Browsing by Author "Duarte, F."
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- Chemical composition of the essential oils from Thymus mastichina over a day periodPublication . Miguel, Maria Graça; Duarte, F.; Venancio, F.; Tavares, R.In the present work, the aerial parts of T. mastichina, were collected over a day period, during the flowering phase. The oil was isolated both from the fresh leaves and the fresh flowers by hydrodistillation and analysed by GC and GC/MS. Significant differences were registered between the content and composition of leaf oil and that of flower oil, while changes in consequence of the day period were less emphasised. The highest oil content was obtained from the flowers (2.0 and 2.2 %) at 12 h and 17 h, respectively. The major component of the essential oils was 1,8-cineole, present in higher amounts in the leaf oils than in the flower oils. Its minimal percentages detected in the leaf and the flower oils were 50.2 % and 46.7 %, respectively, observed at 23 h, while the maximal ones were 61.0 % and 50.2 %, at 12 h. Camphor, delta-terpineol + borneol and terpinen-4-ol were also present in higher amounts in the leaf oils than in the flower oils. In both oils, elevated concentrations of delta-terpineol + borneol were detected at 23 h (9.7 % and 8.2 %, respectively). The concentration of myrcene was ten times superior in the flower oils relatively to the leaf oils. In almost all samples, elemol was the sole sesquiterpene whose concentration exceeded 1.0 %.
- Comparison of the main components of the essential oils from flowers and leaves of Thymus mastichina (L.) L. ssp mastichina collected at different regions of PortugalPublication . Miguel, Maria Graça; Duarte, F.; Venancio, F.; Tavares, R.The chemical composition of the essential oils from the leaves and the flowers of Thymus mastichina collected at different regions of Portugal were analyzed by GC and GC/MS. It revealed that fresh flowers produce larger amounts of oils than the leaves. The highest oil yields were obtained from the flowers collected at Arrabida (3.5%, and Mertola (3.0%, v/w). Two types of oils were differentiated according to their main components. Oils rich in 1,8-cineole whose concentrations ranged from 39.4% (in the flower oils collected at Mertola) to 69.2% (in the leaf oils from Arrabida), and an oil rich in linalool (73.5%) that was only detected in a sole plant group from Sesimbra. Camphor, borneol, terpinen-4-ol and alpha-terpineol appeared in relative high levels in the oils of the plants from Mertola and S. Bras de Alportel. In spite of the samples collected at Arrabida belonging to the 1,8-cineole type, camphene, (E)-beta-ocimene, camphor and borneol were the compounds detected in the smallest amounts in contrast to the two remaining oils. Besides the linalool contents determining the chemotype of the plants collected at Sesimbra, other compounds appeared in different concentrations to the remaining samples making it worthy to differentiate between them. Thus, those samples had the lowest concentrations of many monoterpenes and the highest levels of T-cadinol.
- Composition of the essential oils from Portuguese Thymus albicans collected at different regions of Ria Formosa (Algarve)Publication . Miguel, Maria Graça; Duarte, F.; Venancio, F.; Tavares, R.The chemical composition of the essential oils from the leaves and the flowers of Thymus albicans Hoffin. et Link collected at three regions of Algarve, south of Portugal, was analyzed by GC and GUMS. The oils isolated from the flowers and the leaves were obtained in similar yields, 4.3% (v/w) and 4.2% (v/w), in the samples from Quinta do Lago, and 3.5% and 3.6%, in the samples from Ancao, respectively. in contrast, the oil yields from Gambelas ranged from 5.7%, in the leaf oils, to 9.2%, in the flower oils. The oils isolated from all samples of leaves and flowers were dominated by the oxygenated monoterpene 1,8-cineole (42.1-67.9%). in the samples collected at Quinta do Lago, high levels of linalool were also found (30.3-36.9%). The major monoterpene hydrocarbons in all samples were alpha-pinene (1.7-4.3%), sabinene (1.6-3.4%) and beta-pinene (2.6-4.9%). The concentrations of a-pinene (1.7-1.8%), camphene (0.2%) and beta-pinene (2.6-2.9%) in the samples from Quinta do Lago were in lower amounts than in the remaining samples. The most representative sesquiterpene hydrocarbons were beta-elemene (0.2-0.7%), beta-caryophyllene (0.1-0.8%) and gamma-cadinene (0.2-0.5%). The oxygenated sesquiterpene that was always present in higher amounts in the leaf oils than in the respective flower oils was viridiflorol (0.4-1.0%), the most important compound belonging to this fraction. The previous separation of the leaves and the flowers from this species evidenced the existence of quantitative differences in some components according to the plant part used. Still, for the same chemotype there were quantitative differences in some components, showing the existence of some variability demanding a more careful study to explain it.
- Essential oils of Portuguese Thymus mastichina (L.) L. subsp mastichina grown on different substrates and harvested on different datesPublication . Miguel, Maria Graça; Guerrero, Carlos; Rodrigues, H.; Brito, J.; Duarte, F.; Venancio, F.; Tavares, R.The effects of harvesting date and different substrates on the yield and chemical composition of the essential oils of Portuguese Thymus mastichina (L.) L. subsp. mastichina were compared with samples grown in pots. The best oil yields were obtained in June (3.2, 3.6 and 4.9% in the local sandy soil, in non-fertilized peat, and in fertilized peat, respectively). The essential oils were dominated by 1,8-cineole, the highest concentration of which was detected in June (58.6%) in samples kept in non-fertilized peat, and the lowest values were from plants growing in fertilized peat during April and June (45.1%). The remaining samples always reached the highest percentages in October (around 54% in both oil samples), although the concentration profile over time was similar in every sample. Concerning the monoterpene hydrocarbons, a-pinene, camphene, sabinene and P-pinene were the most significant components. While the amounts of alpha-pinene tended to decrease from April to June, for P-pinene such tendency was observed from October to January, independently of the growing material used. Amounts of camphene, being similar to those of alpha-pinene, decreased successively from October to April. Elemol and intermedeol were the most representative sesquiterpene components, although the concentrations never exceeded 2.2% and 1.3%, respectively. The results obtained in this work suggest that the harvesting dates of Portuguese T mastichina influence oil yields and their chemical compositions much more than the different growing media used, although a higher oil yield was obtained with the fertilized growing material.
