*3.2.1.1.2. Dehydroabietic acid*

Dehydroabietic acid displays not only antiulcer and antimicrobial properties but also antitumor and anti-inflammatory effects (compound 2). Antimicrobial effects of DHA have been studied, specifically against methicillin-resistant strains of *Staphylococcus aureus* [43].

Biological activity: It also showed activity against other Gram-positive organisms such as *Salmonella* sp., *Bacillus subtilis*, and *E. coli* [44]. This latter study also described the inhibition of nitric oxide (NO) production by DHA, which was reported by other researchers as well [49]. Kawada et al. [45] have reported in relation with the inhibition of pro-inflammatory cytokines that DHA is useful for treating obesity-related diseases.

**Figure 6.** Abietane skeleton with some standard compounds [41].

of abietanes are exemplified by carnosol (11,12-dihydroxy-8,11,13-20,7-olide). Carnosol possesses an aromatic C ring, carbon C-20 is a keto group, and carbons C-11 and C-12 are hydroxy groups. This abietane has displayed several biological activities. It displayed antioxidant, antimicrobial, anti-inflammatory, antitumor, and anti-HIV (IC50 = 8.0 μM) properties [57, 58].

Diterpenes from Different Fungal Sources and Their 13C-NMR Data

http://dx.doi.org/10.5772/intechopen.79186

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The abietatetraenes are a group of compounds which possess a fourth double bond which can be located at different positions. Among the 5,6-dehydro derivatives are coleon C and coleon U and related compounds (**Figure 8**). These metabolites are common in plants of the genus *Coleus* (synonym *Plectranthus*) and have described to possess antitumor, antimicrobial, and

*Cyathus* is a genus of fungi in the Nidulariaceae, a family collectively known as the bird's nest fungi. Such compounds are named so, as they resemble tiny bird's nests filled with "eggs," structures large enough to have been mistaken in the past for seeds. The first cyathin

of other diterpenes being isolated and documented from different species belong to genus *Cyathus* [61]. In particular, the species belonging to the genus *Cyathus* is recognized as prolific producer of bioactive cyathane diterpenoids with inimitable tricyclic ring skeleton [62]. Cyathane diterpenoids also represent a group of natural products with versatility both in structure and bioactivity [63, 64]. Cyathane diterpenes are important bioactive metabolites extracted from the genus *Cyathus*, *Hericium*, and *Sarcodon.* Genus *Cyathus* is beneficial in producing healthy food and possesses the potential of nitric oxide (NO) inhibition and anti-

A number of other biologically significant cyathane diterpenoids have been isolated from the fruiting bodies of mushroom *Sarcodon scabrosus* [65–67], *Sarcodon glaucopus* [68, 69], and *Sarcodon cyrneus* [70, 71] and the culture of fungi *C. helenae* [72], *C. africanus* [73], *C. earlei*

were reported from fungus *C. helenae* in 1972, and since then a number

*3.2.3. Abietatetraenes*

antiproliferative activity [59, 60] (**Table 1**).

**3.3. Tetracyclic diterpenoids**

*3.3.1. Cythane diterpenes*

and allocyathin B3

bacterial activities [64].

*3.3.1.1. Diversity of cythane diterpenes*

**Figure 8.** Representative member of tricyclic abietatrienes *Callitris* species.

A3

**Figure 7.** Synthesis of compounds 2–10 [42].
