A chemosystematic study of Scrophulariaceae: Iridoid glycosides

Chemical Characterization and Anti-HIV-1 Activity Assessment of Iridoids and Flavonols from Scrophularia trifoliata

Plants are the everlasting source of a wide spectrum of specialized metabolites, characterized by wide variability in term of chemical structures and different biological properties such antiviral activity. In the search for novel antiviral agents against Human Immunodeficiency Virus type 1 (HIV-1) from plants, the phytochemical investigation of Scrophularia trifoliata L. led us to isolate and characterize four flavonols glycosides along with nine iridoid glycosides, two of them, 5 and 13, described for the first time. In the present study, we investigated, for the first time, the contents of a methanol extract of S. trifoliata leaves, in order to explore the potential antiviral activity against HIV-1. The antiviral activity was evaluated in biochemical assays for the inhibition of HIV-1Reverse Transcriptase (RT)-associated Ribonuclease H (RNase H) activity and HIV-1 Integrase (IN). Three isolated flavonoids, rutin, kaempferol-7-O-rhamnosyl-3-O-glucopyranoside, and kaempferol-3-O-glucopyranoside, 8-10, inhibited specifically the HIV-1 IN activity at submicromolar concentration, with the latter being the most potent, showing an IC50 value of 24 nM.

Harpagide: Occurrence in plants and biological activities - A review

In this review article, the occurrence of harpagide in the plant kingdom and its associated biological activities are presented and detailed for the first time. The presence of harpagide has been reported in several botanical families within Asteridae, and harpagide has been observed to exert a wide number of biological activities such as cytotoxic, anti-inflammatory, and neuroprotective. These results show how harpagide can be recovered from several natural sources for several pharmacological purposes even if there is a lot to still be studied. Nowadays, the interest is related to its presence in phytomedicines. Threfore, these studies are useful to support and validate the large use of several plants in the folklore medicine.

Metabolic Profiling of Buddleia indica Leaves using LC/MS and Evidence of their Antioxidant and Hepatoprotective Activity Using Different In Vitro and In Vivo Experimental Models

LC-ESI-MS (Liquid Chromatography coupled with Electrospray Ionization Mass Spectrometry profiling of a methanol extract from Buddleia indica (BIM) leaves revealed 12 main peaks in which verbascoside and buddlenoid B represent the major compounds. The antioxidant and hepatoprotective activities of BIM were investigated using different in vitro and in vivo experimental models. BIM exhibited substantial in vitro antioxidant properties in DPPH· and HepG2 assays. Regarding CCl4 (carbon tetrachloride) induced hepatotoxicity in a rat model, oxidative stress markers became significantly ameliorated after oral administration of BIM. Lipid peroxide levels showed a 51.85% decline relative to CCl4-treated rats. Super oxide dismutase (SOD), total antioxidant status (TAS), and catalase (CAT) revealed a marked increase by 132.48%, 187.18%, and 114.94% relative to the CCl4 group. In a tamoxifen-induced hepatotoxicity model, BIM showed a considerable alleviation in liver stress markers manifested by a 46.06% and 40% decline in ALT (Alanine Transaminase) and AST (Aspartate Transaminase) respectively. Thiobarbituric acid reactive substances (TBARS) were reduced by 28.57% and the tumor necrosis factor alpha (TNF-α) level by 50%. A virtual screening of major secondary metabolites of BIM to TNF-alpha employing the C-docker protocol showed that gmelinoside H caused the most potent TNF- α inhibition as indicated from their high fitting scores. Thus, BIM exhibited a potent hepatoprotective activity owing to its richness in antioxidant metabolites.

New iridoid glycosides from Anarrhinum pubescens

Six metabolites (1-6) were isolated from the aerial parts of Anarrhinum pubescens Fresen. (Plantaginaceae) growing in Saint Catherine region in Egypt; two of them (1 and 4) are here reported to be newly identified naturally occurring iridoids. The isolated metabolites were identified as 6-O-foliamenthoyl-(6'-O-cinnamoyl)-antirrhinoside (1), 6'-O-cinnamoyl-antirrhinoside (2), the iridoid dimer, pubescensoside (4), antirrhinoside (5), 10-hydroxy-antirrhinoside (6), and the flavonoid, diosmin (3). Identification of the new metabolites was based on analysis of their collected spectroscopic data (NMR and HR-ESI-MS). Furthermore, compounds (1, 4, and 5) were subjected to cytotoxic testing against the human lung carcinoma cell line (A-549); compound 4 showed better cytotoxic activity as indicated by the obtained (IC₅₀).

Iridoid glycosides from Alonsoa meridionalis

A new iridoid glucoside has been isolated from the Chilean native Alonsoa meridionalis (L.f.) Kuntze. Its structure has been assigned as 6'-O-β-d-glucopyranosyl-8-O-acetylharpagide (1) by using spectroscopic methods. Harpagoside (2), laterioside (3) and verbascoside (4) were also identified.

Chemotaxonomy of Veroniceae and its allies in the Plantaginaceae

In a chemosystematic investigation of tribe Veroniceae (Plantaginaceae), representatives of Camptoloma, Sibthorpia, Veronica subg. Pentasepalae and subg. Hebe, Veronicastrum, Wulfenia, and the related Ellisiophyllum and Globularia were examined for non-flavonoid glycosides. From the 14 species studied, 28 different iridoid glucosides and 10 caffeoyl phenylethanoid glucosides (CPGs), as well as salidroside and arbutin were isolated and characterized by NMR; of these, five compounds were previously unknown. It was found that the representatives of Veroniceae, as well as Globularia, were characterized by mannitol, aucubin, catalpol and catalpol esters. Each of the three studied species of Veronica subg. Hebe contained at least one of the 6-O-catalpol esters typical for Veronica s. str. (verminoside), supporting the inclusion of Hebe in Veronica. However, their main constituents were esters of 6-O-rhamnopyranosylcatalpol; a CPG, hebeoside (2'-beta-xylopyranosyl-verbascoside) was isolated from V. (Hebe) salicifolia. The two species of Veronicastrum also contained 6-O-rhamnopyranosylcatalpol esters, including the previously unknown 2'',3''- and 3'',4''-dicinnamoyl derivatives and, in contrast to the earlier reports, they lacked 6-O-catalpol esters. The main iridoid constituents in the three investigated species of Wulfenia were 10-O-aucubin and 10-O-catalpol esters (isoscrophularioside or globularin) while baldaccioside (10-O-cinnamoyl asystasioside E) was isolated from W. baldaccii. Globularia vulgaris contained 10-O-catalpol esters (e.g., globularin) and, in addition, asperuloside together with its benzoyl analogue named besperuloside. The representatives of Sibthorpia and Ellisiophyllum were almost completely devoid of iridoids; this, however, together with the CPGs present implied a close relationship between the two genera. Camptoloma lyperiiflorum lacked hexitols but contained esters of 6-O-rhamnopyranosylcatalpol different from those found in Veroniceae but known from Buddleja, Scrophularia and Verbascum (Scrophulariaceae s. str.).