The
detailed mycochemical analysis of the
n
-hexane
extract of
Pholiota populnea
led to the isolation
of four new lanostane diesters, named pholiols A–D (
1
–
4
), together with an acyclic triterpene, (3
S
,6
E
,10
E
,14
E
,18
E
,22
S
)-2,3,22,23-tetrahydroxy-2,6,10,15,19,23-hexamethyl-6,10,14,18-tetracosatetraene
(
5
), ergosterol (
6
), and 3β-hydroxyergosta-7,22-diene
(
7
). The isolation was carried out by multistep flash
chromatography, and the structures were elucidated using extensive
spectroscopic analyses, including 1D and 2D NMR and MS measurements.
The isolated metabolites (
1
–
6
) were
investigated for cytotoxic activity against Colo205 and Colo320 colon
adenocarcinoma and nontumoral MRC-5 cell lines. Among the tested compounds,
ergosterol (
6
) showed substantial cytotoxic activity
against all cell lines with IC
50
values of 4.9 μM
(Colo 205), 6.5 μM (Colo 320), and 0.50 μM (MRC) with
no tumor cell selectivity. A P-glycoprotein efflux pump modulatory
test on resistant Colo320 cells revealed that pholiols A (
1
) and B (
2
) and linear triterpene polyol
5
have the capacity to inhibit the efflux-pump overexpressed in the
cells. Moreover, the drug interactions of triterpenes with doxorubicin
were studied by the checkerboard method on Colo 320 cells. Pholiols
B (
2
) and D (
4
) interacted in synergistic
and acyclic triterpene
5
in a very strong synergistic
manner; the combination index (CI) values at 50% of the growth inhibition
dose (ED
50
) were found to be 0.348, 0.660, and 0.082, respectively.
Our results indicate that
P. populnea
is a promising
source for finding new triterpenes with significant chemosensitizing
activity on cancer cells.