Open Access

ARTICLE

Chemical Constituents from Turnip and Their Effects on α-Glucosidase

by Swastika Paul, Xuemei Zhang, Yongping Yang, Changan Geng

1 State Key Laboratory of Phytochemistry and Plant Resources in West China, Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
2 Key Laboratory of Biodiversity and Biogeography, Institute of Tibetan Plateau Research at Kunming, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
3 University of Chinese Academy of Sciences, Beijing, 100049, China

* Corresponding Author: Changan Geng. Email:

Phyton-International Journal of Experimental Botany 2020, 89(1), 131-136. https://doi.org/10.32604/phyton.2020.08328

Received 14 August 2019; Accepted 12 October 2019; Issue published 01 March 2020

Abstract

Brassica rapa var. rapa (turnip) is an important crop in Qinghai-Tibet Plateau (QTP) with anti-hypoxic effect. Turnip is rich in glucosinolates, isothiocyanates and phenolic compounds with diverse biological activities, involving anti-oxidant, anti-tumor, anti-diabetic, anti-inflammatory, anti-microbial, hypolipidemic, cardioprotective, hepatoprotective, nephroprotective and analgesic properties. In this study, the ethyl acetate (EtOAc) and butanol parts of Brassica rapa were first revealed with inhibitory effects on α-glucosidase, whereas the water part was inactive. Subsequent bioassay-guided isolation on the EtOAc and butanol parts yielded 12 compounds, involving three indole derivatives, indole-3- acetonitrile (1) 4-methoxyindole-3-acetonitrile (2) and indole-3-aldehyde (3) two flavonoids, liquiritin (4) and licochalcone A (5) two phenylpropanoids, sinapic acid (6) and caffeic acid (7) two phenylethanol glycosides, 2-phenylethyl β- glucopyranoside (8) and salidroside (9) and three other compounds, syringic acid (10) adenosine (11) and (3β, 20E)-ergosta-5, 20 (22)-dien-3-ol (12) Licochalcone A (5) and caffeic acid (7) showed α-glucosidase inhibitory activity with IC₅₀ values of 62.4 ± 8.0 μM and 162.6 ± 3.2 μM, comparable to the positive control, acarbose (IC₅₀ = 142 ± 0.02 μM). Docking study suggested that licochalcone A (5) could well align in the active site of α-glucosidase (docking score = -52.88) by forming hydrogen bonds (Gln1372, Asp1420, Gln1372, Arg1510), hydrophobic effects (Tyr1251, Tyr1251, Trp1355, Phe1560, Ile1587, Trp1355, Phe1559, Phe1559) and π-π stacking interaction (Trp1355). This study provides valuable information for turnip as a new resource in searching anti-diabetic candidates.

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