Abstract: This paper presents for the first time the results of studying the total content of antioxidants in the seeds of Morus L. The composition of fatty and steric acids of the seeds of mulberry fruits Morus L. was also studied: polymorphic species Morus alba (white-fruited, pink-fruited, black-fruited) and Morus nigra (Khartut variety). As a result of the studies, 12 fatty acids were identified. The main ones were linoleic acid, palmitic oleic acid, and stearic acid. The predominant fatty acid in all samples was linoleic, which varied from 67.5 to 79.0%. 15 sterols were found, among which β-Sitosterol accounts for about 90%. Determination of the total antioxidant content of Morus alba seeds (white-fruited, pink-fruited, black-fruited forms) and Morus nigra (Khartut variety) revealed the accumulation of antioxidants in all samples. The highest total content of antioxidants was observed in Morus nigra (4.40 mg/g) and the white-fruited form of Morus alba (5.56 mg/g). © Pleiades Publishing, Inc. 2024. ISSN 1062-3590, Biology Bulletin, 2024, Vol. 51, No. 1, pp. 221–227. Pleiades Publishing, Inc., 2024.