2.2. Cuparene
A chemical study on the extract of the fungus Coprinopsis cinereahas afforded two new skeletal sesquiterpenoids, which have been named
hitoyols A and B (3 and 4 ).[23]C. cinerea from the genus Coprinopsis (Hitoyotake, in
Japanese) plays an important role in model basidiomycete, andCoprinopsis sp. are rich sources of cuparene-type
sesquiterpenoids.[24-26] Structurally, hitoyol A
(3 ), as an unprecedented norsesquiterpenoid, possesses anexo -tricyclo[5.2.1.02,6]decane core. The
novel skeletal sesquiterpenoid hitoyol B (4 ), containing
4-cyclopentene-1,3-dione, has displayed antimalarial activity with an
IC50 of 59 μ M. Moreover, 3 and4 are possibly biosynthesized through decarboxylation-induced
cyclization of lagopodin B, a known cuparene-type sesquiterpenoid (Fig.
4).
Trichothecrotocins A (5 ) and B (6 ) are two new
trichothecene derivatives, which have been obtained from the potato
endophytic fungus Trichothecium
crotocinigenum .[27] Biosynthetically,
trichothecenes have been demonstrated to be derived from an important
precursor trichodiene, also originated from cuparene-skeleton similar to3 and 4 . Moreover, one of the most critical steps of
the proposed biosynthetic pathway for5 would be the formation of a new carbon-carbon bond between
C-9 and C-12 (Fig. 4).[28-30] In addition,5 and 6 exhibit antiphytopathogenic activities with
MIC values of 16−32 μ g/mL.
Fig. 4. Proposed biosynthetic pathways for3 −6 .
2.3. Humulane
Higher fungi (mushroom) are
undoubtedly an important source of
sesquiterpenoids.[13] In the past decade, many
interesting secondary metabolites of higher fungi have been reported by
Liu’s group, such as trefolane A from culture of the mushroomTremella foliacea and conosilane A from culture of the mushroomConocybe siliginea .[31, 32] In this study,
a novel skeletal sesquiterpenoid antroalbocin A (7 ), possessing
a bridged tricyclic system, has been obtained from the
higher fungus Antrodiella
albocinnamomea , a white-rot fungus belonging to the Basidiomycota
(widely distributed in northeast China).[33]7 , an antibacterial sesquiterpenoid, was found to inhibitStaphylococcus aureus with an MIC value of 169μ M,[34] and its structure has been confirmed
by single crystal X-ray diffraction. Furthermore, the key steps of the
plausible biosynthetic pathway derived from humulane would involve a
cyclization of humulene building a backbone of triquinane-type
sesquiterpene and the formation of new C−C bond between C-8 and C-9
(Fig. 5).
The endophytic Fungus Phomopsis sp. TJ507A, isolated from the
medicinal plant Phyllanthus glaucus , has provided a naturally
occurring 2,3-seco -protoilludane-type sesquiterpenoid, named
phomophyllin A (8 ).[35] One new cage-like
cerapicane derivative, cerrenin A (9 ), and two new isohirsutane
derivatives, cerrenins B and C (10 and 11 ), have been
obtained from the broth extract of Cerrena sp.
A593.[36] Three pairs of enantiomeric
sesquiterpenoids, (∓)-syringanoid A
(12a and 12b ) and (±)-pinnatanoids A (13a and13b ) and B (14a and 14b ) have been isolated
from the peeled stems of Syringa
pinnatifolia .[37] 12 −14represent unprecedented 5/4/6 tricyclic backbone and a rare 6/7 bicyclic
backbone, respectively, and their cardiomyocyte-protective and
anti-inflammatory activities were evaluated. In addition, plausible
biosynthetic pathways for 7 and 12 −14 have
been proposed (Fig. 5).
Fig. 5. Proposed biosynthetic pathways for 7 and12 −14 .