Erythroside: A New Cerebroside and Other Compounds From <i>Erythrina Caffra</i> Thunb. (Fabaceae) Stem Bark, With Cytotoxicity and Antioxidant Evaluation

Abstract

The chemical investigation of a CH₂Cl₂:MeOH (1:1) extract of the stem bark of Erythrina caffra resulted in the isolation and characterisation of the novel cerebroside, erythroside (1), alongside eight other known compounds (2-9). The isolated compounds were characterized by FT-IR, 1D and 2D NMR spectroscopy, and ESI-MS analysis. Of the eight known compounds, 2, 3, 5, and 7 are isolated for the first time from the genus Erythrina. The crude extract, its fractions, and selected isolated compounds were evaluated for cytotoxicity against three normal cell lines, human keratinocytes (HaCaT), human melanocytes (NHEM-Ad), and Human Embryonic Kidney 293 (HEK293), using the resazurin/Alamar blue and crystal violet assays. Antioxidant potential was also assessed through both the oxygen radical absorbance capacity (ORAC) and the Trolox equivalent antioxidant capacity (TEAC) assays. Most compounds showed no cytotoxic effects on these cell lines. The antioxidant assay revealed that compound 1 had a moderate antioxidant effect in the ABTS assay (0.50 µmol TE/mg) and good antioxidant capacity in the ORAC assay (0.87 µmol TE/mg). In contrast, almost all these compounds and extracts have shown moderate to good antioxidant effects in the ORAC assay. The results offer valuable insights into the chemical constituents of Erythrina caffra stem bark, their effects on HaCaT, NHEM-Ad, and HEK 293 cells, as well as their antioxidant potential. Future research could focus on identifying additional bioactive compounds within the ethyl acetate fraction that may be responsible for the observed toxicity.