- Essential oils of Rosmarinus officinalis L., effect of harvesting dates, growing media and fertilizersPublication . Miguel, Maria Graça; Guerrero, Carlos; Rodrigues, H.; Brito, J.; Duarte, F.; Venancio, F.; Tavares, R.The effects of the harvesting date, growing media and fertilizers on the yield and chemical composition of the essential oils of Rosmarinus officinalis L. maintained in pots were evaluated. The highest oil yield was always obtained in June, being superior or equal to 1 %. Myrcene was the major component present in the essential oils with concentrations always exceeding 20 %, independent on the factors studied. 1,8-Cineole (8.0-12.2 %), a-pinene (8.8-16.5 %) and, in some instances, camphor (4.4-14.1 %) could be also detected in considerable amounts, however never exceeding the myrcene percentages. The amounts of camphor (4.4-8.5 %) were always inferior to the 1,8-cineole levels (8.8-11.8 %) in the local sandy soil regardless the fertilization used. Generally, the lowest levels of myrcene and verbenone were observed during January and April while the highest amounts of 1,8-cineole was observed in April or June. The yield and the chemical composition of the rosemary oils seemed to be more sensitive to the temperature, photoperiod and collection period than to the growing media material or to the fertilization used.
- Main components of the essential oils from wild Portuguese Thymus mastichina (L.) L. ssp mastichina in different developmental stages or under culture conditionsPublication . Miguel, Maria Graça; Guerrero, Carlos; Rodrigues, H.; Brito, J. C.; Duarte, F.; Venancio, F.; Tavares, R.The aerial parts of wild Thymus mastichina (L.) L. ssp. mastichina were collected during the flowering (May) and vegetative phases (October) at Sesimbra (southwest Portugal). The aerial parts of cultivated plants of T. mastichina maintained in two different substrates, obtained from those plants growing wild at Sesimbra, were collected during the flowering phase (May) at Algarve (southern Portugal). The oils were isolated by hydrodistillation and analyzed by GC and GC/MS. in the wild plants, it was found that harvesting time had a significant effect on the oil yield, but did not greatly affect the composition. The highest oil yield isolated from the wild plants was found to be at the time of full flowering (2.1%, v/w). The oils were comprised mainly of oxygenated monoterpenes, among which linalool (58.7-69.0%) was the most abundant. in the wild plants, alpha-pinene, (E)-beta-ocimene, gamma-cadinene and elemol were the compounds that showed the most important variations, according to the harvesting month. The effect of nutritive elements (NPK) on the yield and on the oil composition was investigated in cultivated plants in two different substrates: a non-fertilized substrate (without N:P:K supply) and a fertilized substrate (with N:P:K, 1:1:1 supply). This study was carried out only in May. in the cultivated plants the highest oil yield (2.7%, v/w) was registered in the plants maintained in the non-fertilized substrate. Although the qualitative composition of the wild and cultivated oil plants was similar, the results showed quantitative variability among the components. The fertilized substrate proved to be the best to obtain a higher concentration of linalool (69.0%), while the non-fertilized substrate provided the lowest percentage (58.7%). The non-fertilized substrate induced a higher accumulation of (E)-beta-ocimelle, gamma-terpinene, sesquiterpene hydrocarbons and oxygenated sesquiterpenes than the fertilized substrate, while this latter supported higher p-cymene and linalool content formation. The wild plant oils were found to be richer in alpha-pinene, camphene, beta-pinene, 1,8-cineole and camphor and poorer in p-cymene, gamma-terpinene, and in sesquiterpene hydrocarbons and oxygenated sesquiterpenes, than the cultivated plant oils. Nevertheless, such quantitative differences can be also explained by the different maturity stage of the wild and cultivated plants though both were in the same developmental stage.
- Variation in the main components of the essential oils from the leaves and flowers of Portuguese Thymus albicans over a single seasonPublication . Miguel, Maria Graça; Duarte, F.; Venancio, F.; Tavares, R.The comparison of the chemical composition of the leaf and the flower oils isolated from Thymus albicans Hoffm. et Link belonging to the 1,8-cineole chemotype, collected at Gambelas, Algarve, during the flowering phase (June to September) %vas carried out. The oils isolated f'roin both the f'resh leaves and the f'resh flowers by hydrodistillation were analyzed and compared by GC and GUMS. The oil yields from the fresh leaves ranged from 3.1% in June, to 6.7% in July (full bloom), while the oil Yields from the fresh flowers ranged from 4.8% in July, to 7.0% in September. Independent of the harvesting period, the oils isolated were characterized by their richness in 1.8-cineole either from the leaves (59.7-66.0%) or from the flowers (57.0-66.7%). The flower oils contained the highest concentration of alpha-pinene, beta-pinene and linalool, while the leaf oils were richest in camphor, citronellol, bornyl acetate and geranyl propionate. Quantitative differences were also found in some oxygenated sesquiterpe-nes according to the developmental flowering stage being one of the most interesting those registered viridiflorol, ledol and intermedeol. The highest amounts of these components in both the leaf and the flower oils were observed in July, starting then to decrease until September just as the behavior already found for 1-8-cineole in the flower oils.