Antiviral Activity of Flavones and Potentiation by Ascorbate

Abstract

SUMMARYWe compared the anti-poliovirus activities of three flavones, quercetin, luteolin and 3-methylquercetin, which differ only at ring position 3. 3-Methylquercetin was the most potent compound. Quercetin exhibited antiviral activity only when protected against oxidative degradation by ascorbate. The antiviral activity of luteolin was comparable to that of ascorbate-stabilized quercetin.Several 3-methoxy derivatives of quercetin (3,3',4',5,7-pentahydroxyflavone) extracted from various plants are known to exhibit antiviral activity. They are not virucidal, but interfere with the replication of several viruses, including poliovirus (Ishitsuka et al., 1982;Van Hoof et al., 1984;Castrillo et al., 1986;Vrijsen et al., 1987). An anti-poliovirus activity of quercetin itself, i.e. a direct virucidal effect as well as interference with plaque formation, has been shown recently (Kaul et al., 1985). However, these results are at variance with previous reports according to which quercetin was virucidal only to enveloped, but not to unenveloped viruses (B61adi et al., 1977;Veckenstedt & Pusztai, 1981).The discrepancies about the antiviral properties of quercetin may originate in the oxidative degradation of this flavone in aqueous solution (Nishinaga et aL, 1979;Rajananda & Brown, 1981). In this communication, the anti-poliovirus activity of quercetin was determined in the presence and absenceof the antioxidant ascorbate. Comparative experiments were also carried out with 3-methylquercetin and luteolin, which differ from quercetin only at ring position 3 (Fig. 1).The antiviral effect of quercetin, luteolin and 3-methylquercetin was tested by the plaque reduction assay (Fig. 2). Both luteolin (not previously reported to possess antiviral activity) and 3-methylquercetin were active; 40 ktM-luteolin or 10 ktu-3-methylquercetin reduced the plaque count by half. Quercetin was inactive, even at the highest concentration tested (100 p,M). However, in the presence of ascorbate it did cause plaque reduction and this enhancement of its activity reached saturation at an ascorbate concentration of 100 ~tM. D-and L-ascorbate were equivalent, whereas dehydroascorbate was inactive (Fig. 3). Ascorbate alone failed to show any antiviral activity.With maximum enhancement by ascorbate, 30 ~tM-quercetin caused 50 % plaque reduction; this figure is close to that previously noted for luteolin (Fig. 2b). The antiviral effect of luteolin OH HO~R~OH OH o 0000-8341 © 1988 SGM

Quercetin supplementation does not alter antioxidant status in humans

“…FRAP and ORAC as well as other antioxi- 12-Weeks strate little evidence of protection from oxidative stress, many studies indicate a decrease in disease risk and improved antioxidant capacity when foods rich in quercetin are consumed in the diet [54]. There is increasing support that co-ingestion of quercetin with other flavonoids and food components improve and extend quercetin's bioavailability and bioactive effects [10,57]. These inclue the flavonoid epigallocatechin 3-gallate (EGCG) from tea [58], iso-quercetin (quercetin-3-glucose or hirsutrin) which is the glycosylated form of quercetin in onions and other Placebo (N=217) Q-500 (N=216) Q-1000 (N=221) Figure 6.…”

“…Dietary flavonols such as quercetin have been reported to have physiological effects, i.e. antioxidative [4,5], anti-inflammatory [6][7][8], anti-pathogenic [9,10], anti-viral [11][12][13], anti-microbial [14], anti-carcinogenic [15], cardioprotective [16] and mitochondrial biogenesis [17] activities and thus provide significant potential in the study of improving human health.…”

The Chemical Analysis of Propolis, Which are Produced in Western of Turkey

“…Additionally it has been showed that aromatic acids and flavanoids have antiviral activity. [45][46][47][48][49]. We found in our study 70% as the highest amount of total aromatic acid esters and some of them …”

Free Radical Quenching and Immunomodulatory Effect of a Modified Siddha Preparation, Kalpaamruthaa

“…[34][35][36] For the reason that, ascorbate is reported to have flavonoid protective 37,38) and flavonoid-enhancing activities. 39,40) But, Ghosal et al (1996), 41) have reported that the potent vitamin C like activity of P. emblica is due to the presence of low molecular weight hydrolysable tannins (emblicanin-A and emblicanin-B). Hence, it can be postulated that the enhanced antioxidant effect of KA than SA alone might be attributed to the synergistic effect of flavonoids, vitamin C and tannins present in KA.…”