Planta Med 2014; 80 - P1N23
DOI: 10.1055/s-0034-1394613

5-Hydroxymethylmellein: An isocoumarin derivative from an endophytic fungus from red alga Asparagopsis taxiformis

R Medina 1, C Biasetto 1, A Somensi 1, N Yokoya 2, M Lopes 1, A Araújo 1, D Silva 1
  • 1NuBBE – Núcleo de Biossíntese, Bioensaios e Ecofisiologia de Produtos Naturais, Instituto de Química – UNESP – Street Professor Francisco Degni, 55. 14800 – 060, Araraquara, São Paulo, Brazil
  • 2Núcleo de Pesquisa em Ficologia, Instituto de Botânica de São Paulo – Avenue Miguel Estéfano, 3687. 04301 – 012, São Paulo, Brazil

Marine microorganisms have attracted considerable attention as important sources of structurally diverse secondary metabolites and as potential leads for drug discovery [1]. Our investigation on endophytic fungi isolated from the red alga Asparagopsis taxiformis led to the isolation and structure elucidation of a known isocoumarin. The alga was collected at the rocky shore of Fortaleza Beach, Ubatuba, SP, Brazil and identified by Dr. Nair S. Yokoya (Instituto de Botânica/SMA – SP, Brazil). To isolate the fungus, the alga was superficially sterilized, fragmented and spread on PDA plates. Then, the fungus was cultivated in sterilized PDB medium with sea water (small scale) for 28 days at 250 °C. The broth was separated from the mycelium by filtration and the crude extract (216 mg) was obtained by extraction with EtOAc (3 × 50% of the broth volume each) and dried in rotatory evaporator. The extract was subjected to bioassays and exhibited moderate antifungal activity against a strain of Cladosporium sphaerospermum and low anticholinesterasic activity. The extract (126.4 mg) was then chromatographed by HPLC using 40 – 100% MeOH:H2O, linear gradient for 40 minutes, flow rate 10 ml/min, which evidenced the presence of four major compounds. Compound 1 (0.9 mg) was eluted at tR 11.57 min and was identified as 5-hydroxymethylmellein, based on 1D and 2D NMR analyses and comparison with literature data [2]. Spectrometric analyses of further isolated compounds have evidenced the presence of additional aromatic compounds including one mellein derivative.

Compound 1 is commonly found in terrestrial fungi [2 – 3], and has also been isolated from marine-derived fungi [4]. It presented mild antifeedant activity towards Spodoptera littoralis (African Cotton Leafworm) [3] and mild antibacterial activity against standard Staphylococcus aureus methicillin-resistant strain [4].

Acknowledgements: CNPq, FAPESP and CAPES.

Keywords: endophytic fungus, alga, Asparagopsis taxiformis, isocoumarin, 5-hydroxymethylmellein

References:

[1] Rateb, M. E.; Ebel, R. (2011) Nat. Prod. Rep. 28: 290 – 344.

[2] Okuno, T. et al. (1986) Agric. Biol. Chem. 50: 997 – 1001.

[3] Kokubun, T. et al. (2003) Phytochemistry 62: 779 – 782.

[4] Rukachaisirikul, V. et al. (2009) Chem. Pharm. Bull. 57: 1409 – 1411.