Tribestan is an original Bulgarian phytochemical product of plan origin. The active components are non-steroidal saponins of furostanol type, isolated from the plant Tribulus terrestris L. It has been standardized on the basis of the main compound protodioscine (not less than 45% of the total quantity).

The substance is yellow-brown amorphous powder with specific aroma and bitter taste; soluble in water, sparingly soluble in methyl alcohol and insoluble in chloroform.