Vanicoside A is a protein kinase C(PKC) inhibitor from Polygonum pensylvanicum[1].
References
[1] Zimmermann ML, Sneden AT. Vanicosides A and B, protein kinase C inhibitors from Polygonum pensylvanicum. J Nat Prod. 1994 Feb;57(2):236-42. DOI:10.1021/np50104a007