Activation of a Sweet Taste Receptor by Oleanane-Type Glycosides from Wisteria sinensis.

The phytochemical study of Wisteria sinensis (Sims) DC. (Fabaceae), commonly known as the Chinese Wisteria, led to the isolation of seven oleanane-type glycosides from an aqueous-ethanolic extract of the roots. Among the seven isolated saponins, two have never been reported before: 3-O-α-L-rhamnopyranosyl-(1→2)-ß-D-glucopyranosyl-(1→2)-ß-D-glucuronopyranosyl-22-O-acetylolean-12-ene-3ß,16ß,22ß,30-tetrol, and 3-O-ß-D-xylopyranosyl-(1→2)-ß-D-glucuronopyranosylwistariasapogenol A. Based on the close structures between the saponins from W. sinensis, and the glycyrrhizin from licorice, the stimulation of the sweet taste receptor TAS1R2/TAS1R3 by these glycosides was evaluated.

ß-Amyrin Synthase1 Controls the Accumulation of the Major Saponins Present in Pea (Pisum sativum).

The use of pulses as ingredients for the production of food products rich in plant proteins is increasing. However, protein fractions prepared from pea or other pulses contain significant amounts of saponins, glycosylated triterpenes that can impart an undesirable bitter taste when used as an ingredient in foodstuffs. In this article, we describe the identification and characterization of a gene involved in saponin biosynthesis during pea seed development, by screening mutants obtained from two Pisum sativum TILLING (Targeting Induced Local Lesions IN Genomes) populations in two different genetic backgrounds. The mutations studied are located in a gene designated PsBAS1 (ß-amyrin synthase1), which is highly expressed in maturing pea seeds and which encodes a protein previously shown to correspond to an active ß-amyrin synthase. The first allele is a nonsense mutation, while the second mutation is located in a splice site and gives rise to a mis-spliced transcript encoding a truncated, nonfunctional protein. The homozygous mutant seeds accumulated virtually no saponin without affecting the seed nutritional or physiological quality. Interestingly, BAS1 appears to control saponin accumulation in all other tissues of the plant examined. These lines represent a first step in the development of pea varieties lacking bitterness off-flavors in their seeds. Our work also shows that TILLING populations in different genetic backgrounds represent valuable genetic resources for both crop improvement and functional genomics.

Triterpenoid Saponins from the Cultivar "Green Elf" of Pittosporum tenuifolium.

Four oleanane-type glycosides were isolated from a horticultural cultivar "Green Elf" of the endemic Pittosporum tenuifolium (Pittosporaceae) from New Zealand: three acylated barringtogenol C glycosides from the leaves, with two previously undescribed 3-O-ß-d-glucopyranosyl-(1→2)-[α-l-arabinopyranosyl-(1→3)]-ß-d-glucuronopyranosyl-21-O-angeloyl-28-O-acetylbarringtogenol C, 3-O-ß-d-galactopyranosyl-(1→2)-[α-l-arabinopyranosyl-(1→3)]-ß-d-glucuronopyranosyl-21-O-angeloyl-28-O-acetylbarringtogenol C, and the known 3-O-ß-d-glucopyranosyl-(1→2)-[α-l-arabinopyranosyl-(1→3)]-ß-d-glucuronopyranosyl-21-O-angeloyl-28-O-acetylbarringtogenol C (Eryngioside L). From the roots, the known 3-O-ß-d-glucopyranosyl-(1→2)-ß-d-galactopyranosyl-(1→2)-ß-d-glucuronopyranosyloleanolic acid (Sandrosaponin X) was identified. Their structures were elucidated by spectroscopic methods including 1D- and 2D-NMR experiments and mass spectrometry (ESI-MS). According to their structural similarities with gymnemic acids, the inhibitory activities on the sweet taste TAS1R2/TAS1R3 receptor of an aqueous ethanolic extract of the leaves and roots, a crude saponin mixture, 3-O-ß-d-glucopyranosyl-(1→2)-[α-l-arabinopyranosyl-(1→3)]-ß-d-glucuronopyranosyl-21-O-angeloyl-28-O-acetylbarringtogenol C, and Eryngioside L were evaluated.

Triterpenoid Saponins from the Caryophyllaceae Family Modulate the Efflux Activity of the P-Glycoprotein in an In Vitro Model of Intestinal Barrier.

