Comparative volatiles profiling in Marjoram products essential oil as extracted using classical and headspace techniques and in relation to antioxidant and antibacterial effects

Recently, the growth of consumer demand for natural herbal products with both safety and efficacy has led to great advances in analytical tools to assess and assure their quality. Marjoram ( Origanum majorana L.), also known as "sweet marjoram" or “sweet oregano” is a Mediterranean herbaceous perennial herb cultivated in Egypt. The main goal of this study was to assess volatiles’ variation in marjoram samples collected from two different commercial products using two different extraction techniques viz. HS-SPME and petroleum ether coupled with GC-MS analysis. A total of 20 major aroma compounds were identified in samples extracted with HS-SPME with abundance of monoterpene hydrocarbons and oxygenated compounds. The major volatiles included β-phellandrene (20.1 and 14.2%), γ-terpinene (13.4 and 11.7%), 2-bornene (12.3 and 11.5%), p-cymene (9.8% and 4.6%) terpenen-4-ol (16.4% and 7.5%), sabinene hydrate (16.02% and 8.8%) and terpineol (4.2 and 3.2%) in MR and MI, respectively. Compared with HS-SPME, 51 aroma compounds were identified in marjoram samples extracted with pet. ether, more enriched in aliphatic hydrocarbons (42.8 and 73.8%) in MR and MI, respectively. While higher identification score was observed in case of solvent extraction, SPME appeared to be more selective in recovery of oxygenated terpenes to more account for marjoram aroma. The total phenolic and flavonoid contents in marjoram samples were at (111.9, 109.1 µg GA/mg) and (18.3, 19.5 µg rutin eq/mg) in MR and MI, respectively. Stronger antioxidant effects were observed in MR and MI samples with IC ₅₀ at 45.5 and 56.8 µg/mL respectively compared to IC ₅₀ 6.57 µg/mL for trolox as assayed using DPPH assay. Moderate anti-bacterial effect was observed in MR and MI samples and expressed as zone of inhibition mostly against Bacillus subtilis (16.03 & 15.9 mm), B. cereus (12.9 & 13.7mm), Enterococcus faecalis (14.03 & 13.97 mm), and Enterobacter cloacae (11.60 & 11.56 mm) respectively.