Inhibitory effects of flavonoids on Moloney murine leukemia virus reverse transcriptase activity

Several flavonoids were tested for their effects on Moloney murine leukemia virus reverse transcriptase activity. Four groups of flavonoids, namely flavones, flavanones, flavonols, and flavanonols, were studied, and it was found that flavonols and flavanonols were very active in this regard while flavones and flavanones displayed very low activity. Among the flavonoids tested, fisetin, quercetin, myricetin, kaempferol, morin, (+/-)-taxifolin, (+)-catechin, and (-)-epicatechin were shown to be highly effective in inhibiting the reverse transcriptase activity. Structure-activity relationship analysis of these flavonoids revealed that the simultaneous presence of free hydroxyl groups at positions 3 and 4' enhanced the reverse transcriptase inhibitory activity. Replacement of the 3-hydroxyl group with a monosaccharide or of the 4'-hydroxyl group with a methyl group reduced inhibitory activity. The double bond at position 2 and 3 of the flavonoid's pyrone ring is not essential for inhibiting reverse transcriptase activity. The flavonoids studied demonstrated ability to inhibit the reverse transcriptase activity using either (rA)n(dT)12-18 or (rC)n(dG)12-18 as template-primers.