Stella Kokkini

Geographic variation of Greek oregano (Origanum vulgare ssp. hirtum) essential oils

Essential oils of Origanum vulgare ssp. hirtum from twenty-three localities, scattered all over Greece, were analysed in order to determine their quantitative and qualitative features. The total oil content of plants and the percentage contribution of the major oil constituents, carvacrol, thymol, γ-terpinene and p-cymene, varied remarkably between localities. The contents of carvacrol and thymol were significantly correlated, varying inversely. The same holds for their sum and the sum of the two major monoterpene hydrocarbons. Altitude seems to be the most important environmental factor influencing the oil content; high values were recorded at low altitudes, coinciding with Mediterranean-type ecosystems. The sum of the four major oil constituents, representing the phenol pathway, seems influenced by the climates thermal efficiency. The hotter the climate, the higher their total concentration.

Composition and antioxidant activity of essential oils from Oregano plants grown wild in Greece

ZusammenfassungBei dieser Arbeit wurden vier Proben etherischer Öle aus Pflanzen gewonnen, die weit verbreitet in Griechenland sind und von ökonomischer Wichtigkeit in der ganzen Welt am Gewürzmarkt sind. Es wurden Carvacrol und Thymol auf ihre wahrscheinliche antioxidative Aktivität getestet. Die vier Pflanzenarten sindOriganum vulgare hirtum, Origanum onites, Coridothymus capitatus und Satureja thymbra. Die etherischen Öle wurden mit Hilfe der Gaschromatographie-Massenspektroskopie charakterisiert. Sowohl die untersuchten etherischen Öle als auch Carvacrol und Thymol wurden durch TLC und auch durch Messung der Peroxid-Werte eines bei 35°C aufbewahrten Schweinefettes getestet. Die Ergebnisse zeigen, daß der antioxidative Effekt auf die Anwesenheit von Carvacrol und Thymol im etherischen Öl zurückgeführt werden kann.AbstractIn this study, four samples of essential oils obtained from plant species with a wide distribution in Greece and economic importance for the world-wide spice market and also carvacrol and thymol were tested for their possible antioxidant activity. The four plant species wereOriganum vulgare subsp.hirtum, O. onites, Coridothymus capitatus andSatureja thymbra. The essential oils were chemically characterised by gas chromatography-ion trap detection. All the essential oils examined and also carvacrol and thymol were found to have antioxidant activity when tested on TLC plates and by measuring peroxide values of lard stored at 35° C. The results indicate that the antioxidant effect may be related to the presence of carvacrol and thymol in essential oils.

AUTUMN ESSENTIAL OILS OF GREEK OREGANO

The essential oils of Origanum vulgare subsp. hirtum plants collected in late autumn from six localities of three distinct geographic areas of Greece were analysed by means of GC and GC-mass spectrometry. A high quantitative variation was found in the amount of the four main components; γ-terpinene ranged from 0.6 to 3.6% of the total essential oil, p-cymeme from 17.3 to 51.3%, thymol from 0.2 to 42.8%, and carvacrol from 1.7% to 69.6%. Plants collected from the northern part of Greece were rich in thymol (30.3–42.8% of total oil), whereas those from the southern part of the country were rich in carvacrol (57.4–69.6% of total oil). Furthermore, comparison with the essential oils obtained from plants collected from the same localities in mid-summer shows noticeable differences in the total oil content and the concentration of the four main oil components.

Pattern of geographic variations of Origanum vulgare trichomes and essential oil content in Greece

Abstract The variation of the total plant pubescence and essential oil content of Origanum vulgare plants grown all over the species range in Greece has been studied. In respect to their glandular and non-glandular trichomes. o. vulgare plants are differentiated along a direction fromeastern and central Aegean islands, through Crete and Peloponnese, to the northern part of Greece. The same variation pattern is found when the essential oil content of O. vulgare plants is considered. Along this direction, a gradual change of the climate from the Real Mediterranean to the Continental Mediterranean type occurs. Plants grown in the Mediterranean climatic zones are characterized by numerous sessile glands and are essential oil-rich (ssp. hirtum), whereas those of the Continental type climate have few glands and are oil-poor (ssp. viridulum and ssp. vulgare).

