Composition of Essential Oil from Actinodaphne sesquipedalis and Its Lipoxygenase Activity

Published in Khimiya Prirodnykh Soedinenii, No. 3, May–June, 2021, pp. 470–471.

The genus Actinodaphne (Lauraceae) comprises 70 species of evergreen trees and shrubs. In Malaysia, it is locally known as medang kuning or medang kunyit and occurs mainly in tropical-subtropical Asia. They are widely distributed in Malaysia, Indonesia, Eastern Asia, and North America [[1]]. This genus has been reported to produce alkaloids [[2]], lactones [[4]], lignans [[5]], and phenolic amides [[6]]. The methanol leaf extract has shown prominent gastroprotective potential in rat stomach against ethanol-induced ulcer [[7]]. Although many members of the family Lauraceae are renowned for their valuable essential oils, the genus Actinodaphne is still poorly explored as far as its essential oil composition is concerned. Therefore, it is interesting to report the essential oil composition of Actinodaphne sesquipedalis Hook. f. & Thomson ex Meisn. leaves for the first time from Malaysia.

The leaves of Actinodaphne sesquipedalis were collected from Behrang, Perak in September 2019 and identified by Shamsul Khamis. A voucher specimen (SK38/19) was deposited at the Herbarium of UKM. The fresh leaves (500 g) were subjected to hydrodistillation in a Clevenger-type apparatus for 5 h. The essential oil obtained was dried over anhydrous magnesium sulfate and stored at 4–6°C. The oil yield was 0.22% based on the fresh weight.

Gas chromatography (GC) analysis was performed on an Agilent Technologies 7890B and an Agilent 7890B FID equipped with HP-5MS (30 m × 0.25 mm × 0.25 μm film thickness) column. Helium was used as a carrier gas at a flow rate of 0.7 mL/min. Injector and detector temperatures were set at 250 and 280°C, respectively. The oven temperature was kept at 50°C, then gradually raised to 280°C at 5°C/min and finally held isothermally for 15 min. Diluted samples (1:100 in diethyl ether) of 1.0 μL were injected manually (split ratio 50:1). In addition, GC-MS chromatograms were recorded using Agilent Technologies 7890A and Agilent 5975 GC MSD equipped with an HP-5MS system. Helium was used as carrier gas at a flow rate of 1 mL/min. For GC-MS detection, an electron ionization system with ionization energy 70 eV was used. A scan rate of 0.5 s (cycle time: 0.2 s) was applied, covering a mass range from 50–400 amu. For identification of essential oil components, co-injection with the standards were used, together with correspondence of retention indices and mass spectra with respect to those occurring in Adams [[8]].

For the lipoxygenase assay, the reagents were prepared according to the standard protocol (lipoxygenase inhibitor screening assay kit, Item No. 760700, Cayman Chemicals) [[9]]. Quercetin was used as a reference.

The chemical composition of the essential oil is listed in Table 1. In total, 35 components, accounting for 98.4% of the total composition, were successfully characterized. Oxygenated sesquiterpenes were the most dominant components, which consisted of 14 components, accounting for 56.4%, while sesquiterpene hydrocarbons comprised 21 components, accounting for 42.0% of the total composition. The major components were spathulenol (25.2%), globulol (16.5%), germacrene D (9.6%), germacrene B (8.2%), and β-caryophyllene (5.4%). Spathulenol is used in aromatizing compositions for food and as a flavoring agent in the food and cosmetics industries. Studies of essential oils containing spathulenol as a major compound have reported some biological activities, such as antiproliferative [[10]], anti-inflammatory [[11]], antimicrobial [[12]], as well as repellent activity against Aedes aegypti and Anopheles stephensi [[13]].

Table 1. Chemical Composition of the Essential Oil from Actinodaphne sesquipedalis

aLinear retention index experimentally determined using homologous series of C6–C30 alkanes.

Anti-inflammatory activity was evaluated using the lipoxygenase assay. The essential oil showed moderate activity with IC50 value of 58.2 μg/mL (quercetin IC50 = 10.5 μg/mL). The high quantity of germacrene B, globulol, and spathulenol obtained in the essential oil may contribute, at least in part, to the activity ascribed to the plant. These components have shown anti-inflammatory activity in the literature [[14]].

Several Actinodaphne essential oils have been reported before. The major components of the studied Actinodaphne essential oils were as follows: A. lancifolia (leaf oil): α,β-selinene (28.9%), caryophyllene (10.0%), and decanal (20.3%) [[15]]; A. lancifolia (mesocarps oil): decanal (15.3%); A. lancifolia (seeds oil): longifolin (64.9%), A. lancifolia (roots oil): sesquirosefuran (79.2%) [[16]]; A. longifolia (leaf oil): caryophyllene (8.3%) and β-elemene (7.5%) [[15]]; A. cupularis (leaf oil): isocaryophyllene (8.3%) and germacrene B (7.1%) [[17]]; A. macrophylla (leaf oil): germacrene B (16.8%) and globulol (16.0%) [[18]]; and A. pruinosa (leaf oil): globulol (17.8%) and spathulenol (12.0%) [[18]]. The variations in the levels of the components may be related to the local environments and conditions to which the assayed plant was exposed. Seasonality, temperature, as well as the stage of development and nutritional factors, are all likely to influence the chemical composition of essential oils [[19]].