open field under uniform conditions. Fractions of the volatile organic compounds of the three species were rich in monoterpene hydrocarbons, representing more than 70% of the total composition. Pinene isomers were the most representative compounds: β-pinene in H. decorum (53.0%), and α-pinene in H. lepidissimum (67.9%) and H. umbraculigerum (54.8%). These latter two species evidenced an important amount of sesquiterpene hydrocarbons (SH) especially represented by γ-curcumene (H. lepidissimum) and α- and β-selinene (H. umbraculigerum). On the contrary, in the EOs, sesquiterpenes compounds prevailed, representing more than 64% of the identified fraction to reach more than 82 and 87% in H. umbraculigerum and H. lepidissimum, respectively. Although the chemical classes and their relative abundances were comparable among the three species, the individual compounds of EOs showed large differences. In fact, caryophyllene oxide (26.7%) and γ-curcumene (17.4%) were the main constituents in H. decorum, and H. lepidissimum respectively, while neo-intermedeol (11.2%) and viridiflorol (10.6%) characterized H. umbraculigerum.

Keywords: Helichrysum decorum, Helichrysum lepidissimum, Helichrysum umbraculigerum, sesquiterpenes, hydrodistillation, SPME, GC-MS

1. Introduction

The genus Helichrysum, belonging to the family Asteraceae, comprises more than 500 species, of which almost half are indigenous to South Africa [1,2,3]. Different species of Helichrysum are widely used in the traditional local medicine, thanks to the variety of secondary metabolites that the plants belonging to this genus can produce [3]. Their aerial parts are employed as herbal teas for the treatment of respiratory issues, digestive problems, as diuretic and anti-inflammatory agents, and for other purposes [4,5]. Several Helichrysum species are appreciated for their aroma profile, strictly connected to the presence of essential oils, produced and stored in the glandular trichomes located in almost all the vegetative epigeal parts of the plant [4]. The essential oil plays an important role for the taxonomic attribution of these species [6], as well as for their biological activities [7]. Helichrysum species are, indeed, characterized by a huge genetic variability, due to their polymorphisms, as a consequence of different environmental and growing conditions. It was observed that both the different morphological characters of the plants and the chemotypes of their EOs are attributable to the genetic heritage as well, and therefore the chemical composition can be used for the taxonomic identification [8]. In the last decades, it is no coincidence that the essential oils obtained from different species of this genus received increasing interest, for both their chemical composition and their biological activities [2,7,9].

Continuing our research on the utilization of Helichrysum spp. indigenous of South Africa, in collaboration with Centro di Ricerca Orticoltura e Florovivaismo (CREA-OF) located in Sanremo (Italy), three new Helichrysum species were investigated. Helichrysum lepidissimum S. Moore and Helichrysum umbraculigerum Less. are biennial or perennial herb shrubs, Helichrysum decorum DC is a plant growing in sandy grassland or open woodland from sea level to 900 m. The African Zulu inzagomas (diviners) smoked/inhaled or burned unspecific parts of the plant, which resulted in a trance state [3]. Growing on rocky grounds in submontane areas, H. lepidissimum is a perennial shrub [10] from which Mkhize (2015) isolated lepidissipyrone [11]. This compound showed a structure similar to arzanol, isolated from H. italicum ssp. microphyllum, and it was known for its antioxidant, anti-inflammatory and anti-HIV activities. According to Lourens et al., 2008 the powder and ointment prepared from this species are used as a body ointment in traditional usage [3]. H. umbraculigerum, instead, is a perennial erected plant reported in several studies as the main natural source of cannabigerol [12].

Despite their important traditional uses, investigations on these Helichrysum species are lacking, and the studies reported in the literature only cite them without any other research on their biological activity or on their secondary metabolites content. This work aims to evaluate the chemical composition of both the spontaneous volatile emissions and the essential oils of the three South African species of Helichrysum cultivated at the CREA-OF (Italy). To the best of our knowledge these investigations have never been previously reported in the literature.

2. Results and Discussions

2.1. Volatiles Organic Compounds (VOCs)

Thirty-six compounds were detected by GC-MS methods in the spontaneous volatile emissions, with a percentage of identification ranging between 99.5% to 100% of the whole volatilome (Table 1). H. umbraculigerum was the richest plant for variety of compounds emitted (21) compared to H. decorum (16) and H. lepidissimum (15). Interestingly, only four constituents were shared by the samples, and two of them (β-pinene and α-pinene) were major ones.

Table 1.

Complete chemical composition of spontaneous emissions of three analyzed Helichrysum samples.

