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Antioxidant, α-glucosidase inhibitory activities, and HPLC quantitative analysis of phenolic compounds isolated from Neptunia oleracea Lour.


Citation

Lee, Soo Yee and Ismail, Intan Safinar and Ang, Eng Loo and Abas, Faridah (2019) Antioxidant, α-glucosidase inhibitory activities, and HPLC quantitative analysis of phenolic compounds isolated from Neptunia oleracea Lour. International Food Research Journal, 26 (2). pp. 679-688. ISSN 1985-4668; ESSN: 2231-7546

Abstract

Neptunia oleracea Lour. is a tropical plant cultivated in Southeast Asia. It is consumed as vegetable and traditional herb for the treatment of several disorders. The objective of the present work was to isolate the phenolic compounds from N. oleracea, followed by their bioactivity evaluation and quantitative analysis. The ethyl acetate (EtOAc) and methanol (MeOH) fractions of N. oleracea were subjected to various chromatographic techniques to isolate the phenolic compounds. The isolated phenolic compounds were characterised by several spectroscopic methods, including mass spectrometry (MS) and nuclear magnetic resonance (NMR). Then, these compounds were subjected to DPPH free radical scavenging as α-glucosidase inhibitory assays for the evaluation of their activities. Their contents in the fractions were analysed via high performance liquid chromatography (HPLC) quantitative analysis. Five phenolic compounds including quercetin-3-O-β-D-xylopyranoside (1), quercetin-3-O-α-L-arabinopyranoside (2), quercetin-3-O-α-L-rhamnoside (3), methylgallate (4) and rutin (5) were isolated from N. oleracea for the first time. Evaluation on the DPPH free radical scavenging and α-glucosidase inhibitory activities of these compounds showed that methylgallate (4) was the most potent antioxidant and α-glucosidase inhibitors among them, with IC50 values of 17.25 and 50.76 μM, respectively. The HPLC quantitative analysis revealed the high content of the quercetin derivatives (compounds 1, 2 and 3) in the EtOAc fraction (ranging from 125.68 to 157.55 μg/mg) and methylgallate (4) in the MeOH fraction (75.25 μg/mg). Comparison of the bioactivities of the isolated phenolic compounds with the fractions indicated their significant contribution for the DPPH free radical scavenging of N. oleracea; while they might be working synergistically for the α-glucosidase inhibitory activity. The results of the present work could help to validate the contribution of phenolic compounds for the studied bioactivities of N. oleracea.


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Additional Metadata

Item Type: Article
Divisions: Faculty of Food Science and Technology
Faculty of Science
Institute of Bioscience
Publisher: Faculty of Food Science and Technology, Universiti Putra Malaysia
Keywords: Neptunia oleracea; Phenolic; DPPH free radical scavenging; α-glucosidase inhibition; HPLC quantification
Depositing User: Nabilah Mustapa
Date Deposited: 11 Jun 2019 01:42
Last Modified: 11 Jun 2019 01:42
URI: http://psasir.upm.edu.my/id/eprint/68876
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