Antifungal activities and action mechanisms of compounds from Tribulus terrestris L.

Introduction

In recent 20 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 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 Candida 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. For example, the use of amphotericin B, known as the “gold standard”, is limited because of its infusion-related reactions and nephrotoxicity. The use of azoles, such as fluconazole, ketoconazole and miconazole, has resulted in clinically resistant strains of Candida spp. A 3.6–7.2% of vaginal isolates of Candida albicans from women with candidal 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, Tribulus terrestris L. is used for treating cutaneous pruritus, edema, inflammation and tracheitis. In our previous study, we isolated and identified 10 compounds from Tribulus terrestris L.. In the present report, eight of the 10 saponins were tested to investigate their antifungal properties, especially against Candida albicans.