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. 2016 Sep 1;21(9):1162. doi: 10.3390/molecules21091162

Comparison of the Essential Oil Composition of Selected Impatiens Species and Its Antioxidant Activities

Katarzyna Szewczyk 1,*, Danuta Kalemba 2, Łukasz Komsta 3, Renata Nowak 1
Editor: Derek J McPhee
PMCID: PMC6274178  PMID: 27598111

Abstract

The present paper describes the chemical composition of the essential oils obtained by hydrodistillation from four Impatiens species, Impatiens glandulifera Royle, I. parviflora DC., I. balsamina L. and I. noli-tangere L. The GC and GC-MS methods resulted in identification of 226 volatile compounds comprising from 61.7%–88.2% of the total amount. The essential oils differed significantly in their composition. Fifteen compounds were shared among the essential oils of all investigated Impatiens species. The majority of these constituents was linalool (0.7%–15.1%), hexanal (0.2%–5.3%) and benzaldehyde (0.1%–10.2%). Moreover, the antioxidant activity of the essential oils was investigated using different methods. The chemical composition of the essential oils and its antioxidant evaluation are reported for the first time from the investigated taxon.

Keywords: Impatiens, Balsaminaceae, herb, root, essential oils, antioxidants, PCA

1. Introduction

The genus Impatiens L. (Balsaminaceae) includes about 850 species, which occur mainly in tropical and subtropical climate zones, in particular in parts of the Old World, such as tropical Africa, India, southern China and the southwestern part of Asia. Some species also occur in Japan, Europe, Russia and North America [1,2]. Three species, Impatiens glandulifera Royle (Himalayan balsam), I. noli-tangere L. (touch-me-not balsam) and I. parviflora DC. (small balsam), occur in Central Europe, and they are perennial plants that grow in riparian zones along rivers on humid soils and in wet woodlands [3,4]. I. glandulifera and I. parviflora are among the invasive plants originally native to Asia that are rapidly spreading across Europe. In Poland, these are two of the top 20 invasive alien plants [2,5]. As I. parviflora is an extremely invasive plant in Europe, its relation with other plants [6] and with soil yeast complexes was recently investigated [7]. Furthermore, the different extracts from I. glandulifera, I. noli-tangere and I. parviflora showed a strong allelopathic effect on the seed germination of Leucosinapis alba and Brassica napus [4].

Many groups of active compounds have been isolated from different species of the genus Impatiens L. Phytochemical studies conducted on various organs of Impatiens have revealed the presence of quinones, flavonoids, phenolic acids, leucocyanidins, anthocyanins, tannins, coumarins, saponins, phytosteroids, peptides, alkaloids and essential oils [8,9,10,11,12,13,14,15,16]. However, only one report is available concerning the volatile constituents of Impatiens species. In the n-hexane extract of I. bicolor growing in Pakistan, fatty acid methyl esters were the major compounds [9].

Because of the rich and varied composition, numerous studies have been conducted to investigate the feasibility of a medicinal use of members of Impatiens. Among the representatives of the genus Impatiens L., some species have been used since a very long time in Asian and American medicine. In traditional therapeutic systems, I. balsamina L. has been the most popular species. Depending on the type of ailment, the dried herb has been used in the form of compresses, directly on the skin, or as a tea prepared by pouring hot water on dried leaves [14]. Moreover, it has been applied in Chinese traditional medicine to treat rheumatism, against fractures, swelling, contusions, beriberi disease and for its anticancer properties [16,17,18]. It has been also used to alleviate parturient and puerperal pain [14]. I. balsamina flowers have been used as a remedy against the effects of snake bites [19]. I. parviflora has been used in the treatment of warts [20]. Flowers of I. glandulifera are used in Bach flower remedies, which causes sedation, relaxes and helps to balance the emotional state, and they are recommended for psychological problems and pain [21]. The rhizomes of Impatiens pritzellii Hook. f. var. hupehensis Hook. f. [22] and whole plant of Impatiens textori MIQ [23] have been also used in Chinese medicine. In our previous study, we confirmed that the extracts from species of Impatiens, especially I. balfourii Hook. f., I. glandulifera and I. parviflora, contained significant amounts of phenols and flavonoids and have interesting multidirectional biological activity, such as antimicrobial and antioxidant abilities [11].

Based on the significance of these plants from an ecological perspective and no available reports on the essential oils of Impatiens species, the aim of the present study was to investigate the essential oil composition of herb and root of the two most invasive in Poland Impatiens species, I. glandulifera Royle and I. parviflora DC. For comparison, herb oils of two other species, I. balsamina L. and I. noli-tangere L., were included. The antioxidant activity of the essential oils of these species was also evaluated.

2. Results and Discussion

2.1. Chemical Composition of Essential Oils from Impatiens L.

Six Impatiens essential oils were obtained by steam distillation from air-dried herbs and roots. All of them were yellowish and fragrant. The highest yield of essential oil (w/w relative to dry material weight) was observed for the herb of I. parviflora (0.24%) and I. glandulifera (0.22%), while for the other materials, the yield amounted to 0.10%–0.16%. The chemical composition was analyzed by the GC-MS method, which resulted in identification of 54–94 volatile compounds comprising from 61.7%–88.2% of the total volume in individual oils. In total of 226 compounds was identified. All identified compounds in Impatiens oils are listed in Table 1.

