Jagdamba P. Maikhuri

In search of new chemical entities with spermicidal and anti-HIV activities

Several compounds belonging to 2-isoxazolines (4,5a-c), isoxazoles (3,6a-c) and 1-amino-1-cycloalkyl-2-substituted phenyl ethanes (16-18,a-e) have been synthesised and found to possess spermicidal activity. Out of these a couple of compounds (5a and 6a) exhibit anti-HIV activity.

Synergistic chemoprotective mechanisms of dietary phytoestrogens in a select combination against prostate cancer

Combination of dietary phytoestrogens with diverse molecular mechanisms may enhance their anticancer efficacy at physiological concentrations, as evidenced in epidemiological studies. A select combination of three dietary phytoestrogens containing 8.33 μM each of genistein (G), quercetin (Q) and biochanin A (B) was found to be more potent in inhibiting the growth of androgen-responsive prostate cancer cells (LNCaP) as well as DU-145 and PC-3 prostate cancer cells in vitro than either 25 μM of G, B or Q or 12.5+12.5 μM of G+Q, Q+B or G+B. Subsequent mechanistic studies in PC-3 cells indicated that the action of phytoestrogens was mediated both through estrogen receptor (ER)-dependent and ER-independent pathways as potent estrogen antagonist ICI-182780 (ICI, 5 μM) could not completely mask the synergistic anticancer effects, which were sustained appreciably in presence of ICI. G+Q+B combination was significantly more effective than individual compounds or their double combinations in increasing ER-β, bax (mRNA expression); phospho-JNK, bax (protein levels); and in decreasing bcl-2, cyclin E, c-myc (mRNA expression); phospho-AKT, phospho-ERK, bcl-2, proliferating cell nuclear antigen (protein levels) in PC-3 cells. Phytoestrogens also synergistically stimulated caspase-3 activity. Our findings suggest that selectively combining anticancer phytoestrogens could significantly increase the efficacy of individual components resulting in improved efficacy at physiologically achievable concentrations. The combination mechanism of multiple anticancer phytochemicals may be indicative of the potential of some vegetarian diet components to elicit chemopreventive effects against prostate cancer at their physiologically achievable concentrations, in vivo.

Effect of spermicides on Lactobacillus acidophilus in vitro- nonoxynol-9 vs. sapindus saponins.

Saponins extracted from the fruit pericarp of Sapindus mukorosii were tested for their bactericidal/bacteriostatic property against Lactobacillus acidophilus. Nonoxynol-9 was used as a reference compound for the comparison of activity. Lactobacillus colonies were grown on specific medium (Rogosa SL agar) containing different concentrations of saponins and nonoxynol-9 in an atmosphere of 5% CO2/95% air at 37 degrees C for 72 h. The number and size of colonies were recorded at the end of the experiment and compared with controls. Results indicated that nearly 90% of Lactobacillus colonies with minor reduction in size thrived at 0.05% concentration of saponins whereas only 18% of colonies with approximately 75% reduction in size grew in dishes containing 0.05% nonoxynol-9. At higher concentrations of saponins, there was a gradual, dose-dependent reduction in the number and size of colonies and at 2.5% concentration there was an approximately 55% reduction in the number and 60% reduction in the size of surviving colonies. No lactobacillus colonies, however, grew in dishes containing 0.1% and higher concentrations of nonoxynol-9. The studies indicate that Sapindus saponins as compared to nonoxynol-9 are far less toxic to lactobacillus species and therefore saponins containing spermicidal preparations are likely to be more vaginal-friendly than equivalent nonoxynol-9 preparations.

Imidazole derivatives as possible microbicides with dual protection

Twenty seven derivatives (2-28) of 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethanol were synthesized and evaluated for anti-trichomonas, spermicidal and antifungal activities. Twenty six compounds were active against Trichomonas vaginalis at MIC ranging from 1-42 microM and seven compounds (9,18,19,22,24,26,28) immobilized 100% human spermatozoa at 1% concentration (w/v). Twenty three compounds (2,3,5,8-26,28) exhibited antifungal activity at 25-50 microg/mL concentration. Seven compounds (9,18,19,22,24,26,28) showed significant anti-trichomonas and spermicidal activities and also exhibited mild antifungal activity. All the compounds were highly safe towards human cervical cell line (HeLa) as shown by the cell-viability assay of HeLa cells at 200 microg/mL concentration, whereas nonoxynol-9 (N-9, the marketed spermicidal microbicide) was highly cytotoxic. Therefore, it may be concluded that introduction of the pharmacophore responsible for spermicidal activity into a proven anti-trichomonas structure may lead to a potent dual function microbicide better and safer than N-9.