Compounds a Class l.r.i exp l.r.i lit Relative Abundance (%) ± SD
H. decorum H. lepidissimum H. umbraculigerum
α-thujene mh 930 930 0.7 ± 0.08 0.3 ± 0.04 -
α-pinene mh 939 935 11.6 ± 0.33 67.9 ± 9.09 54.8 ± 5.88
camphene mh 954 943 0.4 ± 0.13 0.1 ± 0.08 6.4 ± 2.06
β-thujene mh 966 966 - - 0.5 ± 0.46
sabinene mh 975 973 23.8 ± 0.42 0.9 ± 0.11 -
β-pinene mh 979 974 53.0 ± 0.43 1.1 ± 0.08 2.7 ± 1.29
β-myrcene mh 991 991 0.6 ± 0.24 - 4.1 ± 0.21
(Z)-3-hexenyl acetate nt 1005 1009 0.4 ± 0.35 - -
α-terpinene mh 1017 1018 0.3 ± 0.00 - 0.3 ± 0.25
p-methyl anisole nt 1019 1024 - 0.5 ± 0.16 -
o-cymene mh 1026 1027 0.4 ± 0.05 - -
limonene mh 1029 1031 1.8 ± 0.40 - 3.1 ± 0.51
eucalyptol om 1031 1032 0.9 ± 0.64 1.2 ± 0.27 2.3 ± 1.77
γ-terpinene mh 1060 1062 0.7 ± 0.05 - 0.8 ± 0.28
terpinolene mh 1089 1088 - - 2.5 ± 0.52
linalool om 1097 1089 - - 0.6 ± 0.06
β-thujone om 1114 1115 2.7 ± 0.20 - -
α-ylangene sh 1375 1372 - - 0.5 ± 0.08
α-copaene sh 1377 1377 1.0 ± 0.04 - 1.4 ± 0.09
isoitalicene sh 1402 1398 - 0.4 ± 0.22 -
cis-α-bergamotene sh 1413 1415 - 0.4 ± 0.12 -
sesquithujene sh 1414 1417 - 0.5 ± 0.22 -
β-caryophyllene sh 1419 1420 0.6 ± 0.18 - 0.9 ± 0.33
α-humulene sh 1455 1455 - - 4.6 ± 1.56
sesquisabinene sh 1464 1461 - 0.9 ± 0.13 -
γ-muurolene sh 1480 1477 - - 1.9 ± 0.08
ar-curcumene sh 1481 1483 - 1.6 ± 0.51 -
γ-curcumene sh 1483 1484 - 23.1 ± 6.31 -
β-selinene sh 1490 1488 - - 3.9 ± 0.65
α-selinene sh 1498 1497 - - 6.2 ± 0.48
α-muurolene sh 1500 1499 0.6 ± 0.08 - -
epi-zonarene sh 1501 1500 - - 0.9 ± 0.10
β-bisabolene sh 1506 1509 - 0.3 ± 0.11 -
trans-γ-cadinene sh 1514 1514 - - 0.2 ± 0.13
β-curcumene sh 1516 1517 - 0.8 ± 0.37 -
δ-cadinene sh 1523 1524 - - 1.4 ± 0.04
Chemical Classes H. decorum H. lepidissimum H. umbraculigerum
Monoterpene Hydrocarbons (mh) 93.3 ± 1.17 70.3 ± 9.43 75.2 ± 5.35
Oxygenated Monoterpenes (om) 3.6 ± 0.20 1.2 ± 0.27 2.9 ± 1.82
Sesquiterpene Hydrocarbons (sh) 2.2 ± 0.30 28.0 ± 7.99 21.9 ± 3.19
Other non-terpene derivatives (nt) 0.4 ± 0.35 0.5 ± 0.16 -
Total Identified (%) 99.5 ± 0.10 100.0 ± 0.00 100.0 ± 0.00
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a Compounds present with percentage ≥0.1% in at least one of the Helichrysum spp. Data are reported as mean values (n = 3 ± SD); l.r.iexp: linear retention time experimentally determined on HP-5MS capillary column; l.r.ilit: linear retention time reported by Adams 2007 [14], NIST 14 [15], and NIST Chemistry WebBook [16].

The main class of constituents for the three species was represented by monoterpene hydrocarbons, with 93.3% in H. decorum, followed by H. umbraculigerum (75.2%) > H. lepidissimum (70.3%). β-Pinene (53.0%) dominated the composition of H. decorum together with sabinene (23.8%). These two compounds, along with α-pinene (11.6%), represented more than 88% of the volatile fraction. Similar amounts of β-pinene (55.2%) were also found by Bandeira Riedel [1] analyzing the spontaneous emission of the flower of H. arenarum (L.) Moench. Sabinene instead, was the major constituent of H. petiolare Hilliard & B.L. Burtt (about 50% of the whole HS composition) [13], H. cooperi (34.4%), and H. edwardsii (29.2%) [7]. VOCs of H. lepidissimum and H. umbraculigerum were richer in the α-isomer of pinene (67.9% and 54.8%, respectively), compared that of to β-pinene (1.1% and 2.7%, respectively), as also observed in the previously mentioned species. The predominance of α-pinene was also observed for H. pandurifolium (25.7%) and H. trilineatum (64.8%), previously investigated by our research team [7].

Substantial amounts of sesquiterpene hydrocarbons (SH) also characterized H. lepidissimum and H. umbraculigerum, representing 28.0% and 21.9% of the spontaneous emissions, respectively. Nevertheless, they showed quite different main sesquiterpene compounds. In fact, γ-curcumene (23.1%) was the major SH detected in H. lepidissimun, while H. umbraculigerum was characterized by higher percentage of the two isomers of selinene: α (6.2%) and β (3.9%), together with α-humulene (4.6%). γ-Curcumene (10.75) and β- (8.5%) and α-selinene (7.3%) were also the main compounds found in the spontaneous emission of H. araxinum Takht. ex Kirp, which in fact had SH as the most representative chemical class (79.5%) [2].

2.2. Essential Oil Chemical Composition and Yield

The complete chemical composition and the hydrodistillation yields of the essential oils (EOs) obtained from the dried aerial parts of H. decorum, H. lepidissimum and H. umbraculigerum are reported in Table 2. Altogether 112 compounds were identified, representing 92.5 to 97.1% of the total chemical composition. H. umbraculigerum presented the highest number of constituents (47 vs. 41 in both H. decorum and H. lepidissimum), as in VOC analysis. Remarkable was the fact that these oils, apart from 3 minor constituents, had no compounds in common. Moreover, the essential oil yield of H. lepidissimum was 0.6% w/w, while for the other two species it was so low that it could not be determined. In general, the species of this genus are known to produce low amounts of essential oil [7].

