Betulin

Betulin (lup-20(29)-ene-3β,28-diol) is an abundant naturally occurring triterpene. It is commonly isolated from the bark of birch trees and forms up to 30% of the dry weight of the extractive. It can be converted to betulinic acid, which is biologically more active than betulin itself. Betulinic acid and its synthetic analogues exhibit anti-malarial, anti-inflamatory and anti-HIV activity as well as showing cytotoxicity towards a number of tumour cell lines. Even though betulin derivatives are most widely studied for their anticancer activity, also the anti-HIV effect is quite well characterized and it has been demonstrated that betulins can inhibit HIV entry to T cells by binding to the gp41, a HIV protein needed for the invasion of the virus into the cell.