Abstract
For screening the active phloroglucinols on influenza virus (H5N1) from Dryopteris crassirhizoma NaKai, a database was established including twenty-three phloroglucinols that had been isolated from Dryopteris crassirhizoma. Their inhibitory effect on the neuraminidase (NA) of influenza virus H5N1 was screened by molecular docking. As a result, three candidates were selected. The rhizomes of D. crassirhizoma were subjected to isolation and purification processes to obtain the inhibitor candidates. Thirteen phloroglucinols were obtained, including three selected candidates and two new phloroglucinols. The five phloroglucinols were investigated for their inhibitory activity on NA in vitro. The results showed that dryocrassin ABBA and filixic acid ABA exhibited inhibitory effects on NA with IC50 as 18.59 ± 4.53 and 29.57 ± 2.48 μM, respectively, and the other three phloroglucinols showed moderate inhibitory activity. Moreover, the anti-influenza virus (H5N1) activity and cytotoxicity of dryocrassin ABBA and filixic acid ABA were tested on Madin-Darby canine kidney (MDCK) cells with the cell counting kit-8 (CCK8) method. The results confirmed that dryocrassin ABBA exhibited an inhibitory activity with low cytotoxicity (TC50 > 400 μM) against influenza virus (H5N1) which will have to be investigated in further detail. In conclusion, phloroglucinols from D. crassirhizoma were shown to have anti-influenza virus activity, and especially dryocrassin ABBA, one of the phloroglucinols, may have the potential to control influenza virus (H5N1) infection.
Highlights
Pathogenic avian influenza virus (HPAIV), subtype H5N1, is of great concern for infecting and causing an inordinate amount of lethal disease in humans that could evolve into a pandemic risk [1]
Our pilot study suggested that the extract fraction of this plant that was rich in phloroglucinols could reduce mortality and decrease lung index of mice inoculated with avian influenza virus (H5N1)
Dryocrassin ABBA was isolated from this fraction, which could protect mice infected with avian influenza virus via inhibiting inflammation and reducing viral loads [19]
Summary
Pathogenic avian influenza virus (HPAIV), subtype H5N1, is of great concern for infecting and causing an inordinate amount of lethal disease in humans that could evolve into a pandemic risk [1]. Many studies demonstrated that phloroglucinols from DC had a wide range of pharmacological effects, such as antibacterial [12], anti-influenza virus [13], anti-tumor promoting [14,15], anti-reverse transcriptase [16], and antioxidant activities [17]. Our pilot study suggested that the extract fraction of this plant that was rich in phloroglucinols could reduce mortality and decrease lung index (dry lung-to-body weight ratio) of mice inoculated with avian influenza virus (H5N1). Dryocrassin ABBA was isolated from this fraction, which could protect mice infected with avian influenza virus via inhibiting inflammation and reducing viral loads [19]. Virtual screening with molecular docking, isolation, structural characterization, and the activity on neuraminidase (NA) and influenza virus in vitro are described
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