Mentha spicata (Lamiaceae) chemotypes growing wild in Greece

Mentha spicata is the commonest mint species growing wild in Greece, exhibiting great morphological and chemical variability. The oil content from different wild populations examined ranged from 0.3% to 2.2%; the most common value being ca.1%. Though commercially exploited M. spicata plants are always rich in carvone and dihydrocarvone, wild populations are very variable; four different chemotypes were distinguished within the species. These chemotypes are characterized by the high contribution of the following compounds: (1) linalool, (2) piperitone oxide or piperitenone oxide, (3) carvone-dihydrocarvone and (4) pulegone-menthone-isomenthone. This chemical variability suggests the possibility of further developing and exploiting the full potential of the species.

Effects of enhanced UV-B radiation on Mentha spicata essential oils

Abstract In vitro propagated plantlets representing two distinct chemotypes of Mentha spicata, viz. plants producing essential oils rich in piperitone oxide and piperitenone oxide (chemotype I) and rich in carvone and dihydrocarvone (chemotype II), were grown in the field under ambient or ambient plus supplemental UV-B radiation, biologically equivalent to a 15% ozone depletion over Patras (38.3°N, 29.1°E), Greece. Enhanced UV-B radiation stimulated essential oil production in chemotype II substantially, while a similar, non-significant trend was observed in chemotype I. No effect was found on the qualitative composition of the essential oils, whereas the quantitative composition was slightly modified in chemotype I. This is the first investigation reporting an improved essential oil content under UV-B supplementation in aromatic plants under field conditions.

DNA barcoding in native plants of the Labiatae (Lamiaceae) family from Chios Island (Greece) and the adjacent Çeşme-Karaburun Peninsula (Turkey).

The plant family Labiatae (Lamiaceae) is known for its fine medicinal and aromatic herbs like lavender, mint, oregano, sage and thyme and is a rich source of essential oils for the food, pharmaceutical and cosmetic industry. Besides its great economic importance, the Labiatae family contributes significantly to the endemic flora of Greece and Turkey. Owing to its economic and biological significance and to the difficult identification based on morphological characters of several of its taxa, the Labiatae family is an ideal case for developing DNA barcodes. The purpose of this study is to evaluate the utility of DNA barcoding on a local scale in discriminating Labiatae species in Chios Island (Greece) and the adjacent Çeşme‐Karaburun Peninsula (Turkey). We chose three cpDNA regions (matK, rbcL, trnH‐psbA) that were proposed by previous studies and tested them either as single region or as multiregion barcodes based on the criteria determined by Consortium for the Barcode of Life (CBOL). Our results show that matK and trnH‐psbA taken as useful in discriminating species of the Labiatae, for the species we examined, as any multiregion combination. matK and trnH‐psbA could serve as single‐region barcodes for Labiatae species contributing to the conservation and the trade control of valuable plant resources.

Seasonal Variation of Essential Oils in a Linalool-Rich Chemotype of Mentha spicata Grown Wild in Greece

Abstract The seasonal variations of the essential oil content and composition of a Mentha spicata population grown wild in Greece were examined. The oil content ranged from 0.1–1.8%, with the maximum values in late summer/early autumn. The essential oil obtained from the leaves was characterized by a very high content in linalool, i.e. 85.0–93.9% of the total oil (highest percentage in mid-autumn). Other oil constituents occurring in much lower amounts were germacrene D (up to 4.2%), β-caryophyllene (up to 2.6%) and 1,8-cineole (up to 2.1%).

Essential Oil Composition of Greek (Origanum vulgare ssp. hirtum) and Turkish (O. onites) Oregano: a Tool for Their Distinction

Abstract Aiming to find out if any distinction between the Greek (Origanum vulgare ssp. hirtum) and Turkish oregano (O. onites) essential oils exists, the composition of six wild Greek populations of the former and four of the latter taxon were analyzed by means of GC and GC/MS. A PCA analysis showed that Turkish oregano oils had higher amounts of sabinene, myrcene, γ-terpinene, borneol and carvacrol, and Greek oregano oils had higher p-cymene content. The latter were further divided into two subgroups, distinguished respectively by their thymol and carvacrol content. A comparison of our results with the published information showed that p-cymene percentages>14% and/or thymol>6% is found only in Greek oregano, while borneol content>2% is found only in Turkish oregano oils.

Origanum onites (Lamiaceae) in Greece: Distribution, volatile oil yield, and composition

Origanum onites, widely used as a spice, grows wild in southern and southeastern Greece, especially in phryganic ecosystems. Like other woody plants of these ecosystems, it is characterized by seasonal dimorphism, an adaptation to face the summer drought. Its range in Greece is defined, and the features of its volatile oil are studied. It appears to be a fairly stable species, both from the morphological and chemical point of view. The high yields in volatile oil and high contents of carvacrol from all populations studied suggest the possibility of further profitable exploitation.