Merulinic acid C enhances gentamycin antibiotic activity

In a collaborative article with the group of Dr. Andréa Dessen (Bacterial Pathogenesis Group, Institut de Biologie Structurale, Grenoble, France) and researchers from the CNPEM (Campinas, Brazil) Phytobios (São Paulo, Brazil), UNIFESP (Brazil), UFSCar (Brazil) and UNICAMP (Brazil), we described earlier this year the antibiotic activity of merulinic acid C and other anacardic acids, isolated from the mushroom Aurantiopileus mayanensis (Ginns, D.L. Lindner & T.J. Baroni, 2011, Meruliaceae).

Aurantiopileus mayanensis. T. J. Baroni 10228. Basidiomata, in situ. (Ginns, J., Lindner, D.L., Baronia, T.J., & Ryvarden, L. Aurantiopileus mayanensis a new genus and species of polypore (Polyporales, Basidiomycota) from Belize with connections to existing Asian species. North American Fungi, 2010, 5, 1-10).

Merulinic acid C is an anacardic acid, a well-known class of natural products, first isolated from the cashew nut, Anacardium occidentale. Merulinic acid C was isolated along with several additional anacardic acid derivatives from the mushroom. These compounds have double bonds in different positions of a side chain. It was thus necessary to unambiguously establish the position of the unsaturations. A procedure was developed using derivatization with dimethyl disulfide (DMDS), followed by GC–MS analysis. This information was confronted with UPLC-qTOF-MS/MS analysis of the same compounds. In this way, we developed a fragmentation method to establish the position of double bonds in unsaturated chains with no need of derivatization. This method was established by Juliano Slivinski, Vitor Freire, Ariane Bertonha and Laura Ióca at the QOSBio group, São Carlos, SP, Brazil.

Merulinic acid C was identified as the most active anacardic acid derivative obtained against antibiotic-resistant enterococci, among a series of additional anacardic acids, also isolated by researchers at LNBio, CNPEM, from A. occidentale. Fluorescence microscopy analyses showed that merulinic acid C targets the bacterial membrane without affecting the peptidoglycan and causes rapid cellular ATP leakage from cells. Merulinic acid C was shown to act synergistically with gentamicin against Enterococcus faecium. Read here the article “Merulinic acid C overcomes gentamicin resistance in Enterococcus faecium“.