Two-dimensional NMR analysis of Angiopteris evecta rhizome and improved extraction method for angiopteroside

Abstract

Introduction: The rhizome of Angiopteris evecta is of academic interest in Kalimantan, Indonesia, from an ethnobotanical perspective. Angiopteroside is a substance of pharmaceutical importance that is found in the rhizome of A. evecta. Objective: The aims of this research are to improve the extraction method for angiopteroside from the rhizome, compared to that in a previous report, and to determine the yield of angiopteroside from the rhizome of A. evecta, as well as to obtain precise data for extractives from the rhizome of A. evecta by using two-dimensional NMR spectroscopy and liquid chromatography–mass spectrometry (LC–MS). Methodology: We investigated the chemical constituents of the whole rhizome by means of two-dimensional NMR (heteronuclear single quantum coherence or HSQC) spectroscopy, neutral sugar analysis using the alditol acetate method, and lignin analysis using alkaline nitrobenzene oxidation and Klason lignin methods. LC–MS revealed the purity of the angiopteroside. Antimicrobial assays were also performed for the purified angiopteroside by using a broth microdilution method. Results: Angiopteroside was isolated by Soxhlet extraction with aqueous acetone followed by preparative thin-layer chromatography (eluent: 20% methanol/dichloromethane). LC–MS revealed that angiopteroside can be found in the rhizome of A. evecta in 9.9% yield, which is an extremely high yield for a plant extractive. Conclusion: HSQC analysis is a powerful tool for surveying compounds in plant materials, such as the whole rhizome of A. evecta. Soxhlet extraction with aqueous acetone is an effective method for extracting glycosides from plant materials.