The oral bioavailability of drugs is often limited due to the presence of the P-glycoprotein, an efflux pump strongly expressed on the luminal side of the intestinal barrier. In an attempt to circumvent drug efflux, strategies consisting in the coadministration of drugs with surface-active agents have been found to be promising. In this context, the role of saponins on the intestinal permeability of a P-glycoprotein substrate was investigated. The P-glycoprotein inhibition activity of three triterpenoid saponins extracted from several plants of the Caryophyllaceae family was evaluated using an intestinal barrier model comprised of Caco-2 cell lines. The results showed a strong effect of two saponins on P-glycoprotein-mediated transport. At a concentration of 15 µM, the efflux ratio was close to 1 for both saponins, thus suggesting a total inhibition of the efflux pump in contrast to verapamil HCl, a conventional P-glycoprotein inhibitor. In addition, measurements of the transepithelial electrical resistance revealed that the integrity of the monolayers was not altered at such concentrations, thereby reducing potential adverse effects. The presence of acetylated sugars in the saponin structure could possibly facilitate interactions with the efflux pump by an ATP-dependent mechanism or by fluidization of cell membranes.

Millettia dubia De Wild. (Fabaceae): Structural analysis of the oleanane-type glycosides and stimulation of the sweet taste receptors TAS1R2/TAS1R3.

From the root barks of a Central African tree Millettia dubia De Wild. (Fabaceae), ten previously undescribed oleanane-type glycosides were isolated by various chromatographic protocols. Their structures were elucidated by spectroscopic methods, mainly 2D NMR experiments and mass spectrometry, as mono- and bidesmosidic glycosides of mesembryanthemoidigenic acid, hederagenin and oleanolic acid. The stimulation of the sweet taste receptor TAS1R2/TAS1R3 by these glycosides was evaluated, and structure/activity relationships were proposed. Two of them showed an agonist effect on TAS1R2/TAS1R3.

Phytochemical, Geographical, and Pharmacological Retrospect of Genus Torilis.

BACKGROUND: Genus Torilis (Apiaceae) known as hedge parsley, encompasses 11-13 species distributed worldwide and shows potential pharmacological uses. Its phytochemical pattern is highly diversified including many phenolic and terpenic compounds. OBJECTIVE: This research-review provides new highlighting of structural organizations, structure-activity trends, taxonomical, tissue and geographical distribution of phytocompounds of Torilis genus from extensive statistical analyses of available data. METHODS: In extenso, exploration of documented literature and statistical data analyses were applied to update the phytochemical pool of the genus under several aspects including structural diversity, geographical distribution, biological compartmentations and pharmacological activities. RESULTS: Phytoconstituents were classified into homogeneous clusters that revealed to be associated with chemical constitutions (aglycone types, chemical groups) and distributions (through species, tissues, geographical). About bioactivities, terpenes were studied from a pharmacological point of view with relatively high frequencies for antifungal, antibacterial, cytotoxic and anti-inflammatory activities. Preliminary structure-activity relationships were highlighted implying opposite effects between hydroxylation and methylation in favor of different activities. Crude extracts and isolated compounds have shown several biological activities (antibacterial, anticancer, antiangiogenic, antiproliferative, etc.), thus providing authentic scientific proof for their diverse uses in folk medicines. CONCLUSION: The phytochemistry of the genus Torilis promises important perspectives in matters of pharmacological activities. These perspectives call for further investments in pharmacology because of (i) unbalance between phenolic and terpenic compounds according to the countries and (ii) more advanced current states of structural elucidations compared to biological evaluations.

Two new triterpenoid saponins from Pittosporum senacia Putterlick (Pittosporaceae).

From the branches of Pittosporum senacia Putterlick (Pittosporaceae), two new triterpenoid saponins, senaciapittosides A and B (1, 2), were isolated. Their structures were elucidated by extensive analysis of one- and two-dimensional nuclear magnetic resonance spectroscopy, high-resolution electrospray ionization mass spectrometry (HR-ESIMS) and chemical evidence as 3-O-[ß-D-glucopyranosyl-(1 → 2)]-[α-L-arabinopyranosyl-(1 → 3)]-[α-L-arabinofuranosyl-(1 → 4)]-ß-D-glucuronopyranosyl oleanolic acid 28-O-ß-D-glucopyranosyl ester (1) and 3-O-[ß-D-glucopyranosyl-(1 → 2)]-[α-L-arabinopyranosyl-(1 → 3)]-[α-L-arabinofuranosyl-(1 → 4)]-ß-D-glucuronopyranosyl-22-O-α-L-arabinopyranosyl-21-acetoxy R1-barrigenol (2). Compound 2 presents an unusual glycosylation at C-22 of its aglycone.

