Silvia Marquina

Bioactive oleanolic acid saponins and other constituents from the roots of Viguiera decurrens

The bisdesmoside oleanolic acid saponin, 3-0-(methyl-beta-D-glucuronopyranosiduronoate)-28-0-beta-D-glucopyranosyl-oleanolate along with nine known compounds (two diterpenic acids, one chromene, three triterpenes, one steroidal glycoside, and two monodesmoside oleanolic acid saponins), were obtained from Viguiera decurrens roots. The chemical structure of the bisdesmoside oleanolic saponin was determined by chemical and NMR spectral evidence. A mixture of monodesmoside saponins displayed cytotoxic activity against P388 and COLON cell lines (ED50= 2.3 and 3.6 microg/ml, respectively). Two of the known compounds showed insecticidal activity against the Mexican bean beetle larvae (Epilachna varivestis).

Cytotoxic Podophyllotoxin Type-Lignans from the Steam Bark of Bursera fagaroides var. fagaroides

The hydroalcoholic extract of the steam bark of B. fagaroides var. fagaroides displayed potent cytotoxic activity against four cancer cell lines, namely KB (ED50 = 9.6 × 10−2 μg/mL), PC-3 (ED50 = 2.5 × 10−1 μg/mL), MCF-7 (ED50 = 6.6 μg/mL), and HF-6 (ED50 = 7.1 × 10−3 μg/mL). This extract also showed anti-tumour activity when assayed on mice inoculated with L5178Y lymphoma cells. Bioactivity-directed isolation of this extract, afforded seven podophyllotoxin-type lignans identified as podophyllotoxin (1), β-peltatin-A-methylether (2), 5′-desmethoxy-β-peltatin-A-methylether (3), desmethoxy-yatein (4), desoxypodophyllotoxin (5), burseranin (6), and acetyl podophyllotoxin (7) by 1D and 2DNMR and FAB-MS analyses, and comparison with reported values. All the isolated compounds showed potent cytotoxic activity in the cell lines tested, especially compound 3, which exhibited greater activity than camptothecin and podophyllotoxin against PC-3 (ED50 = 1.0 × 10−5 μg/mL), and KB (ED50 = 1.0 × 10−5 μg/mL). This is the first report of the isolation of podophyllotoxin and its acetate in a Bursera species.

Methyl dodonates, a new type of diterpenes with a modified clerodane skeleton from Dodonaea viscosa

Abstract Three new modified clerodanes (10, 12, 17) containing a tricyclo[5.4.0.01,3]undecane ring system were isolated from Dodonaea viscosa. These types of compounds have not been found in nature until now, but they have been proposed as hypothetical intermediates in the biogenetic pathway of diterpenes possessing bicyclo[5.4.0]undecane or bicyclo[5.3.0]decane ring systems. In support of this hypothesis, 17 was transformed into the bicyclo[5.4.0]undecane derivative 20. Additionally, we isolated the new 5,10-secoclerodane 21 and several known diterpenes. The structures were elucidated by spectroscopic methods, chemical reactions and X-ray diffraction analysis.

Hydroxylation of the diterpenes ent-kaur-16-en-19-oic and ent-beyer-15-en-19-oic acids by the fungus Aspergillus niger.

The diterpenes ent-kaur-16-en-19-oic acid (1) and ent-beyer-15-en-19-oic acid (2) are the major constituents of a spasmolytic diterpenic mixture obtained from the roots of Viguiera hypargyrea, a Mexican medicinal plant. Microbial transformation of 1 and 2 was performed with Aspergillus niger. Two metabolites, ent-7alpha,11beta-dihydroxy-kaur-16-en-19-oic acid (4) and ent-1beta,7alpha-dihydroxy-kaur-16-en-19-oic acid (5), were isolated from the incubation of 1, and one metabolite, ent-1beta,7alpha-dihydroxy-beyer-15-en-19-oic acid (6), was isolated in high yield (40%) from 2. The structures were elucidated on the basis of spectroscopic analyses and confirmed by X-ray crystallographic studies. Compounds 1-4 and 6 and methyl ester derivatives 4a and 6a were evaluated for their ability to inhibit the electrically induced contraction of guinea-pig ileum. Compounds 1, 3, 4, 4a and 5 were significantly active. These results showed that dihydroxylation of 1 at 7beta, 11alpha-, and 1alpha, 7beta-positions resulted in a loss of potency.

