56 Khaled A. Selim, Mohamed M. S. Nagia and Dina E. El. Ghwas
C. quercina showed brilliant antifungal activity toward serious human
pathogens Candida albicans and Trichophyton spp. Since fungal infections are
a growing health problem especially among immunocompromised patients,
new antifungals are required to struggle this problem. A cryptocandin is a
unique antimycotic peptide that was isolated from C. quercina (Figure 2). This
compound contains a novel amino acid, 3-hydroxy- 4 - hydroxy methyl proline,
and a number of peculiar hydroxylated amino acids. It was active against a
huge number of plant pathogen as well, including Botrytis cinerea and
Sclerotinia sclerotiorum. Cryptocandin is currently being verified and
industrialized by several pharmaceutical companies for usage against different
skin and nails pathogenic fungi (Strobel, 2003).
9.3. Endophytes Producing Antiviral Agents
(R)- (-)-mellein (Figure 2) is a naturally occurring di-hydroiso coumarin
which was first isolated as a metabolite of Aspergillus melleus (Nishikawa,
1993) and later from a number of endophytic fungi such as Pezicula livida,
Plectophomella sp. and Cryptosporiopsis malicoticis (Krohn et al., 1997).
Recently, (R)-(-)-mellein isolated from Geniculosporium sp., a fungus that is
associated with the red alga Polysiphonia sp. and isolated from the Baltic Sea
at Ahren shoop. It shows a number of interesting biological activities such as
fungicidal, antibacterial and algicidal activity in agar diffusion tests (Holler
et al., 1999) and it inhibits HCV protease with an IC 50 value of 35 mM (Florke
et al., 2006).
9.4. Endophytes with other Important Biological Activities
A surprise was the realization that endophytes produce substances that can
influence the immune system of animals. Subglutinols A and B (Figure 2) are
immunosuppressive compounds produced by the marine-derived Fusarium
subglutinans, and another endophyte from T. wilfordii as illustrated in (Lee et
al., 1995). Both compounds have IC 50 values of 0.1 μM in the mixed
lymphocyte reaction assay. In the same assay, cyclosporin was found roughly
as potent as the sub-glutinols. These compounds are being examined more
thoroughly as immunosuppressive agents. Their role in the endophyte and its
relationship to the host are unknown.