Table 1.

Composition of the essential oils of four Impatiens species. IGH, I. glandulifera herb; IGR, I. glandulifera roots; IPH, I. parviflora herb; IPR, I. parviflora roots; IBH, I. balsamina herb; INH, I. noli-tangere herb; RIexp, experimental retention index; RIlit, literature retention index; t, trace (percentage value less than 0.05%).

No. Constituent RIexp RIlit IGH IGR IPH IPR IBH INH Class of Compound
Content (%)
1 Hexanal 776 771 0.2 1.7 5.3 1.6 0.7 3.6 AO
2 Furfural 803 795 - 0.8 0.7 1.4 - - O
3 (E)-Hex-2-enal 826 822 - 0.3 2.1 1.4 2.9 - AO
4 (E)-Hex-3-en-1-ol 838 838 0.6 - 16.8 0.3 0.7 - AO
5 (Z)-Hex-3-en-1-ol 848 851 0.2 - - - 0.2 9.5 AO
6 Hexanol 852 856 - 1.7 4.9 0.3 - - AO
7 Heptan-2-one 868 871 - 0.2 0.2 0.1 - 0.2 AO
8 Heptanal 878 882 0.1 0.4 1.2 0.5 0.1 0.1 AO
9 2-Butoxyethanol 888 888 - 0.2 0.1 0.6 - - AO
10 Heptan-3-ol 893 884 - 0.1 - - - - AO
11 Butyraldehyde diethyl acetal 896 880 2.4 - - - - - AO
12 Nonane 900 900 - - - 0.1 - - AH
13 1-Butoxypropan-2-ol 926 936 - 0.4 - - - AO
14 Benzaldehyde 929 928 0.1 1.8 10.2 2.3 0.7 4.7 Ar
15 Dimethyl trisulfide 942 942 - 0.4 - - - - O
16 Benzonitrile 945 940 - 0.5 - - - - Ar
17 Isovaleraldehyde diethyl acetal 946 930 0.7 - - - - - AO
18 Hept-1-en-3-one 954 956 - 0.1 - - - - AO
19 Heptanol 956 952 - 0.3 0.9 0.3 - - AO
20 Octane-2,3-dione 961 959 - 0.3 0.4 0.5 - - AO
21 Oct-1-en-3-ol 964 962 - 1.3 0.9 0.7 0.3 - AO
22 6-Methylhept-5-en-2-one 964 962 - - 0.3 - - - AO
23 Octan-3-one 965 963 - 1.2 - - - - AO
24 β-Pinene 969 970 - 0.1 - - - - MH
25 (E,E)-Hepta-2,4-dienal 969 967 - - 0.6 0.2 - - AO
26 2-Pentylfurane 979 981 - 0.3 1.2 0.8 0.4 1.4 O
27 Octanal 980 982 - 0.3 - - - - AO
28 Hexanoic acid 981 973 - - - - 0.6 - AO
29 Hepta-2,4-dienal (isomer) 981 - - - 4.2 1.2 - 1.2 AO
30 (E)-2-(Pent-2-enyl)furan 986 984 - - 0.5 0.2 t - O
31 α-Phellandrene 997 997 0.5 - - - - - MH
32 Decane 1000 1000 - - - 0.1 - - AH
33 Phenylacetaldehyde 1009 1012 t 2.0 2.7 3.3 0.8 3.4 Ar
34 α-Terpinene 1009 1013 0.2 - - - - - MH
35 Salicylaldehyde 1011 1013 - 1.0 0.1 0.4 - - Ar
36 p-Cymene 1012 1015 0.7 - - - - - MH
37 2,2,6-Trimethylcyclohexanone 1013 1013 - - t - t - O
38 2-Ethylhexan-1-ol 1015 1011 - 0.1 0.3 0.5 0.1 - AO
39 β-Phellandrene 1022 1023 7.4 - - - - - MH
40 Limonene 1025 1025 0.3 - - - - - MH
41 (Z)-β-Ocimene 1028 1029 0.6 - - - - - MH
42 (E)-Oct-2-enal 1032 1034 - 0.1 0.2 0.3 - 0.2 AO
43 Acetophenone 1033 1030 - 0.2 - 0.2 - 0.1 Ar
44 2,6,6-Trimethylcyclohex-2-enone 1037 1045 - - 0.1 - - - O
45 Octa-3,5-dien-2-one (isomer) 1043 - - - 0.3 0.4 - - AO
46 γ-Terpinene 1048 1059 0.1 t - - - 0.1 MH
47 (E)-Oct-2-en-1-ol 1052 1052 - 0.2 0.6 0.1 - - AO
48 Octanol 1055 1054 0.2 - - - 0.1 - AO
49 trans-Linalool oxide (F) 1058 1058 - 0.1 2.3 0.4 - 1.0 MO
50 Guaiacol 1061 1059 0.1 - 0.1 0.1 - - Ar
51 (E,E)-Octa-3,5-dien-2-one 1065 1063 - - 0.4 0.4 0.1 - AO
52 Nonan-2-one 1070 1072 - - - 0.1 - - AO
53 cis-Linalool oxide (F) 1072 1072 t - 1.0 0.1 - 0.3 MO
54 6-Methylhepta-3,5-dien-2-one 1077 1075 - - 0.1 0.3 - - AO
55 Terpinolene 1079 1082 0.1 - - - - - MH
56 Nonanal 1083 1086 0.1 1.1 1.9 1.5 0.5 1.2 AO
57 Linalool 1086 1087 0.7 5.3 15.1 4.9 1.6 6.5 MO
58 Isophorone 1092 1094 - - 0.1 - t - MO
59 cis-Rose oxide 1096 1096 - - 0.2 0.5 - 0.1 MO
60 α-Campholenal 1104 1105 t - - - - - MO
61 Oxoisophorone 1105 1005 - - t 0.3 t 0.2 MO
62 (E)-But-1-enylbenzene 1107 1110 0.5 - - - - - Ar
63 trans-Rose oxide 1113 1114 - - 0.1 0.3 - 0.1 MO
64 trans-Pinocarveol 1122 1126 - 0.3 - - - - MO
65 trans-p-Menth-2-en-1-ol 1123 1123 - 0.7 - - - - MO
66 Citronellal 1126 1129 - - 0.4 0.5 - - MO
67 o-Acetylphenol 1129 1135 - - - 0.3 - - Ar
68 Hexyl isobutyrate 1133 1132 0.1 - - - - - AO
69 4-Vinylanisol 1134 1134 - - - - 0.2 - Ar
70 (E)-Non-2-enal 1134 1139 - - - 0.5 - AO
71 (E,E)-Nona-3,6-dien-1-ol 1136 1145 - - - - 0.2 - AO
72 Pinocarvone 1137 1137 - 0.1 - - - - MO
73 Pentylbenzene 1143 1150 0.3 - - - - - Ar
74 Borneol 1149 1150 0.1 4.9 - - - - MO
75 cis- or trans-Linalool oxide (P) 1153 1148 - - 0.1 - - - MO
76 Benzoic acid 1156 1157 - - - - 2.0 - Ar
