Characterization and mechanisms of anti-influenza virus metabolites isolated from the Vietnamese medicinal plant Polygonum chinense.
BACKGROUND
Polygonum chinense Linn. is a common medicinal plant in Southeast Asia and has been used in traditional medicine in Vietnam. The plant contains phytochemicals with various biological properties; however, its antiviral effect has not yet been demonstrated. This study was aimed to evaluate the anti-influenza virus activity of crude extracts of P. chinense, to characterize antiviral metabolites therefrom and to investigate their mechanisms of antiviral action.


METHODS
The methanol (MeOH) extract and organic solvent layers of P. chinense were prepared by extraction and partition with relevant solvents. The ethyl acetate (EtOAc) layer showing antiviral activity was chromatographed repeatedly on SiO2and Sephadex LH-20 columns to give eight pure metabolites. Their chemical structures were determined by NMR and MS spectral data. Anti-influenza virus activity of the eight metabolites against virus strains A/Puerto Rico/8/34 (H1N1, PR8), A/Hong Kong/8/68 (H3N2, HK) and B/Lee/40 (Lee) was evaluated on the basis of cytopathic effect (CPE) and plaque inhibition assays. Time-of-addition, confocal microscopy and neuraminidase inhibition assay were performed for mode-of-action studies of active ingredients.


RESULTS
The MeOH extract of P. chinense showed anti-influenza virus activity with EC50values ranging from 38.4 to 55.5 μg/mL in a CPE inhibition assay. Among the eight pure metabolites isolated from P. chinense, ellagic acid (PC5), methyl gallate (PC7) and caffeic acid (PC8) significantly inhibited viral replication in a dose-dependent manner in both plaque inhibition and CPE inhibition assays with EC50values ranging from 14.7 to 81.1 μg/mL and CC50values higher than 300 μg/mL. Mode-of-action studies suggested that PC5 and PC7 suppress virus entry into or replication in cells, while PC8 targets influenza viral neuraminidase, even oseltamivir-resistant one.


CONCLUSIONS
These results demonstrated that P. chinense and its metabolites possess effective anti-influenza virus activities. The botanical materials of P. chinense could be a promising multitargeted inhibitor of influenza A and B viruses and applied to development of a novel herbal medicine.
R&D Center of Bioactive Compounds, Vietnam Institute of Industrial Chemistry, 2nd Pham Ngu Lao, Hoan Kiem, Hanoi, 10 000, Vietnam.
Thu Thi
TT
Tran
Center for Virus Research and Testing, Korea Research Institute of Chemical Technology, Gajeong-ro, Yuseong, Daejeon, 34114, Republic of Korea.
Meehyein
M
Kim
Center for Virus Research and Testing, Korea Research Institute of Chemical Technology, Gajeong-ro, Yuseong, Daejeon, 34114, Republic of Korea.
Yejin
Y
Jang
Center for Virus Research and Testing, Korea Research Institute of Chemical Technology, Gajeong-ro, Yuseong, Daejeon, 34114, Republic of Korea.
Hye Won
HW
Lee
R&D Center of Bioactive Compounds, Vietnam Institute of Industrial Chemistry, 2nd Pham Ngu Lao, Hoan Kiem, Hanoi, 10 000, Vietnam.|Department of Agricultural Chemistry, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, 77 Yongbong-Ro, Buk-Gu, Gwangju, 500-757, Republic of Korea.
Hoa Thi
HT
Nguyen
Department of Phytochemistry, Vietnam Institute of Industrial Chemistry, 2nd Pham Ngu Lao, Hoan Kiem, Hanoi, Vietnam.
Thanh Ngoc
TN
Nguyen
World Institute of Kimchi, an Annex of Korea Food Research Institute, Gwangju, 61755, Republic of Korea.
Hae Woong
HW
Park
R&D Center of Bioactive Compounds, Vietnam Institute of Industrial Chemistry, 2nd Pham Ngu Lao, Hoan Kiem, Hanoi, 10 000, Vietnam. ledangquang2011@gmail.com.
Quang
Q
Le Dang
Department of Agricultural Chemistry, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, 77 Yongbong-Ro, Buk-Gu, Gwangju, 500-757, Republic of Korea. kjinc@jnu.ac.kr.
Jin-Cheol
http://orcid.org/0000-0003-0753-1966
JC
Kim
D000998:Antiviral Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D002460:Cell Line; D006801:Humans; D007251:Influenza, Human / Q000821:virology*; D009975:Orthomyxoviridae / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D010936:Plant Extracts / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D010946:Plants, Medicinal / Q000737:chemistry; D028502:Polygonum / Q000737:chemistry*; D053586:Virus Internalization / Q000187:drug effects; D014779:Virus Replication / Q000187:drug effects
D000998:Antiviral Agents; D010936:Plant Extracts
Antiviral; Caffeic acid; Ellagic acid; Influenza virus; Methyl gallate; Polygonum chinense