Comparison of Bioactive and Antibacterial Properties of Cell-Free Filtrate and Mycelial Extract of Endophytic Aspergillus oryzae Isolated from Tribulus terrestris

Abstract

Endophytic fungi are an underexploited bioactive secondary metabolite with significant pharmaceutical and agrochemical activities. This study is intended to (1) isolate and molecularly identify endophytic fungi from Tribulus terrestris, a medicinal plant traditionally used in Iraqi folk medicine; and (2) conduct a rigorous comparative study of the bioactive properties and Antibacterial efficacy of the cell-free filtrate (CFF) compared to the Mycelial Extract (ME) of the isolated Aspergillus oryzae. Aspergillus oryzae has been selected because of its detailed chemical description using GC-MS analysis, quantitative phytochemical screening, HPLC-based glucan/chitin quantification, and disk diffusion antibacterial assay against 4 clinically relevant pathogens. The results consistently demonstrate that the mycelial infusion contains a significantly higher concentration of bioactive components compared to the control. Specifically, the infusion exhibited elevated levels of phenolic resin (98.5 mg GAE/g versus 24.6 mg GAE/g), flavonoids (21.0 mg RE/g vs. 6.2 mg RE/g), alkaloids (5.0 mg/g vs. 0.41 mg/g), terpenoids (0.45 mg/g vs. 0.18 mg/g), glycosides (0.97 mg/g vs. 0.23 mg/g), β-glucan (254.6 ppm vs. 6.25 ppm), and chitin (62.5 ppm vs. 4.1 ppm). Furthermore, the infusion demonstrated a significantly enhanced antibacterial activity against the tested pathogens compared to the control. GC-MS analysis of the duo preparation and mycelial infusion showed a simpler, more concentrated fatty acid and alcohol profile. Kojic acid was tentatively detected in the CFF, whereas 7-hexadecyn-1-ol, palmitic acid, and fatty acid methyl esters were prominent in the ME. The ME produced larger inhibition zones than CFF against all four tested bacteria, with Streptococcus pyogenes showing greatest susceptibility.