77 p-Cymen-9-ol 1156 1157 - 0.4 - - - - MO
78 Nonanol 1157 1149 - - - 0.9 - - AO
79 Cryptone 1157 1160 5.7 - - - - - O
80 Terpinen-4-ol 1160 1164 1.5 1.7 0.3 0.2 0.5 0.5 MO
81 Octanoic acid 1164 1160 - - - - 0.1 - AO
82 p-Cymen-8-ol 1166 1169 - - - 0.3 0.5 - MO
83 Methyl salicylate 1168 1171 - - - - 0.1 - Ar
84 Myrtenal 1168 1172 - 0.3 - - - - MO
85 α-Terpineol 1174 1176 1.9 1.5 1.0 0.3 0.4 0.7 MO
86 Safranal 1179 1182 - - 0.3 t 0.5 t MO
87 cis-Piperitol 1181 1181 0.1 - - - - - MO
88 Myrtenol 1181 1184 - 0.6 - 4.2 1.2 - MO
89 Decanal 1184 1184 - 0.8 0.1 1.6 0.4 - AO
90 (E,E)-Nona-2,4-dienal 1186 1188 - - 0.1 - - - AO
91 Benzothiazole 1188 1186 - 0.1 - - - - O
92 3,5,5-Trimethyl-4-methylenecyclohex-2-enone 1190 1200 - - 0.3 - - - O
93 trans-Piperitol 1191 1193 0.3 - - - - - MO
94 Octyl acetate 1193 1191 0.9 - - - - - AO
95 Carvotanacetol 1193 1195 - - - - 0.2 - MO
96 β-Cyclocitral 1195 1195 - 0.1 0.6 0.1 0.5 0.4 MO
97 trans-Carveol 1199 1200 0.1 - - - - - MO
98 p-Isopropylbenzaldehyde 1212 1214 0.9 - - - - - Ar
99 Citronellol 1214 1213 - - 2.5 17.9 - 1.9 MO
100 Carvone 1215 1214 0.6 - - - - - MO
101 Piperitone 1226 1226 0.2 - - - - - MO
102 (2,6,6-Trimethylcyclohex-1-en-1-yl)acetaldehyde 1235 1236 - - - - 0.4 - O
103 2-Phenylbut-2-enal 1235 1237 - 0.2 - - - - Ar
104 Geranial 1240 1235 - - 0.7 12.8 - - MO
105 Phellandral 1251 1250 3.8 - - - - - MO
106 4-Ethylguaiacol 1253 1257 0.2 - - - - - Ar
107 Terpinen-7-al 1257 1257 0.3 - - - - - MO
108 Nonanoic acid 1258 1263 - - - - 0.2 - AO
109 p-Cymen-7-ol 1266 1266 0.9 - - - - - MO
110 Bornyl acetate 1268 1270 0.3 4.3 - - - - MO
111 Thymol 1271 1267 - - - - - 0.2 MO
112 Undecan-2-one 1273 1274 - 0.3 - 0.4 - - AO
113 Carvacrol 1280 1278 0.2 - - - - - MO
114 4-Vinylguaiacol 1284 1282 - - 0.3 1.2 1.7 - Ar
115 Undecanal 1286 1286 - 0.5 - 0.6 - 2.1 AO
116 (E,E)-Deca-2,4-dienal 1289 1288 - - 0.1 0.2 0.1 0.2 AO
117 Theaspirane A 1290 1293 - - 0.1 - - - O13
118 Theaspirane B 1304 1304 - - 0.1 - - - O13
119 Eugenol 1329 1331 - - 1.0 - 0.1 1.1 Ar
120 1,1,6-Trimethyl-1,2-dihydronaphthalene 1335 1336 - - - - 0.1 - Ar
121 α-Terpinyl acetate 1336 1335 16.6 - - - - - MO
122 (E)-Undec-2-enal 1339 1341 - - 0.2 1.6 - - AO
123 Neryl acetate 1341 1342 - - - - - 0.2 MO
124 Decanoic acid 1352 1350 - - - - 0.3 - AO
125 α-Longipinene 1354 1360 - 0.3 - - - - SH
126 Geranyl acetate 1359 1362 0.6 - - - - - MO
127 (E)-β-Damascenone 1361 1361 - - t 0.3 3.6 t O13
128 Methyl eugenol 1369 1369 0.1 - - - - - Ar
129 α-Copaene 1375 1379 0.3 - - - - - SH
130 cis-β-Elemene 1377 1381 - - 0.1 - - - SH
131 Dodecan-2-one 1385 1377 - - - - 0.5 - AO
132 Dodecanal 1385 1386 - - - 0.7 0.2 - AO
133 β-Elemene 1386 1389 0.3 0.9 - - - - SH
134 (E)-β-Damascone 1392 1398 - - - - 1.0 - O13
135 7,8-Dihydro-β-damascenone 1396 1424 - - - - 0.7 - O13
136 Tetradecane 1400 1400 - 0.1 0.1 - - - AH
137 (E)-α-Ionone 1404 1413 - t 0.1 0.1 - 0.2 O13
138 α-Barbatene 1411 1414 - 0.9 - - - - SH
139 cis-α-Bergamotene 1412 1411 - 0.1 - - - - SH
140 α-Santalene 1416 1422 - 2.0 - - - - SH
141 Geranylacetone 1427 1428 0.1 0.6 0.1 0.6 2.7 0.7 O
142 γ-Elemene 1427 1429 0.5 - - - - - SH
143 trans-α-Bergamotene 1431 1434 - 0.1 - - - - SH
144 Isobazzanene 1439 1442 - 0.5 - - - - SH
145 β-Barbatene 1444 1445 - 5.3 - - - - SH
146 Sesquisabinene B 1445 1445 0.6 - - - - - SH
147 4-(2,4,4-Trimethyl-cyclohexa-1,5-dienyl)-but-3-en-2-one 1456 - - - - - 0.8 - O13
148 β-Santalene 1458 1460 - 0.4 - - - - SH
149 β-Ionone epoxide 1459 1456 0.1 0.4 0.2 0.9 3.3 3.7 O13
150 (E)-β-Ionone 1462 1468 t 0.6 0.8 1.1 5.7 t O13
151 4,5-di-epi-Aristolochene 1465 1470 - 0.1 - - - - SH
152 γ-Muurolene 1470 1474 0.5 - - - - - SH
153 ar-Curcumene 1471 1473 - 0.2 - - - - SH
154 γ-Curcumene 1472 1475 - 0.1 - - - - SH
155 5-epi-Aristolochene 1473 1477 0.1 - - - - - SH
156 Tridecan-2-one 1474 1476 - 0.6 - 0.2 - - AO
157 trans-β-Bergamotene 1477 1480 - 0.1 - - - - SH
158 3,4-Dimethyl-5-pentyl-5H-furan-2-one 1480 1481 - 1.1 0.1 - 2.4 1.5 O
159 Aristolochene 1481 1486 0.7 - - - - - SH
160 Dihydroactinidiolide 1487 1487 - - - - 0.8 - O
