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 for36 .
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] 1214represent 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 1214 have been proposed (Fig. 5).
Fig. 5. Proposed biosynthetic pathways for 7 and1214 .