Oleanane-type glycosides isolated from the trunk barks of the Central African tree Millettia laurentii.

Seven previously undescribed oleanane-type glycosides were isolated from the trunk barks of a Central African tree named Millettia laurentii De Wild (Fabaceae). After the extraction from the barks, the isolation and purification of these compounds were achieved using various solid/liquid chromatographic methods. Their structures were established mainly by 1D and 2D NMR (COSY, TOCSY, ROESY, HSQC, HMBC) and mass spectrometry (ESI-MS), as 3-O-ß-D-glucuronopyranosyl-(1 â†’ 2)-ß-D-glucuronopyranosylechinocystic acid, 3-O-ß-D-apiofuranosyl-(1 â†’ 3)-ß-D-glucuronopyranosyl-(1 â†’ 2)-ß-D-glucuronopyranosylechinocystic acid, 3-O-ß-D-apiofuranosyl-(1 â†’ 3)-ß-D-galactopyranosyl-(1 â†’ 2)-ß-D-glucuronopyranosylechinocystic acid, 3-O-ß-D-apiofuranosyl-(1 â†’ 3)-[ß-d-xylopyranosyl-(1 â†’ 2)]-ß-D-galactopyranosyl-(1 â†’ 2)-ß-D-glucuronopyranosylechinocystic acid, 3-O-ß-D-apiofuranosyl-(1 â†’ 3)-[α-L-arabinofuranosyl-(1 â†’ 2)]-ß-D-galactopyranosyl-(1 â†’ 2)-ß-D-glucuronopyranosylechinocystic acid, 3-O-α-L-arabinofuranosyl-(1 â†’ 2)-ß-D-galactopyranosyl-(1 â†’ 2)-ß-D-glucuronopyranosyloleanolic acid, 3-O-ß-D-apiofuranosyl-(1 â†’ 3)-[α-L-arabinofuranosyl-(1 â†’ 2)]-ß-D-galactopyranosyl-(1 â†’ 2)-ß-D-glucuronopyranosyloleanolic acid. In addition, the cytotoxicity of six glycosides among the isolated ones, was evaluated against 4 T1 cell line from a mouse mammary gland tissue, using MTS method.

Glaucasides A-C, three saikosaponins from Atriplex glauca L. var. ifiniensis (Caball) Maire.

From the roots of Atriplex glauca L. var. ifiniensis (Caball) Maire (syn. of Atriplex parvifolia Lowe var. genuina Maire), three new saikosaponins designated as glaucasides A-C (1-3) were isolated together with the known 3-O-ß-D-glucopyranosyl-(1 → 2)-ß-D-galactopyranosyl-saikogenin F (4). The structures of the new compounds were elucidated by extensive analysis of one-dimensional and two-dimensional NMR spectroscopy, FABMS, HR-ESIMS and chemical evidence as 13ß,28-epoxy-16ß,21ß-dihydroxyolean-11-en-3ß-yl O-ß-D-[2-O-sulfate]-glucopyranosyl-(1 → 2)-α-L-arabinopyranoside (1), 13ß,28-epoxy-16ß,21ß-dihydroxyolean-11-en-3ß-yl O-ß-D-[2-O-sulfate]-glucopyranosyl-(1 → 2)-α-L-arabinopyranosyl 21-O-{4-(secbutylamido)-butanoyl ester} (2) and 3-O-ß-D-glucopyranosyl-(1 → 2)-ß-D-galactopyranosyl saikogenin G (3). The cytotoxic activities of these compounds were evaluated against the HT-29 and HCT 116 human colon cancer cell lines.

Anti-phytopathogen terpenoid glycosides from the root bark of Chytranthus macrobotrys and Radlkofera calodendron.

