Bio-guided fractionation of prenylated benzaldehyde derivatives as potent antimicrobial and antibiofilm from Ammi majus L. fruits-associated Aspergillus amstelodami

Ammi majus L. (Apiaceae) is an indigenous plant in Nile Delta regions of Egypt. Its fruits contain bioactive compounds (furanocoumarins and flavonoids) of important biological activities. This work aims to identify A. majus endophytes An endophytic fungus was isolated from the fruits and identified as Aspergillus amstelodami by morphological and microscopic characterization in addition to molecular identification using phylogenetic analysis. The ITS rRNA gene sequence was submitted at the GenBank under the accession number (MK215708). The antimicrobial activity of the 70% ethanol fruits extract and ethyl acetate extract of A. amstelodami were investigated where the fungal extract showed higher antimicrobial activity (using colorimetric broth micro-dilution method to determine MIC), against all the tested standard strains. Phytochemical investigation of the fungal ethyl acetate extract using VLC and preparative HPLC yielded five prenylated benzaldehyde derivative compounds, isolated for the first time from this species, and named: dihydroauroglaucin (1), tetrahydroauroglaucin (2), 2-(-3,6-dihydroxyhepta-1,4-dien-1-yl)-3,6-dihydroxy-5-(dimethylallyl) benzaldehyde (3), isotetrahydroauroglaucin (4) and flavoglaucin (5). Structure elucidation of the isolated compounds was carried out based on their spectral data analysis (¹H-, ¹³C-NMR and MS). Fractions as well as the major isolated compound were evaluated for their antimicrobial and antibiofilm activity. Compound 1 showed highest antimicrobial activity especially against Escherichia coli (MICs=1.95 µg/ml), Streptococcus mutans (MICs=1.95 µg/ml) and Staphylococcus aureus (MICs=3.9 µg/ml). It showed the highest anti-biofilm activity with MBIC=7.81 µg/ml against both Staphylococcus aureus and Escherichia coli biofilms, and moderate MBIC= 15.63 µg/ml against Streptococcus mutans and Candida albicans biofilms and MBIC= 31.25 µg/ml against Pseudomonas aeruginosa biofilm.