Five new phloroglucinol derivatives were isolated from Syzygium brachyantherum, and their structures were elucidated as brachyanones A-E (1-5) on the basis of the extensive spectroscopic analysis. Among them, compounds 1 and 3 exhibited significant inhibitory activity against α-glucosidase with IC50 of 2.57 and 0.97 μM, respectively. Furthermore, compound 4 showed protein tyrosine phosphatase 1B (PTP1B) inhibitory effect with inhibition ratio of 89.42% at 100 μM. This discovery indicates that phloroglucinol derivatives with long aliphatic chain possibly play an important role in antidiabetic activity of Syzygium plants, and they could function as a promising antidiabetic agent.
Keywords: PTP1B; Syzygium brachyantherum; antidiabetic agent; phloroglucinol derivatives; α-glucosidase.