Essential Oil Composition of Hawthorn Crataegus monogyna Inflorescence

Hawthorn (Crataegus) is a large genus of shrubs and trees in the rose family (Rosaceae), native to temperate regions of the Northern Hemisphere in Europe, Asia, and North America. In Poland, it can be found in well-lit forests, thickets, clearings, and on the slopes. It is planted in parks and also as a hedge [1]. Medicinal raw materials (inflorescence and fruit) are derived from two species commonly found in Poland: common hawthorn (Crataegus monogyna Jacq.) and midland hawthorn (Crataegus laevigata (Poir.) DC.). European Pharmacopoeia reports that the medicinal raw material is hawthorn inflorescence with a few leaves [2]. The main active compounds in hawthorn inflorescence are flavonoids (vitexin and its glycosides, rutoside, hyperoside, kaempferol - responsible for the operation relaxant of vascular smooth muscle) and procyanidins (gently lowering blood pressure). Hawthorn inflorescence includes phenolic acids, triterpene acids, nitrogenous compounds, tannins, essential oil, β-sitosterol, and esculin [3, 4]. Both the flowers and fruits of hawthorns are well known in herbal folk medicine as a heart tonic, and modern research has borne out this use. The flowers and fruits have a hypotensive effect as well as acting as a direct and mild heart tonic [1]. The available literature is very poor on the composition of the volatile fraction of hawthorn inflorescence, which prompted the authors to conduct research in this area. The aim of the study was to analyze the chemical composition of the essential oil (EO) derived from the four (A, B, C, D) available pharmaceutical form of hawthorn inflorescence.

Qualitative and Quantitative Analysis of Essential Oil. Assay of the Essential Oil Content. Hydrodistillation of essential oils was carried out according to the Polish Pharmacopoeia VIII [5]. Due to the lack of detailed monographs in Polish Pharmacopoeia VIII [5], distillation time was set at 3 h using the indirect method with xylene. Qualitative and quantitative analysis of the essential oil was carried out by GC/MS.

GC/MS. ITMS Varian 4000 GC-MS/MS (Varian, USA) equipped with a CP-8410 auto-injector and a 30 m × 0.25 mm i.d. VF-5 ms column (Varian, USA), film thickness 0.25 μm; carrier gas He at a rate of 0.5 mL/min; injector and detector temperature 250°C and 200°C, respectively; split ratio 1:50; injection volume 5 μL. A temperature gradient was applied (50°C for 1 min, then incremented by 4°C/min to 250°C, then held at 250°C for 10 min); ionization energy 70 eV; mass range 40-870 Da; scan time 0.80 s.

GC/FID. GC Varian 3800 (Varian, USA) equipped with a CP-8410 auto-injector and a 30 m × 0.25 mm DB-5 column (J & W Scientific, USA), film thickness 0.25 μm, carrier gas helium 0.5 mL/min, injector and detector FID temperatures 260°C; split ratio 1:100; injection volume 5 μL. A temperature gradient was applied (50°C for 1 min, then incremented by 4°C/min to 250°C, then held at 250°C for 10 min).

Qualitative Analysis. The qualitative analysis was carried out on the basis of MS spectra, which were compared with the spectra of the NIST library [6] and with data available in the literature [7, 8]. The identity of the compounds was confirmed by their retention indices [9] taken from the literature [7, 8] and our own data for standards (α-pinene, limonene, linalool, E-caryophyllene, caryophyllene oxide, spathulenol, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, heneicosane, docosane, tricosane, tetracosane, pentacosane, Sigma-Aldrich).

Quantitative Analysis. The quantitative analysis was performed by the internal standard addition method (alkanes C12 and C19) according to procedures described previously [10]. Essential oil was diluted 1000 times using n-hexane to achieve 1 mL volume; then 1 mg of C12 and 1 mg C19 were added to the diluted oil. Samples prepared in this way were subjected to GC-MS and GC-FID determinations. The quantitative analysis was performed as described before [10].

The content of essential oils in the analyzed samples was 0.05% v/w "B," 0.06% v/w "A," 0.12% v/w "C," and 0.20% v/w "D." Literature on the content of essential oils in hawthorn inflorescence and chemical composition is very poor.

In the studied hawthorn essential oils a total of 65 compounds was identified (Table 1). In the essential oil obtained from commercial samples "A" and "B," 58 compounds was detected, while in the EO hydrodistilled from sample "C" and "D," 56 and 63 compounds were identified, respectively. GC/MS analysis showed that aliphatic hydrocarbons are the main fraction occurring in the analyzed essential oils. The dominant components present in all EOs included tricosane (from approx. 12% to approx. 17%), heneicosane (from 11% to 16%), linalool (from approx. 6% to approx. 11%), n-hexadecanoic acid (from approx. 1% to approx. 11%), nonadecane (from approx. 3% to approx. 7%), (E,E)-α-farnesene (from approx. 1% to approx. 5%), caryophyllene oxide (from approx. 1% to approx. 4%), and methyl eugenol (to approx. 6%).

Composition of Essential Oil from Crataegus monogyna Inflorescences, %

RI: retention indices (from temperature-programming, using definition of Van den Dool and Kratz [9].

Tr.: trace (< 0.05%).

Kovaleva et al. [11] showed that the essential oils from the flowers of the other three Crataegus species (C. jackii, C. robesoniana, and C. flabellata) contained 46 compounds, among which were acyclic, monocyclic, and bicyclic mono- and sesquiterpenoids, norterpenoids, and triterpenoids, among which hydrocarbons such as tri-, tetra-, penta-, and nonacosane dominate.

The composition of essential oils from C. monogyna inflorescence was studied for the first time.

Published in Khimiya Prirodnykh Soedinenii, No. 5, September-October, 2018, pp. 844-846.