Ivanka Kostova

Two New Sulfated Furostanol Saponins from Tribulus terrestris

The known furostanol saponins methylprotodioscin and protodioscin and two new sulfated saponins, sodium salt of 26-O-β-glucopyranosyl-22α-methoxy-(25R)-furost-5-ene-3β,26-diol- 3-O-α-rhamnopyranosyl-(1→2)-β-4-O-sulfo-glucopyranoside (methylprototribestin) and sodium salt of 26-O-β-glucopyranosyl-22α-hydroxy-(25R)-furost-5-ene-3β,26-diol-3-O-α-rhamnopyranosyl-( 1→2)-β-4-O-sulfo-glucopyranoside (prototribestin) have been isolated from the aerial parts of Tribulus terrestris L. growing in Bulgaria. The structures of the new compounds were elucidated on the basis of 1D and 2D (DQF-COSY, TOCSY, HSQC-TOCSY, HSQC, HMBC, ROESY) NMR data, ESI mass spectra and chemical transformation.

Fraxinus ornus L.

The literature on the chemical constituents and the biological activity of Fraxinus ornus bark, leaves and flowers has been reviewed. Chemical studies show the presence of many compounds belonging mainly to the groups of hydroxycoumarins, secoiridoid glucosides, phenylethanoids and flavonoids. Biological studies reveal significant antimicrobial, antioxidative, photodynamic damage prevention, wound healing, anti-inflammatory, immunomodulatory and antiviral activities, and support the use of the bark in the folk medicine.

Antioxidative action of the ethanolic extract and some hydroxycoumarins of Fraxinus ornus bark

Abstract The antioxidative effectivity and strength of different concentrations of ethanolic extract from Fraxinus ornus bark, as well as of esculetin, esculin, fraxetin and fraxin during the autoxidation at 100°C of kinetically pure triacylglycerols of lard (TGL) and triacylglycerols of sunflower oil (TGSO) were determined. The extract exhibited a pronounced antioxidative activity. Esculetin and fraxetin considerably retarded the process in both lipid systems, this being more significant in the less oxidizable lipid substrate (TGL). Fraxetin proved to be a more efficient and stronger inhibitor than esculetin. During the oxidation of TGSO the fraxetin caused a stronger decrease in antioxidative activity. The participation of both hydroxycoumarins in the side reactions of inhibited oxidation, which explains their kinetic behaviour, is discussed. Fraxin and esculin displayed a very weak antioxidative action.

Alkaloids and Coumarins from Ruta graveolens

Summary. The aerial parts of Ruta graveolens cultivated in Bulgaria afforded four new 2-alkyl-4-(1H)-quinolone alkaloids together with thirteen known components. The new alkaloids were obtained as a mixture of homologues. The structures of all compounds were determined by spectroscopic methods.Zusammenfassung. Aus den oberirdischen Teilen von in Bulgarien gezogener Ruta graveolens konnten neben dreizehn bereits bekannten Substanzen vier neue 2-Alkyl-4(1H)-chinolonalkaloide als Gemisch homologer Verbindungen isoliert werden. Die Strukturen der neuen Komponenten wurden mit spektroskopischen Methoden aufgeklärt.

Antifeeding activity of rotenone and some derivatives towards selected insect storage pests

Abstract Roteneone and five of its derivatives prepared by appropriate chemical transformations were tested for their feeding deterrrent activity against the adults of Sitophilus granarius and Tribolium confusum , as well as against the larvae of Trilobium confusum and Trogoderma granarium . The strongest deterrent activity against all species was exhibited by rotenone. The total coefficient was 200, which is the maximum value attainable for this kind of test. Rotenone is thus the best antifeedant so far tested in our laboratory. The antifeeding activity of the derivatives of rotenone was considerably lower, but showed a certain selectivity.

