Naturstoffe der neotropischen Art Palicourea luxurians

Die Arbeit hat gezeigt, dass mit den angewandten Methoden eine Gesamtanzahl von zehn verschiedenen Sekundärmetaboliten aus den Blättern der bis jetzt noch nicht untersuchten Pflanze Palicourea luxurians isoliert werden konnte. Dafür wurden verschiedene Extrakte erstellt und diese daraufhin mit mehreren chromatographischen Methoden weiter gereinigt. Hauptsächlich wurde Säulenchromatographie mit diversen mobilen und stationären Phasen für die Trennung eingesetzt. Die Qualität der getrennten Substanzen wurde mit TLC und HPLC überprüft. Für die Strukturaufklärung wurden 1D- und 2D-NMR, Massen-, Infrarot- sowie UV/Vis-Spektroskopie genutzt. Unter anderem konnte ein neues Terpen namens Blumenol C-Sulfat isoliert werden, bei dem es sich um ein Carotinoid-Abbauprodukt handelt. Weiters konnten sechs Secoiridoidglycoside identifiziert werden. Dabei handelt es sich um die in vivo synthetisierten Verbindungen Demethyl-Secologanol, Swerosid, (E)-Aldosecologanin und der Secologaninsäure sowie den beiden chemisch induzierten Artefakten Dimethyl- und Dibutylacetal-Secologanin. Zusätzlich dazu konnten verschiedene Indolalkaloide charakterisiert werden, wie das bereits bekannte 5 alpha-Carboxystrictosidin. Dieses stellt das einzige Indol-Monoterpen-Alkaloid mit einem Verhältnis von 1:1 Indol:Secologanin in dieser Arbeit dar, welches möglicherweise nicht direkt vom Strictosidin abstammt. Das Strictosidin selbst bzw. Derivate davon wurden nicht gefunden. Des Weiteren konnten die Strukturen von zwei Alstrostinen aufgeklärt werden. Die beiden neuen Naturstoffe wurden Palicoureosid und Dehydro-Rudgeifolin genannt. Es lässt sich sagen, dass eine hohe Anzahl sowie eine große Diversität an verschiedenen Naturstoffen in der Pflanze P.luxurians spektroskopisch identifiziert werden konnte. Der Großteil der gefunden Naturstoffe reiht sich gut in die Gattung Palicourea ein und durch die Entdeckung neuer Verbindungen wurde ein Einblick in weitere unbekannte biologische Synthesewege der Pflanzengattung ermöglicht.The investigation of the leaves of the unknown neotropical plant Palicourea luxurians led to the purification and identification of ten different secondary metabolites. Therefore, different extracts were made and afterwards purified with several chromatographic techniques. Mainly column chromatograhpy with several mobile and stationary phases was used for the separation. The quality of the samples was analyzed with TLC and the in-depth measurements were done with HPLC coupled to a UV/Vis detector. For the structure elucidation the purified substances were investigated with 1D/2D-NMR and mass spectrometry. Additionally, UV/Vis- and infrared spectroscopy were performed for the verification. One new terpenoid was isolated and is called blumenol C sulfate, which is the first described megastigmane with an attached sulfate group. Furthermore, four known natural occurring secoiridoid glycosides named (E)-aldosecolganin, demethylsecologanol, sweroside as well as secolocanic acid were found. In addition, two in vitro formed artefacts of the secologanin named secologanin dibutylacetal and secologanin dimethylacetal were isolated. Additionally, more complex natural products like the monoterpene indol alkaloid 5 alpha-carboxystrictosidine were characterized. It is the only isolated 1:1 indol:secologanin compound in this thesis. However, no strictosidine as well as other derivatives of it could be identified. Further on, two new tryptamine iridoid alkaloids were characterized and named palicoureoside as well as dehydro-rudgeifoline. Overall a large number and great chemodiversity of secondary metabolites was identified in this thesis. Those are in good agreement with other known natural products in the genus Palicourea. They also indicate several possible biosynthetic pathways in the plant P.luxurians

Tetraedron minimum, First Reported Member of Hydrodictyaceae to Accumulate Secondary Carotenoids

We isolated a novel strain of the microalga Tetraedron minimum in Iceland from a terrestrial habitat. During long-term cultivation, a dish culture turned orange, indicating the presence of secondary pigments. Thus, we characterized T. minimum for growth and possible carotenoid production in different inorganic media. In a lab-scale photobioreactor, we confirmed that nitrogen starvation in combination with salt stress triggered a secondary carotenoid accumulation. The development of the pigment composition and the antioxidant capacity of the extracts was analyzed throughout the cultivations. The final secondary carotenoid composition was, on average, 61.1% astaxanthin and 38.9% adonixanthin. Moreover, the cells accumulated approx. 83.1% unsaturated fatty acids. This work presents the first report of the formation of secondary carotenoids within the family Hydrodictyaceae (Sphaeropleales, Chlorophyta)

