Exploring the molecular basis of action of ring D aromatic steroidal antiestrogens.

Salpichrolides are natural plant steroids that contain an unusual six-membered aromatic ring D. We recently reported that some of these compounds, and certain analogs with a simplified side chain, exhibited antagonist effects toward the human estrogen receptor (ER), a nuclear receptor whose endogenous ligand has an aromatic A ring (estradiol). Drugs acting through the inhibition or modulation of ERs are frequently used as a hormonal therapy for ER(+) breast cancer. Previous results suggested that the aromatic D ring was a key structural motif for the observed activity; thus, this modified steroid nucleus may provide a new scaffold for the design of novel antiestrogens. Using molecular dynamics (MD) simulation we have modeled the binding mode of the natural salpichrolide A and a synthetic analog with an aromatic D ring within the ERα. These results taken together with the calculated energetic contributions associated to the different ligand-binding modes are consistent with a preferred inverted orientation of the steroids in the ligand-binding pocket with the aromatic ring D occupying a position similar to that observed for the A ring of estradiol. Major changes in both dynamical behavior and global positioning of H11 caused by the loss of the ligand-His524 interaction might explain, at least in part, the molecular basis of the antagonism exhibited by these compounds. Using steered MD we also found a putative unbinding pathway for the steroidal ligands through a cavity formed by residues in H3, H7, and H11, which requires only minor changes in the overall receptor conformation.

Synthesis and biological evaluation of salpichrolide analogs as antiestrogenic agents.

The antiestrogenic activity of three natural salpichrolides A, G and B (1, 3 and 4) and of five synthetic analogs containing an aromatic D ring and a simplified side chain (5-9), was evaluated on MCF-7 cells. The 2,3-ene-1-keto steroids 8 and 9 were obtained from 3ß-acetoxy-17(13→18)-abeo-5αH-pregna-13,15,17-trien-20-one, the key step for these syntheses being a Wharton carbonyl rearrangement of a 1,2-epoxy-3-keto steroid to the allylic alcohol using hydrazine hydrate. The antiestrogenic activity was evaluated by performing dose-response experiments in ER(+) MCF-7 breast cancer cells. Dose-dependent proliferation was quantified via [(3)H]-thymidine incorporation after 3 days treatment. Salpichrolides A, G and B and analogs 5, 8 and 9 were active as antiestrogens with compound 9 being the most active of the synthetic analogs. Compounds 5 and 9 were also evaluated against the ER(-) cell line MDA-MB-231 and shown to be inactive.

Antifeedant activity of withanolides from Salpichroa origanifolia on Musca domestica.

The antifeedant effect of several salpichrolides on larvae of Musca domestica was investigated. Three naturally occurring compounds, salpichrolide A (1), salpichrolide C (2), and salpichrolide G (3), previously isolated from Salpichroa origanifolia, and two known (4, 6) and three new (5, 7, 8) synthetic analogues were tested. The maximal effect on development was observed for salpichrolide A (1), while salpichrolide G (3) was the most toxic. The content of the salpichrolides in S. origanifolia was monitored by HPLC during plant development, reaching a maximum during summer.

Tratamiento de la enfermedad de Chagas / Treatment of Chagas disease

En la actualidad se acepta que la enfermedad de Chagas humana debe ser tratada en cualquier período de su evolución con la única excepción del período crónico terminal. En el período agudo clínico, infección de menos de 2 meses así como en el biológico: pesquisa de parásitos al fresco, frotis, gota gruesa y con serología convencional positiva e IgM(+). El ideal de tratamiento es con nifurtimox (NF) 8-10 mg/kg día en adultos y 15 mg/kg día en niños por 60-90 días. La dosis se reparte en tres tomas. La curación clínica y serológica es de un 60 por ciento. En Brasil donde se utiliza este fármaco se trata con benznidazol (BNZ) 5 mg/kg día (adultos) y 5-10 mg/kg día en niños por 60 días. En las infecciones congénitas la terapia debe ser precoz en cuanto se realice el diagnóstico por clínica y pesquisa del parásito al fresco, frotis, microstraut etc. Muchas veces el diagnóstico se efectúa por persistenica de la serología por más de 6 meses y el recién nacido ya esta en etapa crónica de la infección. Es necesario efectuar seguimiento clínico serológico y parasitológico de los casos. Las infecciones accidentales deben ser tratadas por 10 días. En los trasplantes de órganos en que el receptor o dador es chagásico se debe indicar terapia con NF o BNZ a igual dosis y tiempo que la señalada anteriormente. Las reactivaciones en los casos crónicos ejem: que adquieren un SIDA o que presentan depresiones del sistema inmunidad celular como leucemias, Hodgkin, etc se deben tratar como cuadros agudos con NF ó NBZ por períodos prolongados de 5 ó más meses. En estos casos obviamente la prevención es lo ideal: hacer serología para Chagas a los pacientes con SIDA, etc