Flavane Dimers From Psychotria calocarpa and Their Enzyme Inhibition Activities

ABSTRACT Eight dimeric flavanes were isolated from the plant Psychotria calocarpa (Rubiaceae), including four stereoisomeric flavan‐flavan‐3‐ol dimers ( 1–4 ) and four stereoisomeric flavan‐3‐ol‐flavan‐3‐ol dimers ( 5–8 ). Among them, compounds 1–3 are newly identified flavan‐(4→8)‐flavan‐3‐ol dimers, named psychodiflavanols A–C, respectively. Their structures were elucidated by a comprehensive spectroscopic analysis combined with the quantum chemical calculations of electronic circular dichroism spectra. Compounds 4–8 were determined to be known flavan– (4→8)‐flavan‐3‐ol dimer or flavan‐3‐ol‐(4→8)‐flavan‐3‐ol dimers based on comparison with literature data. All isolates were evaluated for their inhibitory activities against acetylcholinesterase, butyrylcholinesterase (BChE), α‐glucosidase, and α‐amylase. The results demonstrated that psychodiflavanol A ( 1 ) had potent and selective inhibition of BChE, with a half‐maximal inhibitory concentration (IC 50 ) value of 11.47 ± 2.12 µM. In addition, psychodiflavanol B showed a notable α‐glucosidase inhibitory effect with an IC 50 value of 10.15 ± 1.17 µM. These findings suggest that the flavane dimers from P. calocarpa might possess promising potential as lead compounds for developing therapeutic agents that target neurodegenerative and metabolic disorders.