Abstract: Pterin derivatives having the general formula I ##STR1## wherein R.sub.1 represents a group --(CHOH).sub.2 --CH.sub.3 or --(CHOH).sub.2 --CH.sub.2 OH,R.sub.2 and R.sub.3 are not the same and represent either hydrogen or the group --(CH.sub.2).sub.3 CONH(CH.sub.2).sub.4 --NH--R.sub.4, wherein R.sub.4 represents hydrogen or a usual label group for immunoassays or usual coating/support materials for solid phase immunoassays or immunogenic groups for the preparation of antibodiesare useful for the preparation of sensitive immunoassays for the determination of neopterin and biopterin.

Abstract: 5-Aminosalicylic acid O-sulfates of physiologically acceptable bases are new substances which are preparable by esterification of 5-nitrosalicylic acid alkyl esters with carbodiimide and sulfuric acid, alkaline saponification of the alkyl ester group and reduction of the thus obtained 5-nitrosalicylic acid O-sulfates. Said substances are useful as drugs, more specifically for the treatment of colitis ulcerosa, enteritis regionalis Crohn (morbus Crohn), chronic nonspecific colitis and diverticulitis.

Abstract: Salicylazobenzoic acid is more useful than salazosulfapyridine for the treatment of colitis ulcerosa, enteritis regionalis (Morbus Crohn), chronic nonspecific colitis and diverticulitis. Salicylazobenzoic acid is used in the form of tablets and dragees or enemae in which it may be used in the form of free acid, compatible salts or mixtures thereof.

Abstract: 1. Immunological method for the determination of free substances having hapten properties.2.1. Immunological methods for the determination of free substances having hapten properties, especially of free thyroid hormones, are based on various determination principles, all of which either have disadvantages from the practical viewpoint or, by reason of the basic principle of the method, provide limited information in marginal cases. The new method is intended to simplify and improve the routine clinical determination of free substances, because of the avoidance of sources of error associated with known methods, while having a procedure which is straightforward for practical use.2.2.