Essential oil composition, antioxidant and antimicrobial activity of the galbuli of six juniper species

To respond to the market demand for consistency of supply and quality, there are current efforts to develop junipers as agricultural crop for the production of juniper galbuli (berries). However, comparative data on the galbuli essential oil (EO) composition and bioactivity of different juniper species is limited. The objective of this study was to evaluate the EO composition, antimicrobial and antioxidant activity of the galbuli of the six juniper species naturally distributed in Bulgaria: Juniperus communis L. (common juniper), J. oxycedrus L. (red juniper), J. sibirica Burgsd. (Siberian juniper), J. sabina L. (Cossack juniper), J. pygmaea C. Koch. (Alpine juniper), and J. excelsa M. Bieb. (Gracian juniper). The EO content of the galbuli of the six juniper species varied from 0.47% (in J. sibirica) up to 1.6% (in J. sabina). The oil profile of the galbuli was also different among species. Differences and similarities in the groups of terpenes were established between the six juniper species. The three oil constituents with the highest concentration (in descending order) in the galbuli of each of the species were as follows: for J. oxycedrus: beta-Myrcene, alpha-Pinene, and Germacrene D; for J. cornmunis: alpha-Pinene, Germacrene D, beta-Myrcene; for J. excelsa: alpha-Pinene, alpha-Cedrol, Germacrene D; for J. sibirica: alpha-Pinene, beta-Myrcene, Germacrene D; for J. pygmaea: alpha-Pinene, Sabinene, beta-Myrcene; and for J. sabina: Sabinene, alpha-Pinene, Terpinene-4-ol. Overall, the antioxidant capacity of the six oils was as follows: J. sibirica > J. communis = J. excelsa. Out of the six EO, J. oxycedrus galbuli EO was the most effective against Clostridium perfringens, J. communis against Candida clabrata and J. oxycedrus against Staphylococcus aureus. The antioxidant capacity of the juniper galbuli oils were positively affected by the concentrations of beta-Elemene, gamma-Elemene, and tau-Muurolol. Positive relationships were found between the concentrations of some constituents with the antimicrobial activity of juniper EO against Staphylococcus aureus, Bacillus cereus, Yersinia enterocolitica, Clostridium perfringens, and Candida glabrata. The results contribute to further understanding of juniper galbuli EO, can be used by industry utilizing juniper EOs, and may help with policy making processes with respect to conservation and agriculture.