Meroterpenoids with unknown skeletons from the leaves of Psidium guajava including one anti-inflammatory and anticoagulant compound: psidial F.

Four unknown meroterpenoids named as psidials D-G (1-4) together with 5 known compounds (5-9) had been obtained from the leaves of Psidium guajava. Their absolute structures were elucidated by spectral and calculated methods. Psidials DF (1-3) represented unknown carbon skeleton of the 3,5-diformylbenzyl phloroglucinol-coupled sesquiterpenoid. The possible biosynthetic pathway for 1-3 was postulated. In the bioactivity assay, psidial F (3) was found to possess anti-inflammatory and anticoagulant activities.

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 C18 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 mc2 155, with minimum inhibitory concentrations (MICs) of 16, 8, and 0.5 µM, 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.