161 Tridecanal 1488 1490 - 0.3 - 1.0 - - AO
162 α-Selinene 1490 1494 0.7 - - - - - SH
163 Cuparene 1493 1498 - 1.3 - - - - SH
164 Pentadecane 1500 1500 - - - - 0.3 - AH
165 Germacrene A 1500 1503 - - 0.7 - - - SH
166 β-Bisabolene 1502 1503 - 0.2 - - - - SH
167 Methyl dodecanoate 1504 1507 - - - - 0.7 - AO
168 γ-Cadinene 1505 1507 0.2 - 0.3 0.3 - - SH
169 trans-Calamenene 1508 1517 0.1 - - - - - SH
170 Photosantalol 1509 1511 - 0.2 - - - - SO
171 δ-Cadinene 1518 1520 0.7 0.1 - t - - SH
172 Selina-4(15),7(11)-diene 1528 1534 0.4 - - - - - SH
173 Dodecanoic acid 1546 1554 - - - 1.3 4.1 - AO
174 (E,E)-Pseudoionone 1555 1563 - - - - 0.3 - O13
175 (2E)-2-Methyl-4-(2,6,6-trimethylcyclohex-1-en-1-yl)but-2-enal 1568 1584 - - - - 0.4 - O13
176 Maaliol 1573 1565 - 0.5 - - - - SO
177 Globulol 1574 1578 - - - 0.6 1.2 1.7 SO
178 Tetradecanal 1592 1592 - 1.0 - 0.9 - - AO
179 Hexadecane 1600 1600 - - - 0.1 0.1 - AH
180 Butylphthalide 1610 1616 0.4 - - - - - Ar
181 ar-Bisabolol 1613 1619 - 0.1 - - - - SO
182 T-Cadinol 1624 1623 - - - 0.1 - - SO
183 T-Muurolol 1626 1633 0.2 - - - - - SO
184 Vulgarone B 1630 1632 - 14.9 - - - - SO
185 α-Cadinol 1639 1642 - - - 0.2 - - SO
186 Pogostol 1639 1647 - - t - - 0.3 SO
187 (Z)-Butylidenphthalide 1641 1644 8.5 - - - - - Ar
188 α-Barbatenal 1652 1659 - 0.5 - - - - SO
189 Hexahydrofarnesol 1659 1667 - - - - 0.8 - O
190 Tetradecanol 1664 1670 - - - 0.5 - - AO
191 α-Bisabolol 1670 1673 - - - 0.3 0.3 1.0 SO
192 Acorenone 1671 1681 - 4.0 - - - - SO
193 Pentadecan-2-one 1676 1677 - t - 0.2 0.2 - AO
194 (E)-Butylidenphthalide 1681 1673 0.8 - - - - - Ar
195 Pentadecanal 1692 1693 - 5.8 0.6 - 1.6 1.7 AO
196 Heptadecane 1700 1700 - - - 0.1 0.4 - AH
197 (Z)-Ligustilide 1703 1732 11.0 - - - - - Ar
198 Methyl myristate 1710 1713 - - - 0.1 0.5 - AO
199 Phenanthrene 1746 1744 - 0.9 - - - - Ar
200 Myristic acid 1747 1748 0.3 - - 0.9 3.3 - AO
201 (E)-Ligustilide 1756 1782 0.1 - - - - - Ar
202 Hexadecanal 1793 1782 - 0.1 - 0.3 0.2 - AO
203 Octadecane 1800 1800 - t - 0.3 0.5 0.3 AH
204 Hexahydrofarnesyl acetone 1829 1832 1.0 - 0.4 - 13.4 0.3 O
205 Farnesylacetone 1894 1895 - - - - 1.9 - O
206 Nonadecane 1900 1900 - 0.2 - 0.5 0.5 0.7 AH
207 Methyl palmitate 1904 1904 0.2 0.3 0.1 0.7 1.8 3.0 AO
208 Isophytol 1939 1949 - - - 0.4 0.9 0.3 O
209 Palmitic acid 1945 1951 1.1 - - 0.6 0.9 - AO
210 Ethyl palmitate 1974 1954 - - - - - 0.3 AO
211 Eicosane 2000 2000 - - - 0.2 - 0.3 AH
212 Fluoranthene 2026 2020 - 0.9 - - - - Ar
213 Methyl linoleate 2067 2046 - 0.1 - 0.3 0.4 0.2 AO
214 Methyl palmitate 2071 2102 0.1 - - - - - AO
215 Methyl linolenate 2072 2102 - 0.2 - 0.7 1.3 0.3 AO
216 Pyrene 2076 2070 - 0.6 - - - - Ar
217 Methyl oleate 2087 2082 - - - - - 0.2 AO
218 Heneicosane 2100 2100 - 0.3 - 0.3 0.3 0.2 AH
219 Phytol 2107 2104 0.5 0.3 0.1 0.2 2.8 0.1 O
220 Docosane 2200 2200 - - - - 0.2 0.2 AH
221 Tricosane 2300 2300 0.3 0.4 0.1 0.6 1.8 1.4 AH
222 Tetracosane 2400 2400 - 0.1 - - 0.2 0.2 AH
223 Pentacosane 2500 2500 0.5 0.3 0.1 0.4 1.7 1.7 AH
224 Hexacosane 2600 2600 - 0.1 - - - - AH
225 Heptacosane 2700 2700 0.2 - - - - - AH
226 Nonacosane 2900 2900 0.5 - - - - - AH
Total identified constituents 82.5 87.4 88.2 86.3 84.2 61.7
Aliphatic hydrocarbons AH 1.5 1.5 0.3 2.7 6.0 5.0
Oxygenated aliphatics AO 7.2 20.0 42.8 26.1 23.3 24.0
Monoterpene hydrocarbons MH 9.9 0.1 0.1 0.4 - 0.1
Oxygenated monoterpenes MO 28.2 20.3 24.7 42.8 5.4 12.1
Sesquiterpene hydrocarbons SH 5.1 12.6 1.1 0.3 - -
Oxygenated sesquiterpenes SO 0.2 20.2 - 1.2 1.5 3.0
Aromatic compounds Ar 23.0 8.1 14.4 7.8 5.7 9.3
Other O + O13 7.3 + 0.1 3.4 + 1.2 3.7 + 1.1 3.6 + 2.4 26.5 + 15.8 4.3 + 3.9
Identified compounds 76 94 70 88 80 54
Oil yield 0.22 0.19 0.24 0.16 0.10 0.14
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The essential oils differed significantly in their chemical composition. What is more, all investigated oils contained specific constituents that distinguished the essential oils from each other. However, some similarities in the qualitative composition can be observed.

