New insights into the chemical composition of Piper spp. collected in the northern region of Vietnam

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 hydro-distillation 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 com-pound 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-gamma-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 beta-pinene (10.1%). In the other hand, essential oil from P. carni-bracteum was characterized by the dominant amount of trans-caryophyllene (21.7%), alpha-muurolene (21.1%), bicyclo[4.3.0]nonane,7-methylene-2,4,4-trimethyl-2-vinyl-(17.8%) while aromadendrene (25.7%), gamma-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.