Bioassay-Guided Isolation of Guggulsterol I and Evaluation of Its Antioxidant Properties in Ethanol Extracts From Commiphora caudata Leaves

The secondary metabolites of various parts of <i>Commiphora caudata</i> have shown a range of biological activities under both in vivo and in vitro conditions, particularly anti-inflammatory and antioxidant properties. While E-guggulsterone from this plant has been proven to have anti-inflammatory effects, the antioxidant potential of phytochemicals present in the leaves of <i>C. caudata</i> is less explored. This investigation aimed to isolate an antioxidant phytoconstituent from the ethanolic extract of the dried leaves of <i>C. caudata</i> using a bioassay-guided approach. The dried leaves were successively extracted with organic solvents, including ethanol. The presence of phytochemicals was tested using high-performance thin-layer chromatography (HPTLC), and phytoconstituent from ethanol extract was purified by column chromatography. The antioxidant activity of both the crude extract and the purified compound was evaluated and then compared. The radical scavenging activity was measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The ethanolic extract of <i>C. caudata</i> showed 87.6% DPPH radical scavenging activity at a concentration of 250 µg/mL, while standard ascorbic acid showed 94.9% inhibition at the same concentration. The concentrated ethanolic extract of <i>C. caudata</i> was subjected to silica-based column chromatography with an ascending polarity of mobile phase solvents, ethyl acetate, and ethanol (25:75), yielding a single compound. The isolated compound was confirmed as guggulsterol I by ultraviolet (UV), infrared (IR), mass, and nuclear magnetic resonance (NMR) spectroscopy. The radical scavenging activity of the crude ethanolic extract of <i>C. caudata</i> leaves and the isolated compound guggulsterol I was concentration-dependent. The crude ethanolic extract of <i>C. caudata</i> showed significant antioxidant activity in comparison with the standard. However, the isolated guggulsterol I showed less antioxidant activity than the crude ethanolic extract. This study strongly suggests that the crude ethanolic extract of <i>C. caudata</i> leaves had better antioxidant activity due to the synergistic or additive effect of guggulsterol I and other phytoconstituents.