Table 2.

Complete chemical composition and hydrodistillation yield of essential oils obtained from dried aerial parts of three analyzed Helichrysum samples.

Compounds a Class l.r.iexp l.r.ilit Relative Abundance (%) ± SD
H. decorum H. lepidissimum H. umbraculigerum
α-pinene mh 939 935 - 2.3 ± 0.65 -
limonene mh 1029 1031 - - 0.4 ± 0.07
eucalyptol om 1031 1032 - 0.2 ± 0.10 5.5 ± 1.22
γ-terpinene mh 1060 1062 - - 0.2 ± 0.04
terpinolene mh 1089 1088 - - 0.2 ± 0.05
linalool om 1097 1089 - - 0.2 ± 0.01
nonanal nt 1101 1102 0.4 ± 0.06 - -
borneol om 1169 1168 - - 0.5 ± 0.10
4-terpineol om 1177 1179 - - 0.2 ± 0.01
α-terpineol om 1189 1189 - - 0.3 ± 0.01
decanal nt 1202 1205 0.5 ± 0.03 - -
dihydroedulan IA ac 1294 1293 - - 0.2 ± 0.02
p-menth-1-en-9-ol om 1295 1295 * - - 0.2 ± 0.03
α-copaene sh 1377 1377 - 0.2 ± 0.06 -
β-elemene sh 1391 1375 0.5 ± 0.04 - -
n-tetradecane nt 1400 1400 * 0.1 ± 0.19 - -
italicene sh 1404 1403 - 0.6 ± 0.06 -
dihydro- γ-ionone ac 1407 1417 0.8 ± 0.07 - -
cis-α-bergamotene sh 1413 1415 - 0.2 ± 0.00 -
sesquithujene sh 1414 1417 - 0.3 ± 0.00 -
β-caryophyllene sh 1419 1420 8.4 ± 0.45 - -
trans-α-bergamotene sh 1435 1431 0.2 ± 0.12 - -
α-guaiene sh 1440 1438 0.4 ± 0.02 - -
aromadendrene sh 1441 1444 - - 0.3 ± 0.03
α-humulene sh 1455 1455 - - 3.1 ± 0.13
dihydropseudoionone ac 1456 1460 1.4 ± 0.12 - -
(E)-β-Famesene sh 1457 1459 1.4 ± 0.11 - -
sesquisabinene sh 1464 1461 - 0.1 ± 0.06 -
4,5-di-epi-aristolochene sh 1469 1471 - - 0.2 ± 0.02
β-acoradiene sh 1471 1478 - 0.5 ± 0.06 -
γ-muurolene sh 1480 1477 - - 1.4 ± 0.01
ar-curcumene sh 1481 1483 - 3.6 ± 0.35 -
γ-curcumene sh 1483 1484 - 17.4 ± 2.10 -
α-amorphene sh 1485 1488 - - 0.6 ± 0.02
trans-β-ionone ac 1489 1485 3.8 ± 0.51 -
β-selinene sh 1490 1486 - - 6.2 ± 0.30
α-selinene sh 1498 1497 - - 9.2 ± 0.20
α-muurolene sh 1500 1499 - - 0.7 ± 0.00
epi-zonarene sh 1501 1501 - - 0.5 ± 0.05
isodaucene sh 1503 1503 1.0 ± 0.16 - -
β-bisabolene sh 1506 1509 4.2 ± 0.13 0.7 ± 0.10 -
α-bulnesene sh 1510 1508 1.4 ± 0.13 - 0.4 ± 0.04
sesquicineole os 1513 1514 - 0.8 ± 0.15 -
trans-γ-cadinene sh 1514 1514 - - 0.7 ± 0.02
β-curcumene sh 1516 1517 - 2.9 ± 0.10 -
7-epi-α-selinene sh 1522 1526 - - 0.2 ± 0.01
δ-cadinene sh 1523 1524 - - 2.6 ± 0.02
cubenene sh 1533 1531 - - 0.3 ± 0.01
cis-sesquisabinene hydrate os 1544 1559 - 0.4 ± 0.06 -
italicene ether os 1545 1540 - 0.4 ± 0.06 -
α-calacorene sh 1546 1546 - - 0.5 ± 0.03
elemol os 1550 1550 1.6 ± 0.03 - -
(E)-nerolidol os 1563 1560 - 3.0 ± 0.50 -
palustrol os 1568 1567 - - 0.8 ± 0.01
spathulenol os 1578 1578 - 0.2 ± 0.06 5.3 ± 0.20
caryophyllene oxide os 1583 1583 26.7 ± 0.10 - -
globulol os 1585 1584 - - 1.5 ± 0.03
isoaromadendrene epoxide os 1589 1594 0.6 ± 0.10 - -
epi-globulol os 1590 1587 * - 7.4 ± 1.80 -
β-copaen-4α-ol os 1591 1596 - 0.2 ± 0.06 -
viridiflorol os 1593 1595 - - 10.6 ± 0.48
cubeban-11-ol os 1595 1601 - - 1.5 ± 0.13
rosifoliol os 1600 1603 1.9 ± 0.04 7.2 ± 1.20 -
guaiol os 1601 1597 0.3 ± 0.04 2.3 ± 0.40 -
humulene oxide II os 1608 1609 - - 0.7 ± 0.01
epi-cedrol os 1612 1611 - 0.8 ± 0.06 -
humulane-1-6-dien-3-ol os 1613 1619 1.2 ± 0.09 0.2 ± 0.00 1.6 ± 0.01
humulol os 1614 1618 - - 8.0 ± 0.42
1-epi-cubenol os 1629 1629 - - 6.7 ± 0.19
