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Valtcho D. Zheljazkov, Tess Astatkie and Ekaterina Jeliazkova

Rocky Mountain juniper (Juniperus scopulorum Sarg.) is an evergreen dioecious tree (produces male and female plants). The pleasant aroma and the medicinal value of this species are the result of the essential oil. The hypothesis of this study was that the essential oil content and composition may be different in male and in female trees and also may be affected with seasonal changes throughout the year. The objective was to evaluate year-round variations in essential oil composition of Rocky Mountain juniper within single male and female trees. The concentration of essential oil in fresh leaves varied from 0.335% to 0.799%, and at most sampling points, the oil content in the biomass of the male tree was greater than that in the biomass of the female tree. There was a trend toward increased essential oil content in male juniper in 220 to 342 days after the first sampling (DAFS), compared with the one in 35 to 184 DAFS. The concentrations of the oil constituents alpha-pinene, alpha-terpinene, gamma-terpinene, terpinolene, pregeijerene B, elemol, beta-eudesmol/alpha-eudesmol, and 8-alpha-acetoxyelemol were greater in the oil of the female tree than in the oil of the male tree. Conversely, the concentrations of alpha thujene, sabinene, myrcene, limonene, and delta-cadinene were greater in the oil of the male tree than in the oil of the female tree. However, the concentration gradient trends for both female and male trees were similar for myrcene and sabinene, for alpha-terpinene and terpinolene, for pereijerene B and elemol, and for beta-eudesmol/alpha-eudesmol and 8-alpha-acetoxyelemol. Overall, lower concentrations in the oils at 101 to 132 or 163 DAFS were found for myrcene and alpha-pinene sabinene, whereas the concentrations of gamma-terpinene, elemol (female tree), beta-eudesmol/alpha-eudesmol (female tree), and 8-alpha-acetoxyelemol (female tree) were greater during this period. This study demonstrated that the content and composition of the essential oil from Rocky Mountain juniper are subject to seasonal changes and also depend on the sex of the tree.

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Valtcho D. Zheljazkov, Tess Astatkie and Ekaterina Jeliazkova

Spearmint (Mentha spicata L.) is a major essential oil crop in the United States. Developing means for increased biomass and oil yields and increased concentrations of carvone would be beneficial for the essential oil industry. A field experiment was conducted to study the effect of foliar application treatments [water (control), water + Tween20, sagebrush essential oil + Tween20, sagebrush water extract, juniper essential oil + Tween20, juniper water extract, and methyl jasmonate] on ‘Native’ spearmint essential oil content, shoot fresh weight, oil yield, and oil composition. The essential oil content was low in the water + Tween20 and in juniper essential oil (EO) + Tween20 treatments and high in the juniper water extract and in methyl jasmonate (MJ) treatments; however, neither of these were different from the water control or from the sagebrush EO + Tween20. Biomass fresh weight was lower in the sagebrush water extract (SWE) and in the juniper water extract (JWE) relative to the water control. The application of juniper EO + Tween20 reduced the concentration of carvone in the oil relative to the water control or to the water + Tween20 treatment. The sagebrush water extract, juniper EO + Tween20, juniper water extract, and MJ increased the concentrations of beta-caryophyllene relative to the water treatment. The concentration of trans-beta-farnesene was lower in the control water treatment and higher in all other treatments. Also, with the exception of sagebrush EO + Tween20, all treatments increased the concentration of germacrene D relative to the water control but not relative to water + Tween20. This study demonstrated that foliar application of sagebrush EO, sagebrush water extract, juniper EO, or juniper water extract to ‘Native’ spearmint may affect the essential oil profile of spearmint essential oil. Some of the treatments increased the concentrations of beta-caryophyllene, trans-beta-farnesene, and germacrene D in the essential oil; however, neither of the treatments increased the concentration of carvone, the main essential oil constituent of ‘Native’ spearmint oil.

