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Publication date: 4 October 2019

Kholowd AlKhaldi, Manal Daghestani and Thanaa Al-Haddad

The purpose of this paper is to evaluate the inhibition activity of Tribulus terrestris L. (T. terrestris) fruits extracts with solvents of increasing polarity against…

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Abstract

Purpose

The purpose of this paper is to evaluate the inhibition activity of Tribulus terrestris L. (T. terrestris) fruits extracts with solvents of increasing polarity against α-glucosidase and α-amylase, and to determine the inhibition mode of the most effective extract against both enzymes.

Design/methodology/approach

Hexane, acetone, ethanol and aqueous extracts of T. terrestris fruits were prepared using ultrasonic sequential extraction and analyzed for their α-amylase and α-glucosidase inhibitory activities by specific assay for each enzyme. The modes of inhibitions were detected using Lineweaver–Burk plots.

Findings

T. terrestris fruits extracts showed inhibition activity against α-glucosidase and α-amylase which was in the dose-dependent manner. Hexane extract had the highest α-glucosidase inhibition activity (IC50 = 27.28 μg/ml, p =0.003), followed by acetone and ethanol extracts (IC50 = 60.58 μg/ml and IC50 = 84.21 μg/ml, respectively). The inhibition mode of hexane extract was noncompetitive. While acetone extract showed the highest inhibition activity against α-amylase (IC50 = 6.18 mg/ml, p =0.002), hexane and ethanol extracts showed no significant difference (IC50 = 13.04 mg/ml and IC50 = 14.20 mg/ml, respectively, p =0.09). The inhibition mode of acetone extract was competitive.

Originality/value

T. terrestris fruits extracts had strong inhibition activity against α-glucosidase and α-amylase, and they can be used as a promising anti-diabetic agent.

Details

Nutrition & Food Science , vol. 50 no. 4
Type: Research Article
ISSN: 0034-6659

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Article
Publication date: 2 September 2014

Maysoon AlHafez, Fadi Kheder and Malak AlJoubbeh

The purpose of this paper was to determine total polyphenols (TP), total flavonoids (TF) and (-)-epigallocatechin gallate (EGCG) in five commercial tea extracts and in their…

399

Abstract

Purpose

The purpose of this paper was to determine total polyphenols (TP), total flavonoids (TF) and (-)-epigallocatechin gallate (EGCG) in five commercial tea extracts and in their infusions at various temperatures (95-60°C) and brewing times (5-30 min).

Design/methodology/approach

TP was determined by the Folin–Ciocalteu method, TF by the aluminium chloride colorimetric method and EGCG by HPLC method.

Findings

The results showed that White tea – Silver needle had the highest content of TP and EGCG when extracted, but its infusions had very poor concentrations of these compounds. Green tea infusion was better source of TP and EGCG than white or black tea, although its extract did not contain a very high amount of TP compared to the latter two types. Black tea extract had a relatively high content of TP and TF in its extract. Its infusions as well contained higher concentrations of TP than white tea, but lower concentrations of EGCG than all studied teas.

Originality/value

Increasing infusion time and temperature does not necessarily increase the concentration, according to the results. To the authors’ knowledge, this is the first report on comparing these types of tea, especially the white tea, with other well-known teas under various infusion conditions. The extraction of the white tea leaves was also not found in previous works.

Details

Nutrition & Food Science, vol. 44 no. 5
Type: Research Article
ISSN: 0034-6659

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