Food and feed spoilage caused by food-borne fungi and their toxic metabolites can be controlled using synthetic antioxidants to inhibit the production of reactive oxygen species (ROS) that cause rancidity and oxidative damage. However, the use of synthetic antioxidants raises health concerns, leading researchers to seek natural alternatives. This study focused on a terrestrial fungal strain, Aspergillus sydowii 195, isolated, purified, and identified morphologically and genetically. The active constituents and fractions produced by A. sydowii 195 were studied, and the most active fraction underwent chemical structure identification. The suggested chemical structure was a spiroketal compound named Peniciketal A. This research investigated the biological activity of Peniciketal A, including its antioxidant, antifungal, killing kinetics, and minimum inhibitory concentration. The results demonstrate the potent antifungal activity of Peniciketal A against food-borne fungi, and this could make it a useful alternative to synthetic antioxidants. This is the first study to show the production of Peniciketal A from terrestrial A. sydowii 195.