Chemical Composition and in vitro Biological Evaluation of Essential Oil of Euphorbia larica Boiss from Northern Oman

Abstract

Euphorbia larica Boiss is a wild plant of Oman that grows in gravel plains, mountain areas, desert and forest edges. Traditionally, Omani herbalists use the Euphorbia larica plant extract, resins, latex and juice to treat a wide range of ailments such as wounds, burns, insect bites, intestinal parasites, gonorrhea, eye infections, migraines and warts. In an attempt to scientifically validate the traditional uses and to unlock its hidden therapeutic potential, in this work, the chemical composition of E. larica essential oil (ELEO) along with its potential antioxidant, antimicrobial and hemolytic activities is studied. In a GC-MS analysis of the extracted ELEO, 29 chemicals were found, with α-pinene (27.36%) and limonene (11.5%) being the two most abundant volatile components. ELEO exhibited moderate inhibition of DPPH radicals (17.74-40.96%; IC50 = 48.97 μg/mL). It showed antimicrobial activity against S. aureus, B. subtilis, S. pyogenes, E. coli, P. aeruginosa and P. vulgaris but was ineffective against K. pneumoniae bacterial strain however, exhibited the maximum antibacterial activity against S. aureus (11 ± 1.3 and 15 ± 2.3 mm at 5 and 10 μL concentrations, respectively) comparable to positive antibiotic ampicillin (15 mm at 5 μg). Moreover, ELEO exhibited a very low hemolytic activity (0.12 to 1.1% at doses of 50-500 μg) suggesting it to be non-toxic to human or animal cells. Thus, it can be concluded that E. larica plant holds significant potential as a source of bioactive agents for the development of novel therapeutics.