GABAA Receptor-Mediated Sleep-Promoting Effect of Saaz-Saphir Hops Mixture Containing Xanthohumol and Humulone

Hops contain flavonoids that have sedative and sleep-promoting activities such as alpha-acid, beta-acid, and xanthohumol. In this study, the sleep-enhancing activity of a Saaz-Saphir hops mixture was measured. In the caffeine-induced insomnia model, the administration of a Saaz-Saphir mixture increased the sleep time compared to Saaz or Saphir administration alone, which was attributed to the increase in NREM sleep time by the delta-wave increase. Oral administration of the Saaz-Saphir mixture for 3 weeks increased the gamma-amino butyric acid (GABA) content in the brain and increased the expression of the GABA(A) receptor. As the GABA antagonists picrotoxin and bicuculline showed a decrease in sleep activity, it was confirmed that the GABA(A) receptor was involved in the Saaz-Saphir mixture activity. In addition, the GABA(A) receptor antagonist also reduced the sleep activity induced by xanthohumol and humulone contained in the Saaz-Saphir mixture. Therefore, xanthohumol and humulone contained in the Saaz-Saphir mixture showed sleep-promoting activity mediated by the GABA(A) receptors. The mixture of the Saaz and Saphir hop varieties may thus help mitigate sleep disturbances compared to other hop varieties.