Résumé dans la langue de publication Novel aromatic ring derivatives represented by formula (I) or their pharmaceutical acceptable salts are provided. wherein Nu represents a 5- or 6-membered aromatic ring; ch1 and ch2 each represents a cross-linking group; and A represents an aromatic ring. These compounds have blood sugar-depressing activity or PDE 5 inhibitory activity and are useful as medicines for treating impaired glucose tolerance, diabetes, diabetic complications, syndrome of insulin-resistance, polycystic ovary syndrome, hyperlipidemia, atherosclerosis, cardiovascular disorders, hyperglycemia, hypertension, stenocardia, pulmonary hypertension, congestive heart failure, glomerulopathy, tubulointerstitial disorders, renal failure, angiostenasis, distal angiopathy, cerebral apoplexy, chronic reversible obstructions, autoimmune diseases, allergic rhinitis, urticaria, glaucoma, diseases characterized by enteromotility disorders, impotence, nephritis, cachexia, pancreatitis, restenosis after PTCA, etc.