Anthraquinones from the ethyl acetate extract from the stem of Gnetum montanum Markgr

Abstract

Gnetum montanum, called “Dây gắm” in Vietnam, is a perennial plant belonging to the family Gnetaceae. Gnetum montanum is traditionally used in folk medicine to treat conditions such as rheumatism, chronic bronchitis, menstrual disorders, and as an antidote. Studies on the chemical composition of this species have revealed that it contains various valuable compounds, including flavonoids, stilbenoids, lignans and alkaloids. However, no research has been conducted on the presence of anthraquinone compounds in Gnetum montanum. Through applying column chromatography and thin-layer chromatography, six compounds were isolated. Their chemical structures were elucidated by analyzing nuclear magnetic resonance spectroscopy (1D and 2D-NMR) and comparison with reference data. These compounds were identified as chrysophanol (1), emodin (2), physcion (3), questin (4), aloe-emodin (5) and acetyl-aloe-emodin (6). All isolated compounds were reported for the first time in the genus Gnetum. The DPPH free radical scavenging, α-glucosidase inhibition, and xanthine oxidase inhibition assays were performed on all isolated compounds. The results of the α-glucosidase inhibition assay showed that all compounds exhibited activity at the tested concentration of 100 µM, with compounds 2, 3, 5, and 6 have the α-glucosidase inhibitory activity with IC₅₀ values of  73.6, 97.1, 72.2, and 73.5 µM, respectively, that is more potent than acarbose (IC₅₀ = 190.6 µM). The results of the DPPH free radical scavenging assay showed that 3 out of 6 compounds exhibited activity at the tested concentration of 100 µM, while compounds 1, 2, and 3 did not show DPPH free radical scavenging activity at this concentration. All six compounds exhibited relatively weak xanthine oxidase inhibitory activity at the tested concentration of 100 µM. The findings of this study provide the national database on the phytochemical profile of medicinal plants in Vietnam, especially Gnetum montanum.