Abstract
The biotransformation of betulinic (R
=
OH) and betulonic acid (R
=
O) by
Arthrobotrys sp.,
Colletotrichum sp.,
Chaetophoma sp. and
Dematium sp. oxidized the molecules at C-3, C-7, C-15, C-25 and C-30, respectively.
Betulinic acid (
1), a triterpenoid found in many plant species, has attracted attention due to its important pharmacological properties, such as anti-cancer and anti-HIV activities. The closely related, betulonic acid (
2) also has similar properties. In order to obtain derivatives potentially useful for detailed pharmacological studies, both compounds were submitted to incubations with selected microorganisms. In this work, both were individually metabolized by the fungi
Arthrobotrys,
Chaetophoma and
Dematium, isolated from the bark of
Platanus orientalis as well as with
Colletotrichum, obtained from corn leaves; such fungal transformations are quite rare in the scientific literature. Biotransformations with
Arthrobotrys converted betulonic acid (
2) into 3-oxo-7β-hydroxylup-20(29)-en-28-oic acid (
3), 3-oxo-7β,15α-dihydroxylup-20(29)-en-28-oic acid (
4) and 3-oxo-7β,30-dihydroxylup-20(29)-en-28-oic acid (
5);
Colletotrichum converted betulinic acid (
1) into 3-oxo-15α-hydroxylup-20(29)-en-28-oic (
6) acid whereas betulonic acid (
2) was converted into the same product and 3-oxo-7β,15α-dihydroxylup-20(29)-en-28-oic acid (
4);
Chaetophoma converted betulonic acid (
2) into 3-oxo-25-hydroxylup-20(29)-en-28-oic acid (
7) and both
Chaetophoma and
Dematium converted betulinic acid (
1) into betulonic acid (
2). Those fungi, therefore, are useful for mild, selective oxidations of lupane substrates at positions C-3, C-7, C-15, C-25 and C-30.