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Valtcho D. Jeliazkov (Zheljazkov)

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Valtcho D. Zheljazkov and Tess Astatkie

Some agricultural soils in North America are lead (Pb)-enriched as a result of the application of lead arsenate (PbHAsO4) insecticide. A controlled-environment experiment was conducted with Pb-enriched Canning soil series in Nova Scotia, Canada, to evaluate the remediation potential of 10 plant species in combination with the fungicide benomyl applied as a soil drench to suppress mycorrhizae. Overall, the highest biomass was provided by yellow poppy followed by Indian mustard and thorn apple. The application of benomyl increased Pb concentration in thorn apple tissue but not in the other crops. The phytoremediation potential (Pb removal with the harvested biomass) was higher with clary sage, alyssum, garden sage, and Indian mustard with benomyl treatments and lower in the Swiss chard, thorn apple without benomyl, and in the geranium with benomyl treatments. The results suggest that some plants can be used for phytoremediation of mildly Pb-contaminated soils.

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Valtcho D. Zheljazkov and Tess Astatkie

Japanese cornmint (Mentha canadensis L.) is a major essential oil crop grown in Asia, South America, and to a limited extent in eastern Europe. Japanese cornmint oil is the only commercially viable source for crystalline menthol. We hypothesized that the length of the distillation time (DT) will have an effect on Japanese cornmint essential oil content and composition. Therefore, the objective was to evaluate the effect of eight DTs (1.25, 2.5, 5, 10, 20, 40, 80, and 160 min) on essential oil content and composition. The essential oil content (0.43% to 1.06% range) reached maximum at 10 min DT; further increase in DT did not significantly increase essential oil content. The concentrations of alpha-pinene (0.14% to 0.76% range), beta-pinene (0.23–0.81), 3-octanal (0.19–0.34), limonene (0.69% to 1.53%), eucalyptol (0.06% to 0.12%), isopulegone (0.42% to 0.56%), and isomenthone (4.4% to 5.7%) were highest at 1.25 to 5 min DT and generally decreased to their respective minimums at 160 min DT. The concentration of menthone (4.3% to 6.3%) was highest at 1.25 min DT, decreased at 2.5 min, and was lowest at 10 to 160 min DT. The concentration of piperitone (0.98% to 1.27%) was lowest at 1.25 min DT and higher at 5 to 40 min DT compared with other DTs. The concentration of menthol (74% to 79%) was low at 1.25 min, then increased at 10 to 80 min DT, and reached a maximum at 160 min DT. Generally, the yield of most individual essential oil constituents was lower at 1.25 min DT relative to the other DT and reached maximum at 10 to 20 min DT. The yield of menthol was low at 1.25 to 2.5 min DT and rose at 5 min to 160 min DT. The results suggest that different DTs can be used to maximize recovery of certain constituents. Also, the results demonstrated that there are no oil yield gains after 20 min DT, which is much lower than the usual distillation time of 60 min or more. This study can be used as a reference when comparing reports in which different DTs were used.

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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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Kelly M. Bowes and Valtcho D. Zheljazkov

Field and laboratory experiments were conducted at two sites in Nova Scotia during 2001 and 2002 to assess the potential to grow fennel (Foeniculum vulgare Mill.) as an essential oil crop in the Maritime region of Canada. Three cultivars—`Shumen', `Berfena', and `Sweet Fennel'—and two seeding dates—24 May and 8 June—were evaluated. Essential oil yields and composition were determined and compared to commercially available fennel essential oil from the U.S. The highest herbage yields were produced by `Shumen' from the earlier seeding date. Essential oil content and yields were lowest in `Sweet Fennel' and highest in `Shumen'. The major component of the essential oil was anethole, 47% to 80.2%. Other major components of the essential oil were methyl chavicol, fenchone, α-phellandrene, α-pinene, ortho cymene, β-phellandrene, fenchyl acetate, β-pinene, and apiole. The essential oil composition was unique to each cultivar. The highest methyl chavicol content was in `Shumen', while the highest concentration of phellandrene, fenchyl acetate and apiole were detected in `Sweet Fennel' oil. Fenchone, ortho cymene, β-pinene, α-phellandrene, and α-pinene were the highest in `Berfena'. The composition of the oil was similar to the commercially purchased oil and met industry requirements of oil composition. The results suggest there is potential to grow fennel as an essential oil crop in Nova Scotia.