Chytranthus macrobotrys and Radlkofera calodendron are two Sapindaceae characterized by a lack of phytochemical data. Both root barks from the two Sapindaceae species were processed by ethanol extraction followed by the isolation of their primary constituents by liquid chromatography. This process yielded four previously undescribed terpenoid glycosides together with eight known analogues. Extracts and isolated compounds from C. macrobotrys and R. calodendron were then screened for antimicrobial activity against fifteen phytopathogens. The biological screening also involved extracts and pure compounds from Blighia unijugata and Blighia welwitschii, two Sapindaceae previously studied by our group. Phytopathogens were chosen based on their economic impact on agriculture worldwide. The selection was composed primarily of fungal species including; Pyricularia oryzae, Gaeumannomyces graminis var. tritici, Zymoseptoria tritici, Fusarium oxysporum, Botrytis cinerea, Pythium spp., Trichoderma spp. and Rhizoctonia solani. Furthermore, pure terpenoid glycosides were tested for the first time against wood-inhabiting phytopathogens such as; Phaeomoniella chlamydospora, Phaeoacremonium minimum, Fomitiporia mediterranea, Eutype lata and Xylella fastidiosa. Raw extracts exhibited different levels of activity dependent on the organism. Some pure compounds, including 3-O-α-L-arabinopyranosyl-(1 â†’ 4)-ß-D-xylopyranosyl-(1 â†’ 3)-α-L-rhamnopyranosyl-(1 â†’ 2)-α-L-arabinopyranosylhederagenin, 3-O-α-L-rhamnopyranosyl-(1 â†’ 2)-α-L-arabinopyranosylhederagenin (α-hederin), 3-O-ß-D-glucopyranosyl-(1 â†’ 3)-α-L-rhamnopyranosyl-(1 â†’ 2)-α-L-arabinopyranosylhederagenin (macranthoside A) and 3-O-α-L-arabinopyranosyl-(1 â†’ 3)-α-L-rhamnopyranosyl-(1 â†’ 2)-α-L-arabinopyranosylhederagenin (clemontanoside C), exhibited significant growth inhibitions on Pyricularia oryzae, Gaeumannomyces graminis var. tritici, Fomitiporia mediterranea and Zymoseptoria tritici. Monodesmoside triterpene saponins, in particular, exhibited MIC (IC100) values as low as 25 µg/ml and IC50 values as low as 10 µg/ml against these phytopathogens. Structure-activity relationships, as well as plant-microbe interactions, were discussed.

Steroidal glycosides from the Vietnamese cultivar Cordyline fruticosa "Fairchild red".

A phytochemical study of Cordyline fruticosa "Fairchild red" (Asparagaceae) from Vietnam, led to the isolation of fourteen steroidal glycosides, including twelve previously undescribed along with two known ones. Ten compounds were obtained by successive solid/liquid chromatographic methods from an aqueous-ethanolic extract of the roots, and four from the aerial parts. Their structures were elucidated mainly by spectroscopic analysis 2D NMR and mass spectroscopy (ESI-MS), as spirostanol glycosides, 5α-spirost-25(27)-ene-1ß,3ß,4α-triol 1-O-ß-D-fucopyranoside, 5α-spirost-(25)27-ene-1ß,3ß,4α-triol 1-O-ß-D-xylopyranoside, 5α-spirost-(25)27-ene-1ß,3ß,4α-triol 1-O-α-L-rhamnopyranosyl-(1 â†’ 2)-ß-D-fucopyranoside, 5α-spirost-(25)27-ene-1ß,3ß,4α-triol 1-O-α-L-rhamnopyranosyl-(1 â†’ 2)-(4-O-sulfo)-ß-D-fucopyranoside, 5α-spirost-25(27)-ene-1ß,3ß-diol 1-O-α-L-rhamnopyranosyl-(1 â†’ 2)-ß-D-fucopyranoside, and 5α-spirost-25(27)-ene-1ß,3ß-diol 1-O-α-L-rhamnopyranosyl-(1 â†’ 2)-α-L-arabinopyranoside. Furostanol glycosides were also isolated as 26-O-ß-D-glucopyranosyl-5α-furost-(25)27-ene-1ß,3ß,4α,22α,26-pentol 1-O-ß-D-fucopyranoside, 26-O-ß-D-glucopyranosyl-22α-methoxy-5α-furost-(25)27-ene-1ß,3ß,4α,26-tetrol 1-O-ß-D-fucopyranoside, 26-O-ß-D-glucopyranosyl-5α-furost-(25)27-ene-1ß,3ß,22α,26-tetrol 1-O-ß-D-glucopyranoside, 26-O-ß-D-glucopyranosyl-5α-furost-(25)27-ene-1ß,3ß,22α,26-tetrol 1-O-α-L-rhamnopyranosyl-(1 â†’ 2)-ß-D-glucopyranoside, 26-O-ß-D-glucopyranosyl-5α-furost-(25)27-ene-1ß,3ß,22α,26-tetrol 1-O-α-L-rhamnopyranosyl-(1 â†’ 2)-ß-D-fucopyranoside, and 26-O-ß-D-glucopyranosyl-22α-methoxy-5α-furost-(25)27-ene-1ß,3ß,26-triol 1-O-α-L-rhamnopyranosyl-(1 â†’ 2)-ß-D-fucopyranoside. All the isolated compounds were further evaluated for their cytotoxicity against 4T1 cell line, from a mouse mammary gland tissue, using MTS method.

