Chemical constituents of Psidium guajava leaves and their antibacterial activity

Seven undescribed compounds, namely (+)-psiflavanone A, (-)-psiflavanone A, (+)-psiflavanone B, (-)-psiflavanone B, (+)-psiketide, (-)-psiketide, and psidinone, were isolated and chirally separated from the 95%ethanol extract of Psidium guajava leaves. (+)/(-)-Psiflavanone A and (+)/(-)-psiflavanone B are two pairs of rare enantiomeric C-benzoylated flavanones isolated from the title plant for the first time. (+)/(-)-Psiketide are a pair of enantiomeric aromatic polyketides, and psidinone is the first example of a C-18 phenanthrenediquinone with an angle-type 6/6/6 tricyclic skeleton. Their structures were identified by extensive analysis of HRESIMS, UV, IR, NMR, and calculated electronic circular dichroism (ECD) data. Particularly, the structures of (+)-psiflavanone A, (-)-psiflavanone A, (+)-psiflavanone B, and psidinone were further confirmed by X-ray diffraction. Psidinone exhibited antibacterial activity against Staphylococcus aureus, Staphylococcus epidermidis, and Mycobacterium Smegmatis mc(2) 155, with minimum inhibitory concentrations (MICs) of 16, 8, and 0.5 mu M, respectively. These results not only highlight the chemical diversity and biological activity of P. guajava but are also expected to pave way for its further expansion to other applications in future.

Automated summary

Seven previously undescribed compounds were isolated and chirally separated from Psidium guajava leaves, showcasing diverse chemical structures and antibacterial activity. The discovery paves the way for potential future applications of P. guajava.