Valerian-derived sedative agents. I. On the structure and spectral assignment of the constituents of valmane using the selective INEPT nuclear magnetic resonance technique.

The valepotriates, a group of chemically unstable iridoid triesters possessing sedative activity, contain various ester groups at the C-1, C-7, and C-11 positions. Using the selective INEPT NMR technique and employing a suitable polarization delay for long-range coupling, it was possible to achieve the assignment and location of the ester groups directly, without ambiguity, and without chemical modification. Six valepotriates isolated from Valmane tablets served as examples to demonstrate the utility of this NMR technique. During the course of this work, the "acevaltrate" fraction was shown to be a mixture of 1-alpha-acevaltrate (3) and 7-beta-acevaltrate (4), the structures of valtrate (1) and didrovaltrate (2) were confirmed directly, and two new valepotriates, 5a and 5b, were obtained as an inseparable mixture and characterized.