Isolation and characterization of fatty acid esters from Cyperus marginatus Thunb. leaf, their in vitro biological and in silico molecular docking studies

Context: Fatty acid esters (FAEs) are a unique class of secondary metabolites with promising antioxidant and anti-inflammatory properties, making them useful ingredients for cosmetic formulations. So far, many plants in the Cyperus genus (family Cyperaceae) are known to contain FAEs, among other classes of phytochemicals. However, Cyperus marginatus (CM) is one of the under-investigated species in this genus. Aims: To evaluate CM for its antioxidant (AOX) and anti-inflammatory FAEs. Methods: Two FAEs were isolated from CM leaf dichloromethane extract by silica gel column chromatography, while compound characterization was based on organic spectroscopy (NMR and MS). The antioxidant evaluation was by in vitro inhibitory effects against the 2,2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO), and ferric ion (Fe3+) radicals, while anti-inflammatory activity was based on the egg albumin denaturation (EAD) assay. The FAEs were molecularly docked against NADPH oxidase 2 (NOX2) and nuclear factor (NF-κB). Results: The isolated FAEs were elucidated as ethyl margarate, and a newly described FAE, nonadecanoic acid-2-ethoxy ethyl ester. Ethyl margarate demonstrated better AOX properties, with lower inhibition against DPPH (IC50 = 43.82 ± 1.44 µg/mL), NO (60.04 ± 3.28 µg/mL), and Fe3+ (308.01 ± 34.11 µgAAE/mg) radicals. It also demonstrated a better anti-inflammatory response with an IC50 of 12.24 ± 0.69 µg/mL against EAD, which was comparable to diclofenac (IC50 = 11.94 ± 1.37 µg/mL). Molecular docking studies revealed the significant binding affinities of ethyl margarate to NOX2 and NF-κB at -7.2 and -6.1 kcal/mol, respectively. Conclusions: Ethyl margarate isolated from C. marginatus has been shown through this study to be a promising antioxidant and anti-inflammatory FAE.