A method for isolating the bioactive component of the water-soluble extract of Uncaria tomentosa known as C-MED-100, comprising (i) precipitating the spray drying carrier from C-MED-100; (ii) using the resulting C-MED-100 to obtain a spotting mixture for thin layer chromatography (TLC); (iii) spotting the C-MED-100 spotting mixture on pre-run TLC plates and eluting the plates to obtain the fluorescing band with R_f=0.2-0.3; (iv) scraping off the R_f=0.2-0.3 band, eluting it in ammonia and freeze drying the eluted band to form a powder; and (v) extracting the powder with methanol to remove solubilized silica gel, concentrating the methanol solution and crystalizing the concentrated solution to obtain the bioactive component. The isolated bioactive component is a quinic acid analog, preferably quinic acid lactone. A pharmaceutical composition comprising a pharmaceutically effective amount of the bioactive component and a nontoxic inert carrier or diluent. The bioactive component may be used to enhance immune competency, treat disorders associated with the immune system, inhibit the inflammatory response, treat disorders associated with the inflammatory response, enhance the anti-tumor response, and treat disorders associated with the response to tumor formation and growth, all in mammals.