Characteristics of proanthocyanidins in leaves of Chamaecyparis obtusa var. formosana as strong α‐glucosidase inhibitors

• Published in: Journal of the science of food and agriculture 2018-08, Vol.98 (10), p.3806-3814
• Main Authors: Hsu, Chia‐Yun, Lin, Gong‐Min, Lin, Huan‐You, Chang, Shang‐Tzen
• Format: Article
• Language: English
• Subjects: alpha-Glucosidases - chemistry; alpha-Glucosidases - metabolism; antihyperglycemia; Butanol; Chamaecyparis - chemistry; Chamaecyparis obtusa; Degree of polymerization; Dimers; Epicatechin; Glucosidase; Glycoside Hydrolase Inhibitors - chemistry; Glycoside Hydrolase Inhibitors - isolation & purification; Humans; Hyperglycemia; Inhibition; Inhibitors; LC/MS/MS analysis; Leaves; Natural products; Organic chemistry; Plant Extracts - chemistry; Plant Extracts - isolation & purification; Plant Leaves - chemistry; Polymerization; Proanthocyanidins; Proanthocyanidins - chemistry; Proanthocyanidins - isolation & purification; thiolysis; α-Glucosidase; α‐glucosidase‐inhibitory activity
• ISSN: 0022-5142; 1097-0010
• DOI: 10.1002/jsfa.8894

BACKGROUND In recent decades, there has been a growing demand for natural products with a view to using them as α‐glucosidase inhibitors for reducing postprandial hyperglycemia. In this study, the hot water extract (HWE) from Chamaecyparis obtusa var. formosana (Hayata) Rehder (Cupressaceae) leaves and its soluble fractions were screened for α‐glucosidase inhibition properties. The n‐butanol‐soluble fraction of HWE was further fractionated into 14 subfractions (B1–B14) using a Sephadex LH‐20 column. The α‐glucosidase‐inhibitory activities and proanthocyanidin contents of all subfractions were determined. The structural characteristics of proanthocyanidins in proanthocyanidin‐rich fractions were also elucidated. RESULTS HWE produced a dose‐dependent inhibition of α‐glucosidase at low dose. Its IC50 value was 1.4 µg mL−1, showing high inhibitory activity. Subfractions B7–B14 displayed powerful α‐glucosidase‐inhibitory activities with IC50 values ranging between 1 and 0.015 µg mL−1 and contained abundant proanthocyanidins exceeding 300 mg g−1. The proanthocyanidins with higher mean degree of polymerization (mDP), higher proportions of procyanidin dimer (A1 or A2) and (epi)afzelechin of extension units and a lower proportion of epicatechin of terminal units displayed high α‐glucosidase‐inhibitory activities. CONCLUSION Proanthocyanidins in HWE were viewed as potential natural α‐glucosidase inhibitors for decreasing postprandial hyperglycemia. The results indicated that specific structural characteristics of proanthocyanidins would be required for α‐glucosidase‐inhibitory activity. © 2018 Society of Chemical Industry