BackgroundInfluenza is historically an ancient disease that causes annual epidemics and, at irregular intervals, pandemics. At present, the first-line drugs (oseltamivir and zanamivir) don’t seem to be optimistic due to the spontaneously arising and spreading of oseltamivir resistance among influenza virus. Pogostemon cablin (Blanco) Benth. (P. cablin) is an important traditional Chinese medicine herb that has been widely used for treatment on common cold, nausea and fever. In our previous study, we have identified an extract derived from P. cablin as a novel selective neuraminidase (NA) inhibitor.ResultsA series of polyphenolic compounds were isolated from P. cablin for their potential ability to inhibit neuraminidase of influenza A virus. Two new octaketides (1, 2), together with other twenty compounds were isolated from P. cablin. These compounds showed better inhibitory activity against NA. The significant potent compounds of this series were compounds 2 (IC50 = 3.87 ± 0.19 μ mol/ml), 11, 12, 14, 15, 19 and 20 (IC50 was in 2.12 to 3.87 μ mol/ml), which were about fourfold to doubled less potent than zanamivir and could be used to design novel influenza NA inhibitors, especially compound 2, that exhibit increased activity based on these compounds. With the help of molecular docking, we had a preliminary understanding of the mechanism of the two new compounds (1–2)’ NA inhibitory activity.ConclusionsFractions 6 and polyphenolic compounds isolated from fractions 6 showed higher NA inhibition than that of the initial plant exacts. The findings of this study indicate that polyphenolic compounds and fractions 6 derived from P. cablin are potential NA inhibitors. This work is one of the evidence that P. cablin has better inhibitory activity against influenza, which not only enriches the compound library of P. cablin, but also facilitates further development and promises its therapeutic potential for the rising challenge of influenza diseases.Electronic supplementary materialThe online version of this article (doi:10.1186/s13065-016-0192-x) contains supplementary material, which is available to authorized users.
The UV spectra were measured on a Shimadzu UV-2600 spectrometer (Shimadzu, Japan). The NMR spectra were obtained on Bruker AV-400/500 (Bruker, Karlsruhe, Germany) spectrometers with TMS as an internal standard. And the chemical shifts were recorded as δ values. Mass spectra were run on a 6540 UHD Accurate-Mass Q-TOF (Agilent, California, USA). Macro-porous adsorption resin D101 and polyamide (100-200 mesh) was provided by China National Medicine Corporation Ltd, Shanghai, China. Sephadex LH-20 was purchased from GE healthcare, Uppsala, Sweden. The chromatographic silica gel (200-300 meshes) was purchased from Qingdao Marine Chemical Factory. RP-HPLC analysis was conducted in an Agilent 1100 instrument using Kromasil 5 μm C 18 column (250*4.6 mm). Peak detection was made using a diode array detector (DAD). All solvents for extraction and chromatography were commercially purchased and routinely distilled prior to use. Aspirin was purchased from Sigma Aldrich (purity >99%). Purity was assessed by HPLC, NMR as >98%.
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