Identification of phenolic secondary metabolites from Schotia brachypetala Sond. (Fabaceae) and demonstration of their antioxidant activities in Caenorhabditis elegans

Background: Schotia brachypetala Sond. (Fabaceae) is an endemic tree of Southern Africa whose phytochemistry and pharmacology were slightly studied.The present work aimed at profiling the major phenolics compounds present in the hydro-alcoholic extract from S. brachypetala leaves (SBE) using LC/HRESI/MS/MS and NMR and prove their antioxidant capabilities using novel methods. Methods: In vitro assays; DPPH, TEAC persulfate decolorizing kinetic and FRAP assays, and in vivo assays: Caenorhabditis elegans strains maintenance, Intracellular ROS in C. elegans, Survival assay, GFP expression and Subcellular DAF-16 localization were employed to evaluate the antioxidant activity. Results: More than forty polyphenols ,including flavonoid glycosides, galloylated flavonoid glycosides, isoflavones, dihydrochalcones, procyanidins, anthocyanins, hydroxybenzoic acid derivatives, hydrolysable tannins, and traces of methylated and acetylated flavonoid derivatives were identified. Three compounds were isolated and identified from the genus Schotia for the first time, namely gallic acid, myricetin-3-O-α-L- 1 C 4 -rhamnoside and quercetin-3-O-L- 1 C 4 -rhamnoside.The tested extract was able to protect the worms against juglone induced oxidative stress and attenuate the reactive oxygen species (ROS) accumulation. SBE was also able to attenuate the levels of heat shock protein (HSP) expression. Discussion: A pronounced antioxidant activity in vivo, which can be attributed to its ability to promote the nuclear translocation of DAF16/FOXO, the main transcription factor regulating the expression of stress response genes. The remarkable antioxidant activity in vitro and in vivo correlates to SBE rich phenolic profile.