Chemical substances

by Marjan Donko 

   
The name "Sempervivum" reflects the seeming immortality of the plants, but we could interpret that immortality in another way. It has been said that people who use houseleeks will live much longer. That is not quite untrue, for houseleeks do possess many substances that can benefit our health. Chemical compounds in houseleeks have not been thoroughly studied. We can get more data in literature on medicinal herbs than in scientific data. Below are some interesting substances that houseleeks contain:

organic acids
saccharides
phenolic compounds
alkaloids, etc...

The most important of these substances are probably the phenolic compounds. Phenolic is a broad descriptive term for aromatic molecules with at least one hydroxy group. Polyphenols are a very heterogeneous group of organic compounds. In the world of plants, they are represented by pigments, coenzymes, inhibitors, antimicrobial agens and phytoalexins. Some of them are called tannins. One of their qualities is that they can precipitate proteins from a water solution, which is why houseleeks taste bitter. Polyphenols are commonly bound to sugars, amino groups, lipids and terpenoids. It is important to mention that the concentration of compounds is different according to the time of day, the season, or the age of the plant or leaves.

CAM metabolism

Houseleeks have Crassulacean Acid Metabolism (CAM), which is one of their adaptations to arid habitats. CAM can be found in 32 families of plants and 328 genera. It was discovered accidentally when scientists researched pH in the plants during the daytime. CO₂ was found to be bound to phosphoenolpyruvate at night, forming oxalacetate and then malate, so that plants could maintain their stomata closed during the day. The stomata open at night when temperatures are lower.

Arid habitat is not the only stimulus to the evolution of CAM. It is found in habitats with plenty of water. There the concentration of CO₂ is the limiting factor for photosynthesis.