γ-eudesmol os 1632 1630 1.4 ± 0.22 - -
α-acorenol os 1633 1630 - 2.1 ± 0.06 -
β-acorenol os 1637 1637 - 0.6 ± 0.00 -
isospathulenol os 1638 1640 - - 0.5 ± 0.06
T-cadinol os 1640 1640 - - 2.7 ± 0.09
α-muurolol os 1646 1645 - - 1.0 ± 0.11
11,11-Dimethyl-4,8-dimethylenebicyclo[7.2.0]undecan-3-ol os 1647 1646 2.8 ± 0.30 - -
β-eudesmol os 1651 1649 2.1 ± 0.21 0.9 ± 0.20 1.2 ± 0.03
α-eudesmol os 1654 1652 1.8 ± 0.32 - -
neo-intermedeol os 1655 1660 - - 11.2 ± 0.59
pogostole os 1656 1655 1.5 ± 0.41 - -
intermedeol os 1668 1666 - 6.0 ± 0.35 -
14-hydroxy-9-epi-(E)-caryophyllene os 1670 1669 - - 1.2 ± 0.25
bulnesol os 1672 1668 1.6 ± 0.06 1.2 ± 0.15 -
β-bisabolol os 1675 1672 £ - 12.5 ± 0.3 -
aromadendrene epoxide II os 1680 1.9 ± 0.04 - 0.5 ± 0.07
α-bisabolol os 1686 1685 1.7 ± 0.10 6.4 ± 0.25 0.2 ± 0.00
(Z,E)-farnesol os 1701 1700 - 1.3 ± 0.15 -
aristol-1(10)-en-9-ol os 1704 1704 1.0 ± 0.00 - -
pentadecanal nt 1713 1714 6.7 ± 0.37 - -
β-(Z)-santalol os 1715 1713 0.4 ± 0.09 5.6 ± 0.70 -
(E,E)-farnesol os 1755 1740 - 0.2 ± 0.00 -
xanthorrhizol os 1753 1752 - 0.2 ± 0.06 -
tetradecanoic acid nt 1761 1769 - - 1.5 ± 0.13
neocurdione os 1762 1761 - 0.1 ± 0.00 -
(Z)-9-hexadecenal nt 1780 1800 - 0.9 ± 0.06 -
(Z)-7-hexadecenal nt 1798 1798 - 0.7 ± 0.06 -
n-octadecane nt 1800 0.4 ± 0.03 - -
(E,E)-farnesyl acetate os 1843 1843 - 0.4 ± 0.00 -
hexahydrofarnesylacetone ac 1845 1845 5.5 ± 0.43 - 2.6 ± 0.18
Z-(13,14-Epoxy)tetradec-11-en-1-ol acetate nt 1849 1849 0.3 ± 0.04 - -
(Z)-9-Hexadecen-1-ol nt 1863 1863 1.2 ± 0.18 - -
pentadecanoic acid nt 1867 1857 - - 0.3 ± 0.07
1-hexadecanol nt 1876 1883 - 0.3 ± 0.06 -
(E,E)-farnesyl acetone ac 1919 1920 1.0 ± 0.14 - -
cembrene dh 1939 1929 0.4 ± 0.15 - -
phytol od 1945 0.3 ± 0.01 - 0.5 ± 0.10
m-camphorene dh 1952 1960 - 0.2 ± 0.06 -
cembrene A dh 1959 1960 0.3 ± 0.39 - -
hexadecanoic acid nt 1963 1962 - - 0.4 ± 0.05
geranyl linalool od 2034 2034 - 5.6 ± 0.55 -
n-tetracosane nt 0.5 ± 0.68 - -
n-pentacosane nt 2.9 ± 0.44 - -
EO hydrodistillation yield (% w/w) - 0.6 ± 0.01 -
Chemical classes H. decorum H. lepidissimum H. umbraculigerum
Monoterpene hydrocarbons (mh) - 2.3 ± 0.65 0.8 ± 0.12
Oxygenated monoterpenes (om) - 0.2 ± 0.10 6.9 ± 1.44
Sesquiterpenes hydrocarbons (sh) 17.5 ± 1.26 26.5 ± 1.90 26.9 ± 0.52
Oxygenated sesquiterpenes (os) 46.7 ± 0.49 60.4 ± 1.30 55.3 ± 2.26
Diterpenes hydrocarbons (dh) 0.7 ± 0.24 0.2 ± 0.06 -
Oxygenated diterpenes (od) 0.3 ± 0.01 5.6 ± 0.55 0.5 ± 0.10
Apocarotenoids (ac) 12.5 ± 0.13 - 2.80 ± 0.15
Other non-terpene derivatives (nt) 13.0 ± 0.20 1.9 ± 0.06 2.2 ± 0.10
Total identified (%) 92.5 ± 0.84 97.1 ± 0.44 95.3 ± 0.80
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a Compounds present with percentage ≥0.1% in at least one of Helichrysum spp. Data are reported as mean values (n = 3 ± SD); l.r.iexp: linear retention time experimentally determined on HP-5MS capillary column; l.r.ilit: linear retention time reported by Adams 2007 [14], NIST 14 [15], and NIST Chemistry WebBook; * linear retention time in pubchem (www.pubchem.ncbi.nlm.nih.gov (accessed on 25 September 2021)); £: linear retention time in chemspider (www.chemspider.com (accessed on 25 September 2021)).