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Valtcho D. Zheljazkov, Tess Astatkie and Ekaterina Jeliazkova

‘Native’ spearmint (Mentha spicata L.) is one of the two most widely grown spearmints in the United States and in other countries. Recent studies demonstrated the feasibility of growing ‘Native’ spearmint as a cash crop for north–central Wyoming. Transportation and energy costs of commercial mint production can be reduced by drying the spearmint in windrows in the field for a few days after harvest and before oil extraction. This method of drying mint has been a common practice in the traditional mint production regions of the world. However, there is a knowledge gap regarding the effect of this drying method on the yield and composition of ‘Native’ spearmint oil. Field and laboratory experiments were conducted in Wyoming to evaluate the effects of drying duration in days after harvest (DAH: 0, 1, 2, 3, 4, 7, or 11) and drying conditions (shade and sun) on the yield of essential oil (EO) and on the concentrations of different oil constituents (beta-pinene, myrcene, limonene, eucalyptol, cis-sabinene hydrate, 4-terpineol, cis-dihydro carvone, cis-carveol, carvone, iso-dihydro carveol acetate, beta-bourbonene, beta-caryophyllene, alpha-humulene/transbeta-farnesene, and germacrene D). Neither drying duration nor drying condition had a significant effect on oil yield. The average yield of essential oil was 0.25 g of oil per 100 g of fresh weight. Drying duration and drying conditions had a significant effect on the composition of EOs. The concentrations of myrcene and germacrene-D were higher in the EOs from plants dried under shade (3.2% and 2.4%, respectively) than the EOs from plants dried under direct sun (3% and 2.2%, respectively). The concentration of beta-pinene was higher in plants dried under direct sun than under shade (0.92% vs. 0.88%). Carvone ranged from 51% to 53% in the oil and was higher in EOs from plants dried for 1 and 2 DAH and lower in EOs from plants dried for 7 days. Drying of ‘Native’ spearmint under direct sun in Wyoming for up to 11 DAH can be used as an effective tool to reduce transportation and energy costs without affecting oil yields.

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Valtcho Zheljazkov (Jeliazkov), Ekaterina Jeliazkova and Nedko Nedkov

Container and field experiments were conducted to evaluate sheep wool wastes and human hair wastes as soil amendments and nutrient sources for high-value crops. Overall, wool-waste or hair-waste additions to soil increased yields from basil, garden sage, peppermint, valerian, thorn apple, marigold, foxglove, and swiss chard; increased the amount of secondary metabolites (such as essential oils and alkaloids); increased NH4-N and NO3-N in the soil; and increased total N (and protein) content in plant tissue. The wool-waste or hair-waste additions did not affect soil microbial biomass, but decreased mycorrhizae colonization of plant roots. Scanning electron microscopy (SEM) and Energy Dispersive X-ray (EDX) analyses indicated that some of the wool and hair in soil from the container and field experiments (after two field seasons and several harvests) retained its original structure, a significant amount of S, some N, and was not fully decomposed. Results from this study suggest that wool and hair wastes can be used as soil amendment and nutrient source for high-value container or field crops.

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Valtcho D. Zheljazkov, Tess Astatkie, Barry O'Brocki and Ekaterina Jeliazkova

