Volatile Constituents, Antimicrobial and Antioxidant Activities of the Aerial Parts of Origanum majorana L. from Yemen

Aims: There is no report about the analysis of volatile composition of Origanum majorana L. (Lamiaceae) by static headspace method in combination with GC-MS. The present study reports for the first time the volatile composition, antimicrobial and antioxidant activities of O. majorana from aerial parts of plant collected in Yemen.

Methodology: The volatile composition was obtained by headspace vapour of plant aerial parts and determined by gas chromatography-mass spectrometry (GC-MS) analysis. Antioxidant activity of extracts was evaluated by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay and antimicrobial activity by agar diffusion.

Results: The major volatile compounds were found to be monoterpenes: Trans-sabinene hydrate (16.0 %), sabinene (14.1%), cis-sabinene hydrate (11.8 %), γ-terpinene (10.2%),α-terpinyl acetate (10.0%), α-terpinene (8.9%), terpinen-4-ol. In addition, five volatile non terpenoid compounds were identified for the first time: 2-methylpropanal, 2-methylbutanal, 3-methylbutanal, pentanal and methyl 2-methylbutanoate. Furthermore, dichloromethane, methanol and aqueous extracts were tested for their antimicrobial activities against five bacteria and two fungi strains. The most sensitive microorganism was Staphylococcus aureus, reaching MIC values of 50, 100 mg/mL for methanol and dichloromethane extracts, respectively. The methanol extract showed strong radical scavenging activity in the DPPH assay followed by dichloromethane extract.

Conclusion: The O. majorana extracts showed potent antimicrobial and antioxidant activities mostly attributed to identified oxygenated monoterpenes. The obtaining of volatiles of the plant as vapour by headspace method showed more qualitative and accurate quantitative results than by hydrodistillation method. Therefore, the headspace analysis should be useful in analytical control of herbal crude drugs.