Concerning the chemical composition, sesquiterpenes were the most represented class of compounds in all the EOs. The oxygenated form prevailed, accounting for 48.5, 60.4 and 55.2% in H. decorum, H. lepidissimum and H. umbraculigerum, respectively, while the hydrocarbon form ranged from 17.5% in H. decorum to 26.5 and 26.9% in H. lepidissimum and H. umbraculigerum, respectively. These three EO samples showed great differences in their compositions. Caryophyllene oxide was the main constituent in H. decorum (26.7%), followed by β-caryophyllene (8.4%). Despite the oxygenated sesquiterpenes (OS) dominated the H. lepidissimum EO, γ-curcumene, a sesquiterpene hydrocarbons, was the main constituent of this oil (17.4%), followed by β-bisabolol (12.5%), epi-globulol (7.4%), and rosifoliol (7.2%). The H. umbraculigerum essential oil instead was characterized by a predominance of OS, i.e., neo-intermedeol (11.2%) and viridiflorol (10.6%), followed by SH α-selinene (9.2%) and β-selinene (6.2%).

The presence of high percentages of caryophyllene oxide is not very common in the genus Helichrysum, even though this compound was reported by Rabehaja, D.J.R. et al. for the Malagasy H. benthamii Viguier & Humbert (4.0%) [17]. These authors also evidenced a similar behaviour with the same species concerning the predominance of sesquiterpenes, with prevalence of the oxygenated ones (73.5%) in H. hirtum Humbert. Caryophyllene oxide was also detected in other South African species, such as H. cymosum (L.) D. Don subsp. cymosum studied by Giovanelli et al. [4]. γ-Curcumene, a sesquiterpene hydrocarbon typical of the EO of H. italicum (Roth) G. Don was reported as the main component of Serbian samples [18]. This chemical compound, together with rosifoliol, was detected in appreciable percentages in the EO of H. italicum Don. subsp. microphyllum (Willd.) Cambess, also known as H. italicum subsp. tyrrhenicum, which is widely employed in aromatherapy [19]. Aćimović at al. [18], in fact, evidenced that Helichrysum chemotypes containing γ-curcumene as main component could be used in perfumery industries thanks to their appreciated fragrances, as well as in food and pharmaceutical industries as natural preservatives.

H. foetidum (L.) Cass., H. montanum DC. [5], and H. excisum (Thunb.) Less. [20] were characterised by the presence of an amount of viridiflorol comparable to that of H. umbraculigerum (ranged between 10–20%). On the contrary, H. pandurifolium Schrank had nearly six times the amount of viridiflorol found here (60% of the whole EO composition) [7]. Neo-intermedeol was identified only in H. araxinum [2] and in H. italicum subsp. italicum from Montenegro [21], but with content substantially lower than in the sample analyzed herein. Remarkable quantities of β-selinene were also identified in the EOs of H. archimedeum C. Brullo & Brullo [22], H. hyblaeum Brullo [22], H. odoratissimum (L.) Sweet [7], and Helichrysum thianschanicum Regel [23]. α-Selinene, instead, was the major component of the EO of H. araxinum, which showed also good amounts of the β-isomer [2]. Fair amounts of both the molecules were also detected in H. chasmolycicum P.H.Davis [24]. Interestingly, the high percentage of apocarotenoids (AC) in H. decorum (12.5%), mainly represented by hexahydrofarnesylacetone (5.5%), followed by the ionones trans-β-ionone (3.8%), dihydropseudoionone (1.4%), (E,E)-farnesylacetone (1.0) and dihydro-γ-ionone (0.8%). These latter compounds were completely absent in H. umbraculigerum, where a low percentage of AC was observed too (3.2%), and hexahydrofarnesylacetone was almost the unique AC constituent (2.6%). This constituent was also reported in the Turkish species H. chinophilum Boiss. & Balansa (3.2%) [8].

Noteworthy is the appreciable percentage of oxygenated diterpenes in the H. lepidissimum EO (5.6%) with geranyl linalool as unique identified compound. This class of constituent was also found in other Helichrysum species EOs, even though in higher percentages [7,25].

3. Materials and Methods

3.1. Plant Material

The South African Helichrysum plants studied in the present work (see Table 3) belong to the collection of Centro di Ricerca Orticoltura e Florovivaismo (CREA-OF), located in Sanremo, Italy. The seeds were purchased from specialized companies in sailing seeds of African plant species (Silver Hill-PO Box 53108, Kenilworth, 7745 Cape Town, South Africa and B&TWorld Seeds-Paguignan, 34210 Aigues Vives, Gard, France). The plants were grown under the same edaphic substrate (perlite (2:1 v/v added with 4 g/L slow-release fertilizer) and climatic conditions (Csa in Köppen-Geiger climate classification with an average annual temperature of 16 °C and an annual rainfall of about 700 mm; frosts are light and very rare). After clonal propagation, the plants grew in pots in the open air and were periodically watered. Flowering took place after one year. A voucher sample of each plant was deposited at the herbarium of the Hanbury Botanical Gardens (La Mortola–Ventimiglia, Imperia, Italy) (Table 3).

Table 3.

Botanical description of the three analyzed South African Helichrysum species.

