α‑Amylase Inhibitory Activity from Nut Seed Skin Polyphenols. 1. Purification and Characterization of Almond Seed Skin Polyphenols

• Published in: Journal of agricultural and food chemistry 2013-05, Vol.61 (19), p.4570-4576
• Main Authors: Tsujita, Takahiro, Shintani, Tomoyoshi, Sato, Hiroaki
• Format: Article
• Language: English
• Subjects: Absorption; almonds; alpha-amylase; Amino Acids; Animals; Area Under Curve; Biflavonoids - chemistry; Biflavonoids - pharmacology; Biological and medical sciences; blood glucose; Blood Glucose - analysis; Carbohydrates - antagonists & inhibitors; Carbohydrates - pharmacokinetics; catechin; Catechin - analogs & derivatives; Catechin - chemistry; Catechin - pharmacology; Chromium; corn starch; Dextrans - chemistry; Enzyme Inhibitors - chemistry; Enzyme Inhibitors - pharmacology; epicatechin; epigallocatechin; Food industries; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; Inhibitory Concentration 50; Male; Nicotinic Acids; Nuts - chemistry; oral administration; Pancreatic alpha-Amylases - antagonists & inhibitors; Pancreatic alpha-Amylases - metabolism; Plant Extracts - chemistry; Plant Extracts - pharmacology; polymers; Polyphenols - chemistry; Polyphenols - pharmacology; Proanthocyanidins - chemistry; Proanthocyanidins - pharmacology; procyanidins; Prunus - chemistry; Prunus dulcis; Rats; Seeds - chemistry; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; swine; tannins; Tannins - chemistry; Tannins - pharmacology; ultrafiltration
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf400691q

Using α-amylase inhibition as a separation guide, polyphenolic compounds from almond (Prunus dulcis) seed skin were purified using ultrafiltration and Sephadex LH-20 and ODS columns. The purified fraction specifically and strongly inhibited α-amylase; the IC50 value was 2.2 μg/mL for pig pancreatic α-amylase. The fraction contained about 62% of the total polyphenols, 33.8% flavanol-type tannins and 30% procyanidins. Oral administration of the polyphenol fraction to rats fed corn starch significantly suppressed an increase in blood glucose levels and area under the curve (AUC), in a dose-dependent manner. High-resolution MALDI-TOF mass spectra showed that the structure of this sample is a series of polyflavan-3-ol polymers composed of catechin/epicatechin units and gallocatechin/epigallocatechin units up to 11-mer with several interflavanoid ether linkages. The results suggest almond seed skin contains highly polymerized polyphenols with strong α-amylase inhibitory activity, which retard absorption of carbohydrate.