Structurally diverse phenylpropanoyl phloroglucinol derivatives from Mallotus philippensis and their anti-bacterial activities

Fifteen undescribed phenylpropanoyl phloroglucinol derivatives featuring modified isoprenyl and/or geranyl units (1-15), in conjunction with thirteen known analogues (16-28), were obtained from the glandular hairs of the fruit of Mallotus philippensis. Meanwhile, fourteen pairs of new enantiomers [(±)-1-9, (±)-11-15] were further resolved by chiral purification. Their structures were determined by comprehensive spectroscopic analyses, single-crystal X-ray diffraction experiments and quantum chemical calculations. Bioactivity evaluation showed that compound 17 exhibited significant anti-bacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) with MIC of 6 μg/mL, while compounds 3, 4, 8 and 18 displayed moderate effects with MIC of 24, 12, 24, and 12 μg/mL, respectively. The KEGG enrichment analysis of 17 revealed that the phosphotransferase system (PTS) pathway was significantly enriched. In addition, compound 17 was found to affect the amino acids biosynthesis and amino acids/carbohydrate metabolism, and the qRT-PCR verified the accuracy of the transcriptome analysis.