Species Photo Botanical Characters
H. decorum DC graphic file with name molecules-26-07283-i001.jpg Voucher: HMGBH.e/9006.2020.002

  • Biennial or perennial herb up to 1.3 m tall grows in rough grassland or scrub, often on forest margins or in damp gullies and along streambanks.

  • Stem stout: usually simple thinly greyish-white woolly, leafy.

  • Radical leaves rosetted in the first year of growth, wanting at flowering, elliptic, narrowed to a broad clasping base, apex obtuse or subacute, apiculate, both surfaces thinly greyish-white woolly. Cauline leaves diminishing in size upwards, oblong-lanceolate or elliptic-lanceolate, apex usually acute, base clasping, upper surface glandular-setose, thinly cobwebby, lower thinly greyish-white woolly.

  • Heads heterogamous, depressed-globose, across the radiating bracts, many in a large corymbose panicle.

  • Involucral bracts, graded, imbricate, much exceeding the flowers, acute, glossy, bright yellow, radiating.

  • Flowers c. 900–1 260, 35–110 female, 850–1,150 homogamous, yellow.
H. lepidissimum S. Moore graphic file with name molecules-26-07283-i002.jpg Voucher: HMGBH.e/9006.2017.004

  • Highly ramified perennial shrub grows in rocky places, particularly rock mountain tops and cliff.

  • Leaves usually broadly elliptic lightly and loosely greyish-white woollyabove, wool glabrescent to reveal long coarse shaggy hairs, greyish-white woolly-felted below

  • Heads homogamous campanulate, few to many in corymbos clusters terminating the branchlets.

  • Involucral bracts, imbricate, crisped, glossy, white, creamy, or pale straw-colored.

  • Receptacle with fibrils at least equaling ovaries

  • Flowers 10–30, yellow
H. umbraculigerum Less. graphic file with name molecules-26-07283-i003.jpg Voucher: HMGBH.e/9006.2020.001

  • Tufted Perennial Herb grows in rough grassland or scrub.

  • Stems decumbent and rooting then erect, young parts thinly grey-woolly, leafy.

  • Leaves very variable in shape, ranging from linear-lanceolate to elliptic and tapering at both ends; upper surface with stout or delicate glandular hairs, lower surface often thickly greyish white woolly.

  • Heads homogamous, cylindric, many crowded and webbed together, umbrella-like disc

  • Involucral bracts biseriate, not radiating, pellucid, canary-yellow, outer often golden-brow

  • Receptacle nearly smooth

  • Flowers 3–4 (6), yellow [26]
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3.2. Spontaneous Emission Analysis and EO Extraction

Living fresh plant material (almost 1 g) was the subject of the HS-SPME (head space-solid phase microextraction) analyses which was performed using 100 µm polydimethylsiloxanes (PDMS) fiber manufactured by Supelco Ltd. (Bellefonte, PA, USA). As recommended by the manufacturer’s instruction, prior to the analyses, the fiber was conditioned at 250 °C for 30 min in the injector of a gas chromatograph. The plant material was placed in a 50 mL glass vial, covered with an aluminum foil, and then left for 60 min (equilibration time). Exposition of the fiber in the headspace phase of the samples took place for 15 min at a temperature of 23 °C. Subsequently, the fiber was transferred to the injector of the gas chromatograph (temperature 250 °C), where the analytes were thermally desorbed [27]. The composition of the compounds desorbed from SPME fiber was examined using GC-MS.

3.3. Essential Oil Hydrodistillation

The essential oil was obtained from the dried aerial parts of the three species of Helichrysum by hydrodistillation with a Clevenger-type apparatus, performed for 2 h at 100 °C, according to the method reported in the European Pharmacopoeia [28]. The hydrodistillation was carried out in triplicates, on 50 g of plant material and the collected essential oil was refrigerated at 4 °C and maintained far from light sources until analyses.

3.4. Gas Chromatography—Mass Spectrometry Analyses

The essential oils were diluted to 0.5% in HPLC-grade n-hexane before the injection in the GC–MS apparatus. The GC/EI-MS analyses were performed with an Agilent 7890B gas chromatograph (Agilent Technologies Inc., Santa Clara, CA, USA) equipped with an Agilent HP-5MS capillary column (30 m × 0.25 mm; coating thickness 0.25 μm) and an Agilent 5977B single quadrupole mass detector.

The analytical conditions were set as follows: oven temperature ramp from 60 to 240 °C at 3 °C/min; injector temperature, 220 °C; transfer line temperature, 240 °C; carrier gas helium, 1 mL/min. The injection volume was 1 μL, with a split ratio of 1:25. The acquisition parameters were: full scan; scan range: 30–300 m/z; scan time: 1.0 s.

The Identification of the constituents was based on a comparison of the retention times with those of the authentic samples, comparing their linear retention indices relative to the series of n-hydrocarbons. Computer matching was also used against commercial (NIST 14 and ADAMS 2007) and laboratory-developed mass spectra libraries built up from pure substances and components of commercial essential oils of known composition and MS literature data [14,29,30,31,32,33].

4. Conclusions

The present study represents a contribution to increasing the knowledge about the chemical composition of the HSs and the essential oils of three South African Helichrysum species that were not studied yet. It should be a starting point for future investigations, which can lead to a more informed employment of these plants, as they are already used in the traditional local medicine. The studied species showed huge differences in the chemical composition of both the spontaneous emissions and the EOs.

The chemical differences of the aroma profile of the studied samples together with their habitus can be exploited for the ornamental use of these plants.

