GC–MS Phytochemical Characterization and Comparative Antidiabetic Activities of Methanolic Extracts of Calotropis gigantea Leaves, Stem Bark, and Roots in Streptozotocin-Induced Diabetic Rats - Mercy iliya Tumba; Isaac John Umaru; Chinedu Imo (African Journal of Sciences and Traditional Medicine, 2026)