Antibacterial and EGFR-Tyrosine Kinase Inhibitory Activities of Polyhydroxylated Xanthones from Garcinia succifolia

Chemical investigation of the methanol extract of the wood of Garcinia succifolia Kurz (Clusiaceae) led to the isolation of 1,5-dihydroxyxanthone (1), 1,7-dihydroxyxanthone (2), 1,3,7-trihydroxyxanthone (3), 1,5,6-trihydroxyxanthone (4), 1,6,7-trihydroxyxanthone (5), and 1,3,6,7-tetrahydroxyxanthone (6). All of the isolated xanthones were evaluated for their antibacterial activity against bacterial reference strains, two Gram-positive (Staphylococcus aureus ATTC 25923, Bacillus subtillis ATCC 6633) and two Gram-negative (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853), and environmental drug-resistant isolates (S. aureus B1, Enteroccoccus faecalis W1, and E. coli G1), as well as for their epidermal growth factor receptor (EGFR) of tyrosine kinase inhibitory activity. Only 1,5,6-trihydroxy-(4), 1,6,7-trihydroxy-(5), and 1,3,6,7-tetrahydroxyxanthones (6) exhibited antibacterial activity against Gram-positive bacteria, however none was active against vancomycin-resistant E. faecalis. Additionally, 1,7-dihydroxyxanthone (2) showed synergism with oxacillin, but not with ampicillin. On the other hand, only 1,5-dihydroxyxanthone (1) and 1,7-dihydroxyxanthone (2) were found to exhibit the EGFR-tyrosine kinase inhibitory activity, with IC50 values of 90.34 and 223 nM, respectively