Complex phloroglucinols from glandular hairs of Mallotus philippensis and their antiviral activities.

Fourteen previously unknown phloroglucinol derivatives (1-14) and six known analogues (15-20) were extracted from Mallotus philippensis fruit glandular hairs. X-ray diffraction, NMR, ECD, OR calculations, and comprehensive spectroscopic analysis were adopted to determine their structures. Notably, compounds 1-4 represent unprecedented skeletal architectures, wherein 1 and 2 are chalcone-phloroglucinol-monoterpene adducts, 3 is a chalcone-flavonoid hybrid, and 4 is a chalcone-phloroglucinol adduct. All isolates were tested for antiviral activity against RSV and HSV-1 by determining their capability of repressing virus-induced cytopathic effect. Compound 10 stands out as the lead candidate exhibiting high potency and selectivity against both viral targets (IC50 = 3.10 μM, SI > 32.3 for RSV; IC50 = 3.19 μM, SI > 31.3 for HSV-1). Moreover, cellular imaging experiments suggested that compound 10 acts as a potent inhibitor of RSV replication.