<i>Tetraedron minimum</i>, First Reported Member of Hydrodictyaceae to Accumulate Secondary Carotenoids

We isolated a novel strain of the microalga Tetraedron minimum in Iceland from a terrestrial habitat. During long-term cultivation, a dish culture turned orange, indicating the presence of secondary pigments. Thus, we characterized T. minimum for growth and possible carotenoid production in different inorganic media. In a lab-scale photobioreactor, we confirmed that nitrogen starvation in combination with salt stress triggered a secondary carotenoid accumulation. The development of the pigment composition and the antioxidant capacity of the extracts was analyzed throughout the cultivations. The final secondary carotenoid composition was, on average, 61.1% astaxanthin and 38.9% adonixanthin. Moreover, the cells accumulated approx. 83.1% unsaturated fatty acids. This work presents the first report of the formation of secondary carotenoids within the family Hydrodictyaceae (Sphaeropleales, Chlorophyta)

Phytochemistry Meets Geochemistry&mdash;Blumenol C Sulfate: A New Megastigmane Sulfate from Palicourea&nbsp;luxurians (Rubiaceae: Palicoureeae)

There is a previously neglected influence of geochemical conditions on plant phytochemistry. In particular, high concentrations of dissolved salts can affect their biosynthesis of natural products. Detoxification is most likely an important aspect for the plant, but additional natural products can also give it an expanded range of bioactivities. During the phytochemical analysis a Palicourea luxurians plant collected in a sulfate-rich environment (near the R&iacute;o Sucio, Costa Rica) showed an interesting natural product in this regard. The structure of this compound was determined using spectroscopic and computational methods (NMR, MS, UV, IR, CD, optical rotation, quantum chemical calculations) and resulted in a megastigmane sulfate ester possessing a &beta;-ionone core structure, namely blumenol C sulfate (1, C13H22O5S). The levels of sulfur and sulfate ions in the leaves of the plant were determined using elemental analysis and compared to the corresponding levels in comparable plant leaves from a less sulfate-rich environments. The analyses show the leaves from which we isolated blumenol C sulfate (1) to contain 35% more sulfur and 80% more sulfate than the other samples. Antimicrobial and antioxidant activities of compound 1 were tested against Escherichia coli, E. coli ampR and Bacillus subtilis as well as measured using complementary in vitro FRAP and ATBS assays, respectively. These bioactivities are comparable to those determined for structurally related megastigmanes. The sulfur and sulfate content of the plant leaves from the sulfate-rich environment was significantly higher than that of the other plants. Against this background of salt stress, we discuss a possible biosynthesis of blumenol C sulfate (1). Furthermore, there appears to be no benefit for the plant in terms of extended bioactivities. Hence, the formation of blumenol C sulfate (1) probably primarily serves the plant detoxification process

The (Bio)chemical Base of Flower Colour in Bidens ferulifolia

Bidens ferulifolia is a yellow flowering plant, originating from Mexico, which is increasingly popular as an ornamental plant. In the past few years, new colour combinations ranging from pure yellow over yellow-red, white-red, pure white and purple have emerged on the market. We analysed 16 Bidens ferulifolia genotypes to provide insight into the (bio)chemical base underlying the colour formation, which involves flavonoids, anthochlors and carotenoids. In all but purple and white genotypes, anthochlors were the prevalent pigments, primarily derivatives of okanin, a 6&prime;-deoxychalcone carrying an unusual 2&prime;3&prime;4&prime;-hydroxylation pattern in ring A. The presence of a cytochrome-P450-dependent monooxygenase introducing the additional hydroxyl group in position 3&prime; of both isoliquiritigenin and butein was demonstrated for the first time. All genotypes accumulate considerable amounts of the flavone luteolin. Red and purple genotypes additionally accumulate cyanidin-type anthocyanins. Acyanic genotypes lack flavanone 3-hydroxylase and/or dihydroflavonol 4-reductase activity, which creates a bottleneck in the anthocyanin pathway. The carotenoid spectrum was analysed in two Bidens genotypes and showed strong variation between the two cultivars. In comparison to anthochlors, carotenoids were present in much lower concentrations. Carotenoid monoesters, as well as diesters, were determined for the first time in B. ferulifolia flower extracts