Mechanism of action of some acrylophenones, quinolines and dithiocarbamate as potent, non-detergent spermicidal agents

Some suitably substituted acrylophenones, quinolines and dithiocarbamate were synthesized as new generation, non-detergent spermicides and were studied for their mechanism of action in comparison with various known spermicides belonging to several different classes of chemical compound. Nonoxynol-9, benzalkonium chloride, Sapindus saponins, verapamil, emetine and tartaric acid were used as reference molecules to study the effect of new spermicides on human sperm motility parameters (using computer-assisted semen analyzer), plasma membrane integrity, lipid peroxidation and defense system against reactive oxygen species (ROS). Results have indicated that sperm plasma membrane remains the primary site of action of most of the spermicides, though the effect may be predominantly on the physiological integrity rather than the structural integrity in case of the new compounds. Lipid peroxidation may play an important role in disrupting sperm membrane physiology that may or may not be accompanied with a detrimental effect on the defense system of the human spermatozoa against the ROS.

Novel Trichomonacidal Spermicides

ABSTRACT Metronidazole, the U.S. Food and Drug Administration-approved drug against trichomoniasis, is nonspermicidal and thus cannot offer pregnancy protection when used vaginally. Furthermore, increasing resistance of Trichomonas vaginalis to 5-nitro-imidazoles is a cause for serious concern. On the other hand, the vaginal spermicide nonoxynol-9 (N-9) does not protect against sexually transmitted diseases and HIV in clinical situations but may in fact increase their incidence due to its nonspecific, surfactant action. We therefore designed dually active, nonsurfactant molecules that were capable of killing Trichomonas vaginalis (both metronidazole-susceptible and -resistant strains) and irreversibly inactivating 100% human sperm at doses that were noncytotoxic to human cervical epithelial (HeLa) cells and vaginal microflora (lactobacilli) in vitro. Anaerobic energy metabolism, cell motility, and defense against reactive oxygen species, which are key to survival of both sperm and Trichomonas in the host after intravaginal inoculation, depend crucially on availability of free thiols. Consequently, molecules were designed with carbodithioic acid moiety as the major pharmacophore, and chemical variations were incorporated to provide high excess of reactive thiols for interacting with accessible thiols on sperm and Trichomonas. We report here the in vitro activities, structure-activity relationships, and safety profiles of these spermicidal antitrichomonas agents, the most promising of which was more effective than N-9 (the OTC spermicide) in inactivating human sperm and more efficacious than metronidazole in killing Trichomonas vaginalis (including metronidazole-resistant strain). It also significantly reduced the available free thiols on human sperm and inhibited the cytoadherence of Trichomonas on HeLa cells. Experimentally in vitro, the new compounds appeared to be safer than N-9 for vaginal use.

In vitro testing of rationally designed spermicides for selectively targeting human sperm in vagina to ensure safe contraception

BACKGROUND Rational synthesis of novel structures resulted in two unique molecules (DSE-36 and DSE-37, disulphide esters of carbothioic acid) that killed sperm 25 times more strongly and with a precisely targeted action than nonoxynol-9 (N-9). We examine the effects of DSE-36 and DSE-37 on human spermatozoa versus HeLa cells to establish specificity and safety compared with N-9. METHODS AND RESULTS At spermicidal EC(100) (20 microg/ml) DSE-36 and DSE-37 killed 100% sperm in <30 s (Sander-Cramer assay) and at EC(50) induced apoptosis in sperm (Annexin-V-fluorescein isothiocyanate and JC-1 labelling and Flow Cytometry) in 3 h. However, at EC(100) these molecules had no effect on HeLa cells by 24 h or on cell viability [3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay], surface ultrastructure (scanning electron microscopy), Annexin-V and JC-1 labelling pattern and reactive oxygen species (ROS) generation. N-9, with a spermicidal EC(100) of 500 microg/ml, decreased HeLa cell viability at 20 microg/ml in 24 h (P < 0.001), accompanied by acute damage to cell surface ultrastructural topography, induction of apoptosis and ROS generation. Unlike DSE-36 and DSE-37, N-9 also significantly induced mRNA levels (RT-PCR) of pro-inflammatory biomarkers (interleukin (IL)-1 alpha, IL-6, IL-8, RANTES) in HeLa cells and increased IL-6 and IL-8 secretion (P < 0.001, enzyme-linked immunosorbent assay). Furthermore, DSE-36 and DSE-37 did not inhibit Lactobacillus growth at EC(100) and exhibited mild microbicidal activity against Trichomonas vaginalis, while N-9 inhibited Lactobacillus and Trichomonas growth but had a lower prophylactic index. CONCLUSIONS The ability of these novel spermicides to kill sperm almost instantaneously at innocuously low concentration indicates their worth as improved active ingredients for vaginal contraceptive preparations compared with N-9.

