Role of disulfide linkage in action of bis(dialkylaminethiocarbonyl)disulfides as potent double-Edged microbicidal spermicide: Design, synthesis and biology

• 34 compounds synthesized and evaluated for spermicidal and microbicidal activities.
• Spermicidal compounds were up to fifty fold more active than N-9 in vitro.
• Compounds 12 and 17 have exhibited remarkable in vivo efficacy.
• Role of S–S bond was established by the loss of activity on chemical modification.
• Sulfhydryl inhibition over sperm and Trichomonas shown by fluorescence labeling.

Trichomoniasis and candidiasis are amongst the most common morbidity-causing reproductive tract infections, generally treated by Metronidazole and Fluconazole respectively. Poor vaginal efficacy, drug-resistance and non-spermicidal nature limit their use as topical microbicidal contraceptives. Bis(dialkylaminethiocarbonyl)disulfides (4–38) were designed as dually active, non-surfactant molecules capable of eliminating Trichomonas vaginalis and Candida strains as well as irreversibly immobilizing 100% human sperm instantly, at doses non-cytotoxic to human cervical epithelial cells and vaginal microflora in vitro. Compounds 12, 16, 17 were fifty times more active than nonoxynol-9, OTC vaginal spermicide, and compounds 12 and 17 have shown remarkable in vivo activity in rabbit model. Most promising compound 17 has shown promise for further development as a double-edged vaginal microbicide due to their improved activity and safety along with notable in vivo trichomonicidal activity. Role of disulfide group was established by loss of spermicidal activity on chemical modifications (39–56). These disulfides might be targeting thiol groups present over cell membrane of human sperm and Trichomonas as shown by fluorescence labeling of free thiols.

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