Table of Contents:
About 200 of more than 700 Allium Species worldwide belong to the subgenus Melanocrommyum, which is mainly inhabited in the mountainous regions of Central Asia. These species, in Europe and North America only known as ornamental plants, the so called drumstick onions, are used as vegetable, spices and medicinal plants in their countries of origin. In this respect, organosulfur compounds like cysteine sulfoxides are of importance. Interestingly, some of the species produce a red ichor after wounding of the cell tissue, which was identified as a dithiodipyrrol.
New insights into the biosynthesis of this dye were gained. The precursor of the reaction is stable in the intact cell and was found to be a so far unknown cysteine sulfoxide. The enzyme which is catalyzing the reaction to the red dye was purified using a combination of gel- and affinity-chromatography. It shows two main features. First, it catalyzes an Alliinase-like reaction producing the red dye. Second, it oxidizes certain polyphenols like pyrocatechin and dopamin to brown products.
In the plant extracts a multitude of different substances produced in complex enzymatic and non-enzymatic reactions were detected. Only few of those are identified so far. Therefore, further studies are necessary, to address the open questions.
Another pharmaceutically important group of substances in Allium subg. Melanocrommyum species are steroidal saponins. This HPLC-UV-MS/MS study included Allium species, as well as examples of the genera Hoodia, Stapelia and related species.