Anise (Pimpinella anisum L.) is a spice, an essential oil crop, and a medicinal plant with a long history of use. Anise seed oil is extracted from anise seed through steam distillation. There is no experimentally established optimal time for distillation of anise seed. We hypothesized that the distillation time (DT) can be customized for optimum yield and composition of anise essential oil. In this study, we determined the effect of nine steam DTs (5, 15, 30, 60, 120, 180, 240, 360, and 480 minutes) on essential oil yield and essential oil composition of anise seed. We developed regression models to predict essential oil yield, the concentration of individual constituents, and the yield of these constituents as a function of DT. Highest essential oil yield (2.0 g/100 g seed, 2%) was obtained at 360-minute DT. The concentration of transanethole, the major anise oil constituent, varied from 93.5% to 96.2% (as a percent of the total oil) and generally was high at 15- to 60-minute DT and low at 240- to 480-minute DT. However, the yield of transanethole (calculated from the essential oil yield and the concentration of transanethole in the oil) increased with increasing DT to reach maximum at 360-minute DT. The concentration of the other oil constituents varied significantly depending on the DT, and some of them were higher at the shorter DT than at the longer DT. However, the yields of these constituents were highest at longer DT (either 360 or 480 minutes). DT can be used to obtain anise essential oil with different composition that would benefit the essential oil industry. This study demonstrated the need for providing DT in reports where anise seed essential oil yield and composition are discussed. This article can also be used as a reference point for comparing studies in which different DTs were used to extract essential oil from anise seed.

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Valtcho D. Zheljazkov, Charles L. Cantrell, Tess Astatkie and Ekaterina Jeliazkova

‘Native’ spearmint (Mentha spicata L.) is a widely grown essential oil crop worldwide and in the midwest in the United States. There is interest in expanding spearmint production to Wyoming and other states. However, there is no information to determine if spearmint would perform well under the Wyoming high-altitude and short-growing season and if its productivity and oil quality would be affected by fall frosts. The objective of this study was to evaluate the effect of fall frosts at the end of the cropping season on ‘Native’ spearmint productivity and oil profile. Spearmint plants were harvested at the following harvest dates (HDs): 14 Sept., 21 Sept., 28 Sept., 5 Oct., 12 Oct., 24 Oct., and 1 Nov. 2011. The HDs were selected to coincide with the fall frosts in northern Wyoming. Indeed, during that time, frost occurred on the following dates: 21 Sept., 10 Oct., 13 Oct., 15 Oct., 19 Oct., 20 Oct., 24 Oct., 25 Oct., 26 Oct., 27 Oct., 28 Oct., 29 Oct., 30 Oct., 31 Oct., and 1 Nov. 2011. The first heavy snow occurred on 3 Nov. Fresh herbage yields were higher at the 1 Nov. HD relative to the 14 Sept. HD, whereas the yields at the other HD were not significantly different. Generally, the oil content was high at 14 Sept., 21 Sept., and 5 Oct. HD and low at the 24 Oct. and 1 Nov. HD. Carvone concentration (42% to 75% range) in the oil reached a maximum at the 12 Oct. HD. The concentration of limonene was low at the first HD (14 Sept.) and higher at the other HDs. The yield of carvone (a function of the fresh herbage yields, oil content, and the concentration of carvone in the oil) was high at the 12 Oct. HD and low at the other HDs. In the spring of 2012, spearmint emerged in late April and was unaffected by the Wyoming winter or by the early spring frosts. This preliminary study suggests ‘Native’ spearmint may be a viable crop for northern Wyoming at elevation of ≈1170 m.

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Ekaterina A. Jeliazkova, Valtcho D. Jeliazkov, Lyle E. Craker and Baoshan Xing

Phytoremediation has been suggested as a solution to heavy metal—polluted soils, but the choices of suitable plant species for phytoremediation have been limited. Medicinal and aromatic plants appear to be excellent selections for these plantings, since these plants are grown for economically valuable secondary products (essential oils), not for food or feed. Preliminary research indicates that heavy metals are not accumulated in essential oils, permitting the oil to be used commercially. Productivity of some, but not all aromatic plants was reduced, however, by the heavy metals. The objective of our experiment was to distinguish the mechanism of heavy metal tolerance of plants using germinating seeds of medicinal and aromatic plant species. Seeds from medicinal and aromatic plants were germinated in solutions with selected levels of heavy metals (cadmium at 6 and 10 (μg·L-1; copper at 60 and 150 μg·L-1; lead at 100 and 500 μg·L-1; zinc at 400 and 800 μg·L-1) and in distilled water. Tests on Anethum graveolens L., Carum carvi L., Cuminum cyminum L., Foeniculum vulgare Mill., Pimpinella anisum L., Ocimum basilicum L., and the hyperaccumulator species Brassica juncea L. and Alyssum bertolonii established that different plant species reacted in different ways to the heavy metals. For example, cadmium did not decrease seed germination of Alyssum, O. basilicum, and B. juncea compared with germination in water but did decrease germination of C. cyminum. Lead did not affect germination of A. bertolonii and B. juncea as compared with water but did negatively affect germination of P. anisum, F. vulgare, and C. cyminum. Except for B. juncea, F. vulgare, and C. cyminum, copper had a negative effect on germination. Zinc decreased germination in all tested species except B. juncea.

