title: Profiles and α-amylase inhibition activity of proanthocyanidins in unripe Manilkara zapota (chiku).
abstract: Proanthocyanidins in unripe  Manilkara zapota  (chiku) were isolated using solvent extraction followed by Sephadex LH-20 fractionation with a yield of 0.9%. HPLC analysis using a diol column revealed well-resolved oligomers ranging from dimer to hexamer. The majority of the proanthocyanidins are composed of higher-degree oligomers appearing as one large peak in the chromatogram. Analysis of the proanthocyanidins using LC/MS showed that (epi)gallocatechins were the dominant extension unit in the proanthocyanidins. In agreement with this result, thiolysis treatment of the proanthocyanidins using mercaptoacetic acid produced thioether derivatives of (epi)gallocatechins as the major product and (epi)gallocatechin gallate derivatives as the minor product. The mean of the degree of polymerization was estimated to be 9.0. From MALDI-TOF MS, B-type gallocatechin oligomers up to decamer could be detected. The unripe chiku proanthocyanidins are thus good starting material for preparation of (epi)gallocatechin derivatives. The proanthocyanidins was shown to inhibit α-amylase with an IC(50) value of 4.2 ± 0.2 μg/mL and inhibit α-glucosidase with an IC(50) of 16.6 ± 0.3 μg/mL.
authors.affiliation: Food Science and Technology Program, Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Republic of Singapore.
authors.forename: Hongyu
authors.initials: H
authors.lastname: Wang
authors.forename: Tingting
authors.initials: T
authors.lastname: Liu
authors.forename: Lixia
authors.initials: L
authors.lastname: Song
authors.forename: Dejian
authors.initials: D
authors.lastname: Huang
mesh_terms: D002392:Catechin / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005638:Fruit / Q000737:chemistry*; D065089:Glycoside Hydrolase Inhibitors; D032129:Manilkara / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D044945:Proanthocyanidins / Q000032:analysis* / Q000494:pharmacology*; D000516:alpha-Amylases / Q000037:antagonists & inhibitors*
chemical_list: D004791:Enzyme Inhibitors; D065089:Glycoside Hydrolase Inhibitors; D011108:Polymers; D044945:Proanthocyanidins; D002392:Catechin; D000516:alpha-Amylases; C057580:gallocatechol