Research into the chemical composition of saffron, the dried stigmas of Crocus sativus, has seen a renaissance in recent years. Different HPLC protocols for the analysis of saffron constituents have been established, enabling rapid authenticity control of the spice. Saffron flavor has attracted the interest of several research groups. Among the estimated 150 volatile compounds of saffron, approximately 40–50 constituents have so far been identified. Sensory studies allowed the detection of novel key flavor compounds. For some volatiles, generation from acid-labile progenitors was shown. Most recently, a considerable number of non-volatile aroma precursors could be isolated and structurally characterized. This paper reviews the present knowledge about the chemical composition of the world's most expensive spice and gives special emphasis to recent findings on saffron aroma formation.

Saffron - renewed interest in an ancient spice.

Anthocyanins belong to a large group of secondary plant metabolites collectively known as flavonoids, a subclass of the polyphenol family. They are a group of very efficient bioactive compounds that are widely distributed in plant food. Anthocyanins occur in all plant tissues, including leaves, stems, roots, flowers, and fruits. Research on phenolic compounds through the last century, from the chemical, biochemical, and biological points of view, has focused mainly on the anthocyanins. Anthocyanins have structures consisting of two aromatic rings linked by three carbons in an oxygenated heterocycle (i.e., a chromane ring bearing a second aromatic ring in position 2). The basic chromophore of anthocyanins is the 7-hydroxyflavilyum ion. Anthocyanin pigments consist of two or three chemical units: an aglycon base or flavylium ring (anthocyanidin), sugars, and possibly acylating groups. Only six of the different anthocyanidins found in nature occur frequently and are of dietary importance: cyanidin, delphinid...

Analysis and Antioxidant Capacity of Anthocyanin Pigments. Part II: Chemical Structure, Color, and Intake of Anthocyanins

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R(-)-Nipecotic acid was a more potent inhibitor than the S(+)-isomer of the uptake of GABA, (+)-nipecotic acid, and β-alanine in rat brain slices. (-)-Nipecotic acid was an order of magnitude more potent as an inhibitor of GABA uptake than as an inhibitor of β-alanine uptake, whereas the (+)-isomer was less selective. (–)-Nipecotic acid was a weak inhibitor of L-proline uptake and of rat brain acetylcholinesterase activity.



Kinetic studies showed that both isomers of nipecotic acid were competitive inhibitors of GABA uptake when added at the same time as GABA, but non-competitive inhibitors when preincubated with the tissue for 15 min before addition of GABA. The apparent slope inhibition constants, which were not influenced by preincubation, indicated that (–)-nipecotic acid has an affinity for the carrier some 5 times higher than that for (+)-nipecotic acid. (–)-Nipecotic acid stimulated the release of preloaded radioactive GABA from rat brain slices. These observations indicate that (–)-nipecotic acid is a substrate-competitive inhibitor of GABA which combines with the GABA carrier and is taken up.



(−)-Nipecotic acid and (+)-2,4-diaminobutyric acid, on the basis of their absolute structures and inhibition kinetics, are proposed to interact in a similar way with the GABA transport system.

Inhibition of the uptake of GABA and related amino acids in rat brain slices by the optical isomers of nipecotic acid.

From glucose to aromatics: recent developments in natural products of the shikimic acid pathway

P. Karrer

Papers

Die Konfiguration des Nicotins. Optisch aktive Hygrinsäure

Untersuchungen über Pflanzenfarbstoffe I. Über die Konstitution einiger Anthocyanidine. Teilweise mitbearbeitet von H. Hürlimann und O. Nievergelt

Über die Konfiguration der d‐Glutaminsäure, des d‐Ornithins und d‐Lysins

Über Bixin. (XIII. Mitteilung über Pflanzenfarbstoffe.)

Über Pflanzenfarbstoffe IV. Zur Kenntnis der Anthocyane und Anthocyanidine