Identification and in vitro biological activities of hop proanthocyanidins: inhibition of nNOS activity and scavenging of reactive nitrogen species.
Oligomeric proanthocyanidins constitute a group of water-soluble polyphenolic tannins that are present in the female inflorescences (up to 5% dry wt) of the hop plant (Humulus lupulus). Humans are exposed to hop proanthocyanidins through consumption of beer. Proanthocyanidins from hops were characterized for their chemical structure and their in vitro biological activities. Chemically, they consist mainly of oligomeric catechins ranging from dimers to octamers, with minor amounts of catechin oligomers containing one or two gallocatechin units. The chemical structures of four procyanidin dimers (B1, B2, B3, and B4) and one trimer, epicatechin-(4beta-->8)-catechin-(4alpha-->8)-catechin (TR), were elucidated using mass spectrometry, NMR spectroscopy, and chemical degradation. When tested as a mixture, the hop oligomeric proanthocyanidins (PC) were found to be potent inhibitors of neuronal nitric oxide synthase (nNOS) activity. Among the oligomers tested, procyanidin B2 was most inhibitory against nNOS activity. Procyanidin B3, catechin, and epicatechin were noninhibitory against nNOS activity. PC and the individual oligomers were all strong inhibitors of 3-morpholinosydnonimine (SIN-1)-induced oxidation of LDL, with procyanidin B3 showing the highest antioxidant activity at 0.1 microg/mL. The catechin trimer (TR) exhibited antioxidant activity more than 1 order of magnitude greater than that of alpha-tocopherol or ascorbic acid on a molar basis.
Stevens
Jan F
JF
Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331, USA.
Miranda
Cristobal L
CL
Wolthers
Kirsten R
KR
Schimerlik
Michael
M
Deinzer
Max L
ML
Buhler
Donald R
DR
D000872:Anthocyanins / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D044946:Biflavonoids; D002392:Catechin; D019281:Dimerization; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016166:Free Radical Scavengers; D027582:Humulus / Q000737:chemistry*; D015227:Lipid Peroxidation / Q000187:drug effects; D008077:Lipoproteins, LDL / Q000737:chemistry; D015394:Molecular Structure; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009569:Nitric Oxide / Q000737:chemistry*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D052248:Nitric Oxide Synthase Type I; D044945:Proanthocyanidins; D021241:Spectrometry, Mass, Electrospray Ionization; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis
D000872:Anthocyanins; D000975:Antioxidants; D044946:Biflavonoids; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D008077:Lipoproteins, LDL; D044945:Proanthocyanidins; D017392:Thiobarbituric Acid Reactive Substances; C013221:proanthocyanidin; C479580:procyanidin B2; C479581:procyanidin B3; D009569:Nitric Oxide; C002385:linsidomine; D002392:Catechin; D008981:Molsidomine; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I