Enzymatic reduction of 9-methoxytariacuripyrone by Saccharomyces cerevisiae and its antimycobacterial activity.

Biotransformation processes have been successfully utilized to obtain products of pharmaceutical, chemical, food, and agricultural interest, which are difficult to obtain by classic chemical methods. The compound with antituberculous activity, 9-methoxy-tariacuripyrone (1), isolated from Aristolochia brevipes, was submitted to biotransformation with the yeast Saccharomyces cerevisiae under culture, yielding 5-amino-9-methoxy-3,4-dihydro-2H-benzo[h]chromen-2-one (2). The structure of 2 was elucidated on the basis of spectroscopic analyses. The results mainly show the reduction of the double bond and the nitro group of compound 1. Metabolite 2 demonstrated an increase in anti-tuberculous activity (MIC = 3.12 µg/mL) against the drug-sensitive Mycobacterium tuberculosis (H37Rv) strain, with respect to that shown by 1.

Ultrastructural changes on clinical isolates of Trichophyton rubrum, Trichophyton mentagrophytes, and Microsporum gypseum caused by Solanum chrysotrichum saponin SC-2.

Worldwide, dermatophytoses represent a high percentage of all superficial mycoses. The most frequently isolated dermatophyte is Trichophyton rubrum. Solanum chrysotrichum is a vegetal species widely used in Mexican traditional medicine to treat skin infections; its extract has been used to formulate an herbal medicinal product that is used successfully to treat Tinea pedis. Spirostanic saponin SC-2 from S. Chrysotrichum possesses high activity against dermatophytes. The present study reports the ultrastructural changes observed by means of transmission electron microscopy (TEM) in clinical isolates of T. rubrum, T. mentagrophytes, and Microsporum gypseum induced by saponin SC-2. Strains were grown in RPMI 1640 containing SC-2 (1600 microg/mL). Fungi were harvested at 6, 12, 24, and 48 h; controls without SC-2 were included. T. mentagrophytes was the most susceptible to the SC-2 saponin, followed by M. gypseum, while T. rubrum was the most resistant. The main alterations caused by the SC-2 saponin were as follows: i) loss of cytoplasmic membrane continuity; ii) organelle degradation; iii) to a lesser extent, irreversible damage to the fungal wall; and iv) cellular death.

Aryldihydronaphthalene-type lignans from Bursera fagaroides var. fagaroides and their antimitotic mechanism of action

Three new aryldihydronaphthalene-type lignans, namely, 7′,8′-dehydropodophyllotoxin (1); 7′,8′-dehydro acetylpodophyllotoxin (2); and 7′,8′-dehydro trans-p-cumaroylpodophyllotoxin (3), were isolated from the stem bark of Bursera fagaroides var. fagaroides (Burseraceae), together with six known lignans, podophyllotoxin (4), acetylpodophyllotoxin (5), 5′-desmethoxy-β-peltatin A methylether (6), acetylpicropodophyllotoxin (7), burseranin (8), and hinokinin (9). The coumarin scopoletin (10) was also isolated from this bark. The chemical structure of all these compounds was determined by spectroscopic analyses including 2D NMR. We demonstrated that compounds 1–3 show different degrees of cytotoxic activity against human nasopharyngeal (KB), colon (HF-6), breast (MCF-7) and prostate (PC-3) cancer cell lines, with IC50 values ranging from 1.49 to 1.0 × 10−5 μM. In vivo studies of the effect of these natural lignans on the cell cycle, cell migration and microtubule cytoskeleton of developing zebrafish embryos, demonstrated their antimitotic molecular activity by disturbing tubulin. This is the first report on the occurrence of aryldihydronaphthalene lignans in the genus Bursera of the Burseraceae family, as well as on the determination of their cytotoxic activity and mechanism of action.

Sphaeralcic acid and tomentin, anti-inflammatory compounds produced in cell suspension cultures of Sphaeralcea angustifolia.

