In VitroEffect of Valepotriates Isolated fromValeriana glechomifoliaon Rat P-Type ATPases

Abstract

Valepotriates are iridoids found in variable amounts in Valerianaceae and might be among the bioactive compounds which confer anxiolytic properties to the Valeriana species. On the other hand, unspecific cytotoxicity has also been described. Presently, however, no particular molecular target has been defined for these compounds. Here we studied the effect of valtrate, acevaltrate, and 1- β-acevaltrate isolated from Valeriana glechomifolia on the enzymatic activity of rat P-type ATPases. Valepotriates did not affect rat skeletal muscle sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) activity at the highest concentration used (100 µM). In contrast, the same concentration inhibited roughly half of the total H⁺/K⁺-ATPase activity from rat gastric epithelium (valtrate 54.6 ± 3.2 %, acevaltrate 60.7 ± 7.3 %, 1- β-acevaltrate 50.2 ± 3.1 %; mean ± SEM, n = 3-5). Finally, these substances showed the highest inhibitory potency toward Na⁺/K⁺-ATPase, and the inhibition curves obtained provided a similar IC₅₀ (in µM) for rat kidney α1 isoform (valtrate 21.2, acevaltrate 22.8, 1- β-acevaltrate 24.4) and brain hemispheres α2/ α3 isoforms (valtrate 19.4, acevaltrate 42.3, 1- β-acevaltrate 38.3). Our results suggest that P-type ATPases are differentially inhibited by valepotriates and that Na⁺/K⁺-ATPase might be one of their molecular targets in vivo.

21-Benzylidene Digoxin: A Proapoptotic Cardenolide of Cancer Cells That Up-Regulates Na,K-ATPase and Epithelial Tight Junctions

“…The brain tissues, used as a source of ouabain-sensitive (α 2 /α 3 ) Na,K-ATPase isoforms, were homogenized in 250 mM buffered sucrose, 2 mM dithiothreitol, 0.1 mM PMSF and 5 mM Tris/HCl (pH 7.4) with a motor-driven Teflon Potter-Elvehjem homogenizer. Subsequently, chaotropic treatment with 2 M KI was performed for 1 h under constant stirring, followed by centrifugation three times at 100,000× g for 1 h. The final pellet was resuspended in 250 mM sucrose, 0.1% sodium deoxycholate and 20 mM maleate/Tris (pH 7.4), then stored overnight at −20°C and subjected to differential centrifugation after thawing [67] . The pellets were resuspended in the same buffer without PMSF and stored in liquid N 2 .…”

Effects of Diene Valepotriates from Valeriana glechomifolia on Na+/K+-ATPase Activity in the Cortex and Hippocampus of Mice

“…Additionally, Maurman and colleagues demonstrated that a valepotriate fraction from V. glechomifolia displays anxiolytic and sedative effects and impairs behavioral parameters related to recognition memory in rodents [13]. Moreover, we have shown that diene valepotriates isolated from V. glechomifolia (valtrate, acevaltrate, 1-β-acevaltrate, and 1-β-aceacevaltrate) inhibit Na + /K + -ATPase from the rat brain in vitro [17]. Na + /K + -ATPase is a membrane-bound enzyme made up of a catalytic α subunit and a regulatory β subunit [18].…”

“…Most important, this study further supports the hypothesis that the enzyme Na + /K + -ATPase may constitute one of the valepotri-atesʼ molecular targets. In a previous work, we have demonstrated that diene valepotriates (valtrate, acevaltrate, and 1-β-acevaltrate) isolated from V. glechomifolia presented inhibitory activity towards rat cerebral Na + /K + -ATPase in vitro [17]. Herein, we show for the first time that VAL increases the activity of Na + /K + -ATPase and protein expression of the α2 isoform in the cerebral cortex of mice after a repeated treatment.…”

Studies of the structure-antioxidant activity relationships and antioxidant activity mechanism of iridoid valepotriates and their degradation products

“…AV and BAV are isomers, even though their structures have been confused in the literature [ 7 , 30 ]. Thus, LC-MS, UV and NMR analyses were performed to confirm their chemical structures.…”