Volatile Constituents of the Leaves of Kalanchoe pinnata From the Venezuelan Andes

Abstract

The essential oil from the leaves of Kalanchoe pinnata (Lam.) Pers. (Crassulaceae), collected in the Venezuelan Andes, was obtained by hydrodistillation and its composition determined by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). Nineteen compounds were identified, representing 95.2% of the oil. The most abundant components were α-curcumene (44.7%), 1-octen-3-ol (18.1%), β-curcumene (4.9%), and β-caryophyllene (3.7%).

Kalanchoe pinnata (Lam.) Pers. (synonym Bryophyllum calycinum and B. pinnatum), one of the most important medicinal species of the Crassulaceae family, is widely distributed in Asia, Australia, New Zealand, West Indies, Macaronesia, Mascarenes, Galápagos, Melanesia, Polynesia, and Hawaii. ¹ This species is used in folk medicine to treat cardiovascular dysfunctions ² and diabetes. It is also used to heal wounds and to treat inflammation.^3,4

Several studies ⁵ have reported antimicrobial, ⁶ antiulcer, ⁷ antihypertensive, ⁸ antihyperglycemic, antinociceptive, ⁹ anti-inflammatory, ¹⁰ antiedematogenic, ¹¹ antiviral, ¹² and antileishmanial ¹³ activities for the leaves of K. pinnata. Recent studies have reported the potential of this plant to inhibit inflammatory events related to allergic airway diseases. Polyphenolic compounds present in the extract are speculated to be responsible for this activity. ¹⁴ A number of active compounds, including flavonoids, ¹⁵ triterpenes, sterols, ¹⁶ bufadienolides, ¹⁷ and organic acids, ¹⁸ have been identified in K. pinnata.

Hydrodistillation of the leaves yielded a yellowish oil in 0.001%, v/w, yield. The composition of the essential oil was determined by comparison of the mass spectrum of each component with data from Wiley gas chromatography (GC)/mass spectrometry (MS) library and retention index (RI).^19,20 Nineteen components were identified, which represent 95.2% of the total oil, which contained oxygenated hydrocarbons (19.1%), oxygenated monoterpenes (2.1%), sesquiterpenes (64.4%), oxygenated sesquiterpenes (4.2%), other oxygenated compounds (3.3%), and fatty acids (2.1%). The chemical constituents of the oil are listed in Table 1 in order of elution from an HP5-MS capillary column. The main components were α-curcumene (44.7%), 1-octen-3-ol (18.1%), β-curcumene (4.9%), and β-caryophyllene (3.7%).

Table 1.

Percentage Composition of the Essential Oil Isolated From the Leaves of Kalanchoe pinnata.

No	RI	Components	% Area
1	960	1-Octen-3-ol	18.1
2	1091	Nonanal	1.0
3	1295	Carvacrol	2.1
4	1371	α-Cubebene	0.7
5	1385	β-Elemene	1.8
6	1413	β-Caryophyllene	3.7
7	1430	α-Bergamotene	1.0
8	1450	α-Humulene	2.5
9	1479	α-Curcumene	44.7
10	1483	β-Ionone	1.2
11	1492	Ledene	0.7
12	1502	Germacrene A	1.0
13	1507	β-Curcumene	4.9
14	1511	cis-γ-Bisabolene	1.3
15	1519	δ-Cadinene	2.2
16	1573	Caryophyllene oxide	3.1
17	1625	Dillapiole	2.1
18	1644	T-muurolol	1.1
19	1962	Hexadecanoic acid	2.1
		Total identified	95.2

It has been reported that α-curcumene could be used as an anti-inflammatory drug in respiratory infections. ²¹ Additionally, it has been reported that it has larvicidal and oviposition deterrent activity against the malaria vector Anopheles stephensi, the dengue and Zika virus vector Aedes aegypti, and the filariasis and St. Louis encephalitis vector Culex quinquefasciatus. Since the acute toxicity of α-curcumene on the larvivorous fish Poecilia reticulata was extremely low, with LC₅₀ > 1500 ppm, we believe the K. pinnata essential oil could be considered a candidate for the development of effective mosquito larvicides. ²²

To our knowledge, this is the first time that the chemical composition of the essential oil of the leaves of K. pinnata has been reported.

Experimental

Plant Material

Leaves of K. pinnata were collected in January 2017 at San Jacinto, Mérida State, Venezuela. A voucher specimen has been deposited at the MERF Herbarium (Herbarium of the Faculty of Pharmacy and Bioanalysis in Mérida, Venezuela). The botanical identification was made by Forest Engineer Juan Carmona.

Extraction and Analysis of the Essential Oil

Fresh leaves (1000 g) were cut into small pieces and submitted to hydrodistillation for 3 hours using a Clevenger-type apparatus. A volume of 0.1 mL of essential oil was obtained (0.001%, v/w). The composition of the essential oil was determined by comparison of the mass spectrum of each component with Wiley GC/MS library data and also from RI data.^19,20

Gas Chromatography

GC analyses were performed using a Perkin-Elmer Autosystem gas chromatograph equipped with a flame ionization detector (FID) and data-handling system. A 5% phenylmethylpolysiloxane fused silica capillary column was used (30 m × 0.25 mm i.d., film thickness 0.25 m; HP-5, Hewlett-Packard, CA, USA). The oven temperature was programmed from 60°C to 260°C at 4°C/min. The injector and detector temperatures were 200°C and 280°C, respectively. The carrier gas was helium at 0.8 mL/min. The sample (1.0 μL) was injected using a split ratio of 10:1. Retention indices were calculated with reference to C₈-C₂₄ n-alkanes. The percentage composition of the oil was calculated by the normalization method from the GC peak areas.

Gas Chromatography/Mass Spectrometry

GC–MS analyses were carried out on a Model 5973 Hewlett-Packard GC–MS system fitted with a HP-5MS fused silica column (30 m × 0.25 mm i.d., film thickness 0.25 μm, Hewlett-Packard). The oven temperature program was the same as that used for the HP-5 column for GC analysis; the transfer line temperature was programmed from 150°C to 180°C; source temperature, 230°C; quadrupole temperature, 150°C; carrier gas, helium adjusted to a linear velocity of 34 cm/s; ionization energy, 70 eV; scan range, 40 to 500 amu; and 3.9 scans/s. A sample (1.0 μL) was injected using a Hewlett-Packard ALS injector with a split ratio of 50:1. The identity of the oil components was established from their GC retention indices, by comparison of their MS with those of standard compounds available in the laboratory, and by a library search (Nist 05 and Wiley MS Data Library, 6th edition).^19,20