The Inhibition Activities of the Fruit Extract of Plinia cauliflora against Melanoma Cells and the Single-Stranded DNA-Binding Protein (SSB) from Klebsiella pneumoniae

Plinia cauliflora has been associated with numerous ethnobotanical applications. In this study, we uncovered that the fruit extract of P. cauliflora, obtained using 50% ethanol, possesses inhibition activity against the Klebsiella pneumoniae single-stranded DNA-binding protein (KpSSB). SSB plays a critical role in cell survival, making it an attractive target for the development of anti-infective drugs. The inhibition activity against KpSSB by the P. cauliflora extract demonstrated an IC₅₀ value of 73 ± 8 μg/mL. By using gas chromatography–mass spectrometry, the chemical content of this extract was tentatively determined. The top 15 compounds (>0.7%) were as follows: 5-hydroxymethylfurfural, 2,3-dihydro-3,5-dihydroxy-6-methyl-4h-pyran-4-one, 2,5-diformylfuran, furfural, ace-tic acid, citraconic anhydride, formic acid, ethyl 4-hydroxy-3-methylbut-2-enoate, furfuryl alcohol, furyl hydroxymethyl ketone, 3-acetyl-3-hydroxyoxolane-2-one, 2,3-dihydro-5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one, 2(3H)-furanone, dihy-dro-4-hydroxy-, hydroxyacetone, and 1-hydroxybut-3-en-2-one. To analyze the possible binding modes, the three most abundant compounds were then subjected to docking analysis. We also investigated whether the P. cauliflora extract exhibited any cytotoxic and antiproliferative effects on the survival of B16F10 melanoma cells. Additionally, we found that the extract of P. cauliflora could inhibit the migration and induce apoptosis of B16F10 cells. The results of this study collectively suggest that P. cauliflora holds potential pharmacological benefits, warranting further exploration for therapeutic applications.