Production and identification of two antifungal terpenoids from the Posidonia oceanica epiphytic Ascomycota Mariannaea humicola IG100

Abstract

Background Marine fungi are an important repository of bioactive molecules with great potential in different technological fields, the annual number of new compounds isolated from marine fungi is impressive and the general trend indicates that it is still on the rise. In this context, the antifungal and antimicrobial activity of the marine strain Mariannaea humicola IG100 was evaluated and two active terpenoids were isolated and characterized. Methods Preliminary screening of activity of marine strain IG100 was carried out by agar plug diffusion methods against fungal (Penicillium griseofulvum TSF04) and bacterial (Bacillus pumilus KB66 and Escherichia coli JM109) strains. Subsequently, inhibition tests were done by using the cultural broth and the organic extract (ethyl acetate, EtOAc) by the agar well diffusion methods. The main active fractions were identified and tested for their antifungal activity against P. griseofulvum TSF04 in a 24 wells microplate at different concentrations (1000, 100, 10 and 1.0 µg/mL). Two active compounds were characterized and their relative MIC measured by the broth micro-dilution methods in a 96-well microplate against Aspergillus flavus IG133, P. griseofulvum TSF04, and Trichoderma pleuroticola IG137. Results Marine strain IG100 presented significant antifungal activity associated with two active compounds, the terpenoids terperstacin 1 and 19-acetyl-4-hydroxydictyodiol 2. Their MIC values were measured for A. flavus (MIC of 7.9 µg/mL and 31.3 µg/mL for 1 and 2, respectively), P. griseofulvum (MIC of 25 µg/mL and 100 µg/mL for 1 and 2, respectively) and T. pleuroticola (MIC > 500 µg/mL and 125 µg/mL for 1 and 2, respectively). They showed a rather good fungistatic effect. Conclusions In this study, the first marine strain of M. humicola (IG100) was investigated for the production of bioactive molecules. Strain IG100 produced significant amounts of two bioactive terpenoids, terperstacin 1 and 19-acetyl-4-hydroxydictyodiol 2. The two compounds showed significant antifungal activities against A. flavus IG133, T. pleuroticola IG137 and P. griseofulvum TSF04. Compound 2 was identified for the first time in fungi.

Rambellisea gigliensis and Rambellisea halocynthiae, gen. et spp. nov. (Lulworthiaceae) from the Marine Tunicate Halocynthia papillosa

“…Marine habitats cover more than 70% of the planet's surface and host a large amount of unknown biological and chemical diversity [1][2][3][4]. The sea represents a limitless resource of unexploited substrata and new microorganisms [5][6][7][8].…”

Stereochemistries of Mariannamides C and D, Two Lipohexapeptides, Isolated from Mariannaea elegans NBRC102301

“…1,2 Currently, only 20 species 3 of this genus are accepted, and chemical investigation into this genus is not very active. So far, three polyketides, marianins A and B 4 and mariannaeapyrone from M. elegans UR 742, 5 one glycosphingolipid, Glc1-6Galβ1-Cer from M. elegans JCM12789 6 , two terpenoids, terpestacin 7 and 19-acetyl-4-hydroxydictyodiol 7 from M. humicola IG100, and one meroterpenoid, sesquicillin F 8 from M. macrochlamydospora FKI-4735 have been reported. In our continuing efforts to find structurally and biologically attractive natural products from plant-inhabiting fungi, 9 we have recently surveyed the chemical constituents of M. elegans NBRC102301 and isolated two cyclic octapeptides, mariannamides A and B.…”