Seventy six compounds were identified in the herb oil of I. glandulifera, representing 82.5% of the total oil. The oil was dominated by oxygenated monoterpenes (28.2%), and α-terpinyl acetate (16.6%) was the major constituent, followed by phellandral (3.8%). Phthalides were the most characteristic constituents of this oil: (Z)-ligustilide (11.0%) and (Z)-butylidenphthalide (8.5%) were accompanied by small amounts of their (E)-isomers and butylphthalide. This oil was the only one that contain pronounced amounts of monoterpene hydrocarbons (9.9% in total), and β-phellandrene (7.4%) was the main one in this group.

Root oil of I. glandulifera (94 compounds, 87.4%) had a totally different composition than herb oil. Three major groups of the constituent were aliphatic, mono- and sesquiterpene oxygenated compounds, each amounting to ca. 20%. The main component was sesquiterpene ketone vulgarone B (14.9%). Linalool (5.3%), borneol (4.9%) and bornyl acetate (4.3%) were the major monoterpenes. Another important constituent was pentadecanal (5.8%). The main feature of this oil was the presence of sixteen sesquiterpene hydrocarbons (12.7%), with β-barbatene (5.3%) being the major one. Eighteen constituents were identified in both herb and root oils of this species, e.g., hexanal, heptanal, nonanal, benzaldehyde, linalool, borneol and bornyl acetate, terpinene-4-ol, α-terpineol, β-ionone and its epoxide. It is worth mentioning that among the twelve sesquiterpene hydrocarbons ((5.1%) that were identified in the herb oil of this species, only one, δ-cadinene, was common for both oils.