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Valtcho Jeliazkov (Zheljazkov), Glenn Stratton, James Pincock, Stephanie Butler and Ekaterina Jeliazkova

One small-plotfield and five container experiments were conducted to evaluate sheep wool-wastes and human hair-wastes as soil amendments and nutrient sources for high-value crops. Overall, the wool-waste or hair-waste addition to soil: 1) increased yields from basil, garden sage, peppermint, valerian, thorn apple, marigold, foxglove, and swiss chard; 2) increased the amount of secondary metabolites (such as essential oils and alkaloids); 3) increased NH4-N and NO3-N in soil; 4) increased total N (and protein) content in plant tissue; 5) did not affect soil microbial biomass; and 6) decreased mycorrhizae colonization of plant roots. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses indicated that some of the wool and hair in soil from the container and field experiments (after two field seasons and several harvests) retained its original structure, retained a significant amount of S and some N, and was not fully decomposed. Our results indicate that single addition of wool or hair-waste of 0.33% by weight to soil would support two to five harvests or crops, without addition of other fertilizers, and may improve soil biological and chemical characteristics.

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Santosh Shiwakoti, Henry Y. Sintim, Shital Poudyal, Jennifer Bufalo, Charles L. Cantrell, Tess Astatkie, Ekaterina Jeliazkova, Lyn Ciampa and Valtcho D. Zheljazkov

Japanese cornmint, also known as menthol mint (Mentha canadensis L. syn M. arvensis L.), is an essential oil crop cultivated in several countries in Asia and South America. The plant is currently the only commercially viable source for natural menthol as a result of the high concentration of menthol in the oil compared with other crops. The hypothesis of this study was that harvesting at regular intervals within a 24-hour period would have an effect on essential oil concentration and composition of Japanese cornmint grown at high altitude in northern Wyoming. Flowering plants were harvested every 2 hours on 7 to 8 Aug. and on 14 to 15 Aug. and the essential oil was extracted by steam distillation and analyzed by gas chromatography–mass spectroscopy (GC-MS). The effects of harvest date (Harvest 1 and Harvest 2) and harvest time (12 times within a 24-hour period) were significant on oil concentration and yield of menthol, but only harvest date was significant on the concentration of menthol in the oil. The interaction effect of harvest date and harvest time was significant on water content and on the concentrations of menthol and menthofuran in the oil and on the yield of limonene, menthol, and menthofuran. Overall, the oil concentration in grams per 100 g dried material for the two harvests (1.26 and 1.45, respectively), the concentration of menthol in the oil (67.2% and 72.9%, respectively), and menthol yield (1066 to 849 mg/100 g dried biomass) were higher in plants at Harvest 2 as compared with plants at Harvest 1. The oil concentration was higher in plants harvested at 1100 hr or at 1300 hr and lowest in the plants harvested at 1500 hr. Menthol yield was the highest in plants harvested at 1300 hr and lowest in the plants harvested at 0700 hr, 1900 hr, or at 0300 hr. This study demonstrated that harvesting time within a 24-hour period and harvest date (maturity of the crop) may affect essential oil concentration and composition of Japanese cornmint grown at high altitude in northern Wyoming.