Functional Identification of Valerena-1,10-diene Synthase, a Terpene Synthase Catalyzing a Unique Chemical Cascade in the Biosynthesis of Biologically Active Sesquiterpenes in Valeriana officinalis

Valerian is an herbal preparation from the roots of Valeriana officinalis used as an anxiolytic and sedative and in the treatment of insomnia. The biological activities of valerian are attributed to valerenic acid and its putative biosynthetic precursor valerenadiene, sesquiterpenes, found in V. officinalis roots. These sesquiterpenes retain an isobutenyl side chain whose origin has been long recognized as enigmatic because a chemical rationalization for their biosynthesis has not been obvious. Using recently developed metabolomic and transcriptomic resources, we identified seven V. officinalis terpene synthase genes (VoTPSs), two that were functionally characterized as monoterpene synthases and three that preferred farnesyl diphosphate, the substrate for sesquiterpene synthases. The reaction products for two of the sesquiterpene synthases exhibiting root-specific expression were characterized by a combination of GC-MS and NMR in comparison to the terpenes accumulating in planta. VoTPS7 encodes for a synthase that biosynthesizes predominately germacrene C, whereas VoTPS1 catalyzes the conversion of farnesyl diphosphate to valerena-1,10-diene. Using a yeast expression system, specific labeled [13C]acetate, and NMR, we investigated the catalytic mechanism for VoTPS1 and provide evidence for the involvement of a caryophyllenyl carbocation, a cyclobutyl intermediate, in the biosynthesis of valerena-1,10-diene. We suggest a similar mechanism for the biosynthesis of several other biologically related isobutenyl-containing sesquiterpenes

A new triterpene glycoside from Centella erecta

A new (2α,3β)-23-sulphonyl-2,3-dihydroxyurs-12-en-28-oic acid O-α-l-rhamnopyranosyl-(1→4)-O-β-d-glucopyranosyl-(1→6) -O-β-d-glucopyranosyl ester (1) together with eighteen known compounds were isolated from Centella erecta (L.f.) Fern. Their structures were elucidated mainly by NMR and HRESIMS, as well as on comparison with the reported data. © 2010 Elsevier B.V. All rights reserved

Two new triterpene glycosides from centella asiatica

Phytochemical investigation of the leaves of Centella asiatica resulted in the isolation and characterization of eight triterpenes and/or saponins [which were characterized as 23-O-acetylmadecassoside (1), asiatic acid (2), madecassic acid (3), asiaticoside C (4), asiaticoside F (5), asiaticoside (6), madecassoside (7), and 23-O-acetylasiaticoside B (8)] together with sitosterol 3-O-β-glucoside (9), stigmasterol 3-Oβ-glucoside (10), and querectin-3-O-β-D-glucuronide (11). A new ursane-derived saponin (23-O-acetylmadecassoside) and a new oleanane-derived saponin (23-O-acetylasiaticoside B) were found as well. Structure elucidation was done by using spectroscopic techniques (HRESIMS, 1D and 2DNMR), chemical methods, and comparative literature studies. © Georg Thieme Verlag KG Stuttgart - New York

Octulosonic Acid Derivatives from Roman Chamomile (<i>Chamaemelum nobile</i>) with Activities against Inflammation and Metabolic Disorder

Six new octulosonic acid derivatives (<b>1</b>–<b>6</b>) were isolated from the flower heads of Roman chamomile (<i>Chamaemelum nobile</i>). Their structures were elucidated by means of spectroscopic interpretation. The biological activity of the isolated compounds was evaluated toward multiple targets related to inflammation and metabolic disorder such as NAG-1, NF-κB, iNOS, ROS, PPARα, PPARγ, and LXR. Similar to the action of NSAIDs, all the six compounds (<b>1</b>–<b>6</b>) increased NAG-1 activity 2–3-fold. They also decreased cellular oxidative stress by inhibiting ROS generation. Compounds <b>3</b>, <b>5</b>, and <b>6</b> activated PPARγ 1.6–2.1-fold, while PPARα was activated 1.4-fold by compounds <b>5</b> and <b>6</b> only. None of the compounds showed significant activity against iNOS or NF-κB. This is the first report of biological activity of octulosonic acid derivatives toward multiple pathways related to inflammation and metabolic disorder. The reported anti-inflammatory, hypoglycemic, antiedemic, and antioxidant activities of Roman chamomile could be partly explained as due to the presence of these constituents