Caffeic acid esters of phenylethanoid glycosides from Fraxinus ornus bark

Abstract A new phenylethanoid glucoside, 2-(3,4-dihydroxyphenyl)-ethyl- O -β- d -glucopyranosyl-(1→6)-3- O - trans -caffeoyl-β- d -glucopyranoside, named isolugrandoside, was isolated from Fraxinus ornus bark, together with the five known phenylethanoid glycosides 2-(4-hydroxyphenyl)-ethyl-(6- O -caffeoyl)-β- d -glucopyranoside, calceolarioside B, verbascoside, isoacteoside and lugrandoside. Isomerization of lugrandoside to isolugrandoside was not found under the employed conditions of isolation and purification.

A monoterpene glucoside from Paeonia peregrina roots

Abstract A new “cage-like” monoterpene glucoside, named paeonidanin, has been isolated from Paeonia peregrina roots and its structure established on the basis of spectral evidence. In addition, five known substances, paeoniflorigenone, benzoylpaeoniflorin, benzoic, p -hydroxybenzoic and gallic acids, have also been identified.

New furostanol saponins from Smilax aspera L. and their in vitro cytotoxicity

The occurrence of the two new cis-fused A/B rings furostanol saponins (25S)-26-O-β-D-glucopyranosyl-5β-furostan-1β,3β,22α,26-tetraol-1-O-β-D-glucopyranoside and (25S)-26-O-β-D-glucopyranosyl-5β-furostan-1β,2β,3β,5β,22α,26-hexaol and the known compounds (25S)-26-O-β-D-glucopyranosyl-5β-furostan-3β,22α,26-triol-3-O-α-L-rhamnopyranosyl-(1 → 2)-O-β-D-glucopyranosyl-(1 → 2)-O-β-D-glucopyranoside and (25S)-26-O-β-D-glucopyranosyl-5β-furostan-3β,22α,26-triol-3-O-β-D-glucopyranosyl-(1 → 2)-O-β-D-glucopyranoside, trans-resveratrol, (+) catechin and (-) epicatechin in the rhizomes of Smilax aspera is reported. All saponins have been isolated as their 22-OMe derivatives, which were further subjected to extensive spectroscopic analysis. The isolated furostanol saponins were evaluated for cytotoxic activity against human normal amniotic and human lung carcinoma cell lines using neutral red and MTT assays. In vitro experiments showed significant cytotoxicity in a dose dependent manner with IC(50) values in the range of 32.98-94.53 µM.

