Perilla (P. frutescens L.) is widely cultivated across East Asia, and its seeds are highly regarded for their nutritional and functional properties. Seed size reportedly affects seed germination and growth; however, current research comparing the bioactive compounds and physiological activities across different seed sizes remains limited. We investigated the effect of seed size on the chemical composition and the antioxidant and anti-inflammatory activities of Perilla frutescens L. seeds. Seeds were categorized into small (average 1.26 mm), medium (average 1.66mm), and large (average 2.18 mm) categories. Larger seeds showed a higher content of fats, with a total fatty acid content of 48.3% compared to 38.4% in smaller seeds. Notably, α-linolenic acid, a key omega-3 fatty acid, was present at 69.55% in large seeds, whereas small seeds contained 62.25%. Total phenolic content and antioxidant activities, assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, were significantly higher in larger seeds. The total phenolic content was 147.5 GAE μg/g for large seeds, 118.7 GAE μg/g for medium seeds, and 96.1 GAE μg/g for small seeds. For antioxidant activities, DPPH radical scavenging activity (IC50) was 79.5 μg/g in large seeds, 91.2 μg/g in medium seeds, and 121.8 μg/g in small seeds, while ABTS radical scavenging activity (IC50) was 54.3 μg/g in large seeds, 84.1 μg/g in medium seeds, and 105.8 μg/g in small seeds. Additionally, the anti-inflammatory activity, measured using the lipoxygenase (LOX) inhibitory assay, was also more pronounced in larger seeds, with LOX inhibition values of 28.2% for large seeds, 35.5% for medium seeds, and 43.7% for small seeds. These findings suggest that seed size significantly influences the nutritional and functional properties of Perilla frutescens seeds.
