Anti-inflammatory Acylphloroglucinol Derivatives from Hops (Humulus lupulus)

The polyphenol-enriched fraction of an ethanolic hops extract (Humulus lupulus) was separated to provide four acylphloroglucinol-glucopyranosides (1-4). 1-(2-Methylpropanoyl)phloroglucinol-glucopyranoside 1 has been isolated from hops before, whereas 1-(2-methylbutyryl)phloroglucinol-glucopyranoside 2, known as multifidol glucoside, and 1-(3-methylbutyryl)phloroglucinol-glucopyranoside 3 were found in hops for the first time. 5-(2-Methylpropanoyl)phloroglucinol-glucopyranoside 4 was identified as a new natural product. The compounds were tested for inhibition of COX-1 activity. The aglycon 5, obtained by acid hydrolysis of 1, was equally effective as phloroglucinol, with an IC(50) of 3.8 microM. The inhibitory potential of the glucosides was 1>2>3 and decreased with increasing length of the acyl side chain. Compound 4 was about 2.5-fold less active than 1 (IC(50): 23.7 and 58.7 microM, respectively).