Methylated Flavonols from J.F.Gmel. and Their Antimicrobial and Antioxidant Activities.

Methylated flavonols form a special group with modulating biological activities in comparison with kaempferol and quercetin. The present study isolated ten compounds including two kaempferol methyl ethers: 5-hydroxy-3,7,4'-trimethoxyflavone (), 3-hydroxy-5,7,4'-trimethoxyflavone (); four quercetin methyl ethers: retusin (5-hydroxy-3,7,3',4'-tetramethoxyflavone) (), 3,5-dihydroxy-7,3',4'-trimethoxyflavone (), 3,4'-dihydroxy-5,7,3'-trimethoxyflavone (), and 3,5,7,3',4'-pentamethoxyflavone (); -sitosterol (); 5-hydroxy-1-(4'-hydroxyphenyl)eicosan-3-one (); -hydroquinone (); and vanillic acid () from the rhizomes and fruit of J.F.Gmel. (Zingiberaceae). Their structures were determined by MS, NMR, and X-ray spectroscopic techniques. Among the methylated flavonols, , -, and were isolated for the first time from the rhizomes, while , , and were isolated from the fruit. Compounds , , , , and were reported for the first time from the species. Three main methylated flavonols , , and were quantitatively analyzed in the rhizomes of by RP-HPLC-DAD; their contents were determined to be 1.81% (), 1.38% (), and 1.76% (). The antimicrobial assay against , , , , , , , and and antioxidant DPPH scavenging test were performed for the isolated methylated flavonols.