Antihistaminic and other pharmacological actions both in vitro and in vivo were evaluated on 18 compounds involving octahydro-2H-pyrido1, 2-apyrazine (I), decahydropyrido1, 2-d1, 4diazepine (II), and ...decahydropyrido1, 2-a1, 4diazepine (III) derivatives, and correlation between chemical structure and antihistaminic activity was investigated. Since it was found that the most effective gross structure and substituent was I and a benzhydryl grouping, respectively, 2-benzhydryloctahydro-2H-pyrido1, 2-apyrazine (I-2) was established as the most powerful agent among these compounds. This was demonstrated by the fact that I-2 exhibited a high antihistaminic potency both in vitro and in vivo, as well as a strong adsorbability to guinea pig ileum which was estimated to be equivalent to diphenhydramine (IV). Furthermore, I-2 gave a lower acute toxicity than IV or homochlorcyclizine and was more effective than IV not only in antiserotoninic and anticholinergic activities but also in anti-barium activity. A weak surface anesthetic effect of I-2 was also observed on the cornea of a guinea pig.
Gallic acid, methyl gallate, dehydrodigallic acid, three tannic constituents named MP-2, MP-3, MP-4 and a related substance MP-10 were isolated from chestnut galls by solvent fractionation and column ...chromatography. Hydrolysis with tannase revealed the components of these tannic substances as follows, MP-2: d-glucose, gallic acid and compound I (3,4, 5-trihydroxybenzyl alcohol); MP-3 and MP-4: d-glucose, compound I and compound II (dehydrodigallic acid); MP-10: d-glucose and compound I.
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