Author Contributions

Conceptualization, C.C., L.P.; methodology, B.N., Y.P., G.F. and L.P.; software, B.N., Y.P.; validation, B.N., Y.P.; formal analysis, B.N., Y.P; investigation, B.N., Y.P; resources, C.C., G.F. and L.P.; data curation, B.N., Y.P., G.F. and L.P.; writing—original draft preparation, B.N., Y.P.; writing—review and editing, C.C., G.F. and L.P.; visualization, B.N., Y.P., G.F. and L.P.; supervision, G.F. and L.P.; project administration, G.F. and L.P.; funding acquisition, G.F. and L.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflict of interest.

Sample Availability

Samples of the compounds are not available from the authors.

Footnotes

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

References

  • 1.Reidel R.V.B., Cioni P.L., Ruffoni B., Cervelli C., Pistelli L. Aroma Profile and Essential Oil Composition of Helichrysum species. Nat. Prod. Commun. 2017;12:1507–1512. doi: 10.1177/1934578X1701200636. [DOI] [Google Scholar]
  • 2.Najar B., Nardi V., Cervelli C., Mancianti F., Nardoni S., Ebani V.V., Pistelli L. Helichrysum araxinum Takht. ex Kirp. grown in Italy: Volatiloma composition and in vitro antimicrobial activity. Zeitschrift für Naturforschung C. 2020;75:265–270. doi: 10.1515/znc-2020-0025. [DOI] [PubMed] [Google Scholar]
  • 3.Lourens A.C.U., Viljoen A.M., van Heerden F.R. South African Helichrysum species: A review of the traditional uses, biological activity and phytochemistry. J. Ethnopharmacol. 2008;119:630–652. doi: 10.1016/j.jep.2008.06.011. [DOI] [PubMed] [Google Scholar]
  • 4.Giovanelli S., De Leo M., Cervelli C., Ruffoni B., Ciccarelli D., Pistelli L. Essential Oil Composition and Volatile Profile of Seven Helichrysum Species Grown in Italy. Chem. Biodivers. 2018;15:e1700545. doi: 10.1002/cbdv.201700545. [DOI] [PubMed] [Google Scholar]
  • 5.Najar B., Cervelli C., Ferri B., Cioni P.L., Pistelli L. Essential oils and volatile emission of eight South African species of Helichrysum grown in uniform environmental conditions. South Afr. J. Bot. 2019;124:178–187. doi: 10.1016/j.sajb.2019.05.015. [DOI] [Google Scholar]
  • 6.Mashigo M., Combrinck S., Regnier T., Du Plooy W., Augustyn W., Mokgalaka N. Chemical variations, trichome structure and antifungal activities of essential oils of Helichrysum splendidum from South Africa. South Afr. J. Bot. 2015;96:78–84. doi: 10.1016/j.sajb.2014.10.006. [DOI] [Google Scholar]
  • 7.Najar B., Nardi V., Cervelli C., Mecacci G., Mancianti F., Ebani V.V., Nardoni S., Pistelli L. Volatilome Analyses and In Vitro Antimicrobial Activity of the Essential Oils from Five South African Helichrysum Species. Molecules. 2020;25:3196. doi: 10.3390/molecules25143196. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Kürkçüoğlu M., Ağalar H.G., Aksoy A., Başer K.H.C. Composition of the Essential Oils of Two Endemic Helichrysum Species in Turkey. Rec. Nat. Prod. 2019;13:236–242. doi: 10.25135/rnp.93.18.06.113. [DOI] [Google Scholar]
  • 9.Ben Hassine D., Khlifi D., Ferhout H., Raoelison E.G., Bouajila J. Essential Oils in Food Preservation, Flavor and Safety. Elsevier; Amsterdam, The Netherlands: 2016. Curry Plant (Helichrysum sp.) Oils; pp. 395–403. [Google Scholar]
  • 10.Flora of Zimbabwe. Helichrysum lepidissimum S. Moore. [(accessed on 1 September 2021)]. Available online: https://www.zimbabweflora.co.zw/speciesdata/species.php?species_id=159690.
  • 11.Mkhize Z. Ph.D. Thesis. University of KwaZulu-Natal; Pietermaritzburg, South Africa: 2015. Structure and Synthesis of Bioactive Natural Products. [Google Scholar]
  • 12.Pollastro F., De Petrocellis L., Schiano-Moriello A., Chianese G., Heyman H., Appendino G., Taglialatela-Scafati O. Amorfrutin-type phytocannabinoids from Helichrysum umbraculigerum. Fitoterapia. 2017;123:13–17. doi: 10.1016/j.fitote.2017.09.010. [DOI] [PubMed] [Google Scholar]
  • 13.Caser M., D’Angiolillo F., Chitarra W., Lovisolo C., Ruffoni B., Pistelli L., Pistelli L., Scariot V. Water deficit regimes trigger changes in valuable physiological and phytochemical parameters in Helichrysum petiolare Hilliard & B.L. Burtt. Ind. Crops Prod. 2016;83:680–692. doi: 10.1016/j.indcrop.2015.12.053. [DOI] [Google Scholar]
  • 14.Adams R.P. Identification of Essential Oil Components by Gas Chromatography/Quadrupole Mass Spectroscopy. Allured Publishing Corporation; Carol Stream, IL, USA: 1995. [Google Scholar]
  • 15.National Institute of Standards and Technology (NIST) NIST/EPA/NIH Mass Spectral Library. The NIST Mass Spectrometry Data Center; Gaithersburg, MD, USA: 2014. [Google Scholar]