Seasonal variations in daily sperm production rate of rhesus and bonnet monkeys

Daily sperm production (DSP) rate was estimated in adult male rhesus and bonnet monkeys to evaluate seasonal changes in the gametogenic activity of the testes. Three monkeys of each species were castrated during breeding and non‐breeding seasons and DSP rate was estimated by enumerating the homogenization‐resistant spermatid nuclei of steps 13 and 14. Results indicated a significant reduction in the DSP rate per testis during the non‐breeding season in two species, along with a marked decline in the testis weight. However, the gametogenic capacity of seminiferous tubules did not appear to be markedly affected during non‐breeding season, as the DSP rate per gram parenchyma of testis was only marginally reduced. The seasonal changes in DSP were much more pronounced in the rhesus than in the bonnet monkey. The feasibility of circanual rhythm in DSP of sub‐human primates to form a baseline for the study of reproductive function in male is discussed.

Functional attenuation of human sperm by novel, non-surfactant spermicides: precise targeting of membrane physiology without affecting structure

BACKGROUND We have attempted to identify structural, physiological and other targets on human sperm vulnerable to the spermicidal action of two novel series of non-detergent molecules, reported to irreversibly immobilize human sperm in <30 s, apparently without disrupting plasma membrane. METHODS Three sperm samples were studied. Scanning and transmission electron microscopy were used to assess structural aberrations of sperm membrane; plasma membrane potential and intracellular pH measurements (fluorometric) were used to detect changes in sperm physiology; reactive oxygen species (ROS, fluorometric) and superoxide dismutase activity (colorimetric) were indicators of oxidative stress; and sperm dynein ATPase activity demonstrated alterations in motor energy potential, in response to spermicide treatment. Post-ejaculation tyrosine phosphorylation of human sperm proteins (immunoblotting) was a marker for functional integrity. RESULTS Disulfide esters of carbothioic acid (DSE compounds) caused complete sperm attenuation at > or =0.002% concentration with hyper-polarization of sperm membrane potential (P < 0.001), intracellular alkalinization (P < 0.01), ROS generation (P < 0.05) and no apparent effect on sperm (n = 150) membrane structure. Isoxazolecarbaldehyde compounds required > or =0.03% for spermicidal action and caused disrupted outer acrosomal membrane structure, depolarization of membrane potential (P < 0.001), intracellular acidification (P < 0.01) and ROS generation (P < 0.01). Detergent [nonoxynol-9 (N-9)] action was sustainable at > or =0.05% and involved complete breakdown of structural and physiological membrane integrity with ROS generation (P < 0.001). All spermicides caused functional attenuation of sperm without inhibiting motor energetics. Unlike N-9, DSE-37 (vaginal dose, 200 microg) completely inhibited pregnancy in rats and vaginal epithelium was unchanged (24 h,10 mg). CONCLUSIONS The study reveals a unique mechanism of action for DSE spermicides. DSE-37 holds promise as a safe vaginal contraceptive. CDRI Communication No. 7545.

Potentiating Metronidazole Scaffold against Resistant Trichomonas: Design, Synthesis, Biology and 3D-QSAR Analysis.

Metronidazole (MTZ), the FDA-approved drug against Trichomonas vaginalis (TV), is being challenged seriously by drug resistance, while its inertness to sperm makes it ineffective as a vaginal contraceptive. Thirteen piperidine dithiocarbamate hybrids of 2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethane (8-20) were designed to potentiate the MTZ framework against drug resistance and sperm. New compounds were 1.2-12.1 times more effective against MTZ-susceptible and -resistant strains of TV. All of the compounds exhibited high safety toward cervical (HeLa) cells and Lactobacillus. Thirty-eight compounds were scrutinized by CoMFA and CoMSIA techniques of 3D quantitative structure-activity relationship. Good predictive r pred (2) values for CoMFA and CoMSIA models reflected the robustness of the predictive ability. This was validated by designing five new analogues (46-50), which were potently microbicidal (3-10 and 10-20 times against MTZ-susceptible and -resistant TV, respectively) and spermicidal. This in vitro study may have significant clinical relevance, which could become evident in due course.