Betulin
Betulin is an abundant, naturally occurring triterpene. It is commonly isolated from the bark of birch trees. It forms up to 30% of the dry weight of silver birch bark. It is also found in birch sap. Inonotus obliquus and red alder also contain betulin.
The compound in the bark gives the tree its white color which appears to protect the tree from mid-winter overheating by the sun. As a result, birches are some of the northern most occurring deciduous trees. It can be converted to betulinic acid, which is biologically more active than betulin itself.History
Betulin was discovered in 1788 by German-Russian chemist Johann Tobias Lowitz.Chemistry
Chemically, betulin is a triterpenoid of lupane structure. It has a pentacyclic ring structure, and hydroxyl groups in positions C3 and C28.Biological activities
In vitro studies have shown that betulin was effective against a variety of tumors. Betulin causes some types of tumor cells to start a process of self-destruction called apoptosis, and can slow the growth of several types of tumor cells.
Another study has shown that betulin inhibited the maturation of sterol regulatory element-binding protein. Inhibition of SREBP by betulin decreased the biosynthesis of cholesterol and fatty acids. In vivo, betulin ameliorated diet-induced obesity, decreased the lipid contents in serum and tissues, and increased insulin sensitivity. Furthermore, betulin reduced the size and improved the stability of atherosclerotic plaques.
Native Americans used red alder bark to treat poison oak, insect bites, and skin irritations. Blackfoot Indians used an infusion made from the bark of red alder to treat lymphatic diseases and tuberculosis.
