Isolation and Structure Elucidation of Isovaltral, a Decomposition Product of Isovaltrate

Abstract

Decomposition products of the valepotriates are formed during the e1,ution process on columns using silica and alumina as stationary phase. Some of these decomposition products were identified as baldrinal and homobaldrinal and a new one, isovaltral, was found. the valepotriates were isolated by T H I E~ [ I 4 1 from some dried roots of Valeriana species and from Valeriana tinctures. The most important of these decomposition products are baldrinal and homobaldrinal, which are formed from valtratelacevaltrate respectively isovaltrate under the influence of acid andheat.

Three decomposition products of valepotriates fromValeriana jatamansiand their cytotoxic activity

“…As expected, a notable NOE correlation of H-1 and H-9 could be discerned in the NOESY spectrum of 1, S. Lin et al 2 in full support of this assignment. Since isovaltrate could successfully convert into isovaltral during the elution process under the influence of acid and heat [13], the stereochemistry of C-1, C-8, and C-9 still remained the 1S, 8R, 9S configuration. On the basis of these data and chemical transformation grounds, the structure of 1 was consequently established as shown.…”

“…The residue (630 g) was suspended in H 2 O (1500 ml) and then partitioned with EtOAc (5 £ 1000 ml). The EtOAc fraction (420 g) was chromatographed over silica gel, Sephadex LH-20, and preparative TLC to isolate (Table 1), the 1 H NMR, 13 C NMR and DEPT spectra of 1 in CDCl 3 showed the same iridoid nucleus resonances as isovaltral, a decomposition product of isovaltrate [13], exhibiting signals for an a,b- . These spectroscopic data revealed that 1 was the isovaltral analog but with one b-(acetoxy) isovaleroxy and acetoxy groups substituted at C-1 and/or C-8 and/or C-11.…”

“…Comparison of the NMR and HR-ESI-MS data of 3 and 2 indicated that the R-a-(isovaleroxy)isovaleroxy moiety of 2 was replaced by an isovaleroxy residue in 3 (Table 1). In addition, the isovaleroxy and acetoxy of 3 were determined to be placed at C-8 and C-11, respectively, by comparison of the 13 C NMR data of the ester carbonyl carbon in 1, 2 and isovaltral [13]. Thus, 3 was characterized as valtral C.…”

“…Some valepotriates, such as valtrate and acevaltrate, are very unstable and they could be easily decomposed during the isolation procedure [12]. The most important of these decomposition products are baldrinal, homobaldrinal, and isovaltral, which are formed from valtrate and acevaltrate, respectively, during the elution process on columns using silica gel and alumina as stationary phase [13]. Our ongoing effort to search for valepotriates from this medicinal plant has also resulted in the isolation of three new decomposition products of valepotriates, valtrals A -C (1 -3) (Figure 1), together with baldrinal and homobaldrinal during the elution process.…”

Mass spectrometry of iridoids

“…Isovaltral (76) is a degradation product of valtrate 58 (71). The molecular ion produces a low peak and undergoes loss of an isovaleroxy radical, than acetic acid and a hydrogen atom.…”