In the essential oil of I. parviflora herb, seventy compounds were identified amounting to 88.2%, and among them, (E)-hex-3-en-1-ol (16.8%), linalool (15.1%) and benzaldehyde (10.2%) were the most prominent. The number of identified components in the oil of I. parviflora roots was eighty nine (86.3% of the total oil), and the major compounds were citronellol (17.9%), geranial (12.8%) and linalool (4.9%). Despite significant differences in the content of major constituents, both herb and root oils contained the same aliphatic saturated and unsaturated alcohols, aldehydes and ketones C6–C16, which were their common distinctive features and constituted 42.8% and 26.1%, respectively. Isomeric heptadienals and octadienones that were identified in these oils were only rarely identified in the remaining investigated oils.

The yield of essential oil obtained from I. balsamina herb was 0.1%. Eighty components were identified, representing 84.2% of this oil. The major constituent was hexahydrofarnesyl acetone (13.4%). Pronounced contents of ionones and damascones (15.8%), as well as fatty acids C6-C16 (9.5%) and alkanes (5.9%) were characteristic features of this oil. The main member of the first group was (E)-β-ionone (5.7%), and of the second group, dodecanoic acid (4.1%), ionones and damascones, which occur in a variety of essential oils, are degradation products of carotenoids and have the same C13 carbon skeleton, but differ in the site of oxygenation. (E)-β-Ionone and its epoxide were also found in other investigated oils, however in smaller amounts. Among 54 identified constituents, which accounted for 61.7% of the total essential oil from I. noli-tangere herb, the main compounds were (Z)-hex-3-enol (9.5%), linalool (6.5%) and benzaldehyde (4.7%).

Fifteen compounds were shared among the essential oils of all investigated Impatiens species. The majority of these constituents was linalool (0.7%–15.1%), hexanal (0.2%–5.3%) and benzaldehyde (0.1%–10.2%). Linalool is a naturally occurring monoterpene constituent found in more than 200 oils obtained from herbs, leaves, flowers and wood. This compound has many proven activities and is present in several remedies used in traditional medicine for sedative purposes. Moreover, linalool revealed antimicrobial, anti-inflammatory, antihyperalgesic and analgesic properties [24]. Chang and Shen investigated the cytotoxic activity of linalool. This study suggested good inhibitory effects against breast, colorectal and liver cancer cells [25].

According to the only available report on the composition of Impatiens volatiles, 42 components were characterized in the n-hexane extract of I. bicolor growing in Pakistan. The major ones were fatty acid methyl esters, such as trans-methyl 13-octadecenoate, methyl heptadecanoate, methyl octadecanoate, methyl docosanoate, methyl tetracosanoate, and methyl eicosanoate and aliphatic hydrocarbons [9].

Compounds of these two groups were identified in the essential oils of all investigated Impatiens species. However, their content was significantly lower.

The invasive ability of some vigorous nonnative plants was thought to be associated with the competitive ability of the invasive species or a release from natural enemies. The allelopathic activity of invasive species also has recently been reported as a significant factor that negatively influences species biodiversity and ecosystem succession [26]. Among the allelochemicals, essential oils and their individual components belong to the most investigated [27]. Oxygenated monoterpenes were proven to possess high phytotoxic activity that inhibits the seed germination and seedling growth of many plants [28]. Terpinene-4-ol, which is a minor constituent of each investigated oil, appeared to be the most active of the 47 monoterpenes against Lactuca sativa, and the linalool, citronellol and geranial, major constituents of I. glandulifera and/or I. parviflora, revealed a pronounced phytotoxic effect [29].

2.2. Chemometric Analysis

The main constituents common for all tested essential oils (hexanal, heptanal, benzaldehyde, phenylacetaldehyde, nonanal, linalool, terpinen-4-ol, α-terpineol, geranylacetone, β-ionone epoxide, (E)-β-ionone, methyl palmitate, phytol, tricosane, pentacosane) were compared with hierarchical cluster analysis with Euclidean distance as the similarity measure. The so-called “heatmap” with corresponding dendrograms is presented in Figure 1. Benzaldehyde and linalool form distinct cluster with different values than the rest of the analyzed main constituents. However, Euclidean distance does not uncover any distinct cluster among plant material samples, besides a distinct difference of I. parviflora herb (IPH) compared to the other samples.

