Sesquiterpenes from the Mycelial Cultures of Dichomitus squalens

Abstract

Three new sesquiterpenes including a rearranged hirsutane, dichomitol (1), an aromadendrane, 2beta,13-dihydroxyledol (2), and a 1,10-seco-2,3-seco-aromadendrane, dichomitone (3), were isolated from mycelial solid cultures of Dichomitus squalens. Their structures were elucidated by spectroscopic methods, and their nematicidal activities against Bursaphelenchus xylophilus were assessed.

Novel Sesquiterpenes from the Mycelial Cultures of Dichomitus squalens

“…In the NOESY spectrum, correlations were observed between HÀC(2) and Me(12), HÀC (9) and Me(12), Me(12) and H b ÀC(10), HÀC(8) and H a ÀC(10), CH 2 (13) and H a ÀC(1), CH 2 (13) and H a ÀC(10), and HÀC (9) Table 2), and DEPT spectra revealed the presence of two tertiary Me groups, a secondary Me group, four CH 2 groups, six CH groups, and two quaternary C-atoms, of which a CH 2 group, a CH group, and a quaternary C-atom were O-bearing. Combined analysis of the C-NMR data as compiled in Table 2, indicating a structure closely similar to 2b,13-dihydroxyledol (5) [3], a known aromadendrane sesquiterpene occurring in this fungus and re-isolated in the present study, except that HO at C(2) in 5 migrated to C(3) in 3. The b-orientation of HOÀC(3) was deduced from the NOE correlations of HÀC (3) with both HÀC(6) and Me(15) observed in the NOESY spectrum.…”

“…A total synthesis of the previously reported dichomitol [3] had been accomplished by Mehta and Pallavi [5]. It became clear that the compound isolated in our studies was different from the authentic synthetic product.…”

“…Subsequent screening of the petroleum ether-, CHCl 3 -, and AcOEtsoluble fractions from this extract showed that the CHCl 3 -soluble fraction was more potent than the others. Our previous investigation on the CHCl 3 -soluble fraction led to the isolation of three new sesquiterpenes, dichomitol, 2b,13-dihydroxyledol, and dichomitone, of which the second one was found to be nematicidal [3]. In continuation of our studies on this fungus, the AcOEt-soluble fraction was investigated, and four new sesquiterpenes, 5-hydroxydichomitol (1), dichomilludol (2), 3b,13-dihydroxyledol (3), and 2b,3b,13-trihydroxyledol (4), were isolated along with a previously isolated sesquiterpene, 2b,13-dihydroxyledol (5).…”

“…-The AcOEt-soluble fraction, previously obtained from the EtOH extract of the mycelial solid cultures of D. squalens by liquid-liquid partition [3], was separated by silica-gel and Develosil ODS column chromatography and preparative HPLC to give compounds 1 -5 (see Exper. Part).…”

“…Compounds 1 -4 were evaluated for the cytotoxicity and nematicidal activity according to the previously described methods [3] [9]. However, they were all found to be relatively non-cytotoxic (IC 50 > 35 mm) against the test cancer cell lines, including human breast cancer (MCF-7 and MDA-MB-231/ATCC), leukemia (K-562), and non- Table 2.…”