Steroidal saponins from Chlorophytum orchidastrum.

Six new spirostane-type saponins (1-6), named orchidastrosides A-F, and chloromaloside D were isolated from an ethanol extract of the roots of Chlorophytum orchidastrum. The saponins have neotigogenin or neogitogenin as the aglycon and oligosaccharidic chains possessing seven to nine sugar units. Their structures were elucidated mainly by 2D NMR spectroscopic analyses (COSY, TOCSY, NOESY, HSQC, and HMBC) and FABMS and HRESIMS. Compounds 1-6 were tested for cytotoxicity against two human colon cancer cell lines, HCT 116 and HT-29.

Steroidal saponins from two species of Dracaena.

Four new steroidal saponins (1-4) were isolated from the stem and bark of two species of Dracaena: deistelianosides A and B (1 and 2) from D. deisteliana and arboreasaponins A and B (3 and 4) from D. arborea. Six known saponins and one known sapogenin were also isolated. The structures of 1-4 were established as diosgenin 3-O-[3-O-sulfate-alpha-l-rhamnopyranosyl-(1-->4)]-beta-d-glucopyranoside (1), 1-O-beta-d-xylopyranosyl-(1-->2)-[alpha-l-rhamnopyranosyl-(1-->3)]-beta-d-fucopyranosyl(23S,24S)-spirosta-5,25(27)-diene-1beta,3beta,23alpha,24alpha-tetrol 24-O-alpha-l-arabinopyranoside (2), pennogenin-3-O-alpha-l-rhamnopyranosyl-(1-->2)-[alpha-l-rhamnopyranosyl-(1-->3)]-[6-O-acetyl]-beta-d-glucopyranoside (3), and 24alpha-hydroxypennogenin 3-O-alpha-l-rhamnopyranosyl-(1-->2)-[alpha-l-rhamnopyranosyl-(1-->3)]-beta-d-glucopyranoside (4) using extensive 1D and 2D NMR spectroscopic analyses and mass spectrometry. Cytotoxic activity of several of these compounds was evaluated against the HT-29 and HCT 116 human colon cancer cell lines.

Triterpene saponins from Cyclamen trocopteranthum.

Two new triterpene saponins ( 1- 2) together with three known saponins, deglucocyclamin I ( 3), cyclamin ( 4), and mirabilin ( 5), were isolated from the tubers of Cyclamen trocopteranthum. They were elucidated as 3 beta- O-{4- O-[3-hydroxyl-3-methylglutaryl]- beta-D-xylopyranosyl-(1 --> 2)- beta-D-glucopyranosyl-(1 --> 4)-[ beta-D-glucopyranosyl-(1 --> 2)]- alpha-L-arabinopyranosyl}-16 alpha-hydroxy-13 beta,28-epoxy-oleanan-30-al ( 1) and 3 beta- O-{4- O-[3-hydroxyl-3-methylglutaryl]- beta-D-xylopyranosyl-(1 --> 2)-[ beta-D-glucopyranosyl-(1 --> 6)]- beta-D-glucopyranosyl-(1 --> 4)-[ beta-D-glucopyranosyl-(1 --> 2)]- alpha-L-arabinopyranosyl}-16 alpha-hydroxy-20,30-lactone-olean-12-ene ( 2). Their structures were characterized mainly by a combination of 1D- and 2D-NMR techniques ( (1)H- (1)H COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectroscopy. Saponins 1, 3, and 4 showed a weak cytotoxic activity when tested against HT-29 and HCT 116 tumor colon cancer cells.