Figure 1.

Figure 1

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The heatmap analysis of the essential oil constituents. IBH, I. balsamina herb; IGH, I. glandulifera herb; IGR, I. glandulifera roots; INH, I. noli-tangere herb; IPH, I. parviflora herb; IPR, I. parviflora roots.

To the compare correlation between constituents (regardless of the absolute concentrations), scaled principal component analysis was carried out. Forty eight-point-four percent and 32.4% of variance was explained by the first two PCs, respectively (Figure 2). Analyzing the loading vectors (Figure 3), it can be concluded that the compounds form three intercorrelated groups:

  1. Terpinen-4-ol and α-terpineol, explained mainly with PC2 and weakly (reversely) correlated with other compounds;

  2. Hexanal, nonanal, linalool, heptanal and benzaldehyde, located mainly in PC1, intercorrelated and reversely correlated with Group 3;

  3. Geranyl-acetone, β-ionone-epoxide, methyl-palmitate, phytol, tricosane and pentacosane, explained by PC1 and negatively correlated with Group 2.

Figure 2.

Figure 2

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Scores of scaled principal component analysis: a comparison of the correlations between constituents among investigated materials. IBH, I. balsamina herb; IGH, I. glandulifera herb; IGR, I. glandulifera roots; INH, I. noli-tangere herb; IPH, I. parviflora herb; IPR, I. parviflora roots.

Figure 3.

Figure 3

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Loading vectors of scaled principal component analysis presented in Figure 2.

I. glandulifera roots (IGR) and I. glandulifera herb (IGH) contain the high concentration of group (1), whereas other material samples have smaller concentrations of them, and the differences arelocated mainly along the PC1 axis.

2.3. Antioxidant Activity

In the present study, the antioxidant activities of the essential oils from herb and roots of Impatiens species were determined using two different methods. The free radical scavenging activity of essential oils was evaluated by the DPPH method in comparison with that of ascorbic acid, at different concentrations. Radical scavenging activity was expressed as the amount of antioxidants necessary to decrease the initial DPPH absorbance by 50% (EC50). The highest antiradical activity was detected for herb oils of I. glandulifera (3.96 ± 0.03 µg/mL) and I. noli-tangere (4.76 ± 0.05 µg/mL), whereas the lowest was detected for herb oil of I. balsamina (Table 2). The EC50 value of ascorbic acids to scavenge hydroxyl radicals was 2.05 ± 0.01 µg/mL. Our results are comparable to those obtained by Nisar and co-authors for the hexane extract of I. bicolor. The EC50 values obtained for different fractions ranged from 23.22 ± 0.75 µg/mL–59.00 ± 2.01 µg/mL, while the value for ascorbic acid was 7.80 ± 0.14 µg/mL [9].

Table 2.

Comparison of the antioxidant activity of Impatiens L. essential oils and standard antioxidants. Different superscripts in each column indicate significant differences in the means at p < 0.05.

Essential Oils Radical Scavenging Activity DPPH (EC50, µg/mL) Inhibition of Linoleic Acid Peroxidation (IC50, µg/mL)
I. balsamina herb (IBH) 16.14 ± 0.68 g 468.06 ± 2.03 f
I. glandulifera herb (IGH) 3.96 ± 0.03 b 102.08 ± 0.71 b
I. glandulifera roots (IGR) 5.84 ± 0.03 d 116.98 ± 0.43 c
I. noli-tangere herb (INH) 4.76 ± 0.05 b,c 123.18 ± 1.34 c
I. parviflora herb (IPH) 9.06 ± 0.07 e 190.94 ± 0.76 d
I. parviflora roots (IPR) 10.38 ± 0.17 f 323.66 ± 0.24 e
Ascorbic acid 2.05 ± 0.01 a -
BHT - 18.21 ± 0.11 a
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Means values followed by different superscripts (a–g) in a column are significantly different (p < 0.05).

The inhibition of linoleic acid peroxidation revealed low capacities of the essential oils of Impatiens species in comparison to the DPPH test (Table 2). The most active essential oils from herb and roots of I. glandulifera showed even up to six-times higher IC50 values than the lipophilic antioxidant BHT.

3. Experimental Section

3.1. Reagents and Materials

Aerial parts and roots of plants were collected during July–September 2014. I. balsamina L. (No. IB-0714) was collected in the Maria Curie-Skłodowska University (UMCS) Botanical Garden, which is a part of Maria Curie Sklodowska University in Lublin, Poland, at an altitude of 197 m a.m.s.l. (coordinates N 51°08’41’’; E 22°18’17’’). I. glandulifera Royle (No. IG-0814) and I. noli-tangere L. (No. INT-0914) were gathered in Józefów near Biłgoraj (Poland) at an altitude of 240 m a.m.s.l. (coordinates N 50°29’06’’; E 23°02’12’’ and N 52°57’58’’; E 23°04’46’’ respectively). I. parviflora DC. (No. IP-0914) was collected in Motycz Leśny near Lublin (Poland) at an altitude of 180 m a.m.s.l. (coordinates N 51°14’57’’; E 22°20’36’’). Voucher specimens were deposited in the Department of Pharmaceutical Botany, Faculty of Pharmacy, Medical University of Lublin. Plants were identified by Prof. Tadeusz Krzaczek.

