Isolation and identification of antioxidant and α-glucosidase inhibitory compounds from fruit juice of Nitraria tangutorum

Abstract

Nitraria tangutorum Bor., having edible berries, is valued for reputed health benefits in Qinghai-Tibet plateau. The phytochemical research on the fruit juice of N. tangutorum led to the isolation of twenty-six compounds including five new compounds, tangutorids A-D (1, 2, 3a, and 3b), and (3E,5E)-7-O-β-glucosyl-4-(2-methoxy-2-oxoethyl)hepta-3,5-dienoic acid (15). The structures of these compounds were elucidated through comprehensive spectroscopic analyses. Tangutorids A-F were the first examples of glucose-derived β-carbolines from natural products. The biogenetic pathways of 1-8 were proposed to involve Pictet-Spengler reactions and described starting from the co-isolated tryptophan (10) and corresponding aldehydes. All isolates were evaluated for their antioxidant and α-glucosidase inhibitory activities. Compounds 21, 22, and 24 showed antioxidant activity with SC₅₀ values ranging from 12.2±1.9 to 30.4±2.7μg/mL, and compound 1 showed strong α-glucosidase inhibitory effect with IC₅₀ value of 63.3±4.6μg/mL.

Keywords: 1,1-Diphenyl-2-picrylhydrazyl radical (PubChem CID: 2735032); 2,2′-Azino-di(3-ethyl-benzthiazoline sulphonic acid (PubChem CID: 9570474); 4-Nitrophenyl α-d-glucopyranoside (PubChem CID: 92930); Acarbose (PubChem CID: 444254); Antioxidants; Ascorbic acid (PubChem CID: 54670067); Glucose-derived β-carbolines; Nitraria tangutorum; α-Glucosidase inhibitory.