Hydroxy-methyl-methoxyflavone

EGTA, ethyleneglycol bis(2-aminoethyl ether)-A/,A/,W, W -tetraacetic acid DTNB, 5,5 -dithiobis-(2-nitrobenzoic acid) MTB, Methyl-thymol Blue PT, pyridoxal thiosemicarbazone DGT, dipyridylglyoxal dithiocarbazone HMF, 3-hydroxy-7-methoxyflavone TCSP, 5,10,15,20-tetrakis-(3-chloro-4-sulfophenyl)porphine BSD, relative standard deviation PAR 4- 2 -pyridylazo)resorcinol DCTA, 1,2-diaminocyclohexane-N,N,N, N tetraacetic acid. 

The antimicrobial polymethylated flavones, 5-hydroxy-3,6,7,8,4 -pentamethoxyflavone, 5-hydroxy-3,6,7,8-tetramethoxyflavone and 5,6-dihydroxy-3,7-dimethoxyflavone, have been isolated from Gnaphalium affine D Don. [229,230], These flavonoids showed antimicrobial activity against Spodoptera litura. Structure-activity studies suggested the importance of the 6-position substitution of the flavonoid however, hydrophilic substituents decreased the activity. The flavonoid 8-0-(2-methyl-2-butenoyl)-5,7-dihydroxy-3-methoxyflavone isolated from Gnaphalium robustum L. also inhibited the growth of Escherichia coli [231]. 

Pisutthanan et al. (27) isolated six flavonoids out of which three were reported in this plant for the first time. They include 3,5,4 -trihydroxy-7-methoxyflavanone 5,7,3 -trihydroxy-5 -methoxyflavanone and 3,5,7-trihydroxy-4 -methoxyflavanone. Ling et al. (28) also isolated a total of eleven flavonoids from the leaf extract and identified them as eriodictyol 7,4 -dimethyl ether, quercetin 7,4 -dimethyl ether, naringenin 4 -methyl ether, kaempferol 4 -methyl ether, kaempferol 3-0-mtinoside, taxifolin 4 -methyl ether, taxifolin 7-methyl ether and quercetin 4 -methyl ether. Suksamram et al. (23) isolated the flavanones, isosakuranetin (5,7-dihydroxy-4 -methoxyflavanone), persicogenin (5,3 -dihydroxy-7,4 -dimethoxyflavanone), 5,6,7,4 -tetramethoxyflavanone and 4 -hydroxy-5,6,7-trimethoxyflavanone, the chalcones, 2 -hydroxy-4,4, 5, 6 -tetramethoxychalcone and 4,2 -dihydroxy-4, 5, 6 -trimethoxychalcone, and the flavones, acacetin (5,7-dihydroxy-4 -methoxyflavone) and luteolin (5,7,3, 4 -tetrahydroxyflavone) from the flowers. 

Obtained by alkaline degradation of quercetin 3,7,3, 4 -tetra-methyl ether (m.p. 159-160°) CH30 OH (5-hydroxy-3,7,3, 4 -tetra-methoxyflavone)... 

Butyryloxy-3,5-dihydroxy-7-methoxyflavone (8-Hydroxy-galangin 8-butyrate 7-methyl ether) (172) 119, 142 144... 

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