Chemotypes of Juniperus oxycedrus in Bulgaria and the antimicrobial activity of galbuli essential oils

Abstract

Juniperus oxycedrus L. (Cupressaceae Bartlett) sensu lato is a species of high phenotypic and phytochemical variability. There is interest in the development of this species into cultivated crop because wild collection of galbuli or leaves result in significant variation in the essential oil (EO) profile and bioactivity. The objectives of this study were tо assess the variability of EO content and composition of J. oxycedrus collected at 20 populations (interpopulation) across Bulgaria and also intrapopulation variability using advanced statistical methods, and to identify promising clones that can be propagated and further investigated under cultivation. Overall, the EO yield of leaves varied from 0.03 % to 0.20 % (interpopulation), from 0.04 % to 0.18 % (intrapopulation), whille the galbuli EO varied from 0.83 % to 2.6 % (interpopulation) and from 1.2 % tо 1.9 % (intrapopulation), respectively. Monoterpenes was the predominant chemical class of galbuli ЕO, ranging from 53.4%to–69.5% (intrapopulation), while in leaf EO, the predominant class was sesquiterpenes (46.2 %–67.4 %) (intrapopulation). The major constituents (α-pinene, limonene, α-curcumene, γ-cadinene, δ-cadinene, manoyl oxide, germacrene D, β-caryophyllene, α-caryophyllene, caryophyllene oxide) of leaf EO were considered for grouping the populations in eight chemotypes, whereas twenty-seven chemical groups were established for the interpopulation study. The EO of galbuli in the interpopulation study formed five chemical groups. The present study is the first report to demonstrate such variability of EO between and within the populations of J. oxycedrus, and the first report to identify so many chemical groups based on the leaf and galbuli EO. Galbuli ЕO showed different аntimicrobial activity towards Yersinia enterocolitica, Staphylococcus aureus subsp. aureus, Enterococcus faecalis, Streptococcus pneumoniae, Candida kruseii, and C. tropicalis. This study identified promising genetic material (clones) that could be further propagated and developed into cultivars for commercial production of J. oxycedrus oil with desirable profile, aroma, and bioactivity to meet specific market demands.