Evaluation of biological activities of essential oil and extracts of gum Vasha (Dormea ammoniacum D.)

Vasha is a monocarpic plant endemic to central Iran. The sesquiterpens in the oleo gum resins of vasha display important defense role against fungi and pathogenic bacteria. The aim of the present study was to evaluate the antioxidant and antibacterial activities of essential oil as well as ethyl acetate, chloroform, hexane and methanolic extracts from the gum-resin of Dorema ammoniacum and investigating its essential oil constituents. As the biosynthesis of secondary metabolites is affected by the prevailing environmental conditions, in this study, the extracted gum of Dorema ammoniacum from Shahrood region was phytochemically characterized.

Oleo gum resin of vasha was collected from Shahroud (Torud) desert and essential oils were analyzed using GC and GC/MS and extraction was done using Soxhlet extractor with organic solvents of different polarity including hexane, chloroform, ethyl acetate, and methanol. Evaluation of the antioxidant activities of essential oil as well as ethyl acetate, chloroform, hexane and methanolic extracts from gum-resin of Dorema ammoniacum were done using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, and for the antibacterial screening disk diffusion and Broth micro dilution methods were employed. The minimum inhibition concentration (MIC) and the minimum bactericidal concentration (MBC) were measured against a number of bacteria.

The ethyl acetate extract with IC50=69.0 μg/mL showed highest antioxidant activity and essential oil with IC50 = 166.0 μg/ml displayed a moderate antioxidant activity. The methanolic (31.25 μg/mL) and chloroformic (62.50 μg/mL) extracts exhibited high antibacterial activities. Analysis of essential oil of oleo-gum resin by GC-MS led to the identification of 51 compounds. Methyl oleate (20.2%), Methyl palmitoleate (15.9%), Fenchyl acetate (7.25%), Methyl linoleate (6.87%), Methyl stearate (6.64%), Oleic acid, trimethylsilyl ester (4.97%), Pentadecane (3.14%), alpha.-Gurjunene (2.66%), beta.-Bisabolene (2.6%) were identified as the dominant compounds.

D. ammoniacum is one of the most important species of Dorema. The established phenolic and polyphenolic compounds in the extracts or essential oil as well as the presence of sesquiterpens coumarines / phenols in the oleo gum resin extract with biological activities such as antioxidant and antimicrobial and even anti-Alzheimer's makes D. ammoniacum plant as a good candidate for medicinal uses. These results showed that some extrinsic factors such as climate, soil properties, insect and microorganisms stress, harvest time, plant preparation procedure and the method of essential oil extraction in D. ammoniacum may affect chemical composition of the extracts and essential oils. Keywords: Antioxidant activity, Antibacterial activity, Essential oil, Dorema ammoniacum