Juniperus sabina L. essential oils and podophyllotoxin seasonal and interpopulation dynamics

Juniperus sabina L., commonly known as Savin, is an evergreen shrub from Cupressaceae family, grown as an ornamental all over the world. J. sabina contains two valuable metabolites: essential oil (EO) and podophyllotoxin. The EO is known for various bioactivities, while podophyllotoxin, is currently used as a precursor for anticancer drugs. The hypothesis of this work was that J. sabina plants from natural populations in Bulgaria would have desirable EO profiles and bioactivity. Furthermore, accessions with high concentrations of podophyllotoxin may be discovered. The objectives were: (1) Assessment of the EO profile and podophyllotoxin variability, including seasonal, within populations, and between populations of J. sabina in Bulgaria; (2) Evaluation of the potential biopesticidal effect of J. sabina EO from natural populations; and (3) Assessment of antioxidant and enzymatic activities of J. sabina EO. Overall, the EO content and composition varied between natural populations, within a population, between female (F) and male (M) plants, and between different seasons (months) of the year. Sabinene (10.1-66.8% of the total EO), myrtenyl acetate (0-57.2%), alpha-pinene (2.6-8.6%), myrcene (2.85-4.5%), alpha-thujone (0-10.9%), beta-thujone (0-9.9%), and germacrene-4-ol (3.0-10.3%) were the major EO constituents. Monoterpenes represented 89.5-92.8% and sesquiterpenes were 6.7-7.1% of the EO. The EO yield was 0.61-3.8% in dried biomass, while the concentration of podophyllotoxin varied from undetected to 0.19%. Antioxidant activity was higher in EOs from female (F) plants in DPPH assay; in the FRAP assay, some EOs from male (M) plants collected in January, March, May, and July were the most active. Moreover, EO from F plants exhibited good activity on alpha-amylase and alpha-glucosidase enzymes. The tested EOs from both M and F plants at 5 mu L, 10 mu L, and 20 mu L significantly reduced or completely suppressed the germination and sprout length of seeds of five weed species. Eight chemotypes of J. sabina were identified and the EO of these were tested for suppression of soft white winter wheat, SWWW ( Triticum aestivum L.) germination and root and shoot growth. About half of the chemotypes suppressed wheat seed germination, root, and shoot growth. J. sabina EO could potentially be further explored for the development of biopesticides to be utilized for weed control in organic production systems and possibly for control of pre-harvest sprouting in wheat.