Preliminary Spectroscopic and Chromatographic Characterization of a Steroid-Rich Fraction from Cola acuminata (Kolanut) Leaves

Abstract

Cola acuminata leaves contain a variety of phytochemicals, including steroid-related compounds that may contribute to their pharmacological properties. However, information on the composition and structural diversity of these compounds remains limited. This study aimed to characterise the steroid-rich fraction of Cola acuminata leaf extract using chromatographic and spectroscopic techniques. Dried leaves were extracted with ethanol using Soxhlet extraction and fractionated by column chromatography. The resulting steroid-rich fraction was analysed by thin-layer chromatography (TLC), UV-Visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and high-performance liquid chromatography (HPLC). TLC analysis resolved three distinct spots with Rf values of 0.14, 0.37, and 0.94, indicating the presence of multiple constituents. UV-Visible spectroscopy revealed absorption maxima at 260, 290, 400, 450, 470, 550, and 600 nm, suggesting the occurrence of conjugated chromophoric systems. FTIR spectra showed characteristic absorptions associated with hydroxyl, aliphatic C–H, carbonyl, and unsaturated functional groups, with prominent bands observed at 3393.17, 3001.97, 1623.31, and 1036.69 cm⁻¹. HPLC analysis resolved seventeen peaks with retention times ranging from 2.638 to 18.456 min and concentrations ranging from 2.598 to 9.837 µg/mL. Tentative assignments based on retention-time comparison suggested the presence of steroid-related compounds, including cortisol, prednisolone, progesterone, androstane, pregnane, and cholestane. The findings indicate that the steroid-rich fraction of Cola acuminata leaves is chemically diverse and contains multiple structurally distinct constituents. Further confirmation using authenticated reference standards and advanced techniques such as LC-MS/MS, GC-MS, or NMR spectroscopy is recommended to establish definitive compound identities.