Structure elucidation of new oleanane-type glycosides from three species of Acanthophyllum.

From the roots of three species of Acanthophyllum (Caryophyllaceae), two new gypsogenic acid glycosides, 1 and 2, were isolated, 1 from A. sordidum and A. lilacinum, 2 from A. elatius and A. lilacinum, together with three known saponins, glandulosides B and C, and SAPO50. The structures of 1 and 2 were established mainly by 2D NMR techniques as 23-O-beta-D-galactopyranosylgypsogenic acid-28-O-beta-D-glucopyranosyl-(1-->3)-[beta-D-glucopyranosyl-(1-->6)]-beta-D-galactopyranoside (1) and gypsogenic acid-28-O-beta-D-glucopyranosyl-(1-->3)-[beta-D-glucopyranosyl-(1-->6)]-beta-D-galactopyranoside (2). The cytotoxicity of several of these saponins was evaluated against two human colon cancer cell lines (HT-29 and HCT 116).

Structure elucidation of new acacic acid-type saponins from Albizia coriaria.

Three new acacic acid derivatives, named coriariosides C, D, and E (1-3) were isolated from the roots of Albizia coriaria. Their structures were elucidated on the basis of extensive 1D- and 2D-NMR studies and mass spectrometry as 3-O-[ß-D-xylopyranosyl-(1 → 2)-ß-D-fucopyranosyl-(1 → 6)-2-(acetamido)-2-deoxy-ß-D-glucopyranosyl]-21-O-{(2E,6S)-6-O-{4-O-[(2E,6S)-2,6-dimethyl- 6-O-(ß-D-quinovopyranosyl)octa-2,7-dienoyl]-4-O-[(2E,6S)-2,6-dimethyl-6-O-(ß-D-quinovopyranosyl)octa-2,7-dienoyl]-ß-D-quinovopyranosyl}-2,6-dimethylocta-2,7-dienoyl}acacic acid 28-O-ß-D-xylopyranosyl-(1 → 4)-α-L-rhamnopyranosyl-(1 → 2)-ß-D-glucopyranosyl ester (1), 3-O-{ß-D-fucopyranosyl-(1 → 6)-[ß-D-glucopyranosyl-(1 → 2)]-ß-D-glucopyranosyl}-21-O-{(2E,6S)-6-O-{4-O-[(2E,6S)-2,6-dimethyl-6-O-(ß-D-quinovopyranosyl)octa-2,7-dienoyl]-4-O-[(2E,6S)-2,6-dimethyl-6-O-(ß-D-quinovopyranosyl)octa-2,7-dienoyl]-ß-D-quinovopyranosyl}-2,6-dimethylocta-2,7-dienoyl}acacic acid 28-O-α-L-rhamno pyranosyl-(1 → 2)-ß-D-glucopyranosyl ester (2), and 3-O-[ß-D-fucopyranosyl-(1 → 6)-ß-D-glucopyranosyl]-21-O-{(2E,6S)-6-O-{4-O-[(2E,6S)-2,6-dimethyl-6-O-(ß-D-quinovopyranosyl)octa-2,7-dienoyl)-ß-D-quinovopyranosyl]octa-2,7-dienoyl}acacic acid 28-O-ß-D-glucopyranosyl ester (3).

Two new sesquiterpene derivatives from the Tunisian endemic Ferula tunetana Pom.

A new sesquiterpene ester, tunetanin A (1), a new sesquiterpene coumarin, tunetacoumarin A (2), together with eight known compounds, i.e., coladin (3), coladonin (4), isosmarcandin (5), 13-hydroxyfeselol (6), umbelliprenin (7) propiophenone (8), beta-sitosterol (9), and stigmasterol (10), were isolated from the roots of Ferula tunetana. Their structures were elucidated on the basis of extensive spectroscopic methods, including 1D- and 2D-NMR experiments and MS analysis, as well as by comparison with published data. The cytotoxicity of compounds 1-7 towards two human colon cancer cell lines, HT-29 and HCT 116, was evaluated. Compounds 3, 4, and 6 showed weak cytotoxic activities.