Elucidation of flavonoids from potent Iranian Scutellaria species against Influenza A (H1N1) virus

Influenza A virus (IAV) is a contagious illness. Different species of Scutellaria genus are used as a traditional remedy to reduce influenza symptoms. This study aimed to investigate the anti-influenza capacity of several species of Iranian Scutellaria and identify active compounds of the most potent species for the first time.

Some Iranian species of Scutellaria were collected from different regions of Iran, including S. pinnatifida with mucida, viridis, and alpina subspecies; S. tournefortii; S. tomentosa; S. persica. They were fractionated to chloroform and methanol. The total phenols and flavonoids of samples were examined by the folin-ciocalteau and aluminum-flavonoid complex methods, respectively. The 50% cytotoxic concentrations (CC50) on MDCK cells and non-cytotoxic concentrations (NCTC) were determined by MTT assay. The percentage of cell protection against IAV and their effect on virus titer were investigated in pre-, post-, and co-penetration treatment groups. Phytochemicals of the most effective species were isolated by various chromatographic methods and identified by different spectroscopic methods.

Methanol fraction of S. pinnatifida subsp. viridis demonstrated the highest amounts of flavonoid content and best activity against influenza A virus in all combination treatments, which reduced the virus titer by 5 logs with no cytotoxicity. Kaempferol-3-O-glucoside, quercetin-3-O-glucoside, apigenin-4′-methoxy-7-O-glucoside, luteolin, and luteolin-7-O-glucoside were purified and identified from this species.

Scutellaria pinnatifida subsp. viridis can be introduced as a source of flavonoids with acceptable anti-influenza activity. S. tomentosa also showed potent antiviral effects and is a candidate for elucidation in further studies.