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The chemical composition of the essential oils obtained by hydrodistillation of the stems and leaves of Michelia alba D.C. growing in North Vietnam was analyzed using GC/MS. In total, 28 com¬pounds were identified in both stem and leaf oils, accounting for 99.33% and 99.54% of the oils, respectively. Linalool was the major component of both oils (80.65% and 72.89%, respectively), and other 22 compounds were also present as the constituents of both oils with varying amounts except 1,10-di-epi-cubenol present only in stem oil, whereas borneol (=endo-borneol), α-copaene, α-selinene and ethyl 2-phenylhexanoate were found only in leaf oil. In the stem oil, (Z)-β-ocimene (1.94%), (E)-β-ocimene (2.28%), β-caryophyllene (1.26%), (E)-nerolidol (1.15%), caryophyllene oxide (2.26%) and epi-α-muurolol (=T-muurolol) (1.80%) were present in sizeable amounts. The minor components detected in the leaf oil were (Z)-β-ocimene (1.73%), (E)-β-ocimene (2.28%), Cis-β-elemene (3.03%), P-caryophyllene (4.04%), α α-humulene (1.44%), (E)-nerolidol (4.42%) and caryophyllene oxide (1.36%). Antibiotic activity of the essential oil samples was tested against Gram positive bacteria Staphylococcus aureus, Gram negative bacteria Escherichia coli, and yeast Candida albican using an agar disk diffusion method. The antimicrobial activity of leaf oil was stronger than that of stem oil, although both oils have significant inhibitory activity against all three microorganisms tested with the inhibitory zone diameters ranging from 15.5 to 46.5 mm. [ABSTRACT FROM AUTHOR]

Our study aimed to compare the essential oil composition of Piper species (Piperaceae) collected in the northern region of Vietnam and find possible fingerprints of different species. The aerial parts of seven Piper species including P. mutabile , P. leptostachyum , P. laosanum , P. boehmeriifolium , P. carnibracteum , P. albispicum , and P. longum were collected, shade-dried and chopped into small pieces before being submitted to the hydrodistillation of essential oils. The yields of essential oils ranged from 0.12 to 0.85%. GC-MS analysis of the essential oils led to the identification of 99 volatile components, accounting for 92.5–99.6% of the total oils. Sesquiterpenes (40.3–93.0%) were commanding in all essential oils while monoterpenes were only dominant in essential oils from P. albispicum (29.8%) and P. longum (29.4%). The distances between groups of seven Piper essential oils were measured using multivariate analysis. Elemene isomer seems to be the characteristic compound of all seven Piper essential oils. Besides, the essential oil from P. mutabile in the present study was characterized by the very high content of safrole (20.9%) while epi-γ-eudesmol (15.9%), cis -caryophyllene (14.4%), trans -caryophyllene (10.6%), guaiol acetate (10.1%), eremophilene (9.6%) were main components in essential oil from P. laosanum. Essential oil of P. boehmeriifolium was dominated by elemene isomer (15.6%), eremophilene (14.2%), and trans -caryophyllene (9.3%). Essential oil from P. albispicum in our study featured by high contents of eremophilene (11.1%) and β-pinene (10.1%). In the other hand, essential oil from P. carnibracteum was characterized by the dominant amount of trans -caryophyllene (21.7%), α-muurolene (21.1%), bicyclo[4.3.0]nonane,7-methylene-2,4,4-trimethyl-2-vinyl- (17.8%) while aromadendrene (25.7%), γ-cadinene (20.3%) were ascendant in essential oil from P. leptostachyum. To the best of our knowledge, this is the first time that the essential oil composition of P. leptostachyum and P. carnibracteum were investigated. Besides, the volatile components in the essential oils from P. albispicum , P. laosanum , and P. mutabile showed some differences in the comparison to the data published previously on the chemical composition of these aforesaid species which could depend on many factors. [Display omitted] • The essential oil content and composition of seven Piper spp. have been studied. • The yields of essential oils in seven whole plants were ranged from 0.12 to 0.85%. • GC-MS analysis of the essential oils led to the identification of 114 components. • The oils of P. leptostachyum and P. carnibracteum were studied for the first time. • Data acquired are useful as chemosystematic markers of Piper spp. oils. [ABSTRACT FROM AUTHOR]