Catherine Harvala

UV-B PROTECTIVE POTENTIAL AND FLAVONOID CONTENT OF LEAF HAIRS OF QUERCUS ILEX

Flavonoids of non-glandular leaf hairs from Quercus ilex were analysed. The main compounds were acylated kaempferol glycosides. Acylation shifted the absorption peak into the ultraviolet-B region of the spectrum in which intact trichome layers absorbed strongly. Ultraviolet-B radiation caused a considerable reduction of photosystem II photochemical efficiency only in dehaired leaves. It is suggested that leaf hairs, besides other roles, may function as an effective filter against the harmful ultraviolet-B radiation.

Samioside, a new phenylethanoid glycoside with free-radical scavenging and antimicrobial activities from Phlomis samia.

A new phenylethanoid glycoside, samioside, was isolated from the aerial parts of Phlomis samia and identified as 1-O-3,4-(dihydroxyphenyl)ethyl beta-D-apiofuranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->3)-4-O-caffeoyl-beta-D-glucopyranoside (1). In addition, one known phenylethanoid glycoside and three known flavonoids were identified as acteoside (2), apigenin, chrysoeriol, and ermanin, respectively. The structure of 1 was elucidated on the basis of its spectroscopic data. Samioside (1) demonstrated scavenging properties toward the DPPH radical and antimicrobial activity against Gram-positive and -negative bacteria.

C15 Acetogenins from the red alga Laurencia obtusa

Four C(15) acetogenins, 13-epilaurencienyne (3Z) (1), 13-epipinnatifidenyne (3E) (2), (3E, 6S(*), 7R(*), 9S(*), 10S(*), 12R(*))-9-chloro-13-bromo-6:12-epoxy-7, 10-diacetoxypentadec-3-en-1-yne (3), (3Z, 6S(*), 7R(*), 9S(*), 10S(*), 12R(*))-9-chloro-13-bromo-6:12-epoxy-7, 10-diacetoxypentadec-3-en-1-yne (4), along with the known 13-epilaurencienyne (3E) (5), have been isolated from the organic extract of the red alga Laurencia obtusa, collected in the Aegean Sea, Greece. The structures of the new natural products, as well as their relative stereochemistry, were established by means of spectral data analysis, including 2D NMR spectroscopic experiments. Some of the new metabolites exhibited significant insecticidal activity.

Chemical Defense and Antifouling Activity of Three Mediterranean Sponges of the Genus Ircinia

The defense roles and the antifouling activity of the organic extracts and the major metabolites of the sponges Ircinia oros, I. variabilis and I. spinosula were investigated. The antifeedant activity was tested in experimental aquaria on the generalist predator fish Thalassoma pavo as well as in coastal ecosystems rich in fishes. Some of the major metabolites exhibited high levels of antifeedant activity. The antifouling activity was tested in laboratory assays, against representatives of the major groups of fouling organisms (marine bacteria, marine fungi, diatoms, macroalgae and mussels). All extracts showed promising levels of activity. As was expected, no single extract was active in all tests and some fractions that were effective against one organism showed little or no activity against the others. The high but variable level of antifouling activity in combination with the absence of toxicity (tested on the development of oyster and sea urchin larvae) shows the potential of these metabolites to become ingredients in environmentally friendly antifouling preparations.

Methanolic Extract of Verbascum macrurum as a Source of Natural Preservatives against Oxidative Rancidity

The antioxidant properties of various fractions of a methanolic extract obtained from the aerial parts of Verbascum macrurum have been determined by monitoring their capacity to scavenge the stable free-radical DPPH. They were also evaluated as natural preservatives against oxidative rancidity using the accelerated Rancimat method. Their activities expressed as protection factor (PF(r)) indicated that the fractions rich with phenylpropanoid glycosides were more potent compared to alpha-tocopherol and of the same magnitude as BHT, which were used as reference standards. Ten natural compounds were identified as components of this methanolic extract and were isolated by medium-pressure liquid chromatography (MPLC). Assessment of their antioxidant activities established that acteoside, a polyhydroxylated phenylpropanoid glycoside derivative, is the most potent free radical scavenger and showed the highest protection factor (PF(r)) against sunflower-oil-induced oxidative rancidity. Its activity is comparable to the synthetic antioxidant BHT and clearly superior to natural alpha-tocopherol. This compound therefore represents a very interesting candidate for use in food preservation as natural protecting agent against oxidative rancidity.