Anthraquinone, naphthalene, and naphthoquinone components of Asphodeline lutea

The genus Asphodeline belongs to the family Asphodelaceae, subfamily Asphodeloideae. The 1,8-dihydroxyanthraquinones based on a chrysophanol unit are characteristic compounds of this subfamily. Anthraquinones, flavonoids, oxepines, and sesquiterpene lactones have been reported to occur in the genus Asphodeline [1–4]. Asphodeline lutea is a perennial plant growing in the Mediterranian region. The only report found on this plant species reveals the presence of 1,8-dihydroxyanthraquinones, flavonoids, and a chlorogenic acid [5]. Data on the biological activity and the medicinal use of A. lutea are not available. However, the edible use of its roots, shoots, and flowers has been reported [6]. The ancient Greeks roasted the roots like potatoes and ate them with salt and oil or mashed them with figs. The raw fresh flowers are very decorative and a tasty addition to salad, while the young shoots are eaten cooked. The roots of A. lutea were collected in June 2005 near the town of Pernik, Bulgaria. The dried roots (0.70 kg) of A. lutea were extracted with methanol (3 times 24 h 2.7 L) at room temperature, then concentrated in vacuum to give a crude methanol extract (22.0 g). Solvent-solvent partition of this extract using petroleum ether, chloroform, and ethylacetate afforded the corresponding petroleum ether (4.3 g), chloroform (5.2 g), and ethylacetate (0.5 g) extracts and an aqueous residue (15.2 g). The petroleum ether extract was subjected to liquid vacuum chromatography (LVC) on silica gel using PE, PE–CHCl3 (3:1 1:3), CHCl3, CHCl3–EtOAc (1:1), and EtOAc to give fractions F1-F6. Silica gel CC and repeated pTLC of F6 afforded compounds 1 (2 mg), 2 (6 mg), 3 (7 mg), 4 (3 mg), and 5 (1 mg). LVC of the chloroform extract with PE–CHCl3 (20:1 1:1) and CHCl3 gave fractions F1-F4. From F4 after silica gel CC and pTLC separation components 6 (4 mg), 7 (2 mg), 5 (5 mg), and 8 (6 mg) were isolated. The chemical structures of the isolated compounds were determined by a combination of spectral methods (UV, IR, 1D and 2D NMR, and MS) and comparison with literature data as chrysophanol (1) [7], 1,5,8-trihydroxy-3-methylanthraquinone (2) [8], 2-acetyl-1,8-dimethoxy-3-methylnaphthalene (3) [9, 10], 1-hydroxy-8-methoxy-3-methylanthraquinone (4) [11], asphodeline (5) [12], 2-acetyl-1-hydroxy-8-methoxy-3-methylnaphthalene (6) [9, 10], 2-acetyl-8-methoxy-3methylnaphthoquinone (7) [13], and 1,1 ,8,8 ,10-pentahydroxy-3,3 -dimethyl-10,7 -bianthracene-9,9 ,10 -trione (8) [14]. Of them only chrysophanol (1) and asphodeline (5) have been reported to occur in A. lutea [5]. The anthraquinones 2 and 4 and the naphthalene compounds 3 and 6 are new for the genus Asphodeline. The naphthoquinone 7 is a known synthetic compound [13]. However, this is the first report on its natural occurrence and on the presence of naphthoquinones in Asphodeline species. A full assignment of all protons and carbons in the molecule of 3 was undertaken by detailed 1D and 2D NMR measurements because of the discrepancy between the assignments of C signals in previous reports [9, 10]. Our data are presented in Table 1. The 13C NMR data of 7 have been reported by Piggot and Wege without any assignment [13]. Our results from the complete assignment of all protons and carbons achieved by 1D and 2D NMR experiments are presented in Table 1. 2-Acetyl-1,8-dimethoxy-3-methylnaphthalene (3). UV (EtOH, max, nm): 225, 299, 313 sh, 329; IR (KBr, max, cm–1): 2924, 2839, 1700, 1623, 1568, 1460; EI-MS (m/z, Irel.,%): 244 (M+, 70.9), 229 (100), 214 (8.1), 201 (1.5), 186 (25.8), 158 (4.8), 128 (19.3), 127 (9.7), 115 (20.9), 43 (5.6). For 1H and 13C NMR data, see Table 1.

Steroidal saponins from Smilax excelsa rhizomes

From the n-butanol soluble fraction of the methanol extract of the rhizomes of Smilax excelsa, three new furostanol saponins 3-O-[4-O-acetyl-α-L-rhamnopyranosyl-(1 → 2)-{α-L-rhamnopyranosyl-(1 → 4)}-β-D-glucopyranosyl]-26-O-[β-D-glucopyranosyl]-22α-hydroxy-(25R)-furost-5-ene-3β,26-diol (1), 3-O-[2-O-acetyl-α-L-rhamnopyranosyl-(1 → 2)-{α-L-rhamnopyranosyl-(1 → 4)}-β-D-glucopyranosyl]-26-O-[β-D-glucopyranosyl]-22α-hydroxy-(25R)-furost-5-ene-3β,26-diol (2), 3-O-[3-O-acetyl-α-L-rhamnopyranosyl-(1 → 2)-{α-L-rhamnopyranosyl-(1 → 4)}-β-D-glucopyranosyl]-26-O-[β-D-glucopyranosyl]-22α-hydroxy-(25R)-furost-5-ene-3β,26-diol (3), and three known saponins: protodioscin (4), pseudoprotodioscin (5) and dioscin (6) were isolated.