Modes of Antiviral Action of Chemical Portions and Constituents from Woad Root Extract against Influenza Virus A FM1

Abstract

Woad root has been used for the prevention of influenza for hundreds of years in many Asian countries. In this study, the antiviral modes of clemastanin B (CB), epigoitrin, phenylpropanoid portion (PEP), and the mixture of phenylpropanoids, alkaloids, and organic acid portions (PEP + ALK + OA) from wood root extract against influenza virus A FM1 were investigated. The results revealed that CB, epigoitrin, PEP, and PEP + ALK + OA exert their anti-influenza activity via inhibiting the virus multiplication, prophylaxis, and blocking the virus attachment. The primary mode of action of PEP and PEP + ALK + OA is the inhibition of virus replication. The inhibitory effect on virus attachment and multiplication is the main modes for epigoitrin. All the compounds or chemical portions from woad root extract tested in this study do not have direct virucidal activity. Our results provided the comprehensive analysis of the antiviral mechanism of wood root extract.

Figure 1

Chemical structure of clemastanin B (CB) and epigoitrin.

Figure 2

Effect of different dilutions of pure compounds and chemical portions from woad root on the viability of MDCK cells preinfected with 100 TCID₅₀ of influenza A H1N1 virus: (a) microscopic analysis; (b) MTT assay; (c) cell protection rate (%). CB: clemastanin B; PEP + ALK + OA: the mixtures of phenylpropanoids, alkaloids, and organic acid portions. Cell control: normal MDCK cells without virus infection and drugs treatment; virus control: cells infected with the virus without drug treatments. Ribavirin (1 : 4): error bars represent standard deviation. The asterisks indicate a significant difference between the test samples and the virus control according to Student's t-test.

Figure 3

Direct virucidal effect of pure compounds and chemical portions from woad root extract on influenza A1 virus FM1: (a) cell control; (b) virus control; (c) CB (1 : 2); (d) epigoitrin; (e) PEP (1 : 2); (f) PEP + ALK + OA (1 : 2); (g) ribavirin (1 : 4).

Figure 4

Differences on the major modes of antiviral action in the pure compounds and chemical portions from woad root extract. A1: therapeutic action; A2: prophylaxis; A3: inhibition of virus attachment. CB: clemastanin B; PEP + ALK + OA: the mixtures of phenylpropanoids, alkaloids, and organic acid portions. The concentration for CB: A1 (1 : 4 dilution), A2 (1 : 8 dilution), and A3 (1 : 2 dilution); epigoitrin concentration: A1 (1 : 4), A2 (1 : 16), and A3 (1 : 2); PEP + ALK + OA concentration: A1 (1 : 4), A2 (1 : 2), and A3 (1 : 4); PEP concentration: A1 (1 : 8), A2 (1 : 2), and A3 (1 : 2).