  • 16.NIST Chemistry WebBook. [(accessed on 25 September 2021)]; Available online: https://webbook.nist.gov.
  • 17.Rabehaja D.J.R., Bezert G., Rakotonandrasana S.R., Ramanoelina P.A.R., Andrianjara C., Bighelli A., Tomi F., Paoli M. Chemical Composition of Aerial Parts Essential Oils from Six Endemic Malagasy Helichrysum Species. Plants. 2020;9:265. doi: 10.3390/plants9020265. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Aćimović M., Ljujić J., Vulić J., Zheljazkov V.D., Pezo L., Varga A., Tumbas Šaponjac V. Helichrysum italicum (Roth) G. Don Essential Oil from Serbia: Chemical Composition, Classification and Biological Activity—May It Be a Suitable New Crop for Serbia? Agronomy. 2021;11:1282. doi: 10.3390/agronomy11071282. [DOI] [Google Scholar]
  • 19.Appendino B.G., Taglialatela-Scafati O. Helichrysum italicum: Sleeping Giant of the Mediterranean Herbal Medicine. HerbalGram. 2015;34–45:36–47. [Google Scholar]
  • 20.Lourens A.C.U., Reddy D., Başer K.H.C., Viljoen A.M., Van Vuuren S.F. In vitro biological activity and essential oil composition of four indigenous South African Helichrysum species. J. Ethnopharmacol. 2004;95:253–258. doi: 10.1016/j.jep.2004.07.027. [DOI] [PubMed] [Google Scholar]
  • 21.Kladar N.V., Anačkov G.T., Rat M.M., Srđenović B.U., Grujić N.N., Šefer E.I., Božin B.N. Biochemical Characterization of Helichrysum italicum (Roth) G.Don subsp. italicum (Asteraceae) from Montenegro: Phytochemical Screening, Chemotaxonomy, and Antioxidant Properties. Chem. Biodivers. 2015;12:419–431. doi: 10.1002/cbdv.201400174. [DOI] [PubMed] [Google Scholar]
  • 22.Leonardi M., Giovanelli S., Ambryszewska K.E., Ruffoni B., Cervelli C., Pistelli L., Flamini G., Pistelli L. Essential oil composition of six Helichrysum species grown in Italy. Biochem. Syst. Ecol. 2018;79:15–20. doi: 10.1016/j.bse.2018.04.014. [DOI] [Google Scholar]
  • 23.Sharopov F.S., Sulaymonova V.A., Sun Y., Numonov S., Gulmurodov I.S., Valiev A.K., Aisa H.A., Setzer W.N. Composition of Helichrysum thianschanicum Regel Essential Oil from Pamir (Tajikistan) Nat. Prod. Commun. 2018;13:99–100. doi: 10.1177/1934578X1801300129. [DOI] [Google Scholar]
  • 24.Chalchat J.C., Özcan M.M. Composition of the Essential Oil of Helichrysum chasmolycicum Growing Wild in Turkey. J. Med. Food. 2006;9:287–289. doi: 10.1089/jmf.2006.9.287. [DOI] [PubMed] [Google Scholar]
  • 25.Najar B., Nardi V., Cervelli C., Pistelli L. Volatiloma analyses of four South African Helichrysum spp. grown in Italy. Nat. Prod. Res. 2020:1–7. doi: 10.1080/14786419.2020.1791114. [DOI] [PubMed] [Google Scholar]
  • 26.Helicrysums of Southern Africa. [(accessed on 8 October 2021)]. Available online: https://keys.lucidcentral.org/keys/v3/helichrysum/key/Helichrysum/Media/Html/home.htm.
  • 27.IOFI Working Group on Methods of Analysis Guidelines for solid-phase micro-extraction (SPME) of volatile flavour compounds for gas-chromatographic analysis, from the Working Group on Methods of Analysis of the International Organization of the Flavor Industry (IOFI) Flavour Fragr. J. 2010;25:404–406. doi: 10.1002/ffj.1991. [DOI] [Google Scholar]
  • 28.Europarådet. European Pharmacopoeia Commission . European Pharmacopoeia. Volume 3. Maisonneuve; Sainte Ruffine, France: 1975. [(accessed on 8 October 2021)]. p. 68. Available online: https://www.worldcat.org/title/european-pharmacopoeia/oclc/474280471. [Google Scholar]
  • 29.Davies N.W. Gas chromatographic retention indices of monoterpenes and sesquiterpenes on Methyl Silicon and Carbowax 20M phases. J. Chromatogr. A. 1990;503:1–24. doi: 10.1016/S0021-9673(01)81487-4. [DOI] [Google Scholar]
  • 30.Jennings W., Shibamoto T. Qualitative Analysis of Flavor and Fragrance Volatiles by Glass Capillary Gas Chromatography. Volume 26 Academic Press; New York, NY, USA: 1982. [Google Scholar]
  • 31.Masada Y. Analysis of Essential Oils by Gas Chromatography and Mass Spectrometry. John Wiley & Sons; New York, NY, USA: 1976. [Google Scholar]
  • 32.Stenhagen E., Abrahamsson S., McLafferty F.W. Registry of Mass Spectral Data. Wiley & Sons; New York, NY, USA: 1974. [Google Scholar]
  • 33.Swigar A.A., Silverstein R.M. Monoterpenes. Aldrich Chemical Company; Milwaukee, WI, USA: 1981. [Google Scholar]

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Data Availability Statement

Data are contained within the article.

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