Sphaeralcea angustifolia, an endangered plant species in Mexico, is employed to treat inflammatory processes and as a wound healing remedy. Scopoletin (1) was reported as one of the main bioactive compounds in this plant. Here, we isolated and identified compounds with anti-inflammatory properties from the suspension-cultured cells of S. angustifolia. The CH2Cl2 : CH3OH extract of the cells exhibited anti-inflammatory properties in acute inflammation models. Two compounds were isolated, 5-hydroxy-6,7-dimethoxycoumarin, named tomentin (2), and 2-(1,8-dihydroxy-4-isopropyl-6-methyl-7-methoxy)-naphthoic acid, denominated as sphaeralcic acid (3). Their structures were determined by spectroscopic and spectrometric analyses. The anti-inflammatory effects of both compounds were also evaluated. At a dose of 45 mg/kg, compound 2 inhibited the formation of λ-carrageenan footpad edema at 58 %, and compound 3 at 66 %. Local application of compound 2 (225 mM per ear) or 3 (174 mM per ear) inhibited the phorbol ester-induced auricular edema formation by 57 % or 86 %, respectively. The effect of compound 3 was dose-dependent and the ED50 was 93 mM.

Production of the Anti-Inflammatory Compound 6-O-Palmitoyl- 3-O-β-D-glucopyranosylcampesterol by Callus Cultures of Lopezia racemosa Cav. (Onagraceae)

Lopezia racemosa Cav. is a plant used in Mexican traditional medicine to heal inflammatory diseases. From this plant we isolated the novel compound 6-O-palmitoyl-3-O-β-D-glucopyranosylcampesterol (1) and 6-O-palmitoyl-3-O-β-D-glucopyranosyl-β-sitosterol (2), previously reported to have cytotoxic activity on several cancer cell lines. We evaluated the anti-inflammatory activity of 1 in vivo by mouse ear edema induced with 12-O-tetradecanoylphorbol-13-acetate (TPA) and 57.14% inhibition was observed. The aim of our study was to obtain callus cultures derived from this plant species with the ability to produce the compounds of interest. Callus cultures were initiated on MS basal medium amended with variable amounts of naphthaleneacetic acid (NAA), or 2,4-dichlorophenoxyacetic acid (2,4-D), combined or not with 6-benzylaminopurine (BAP). Ten treatments with these growth regulators were carried out, using in vitro germinated seedlings as source of three different explants: hypocotyl, stem node, and leaf. Highest yield of 1 was observed on callus derived from leaf explants growing in medium containing 1.0 mg/L 2,4-D and 0.5 mg/L BAP. Selected callus lines produced less 1 than wild plants but the in vitro cultured seedlings showed higher production. So we conclude that it could be attractive to further investigate their metabolic potential.

A Cytotoxic and Anti-inflammatory Campesterol Derivative from Genetically Transformed Hairy Roots of Lopezia racemosa Cav. (Onagraceae)

The genetically transformed hairy root line LRT 7.31 obtained by infecting leaf explants of Lopezia racemosa Cav with the Agrobacterium rhizogenes strain ATCC15834/pTDT, was evaluated to identify the anti-inflammatory and cytotoxic compounds reported previously for the wild plant. After several subcultures of the LRT 7.31 line, the bio-guided fractionation of the dichloromethane–methanol (1:1) extract obtained from dry biomass afforded a fraction that showed important in vivo anti-inflammatory, and in vitro cytotoxic activities. Chemical separation of the active fraction allowed us to identify the triterpenes ursolic (1) and oleanolic (2) acids, and (23R)-2α,3β,23,28-tetrahydroxy-14,15-dehydrocampesterol (3) as the anti-inflammatory principles of the active fraction. A new molecule 3 was characterized by spectroscopic analysis of its tetraacetate derivative 3a. This compound was not described in previous reports of callus cultures, in vitro germinated seedlings and wild plant extracts of whole L. racemosa plants. The anti-inflammatory and cytotoxic activities displayed by the fraction are associated to the presence of compounds 1–3. The present study reports the obtaining of the transformed hairy roots, the bioguided isolation of the new molecule 3, and its structure characterization.