The hydrodistilled volatile constituents of Cistanche tubulosa (commonly known as Desert Ginseng) have been chemically and biologically investigated. Based on the retention times and mass fragmentation of the obtained GC-MS chromatogram, 106 individual components which representing ≈ 99.29 % of the total volatile constituents have been identified. The major compounds (66.57% of the total composition) were identified as hexanal (15.98%), trans-sabinyl acetate (12.22%), allo-aromadendrene (9.30%), nonanoic acid (6.66%), 3Z- hexeny-2-methyl butanoate (6.09%), valeranone (5.25%), (E, E)-α-Farnesene (3.18%), a-pinene (3.06%), linalool isovalerate (3.03%) and a-humulene (1.8%). Estimation of the antioxidant activity of EO showed promising effect at 80 mg/mL concentration, it exerted 62.40, 863.29 and 62.72 % inhibition compared to TBHQ that showed 78.62, 77.56 and 79.23 % inhibition using DPPH, ABTS and β-carotene/Linoleic acid, respectively. The antioxidant activity was pronounced at 80 mg/mL than other concentrations. The volatile constituents showed inhibitory activity against gram positive bacteria ranged from 2.23 mg/100 mL ( for staphylococcus aureus ), and 15.68 mg/100 mL (for Bacillus cereus) compared to ciprofloxacin which showed inhibitory activity 0.185, and 0.182 mg/100 mL, respectively. Moreover, the MIC of volatiles towards gram negative bacteria are ranged from 18.35 (Escherichia coli) to 31.61 mg/100 mL (Klebsiella pneumonia) compared to ciprofloxacin with 0.184 to 0.188 mg/mL respectively. Additionally, the antifungal activity against candida albicans was rather promising (4.36 mg/mL).

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