In recent twenty years, the risk of opportunistic fungal infections has greatly increased in patients who are severely immunocompromised due to cancer chemotherapy, organ or bone marrow transplantation, and human immunodeficiency virus infection. Candida albicans (C. albicans) is an organism that is most often associated with serious fungal infections, and can cause fungal diseases in immunocompromised patients, including cancer patients, organ transplant patients, and those with human immunodeficiency virus infections. Candidal vaginitis is predominantly caused by strains of C. albicans (90%), and remains to be a common problem in immunocompetent or healthy women.
Despite advances in antifungal therapies, many problems remain to be solved for most antifungal drugs available. Fluconazole was the mostly used azole drugs, and its use has resulted in clinically resistant strains of Candida spp. Especially, 3.6—7.2% of vaginal isolates of Candida spp. from women with Candida vaginitis is resistant to fluconazole. This situation highlights the need for advent of safe, novel and effective antifungal compounds.
Plants provide abundant resources of antimicrobial compounds and have been used for centuries to inhibit microbial growth. Tribulus terrestris L. (Zygophyllaceae) is an annual creeping herb widely growing in China. It is also distributed in Japan, Korea, western Asia, southern Europe, and Africa. In traditional Chinese pharmaceuticals, the fruit of T. terrestris L. is used for treating cutaneous pruritus, edema, inflammation and tracheitis. In our previous study, we isolated and identified eight steroid saponins from T. terrestris. In the present report, eight steroid saponins were tested to investigate their properties against fluconazole-resistant yeasts often encountered clinically, especially C. albicans.