New Antioxidant Caffeate Esters of Fatty Alcohols Identified in Robinia pseudoacacia

• Published in: Molecules (Basel, Switzerland) Switzerland), 2024-11, Vol.29 (23), p.5673
• Main Authors: Móricz, Ágnes M, Baglyas, Márton, Darcsi, András, Balla, József, Morlock, Gertrud E
• Format: Article
• Language: English
• Subjects: Acids; Allelopathy; antioxidant assay; Antioxidants; Antioxidants - chemistry; Antioxidants - pharmacology; bioassay-guided isolation; Biphenyl Compounds - antagonists & inhibitors; Biphenyl Compounds - chemistry; black locust (Robinia pseudoacacia L.); Caffeic Acids - chemistry; Caffeic Acids - isolation & purification; Chemical properties; Chromatography; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Esters - chemistry; Flavonoids; Free radicals; Gas Chromatography-Mass Spectrometry; heated electrospray high-resolution mass spectrometry (HESI-HRMS); High performance liquid chromatography; high-performance thin-layer chromatography—effect-directed analysis (HPTLC–EDA); Infrared spectroscopy; Magnetic Resonance Spectroscopy; Mass spectrometry; Molecular Structure; Natural products; NMR; Nuclear magnetic resonance; Organic compounds; phenolic esters of fatty alcohols; Plant Bark - chemistry; Plant Extracts - chemistry; Plant Extracts - pharmacology; Reagents; Robinia - chemistry; Scientific imaging; Spectroscopy, Fourier Transform Infrared
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules29235673

The stem bark of black locust ( L.) was extracted, and nine antioxidant compounds ( - ) were detected by high-performance thin-layer chromatography combined with the radical scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assay, multi-detection, and heated electrospray high-resolution mass spectrometry. For structure elucidation, the methanolic crude extract was fractionated by solid-phase extraction, and the compounds were isolated by reversed-phase high-performance liquid chromatography with diode array detection. The structures of isolated compounds were elucidated by nuclear magnetic resonance and attenuated total reflectance Fourier-transform infrared spectroscopy as well as gas chromatography-mass spectrometry to determine the double bond position. 3- -Caffeoyl oleanolic acid ( ), oleyl ( ), octadecyl ( ), gadoleyl ( ), eicosanyl ( ), ( )-9-docosenyl ( ), docosyl ( ), tetracosyl ( ), and hexacosanyl ( ) caffeates were identified. While has been reported in stem bark, the known , , , , and are described for the first time in this species, and the , , and are new natural compounds. All nine caffeates demonstrated antioxidant activity. The antioxidant effects of the isolated compounds - were quantified by a microplate DPPH• assay, with values ranging from 0.29 to 1.20 mol of caffeic acid equivalents per mole of isolate.