All chemical reagents used in the experiment were purchased from various commercial suppliers and were of the highest purity available. 2,2-diphenyl-1-picrylhydrazyl (DPPH), ascorbic acid, 2,6-di-tert-butyl-4-methylphenol (BHT) and linoleic acid (LA) were purchased from Sigma-Aldrich (St. Louis, MO, USA).

3.2. Isolation Procedure

The essential oils (EOs) of 100 g of dried herb or roots of Impatiens species were obtained by hydrodistillation for 3 h using the Clevenger-type apparatus, according to European Pharmacopoeia 5.0. Next, the EOs were trapped in 2 mL of freshly-rectified diethyl ether. After distillation, the organic layers were collected and dried over anhydrous magnesium sulfate. After filtration and additional washing of diethyl ether, the solvent was evaporated at room temperature, and the residues were weighed. The oil yields were calculated on the basis of the dry weight of plant material and according to the formula [30]:

EO (%) = W1/W2 × 100 (1)

where W1 is the net weight of oils (g) and W2 is the total weight of dry samples (g).

3.3. GC-MS Analysis

The chemical composition of the essential oils was analyzed using GC-MS on a Trace GC Ultra apparatus (Thermo Electron Corporation, Milan, Italy) with FID and the MS DSQ II detector after dilution in diethyl ether (10 μL in 1 mL). A simultaneous GC-FID and MS analysis was performed using an MS-FID splitter (SGE, Analytical Science, Austin, TX, USA). Operating conditions: apolar capillary column Rtx-1ms (Restek), 60 m × 0.25 mm i.d., film thickness 0.25 μm; temperature program, 50–310 °C at 2 °C/min; SSL (splitless) injector temperature 280 °C; FID temperature 300 °C; split ratio 1:20; carrier gas helium at a regular pressure 300 kPa. Mass spectra were acquired over the mass range of 30–400 Da, ionization voltage 70 eV; ion source temperature 200 °C. Identification of the components was based on a comparison of their mass spectra and relative retention indices with data stored in computer libraries NIST 98.1, Wiley 8th Ed. and MassFinder 4.1. Retention indices (RI, apolar column) were determined with relation to a homologous series of alkanes (C8–C26) under the same conditions with linear interpolation. Percentages were calculated from the FID response without the use of correction factors.

3.4. Free Radical Scavenging Activity

To determine the antioxidant activity of essential oils from Impatiens species, the method based on the reduction of the methanolic solution of colored free radical DPPH· was used. The changes in color from deep-violet to light-yellow were measured at 515 nm in a UV/visible light spectrophotometer (Thermo Evolution 300, Madison, WI, USA). Radical scavenging activity was measured according to the Brand-Williams et al. [31] method with the use of six dilutions of the analytes in methanol. The activity of ascorbic acid was evaluated for comparison. Antioxidant activity was expressed as EC50 (efficient concentration): the amount of dry extract (µg of DW) needed to obtain 50% activity per 1.0 mL of the initial solution.

3.5. Inhibition of Linoleic Acid Peroxidation

The antioxidant activity was also determined as the degree of inhibition on the hemoglobin-catalyzed peroxidation of linoleic acid according to the method described in previous studies [32,33] with a slight modification. The hydroxyperoxide formed was assayed according to the ferric thiocyanate method with mixing with 0.02 M FeCl2 followed by 30% ammonium thiocyanate. The absorbance of the sample (As) was measured at 480 nm. The absorbance of blank (A0) was obtained without hemoglobin to the reaction mixture; the absorbance of the control (A100) was determined without the sample added to the mixture. Thus, the antioxidative activity of the sample was calculated according to the formula:

AA [%] = [(1 − (As − A0) / (A100 − A0)] × 100 (2)

Antioxidant activity was expressed as IC50 (inhibition concentration): the amount of antioxidant needed to decrease the linoleic acid peroxidation by 50%.

3.6. Data Analysis

All measurements were performed at least in triplicate and expressed as the means ± standard deviations (±SD). Statistical significance was estimated through Tukey’s test for the data obtained from three independent samples of each essential oil in three parallel experiments (n = 9). Besides the classical pairwise correlation check, we applied the scaled principal component analysis. Statistical tests were performed using Statistica 6.0 software (Stat-Soft, Inc., Tulsa, OK, USA).

4. Conclusions

It is well understood that invasive species produce specific compounds affecting native plants occurring in the same habitat. This phenomenon is known as allelopathy. Identification of chemical constituents produced and emitted by invasive species helps to understand their impact on the local environment.

Taking into account the chemical composition of I. glandulifera and I. parviflora essential oils and previous data on the allelopathic activity of monoterpenoids, it seemed possible that the emission of monoterpenes by herb and root of these two Impatiens species plays a role in their invasive ability. However, this hypothesis needs further research.

Author Contributions

K.S. conceived and designed the experiments, and wrote the paper; K.S. and D.K. performed the experiments and analyzed the data; Ł.K. performed the statistical analysis; R.N. contributed reagents/materials/analysis tools.

Conflicts of Interest

The authors declare no conflict of interest.

Footnotes

Sample Availability: Not Available.

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