Betulinic acid (ALS-357) is a pentacyclic lupane-type triterpene derivative of betulin (isolated from the bark of Betula alba, the common white birch) which has antiretroviral, antimalarial, and anti-inflammatory properties, as well as a more recently discovered potential as an anticancer agent, by inhibition of topoisomerase.

Topo I (eukaryotic):5 μM, Aminopeptidase N:7.3 μM, HIV-1:1.4 μM(EC50)

在无胸腺裸鼠LNCaP细胞中,Betulinic acid对前列腺癌细胞和肿瘤(异种移植)的生长有抑制效果,该作用部分是由于蛋白酶依赖性Sp1/3/4及一些SP-调节基因的下调.

作为抗黑色素瘤剂,Betulinic acid可抑制氨肽酶N的活性（IC50：7.3 μM）。通过阻断H9淋巴细胞中HIV复制（EC50：1.4 μM）和未感染的H9细胞生长（IC50：13 μM）的抑制,Betulinic acid产生抗HIV活性。Betulinic acid还是十分有潜力的抗肿瘤候选药物,对真核生物拓扑异构酶I的活性有抑制作用（IC50：5 μM）。

Topoisomerase I-DNA interaction: Annealed 25-mer duplex of oligonucleotide-1 and oligonicleotide-2 is incubated with 25 or 50 units of rat liver topoisomerase I at 8 °C for 15 min in the presence or absence of betulinic acid in binding buffer. After incubation the reaction mixtures are electrophoresed in 7% non-denaturing polyacrylamide gel at 4 °C in 0.167 × TBE buffer and DNA bands are stained with ethidium bromid