Methyl brevifolincarboxylate, a novel influenza virus PB2 inhibitor from Canarium Album (Lour.) Raeusch.

Methyl brevifolincarboxylate (MBC) was isolated from ethyl acetate extract of Canarium album (Lour.) Raeusch. The structure was identified, and the effect on influenza A virus infection was evaluated. MBC exhibited inhibitory activity against influenza virus A/Puerto Rico/8/34 (H1N1) and A/Aichi/2/68 (H3N2) with IC50 values of 27.16 ± 1.39 µM and 33.41 ± 2.34 µM. Mechanism studies indicated that MBC inhibited the replication of influenza A virus by targeting PB2 cap-binding domain. Our results demonstrated MBC was a potent PB2 cap-binding inhibitor and represented as a new type of promising lead compound for the development of anti-influenza virus drugs from natural products.

Isocorilagin, isolated from Canarium album (Lour.) Raeusch, as a potent neuraminidase inhibitor against influenza A virus.

Canarium album (Lour.) Raeusch (C. album) as a normally medicinal and edible plant has been used widely in Asian countries and is considered a source of phytochemicals that are beneficial to human health. Here, we showed at the first time isocorilagin, a polyphenolic compound isolated from C. album, displayed antiviral activity against diverse strains of influenza A virus (IAV), including A/Puerto Rico/8/34 (H1N1), A/Aichi/2/68 (H3N2) and NA-H274Y (H1N1) with IC50 value of 9.19 ±â€¯1.99, 23.72 ±â€¯2.51 and 4.64 ±â€¯3.01 µM, respectively. Further mechanistic studies revealed that it clearly inhibited neuraminidase activity of IAV and directly influenced the virus release. The molecular docking studies presented isocorilagin could bind to the highly conserved residues in the active sites of NA, implying that isocorilagin may be effective against various influenza strains and not susceptible to produce drug resistance. Taken together, the results strongly suggest that isocorilagin has potential to be an effective, safe and affordable neuraminidase inhibitor against a diverse panel of IAV strains. More importantly, our work expands the biological activities of C. album extracts and provide a new option for the development of anti-influenza drug.

Chemical constituents from Canarium album Raeusch and their anti-influenza A virus activities.

Two new dyhydrophaseic acid glucoside isomers, (1'S, 3'R, 5'S, 8'R, 2Z, 4E)-dihydrophaseic acid-3'-O-ß-D-glucopyranoside (2) and (1'R, 3'S, 5'R, 8'R, 2Z, 4E)-dihydrophaseic acid-3'-O-ß-D-glucopyranoside (4), together with 10 known compounds [myo-inositol (1), 3,4-dihydroxybenzoic acid (3), 3-O-galloyl quinic acid (5), ellagic acid (6), gallic acid (7), ethyl gallate (8), scopoletin (9), ellagic acid-4-O-ß-D-glucopyranoside (10), ellagic acid-4-O-α-L-rhamnopyranoside (11), and isocorilagin (12)] were isolated from the chloroform extract of Canarium album Raeusch fruits by repeated chromatography on macroporous adsorption resin, silica gel, Sephadex LH-20, Toyopearl HW-40F, and reverse-phase C18 columns, etc. Their structures and absolute configurations were determined by comprehensive analysis of 1D- and 2D-nuclear magnetic resonance (NMR), high-resolution electron spray ionization mass spectrometry (HR-ESI-MS), ESI-MS, optical rotation, circular dichroism spectra, and comparison of NMR data with data of known compounds. Bioassay of their anti-influenza virus A activities showed that compounds 9 and 12 displayed a significant inhibitory effect with IC50 values of 22.9 ± 3.7 and 5.42 ± 0.97 µg/ml, respectively.