Antimicrobial potential and GC-MS fragmentation patterns of secondary metabolites of fungal extract from maize leaf

Abstract

Natural products have long been a vital source of human therapies, with a significant proportion of approved small-molecule medicines linked to natural chemicals. Fungal endophytes, in particular, have emerged as a promising source of novel bioactive compounds, producing a wide range of secondary metabolites with pharmacological significance. Studies report that the leaves of Zea mays contain high levels of secondary metabolites with significant antibacterial, antifungal and antioxidant effects. In contrast, endophytic fungi are still underexplored, particularly those in Zea mays leaves in Akatsi North, Ghana while ongoing research shows their great potential for discovery. In this study, the leaves of Zea mays found close to Akatsi North District Assembly, Ave-Dakpa were screened for their endophytic fungi in a malt-glucose culture media containing 3%(w/w) malt extract and 6%(w/w) glucose. The study aimed to isolate, characterize, and identify bioactive compounds from endophytic fungal extract of Zea mays leaves. Fungal isolation and culture were performed, and the resulting crude extract was analyzed using Thin-Layer Chromatography (TLC) and Gas Chromatography-Mass Spectrometry (GC-MS). The GC-MS analysis revealed the presence of twenty compounds, including tyrosol acetate, N-acetyl tyramine, diisooctyl phthalate, and 3,5-Di-tert-butyl-4-hydroxybenzaldehyde as the major compounds. The structural identification of these compounds was confirmed through the rationalization of their respective fragment ions. The crude extract was evaluated for antimicrobial and antioxidant properties against five pathogenic microorganisms such as Enterococcus faecalis (NCTC 13379), Streptococcus pyogenes (NCTC 12696), Klebsiella pneumoniae (NCTC 13348), Staphylococcus aureus (NCTC 12973), and Candida albicans (ATCC 90028). The extract demonstrated significant antimicrobial activity, with the broadest zone of inhibition (30 mm) recorded against S. aureus. The minimum inhibitory concentration (MIC) values ranged from 0.8 to 1.0 mg/mL. DDPH free radicals scavenging activities were also tested for with the crude extract. The result indicates that the extract has an antioxidant activity with an inhibition percentage of 26.94%. The findings from the study show that the crude extract has a high antibacterial effect against S. aureus indicating its potential as a source of novel bioactive compounds. To the best of my knowledge, this is the first report on the antimicrobial potential of endophytic fungal extracts from Zea mays leaves.