New cyclic peptides with osteoblastic proliferative activity from Dianthus superbus.

Two new cyclic peptides, dianthins G-H (1 and 2), together with the known dianthin E (3), were isolated from the traditional Chinese medicinal plant Dianthus superbus. The sequences of cyclic peptides 1 and 2 were elucidated as cyclo (-Gly(1)-Pro(2)-Leu(3)-Thr(4)-Leu(5)-Phe(6)-) and cyclo (-Gly(1)-Pro(2)-Val(3)-Thr(4)-Ile(5)-Phe(6)-), on the basis of ESI tandem mass fragmentation analysis, extensive 2D NMR methods and X-ray diffraction. The isolated three compounds all increase proliferation of MC3T3-E1 cells in vitro using MTT method.