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Valtcho D. Zheljazkov, Tess Astatkie and Vicki Schlegel

Oregano (Origanum vulgare L.) is an important medicinal, culinary, and essential oil plant. Oregano essential oil is extracted from either leaves or shoots through steam distillation. Researchers and industry in various countries reported different distillation times (DTs) for oregano; however, there are no reports on optimum DT. This study evaluated the effect of DT (1.25, 2.5, 5, 10, 20, 40, 80, 160, 240, 360 min) on essential oil yield, composition, and antioxidant activity of the oregano essential oil. In general, the concentration of the low boiling essential oil constituents (alpha-thujene, alpha-pinene, camphene, l-octen-3-ol, myrcene, alpha-terpinene, paracymene, beta-phellandrene/limonene, gamma-terpinene, cis-sabinene hydrate, terpinolene) were highest at the shortest DT (1.25 or 2.5 min), reduced with increasing DT up to 40 min, and then stayed the same. However, the concentration of the major oil constituent, carvacrol, was lowest at the shortest DT of 1.25 min (18%) and increased steadily with increasing DT up to 40 min, where it leveled at 80% to 82%. The concentration of other higher boiling constituents (borneol, 4-terpineol, beta-bisabolene, beta-caryophylenne) was maximum at 5 to 20 min DT. Maximum yield of the low boiling constituents was achieved at relatively short DT, at ≈20 min DT, and peaked again at 240 min DT. Maximum yields of alpha-terpinene, beta-phellandrene/limonene, and gamma-terpinene were reached at 240 min DT. Maximum yields of paracymene cis-sabinene hydrate, terpinolene, and transsabinene hydrate were also achieved at 240 min DT, but yields at 20 min DT were not different. Yields of borneol, 4-terpinenol, carvacrol, beta-caryophyllene, and beta-bisabolene also were highest at 240 min DT. Distillation time at 20, 80, or 360 min did not alter antioxidant or antimicrobial activity of oregano oil. The relationship between the concentration and yield of the constituents with DT was adequately modeled by the asymptotic and Michaelis-Menten nonlinear regression models, respectively. Results demonstrated that 1) DT can be used to obtain oregano essential oil with differential composition; 2) maximum essential oil yield of steam-distilled oregano leaves could be obtained at 240 min DT; and 3) reports on oregano essential oil yield and composition using different DTs may not be comparable. Results from this study will aid in comparing published reports on oregano essential oil that used different lengths of DT.

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Valtcho D. Zheljazkov, Tess Astatkie and Vicki Schlegel

This study evaluated the effect of distillation time (DT; 1.25, 2.5, 5, 10, 20, 40, 80, 160, 240, and 360 min) on essential oil yield, composition, and the antioxidant activity of ponderosa pine essential oil. Pine essential oil yield increased with length of the DT and reached maximum at 160 min DT. The major oil constituents were alpha-pinene and beta-pinene, ranging from 17% to 40% and from 21% to 29%, respectively, of the total oil. Overall, the concentration of alpha-pinene and beta-pinene was high at the initial DT (5–20 min) and decreased with increasing DT. The concentration of myrcene (range, 0.9% to 1.5%) was lowest at 5 min DT, then increased at 10 min DT, and did not change with longer DT. Overall, the concentrations of most other constituents (delta-3-carene, limonene, cis-ocimene, alpha-terpinyl acetate, germacrene-D, alpha-muurolene, gamma-cadinene, delta-cadinene, and germacrene-D-4-ol) were low at the initial DT and increased with increasing DT. Total yields (a function of oil yield and the concentration of individual constituents) of all constituents were generally the lowest at 5 min DT, increased with increasing DT, and reached maximum at 160 min DT. The antioxidant capacity of the pine oil in this study varied between 7.0 and 14.5 μmole Trolox/g and was unaffected by DT. This study demonstrated that DT can significantly modify the essential oil yield and composition of ponderosa pine needles. Furthermore, DT could be used to obtain pine oil with targeted chemical profiles. This report can also be used as a reference point for comparing literature reports, in which different DTs are used to extract essential oil of ponderosa pine.

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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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Natasha Kovatcheva, Valtcho D. Zheljazkov and Tess Astatkie

Rose oil production worldwide is based on different oil-bearing Rosa species. This 4-year study determined the essential oil content, constituents, and morphologic/phenologic characteristics of 25 varieties, chemotypes, and hybrids belonging to five Rosa species (R. damascena Mill., R. gallica L., R. centifolia L., and R. alba L.). Limits of variation of these indices were established for each variety, chemotype, and hybrid group. The essential oil content of R. damascena varied from 0.032% to 0.049% and that of hybrid roses from 0.037% to 0.05%. The highest essential oil content was found in R. damascena accession Svejen 74 and the lowest in R. alba. Within R. damascena, the weight of single flowers varied from 2.09 to 3.44 g, the number of petals from 22 to 28, the height of the plants from 61 to 128 cm, and the diameter of bushes from 53 to 118 cm. R. centifolia had the largest flowers. The essential oil of the various species showed moderate to no antimicrobial activity at 50 μg/mL and no significant antibacterial, antifungal, antileishmania, or antimalarial activity at this concentration. All the tested species and accessions could be grown in Bulgaria (and possibly in southeastern Europe and the northern Mediterranean) and provide comparable productivity to the traditional species R. damascena. Wide variations occurred in essential oil content and constituents and morphologic/phenologic characteristics of the tested Rosa species and accessions. The availability of various species and chemotypes within specific species offer an opportunity for production of oil-bearing roses and essential oils to meet market requirements of specific rose oils.