Comparative Study of the Secondary Metabolites of Sponge-derived Aspergillus flavus

Kamilia Tawfik,Eric Schmidt,Sherief Khalifa,Mostafa Mesbah,Diaa Youssef

doi:10.21608/rpbs.2017.9855

Abstract

The fungal sources of novel metabolites have broadened from saprophytic terrestrial strains to marine habitats and living plants with their endophytes. Specifically, metabolites isolated from species of genus Aspergillus have continually attracted the interest of pharmacologists due to their broad array of biological activities and their structural diversity. Bioassay guided fractionation of the extract of saline culture of marine-derived Aspergillus flavus led to the isolation of eight compounds; kojic acid (1), aflatoxin B1 (2), maculosin1(3), hexahydro-3-(4-hydroxybenzyl)pyrrolo[1,2-a]pyrazine-1,4-dione (4), cyclopiazonic acid (5), cyclopiazonic acid imine (6), aspergillic acid (7) and hydroxyaspergillic acid (8). Structure elucidation of the compounds was based on dereplication using NMR and MS data. A cultivation-based approach was employed to compare the secondary metabolites diversity associated with A. flavus in eight sea water culture media. The type of medium exhibited a significant difference in the yield and the chemistry of compounds responsible for biological activities of the corresponding extract.

Highlights

The quest to exploit factors leading to the production of diverse molecular structures from cultured microorganisms represents a continuing challenge for natural products research (Firn and Jones, 2003) Filter-feeding marine invertebrates, such as sponges, have been shown to host a variety of microorganisms that do not merely reflect the microbial communities present in the surrounding seawater but appear to constitute a more specialized association between sponge hosts and microbial associates (Friedrich et al, 1999)
Analysis of HPLC data using the proposed method with peak area measurement revealed that A. flavus synthesized higher concentration of compound 3 in Sabouraud dextrose broth (SDB) than it did with any other substrate tested
The production of compound 2 was three fold more in malt broth (MB) than in czapek’s dox yeast broth (CZYB) and M.CZYB4 while it is not produced in cultures of M.CZYB3 and yeast peptone dextrose broth (YPDB) (Table 2)

Summary

Introduction

The quest to exploit factors leading to the production of diverse molecular structures from cultured microorganisms represents a continuing challenge for natural products research (Firn and Jones, 2003) Filter-feeding marine invertebrates, such as sponges, have been shown to host a variety of microorganisms that do not merely reflect the microbial communities present in the surrounding seawater but appear to constitute a more specialized association between sponge hosts and microbial associates (Friedrich et al, 1999). Conservative estimate based upon thousands of assayed sponge species suggested that as many as 11% produce cytotoxic compounds (Garson, 1994). This percentage is high compared to other organisms and possibly may result from the intimate. The sponge derived A. flavus was chosen for chemical and biological investigation of its secondary metabolites in saline cultures. Eight saline culture media were prepared; czapek’s dox yeast broth (CZYB), four modified czapek’s dox yeast (M.CZYB), Sabouraud dextrose broth (SDB), malt broth (MB) and yeast peptone dextrose broth (YPDB) in order to find the optimal culture composition for A. flavus to produce its biologically active metabolites in respect to concentration and diversity

Methods

Results

Conclusion