The Antimicrobial Activity of the Essential Oils of Four Juniperus Species Growing Wild in Greece

The antimicrobial activity of the essential oils from the leaves and berries of four Juniperus species (Cupressaceae) was studied. The essential oil of the berries of Juniperus oxycedrus L. subsp. oxycedrus, which was the most active, was fractionated by CC and the antimicrobial activity of each fraction was tested. The fraction with the highest activity was analysed by GC-MS and was found to contain mainly α-terpineol.

ESSENTIAL OIL COMPOSITION OF NEPETA ARGOLICA BORY ET CHAUB. SUBSP. ARGOLICA

The chemical composition of the essential oils obtained from the herbal parts and different plant parts of Nepeta argolica Bory et Chaub. subsp. argolica was examined by GC and GC–MS. Sixty-two con-ystituents were identified. The major constituents were found to be stereoisomers of nepetalactones (94.5–68.0%). 4aα,7α,7aβ-nepetalactone was isolated and identified by 1H- and 13C-NMR. Copyright

Volatile Needle Terpenoids of Six Pinus Species

Abstract The terpenoid composition of the needle oils of syntopically grown Pinus armandi Franch, P. densiflora Sieb. & Zucc., P. longaeva Bailey, P. mugo Turra, P. pumila (Pall.) Regel and P. sylvestris L. were analyzed by GC and GC/MS. Seventy-six compounds were identified in the oils. P. armandi was found to be rich in β-caryophyllene (36.3%) and γ-muurolene (40.7%). P. densiflora contained α-pinene (13.2%), β-phellandrene (11.6%) and germacrene D as major compounds. The predominant compounds in P. longaeva oil were α-pinene (17.1%), β-pinene (17.7%) and β-phellandrene (32.5%), the major component of P. mugo oil was α-pinene (33.3%) while P. pumila oil was rich in δ-3-carene (14.9%), β-phellandrene (10.7%) and terpinolene (37.7%). An unusual strain of P. sylvestris possessed an oil rich in caryophyllene oxide (12.7%) and manoyl oxide (30.2%) rather than the usual monoterpene hydrocarbons

Flavonoids and bioactive coumarins of Tordylium apulum

Abstract The new flavonol quercetin-3- O -[3,4 diacetyl-α-l-rhamnopyranosyl-(1–6)β-d-glucopyranoside], 2′( S ),3′( R )-2′-acetoxyisopropyl-3′-acetoxy-2′,3′dihydroangelicin were fully elucidated together with 11 other flavonoids and bioactive coumarins from Tordylium apulum . A new flavonol diglycoside, quercetin-3- O -[3,4 diacetyl-α-l-rhamnopyranosyl-(1–6)β-d-glucopyranoside] and an antifungal dihydrofuranocoumarin, 2′( S ),3′( R )-2′-acetoxyisopropyl-3′-acetoxy-2′,3′-dihydroangelicin, together with four other known flavonoids and seven known bioactive coumarins, were isolated from the aerial parts of Tordylium apulum and their structures elucidated by NMR and mass spectroscopy.

Secondary metabolites from Centaurea deusta with antimicrobial activity

The aerial parts of Centaurea deusta Ten. afforded in addition to several known compounds, mainly sesquiterpene lactones, one new eudesmanolide and one new elemane derivative. Structures of the new compounds were elucidated by spectroscopic methods. The in vitro antifungal and antibacterial activities of the isolated compounds was tested, using the microdilution method. All compounds tested showed high antifungal activity.