ABSTRACT
Four pyrazines were isolated from the n-butanol fraction of Hypecoum erectum L. by using various chromatographic methods, including MCI gel, ODS, silica gel and semi-preparative HPLC. The structures of the isolated compounds were identified as hyperectpyrazin A (1), 1′S-(6-methylpyrazin-2-yl)-ethane-1′,2′-diol (2), 2-hydroxymethyl-6-methylpyrazin (3) and pyrazine-2-carboxylic acid (4) by spectroscopy methods (1D NMR, 2D NMR, UV, IR, MS, etc.). The absolute configuration of compound 2 was determined by using the Mo2(OAc)4 induced CD analysis for the first time. Compound 1 was a new compound, compounds 2-4 were isolated from H. erectum for the first time. Compounds 1-4 were evaluated for their inhibition against acetylcholinesterase and nitric oxide generation induced by lipopolysaccharide-RAW264.7 macrophage cells. At a concentration of 50 μmol·L-1, compounds 2 and 4 displayed inhibitory effects on acetylcholinesterase with the inhibition rates of 44.40% and 43.99%, respectively.
ABSTRACT
Syncope is a common emergency of children and adolescents,which has serious influence on the quality of life.Neurally-mediated syncope,including postural tachycardia syndrome,vasovagal syncope,orthostatic hypotension and orthostatic hypertension,is the main cause of syncope in children and adolescents.The main manifestations of neurally-mediated syncope are diverse,such as dizziness,headache,chest tightness,chest pain,pale complexion,fatigue,pre-syncope and syncope.Although the clinical manifestations are similar,each subtype of syncope has its hemodynamic feature and optimal treatment option.The diagnosis rate of syncope in children has been greatly improved on account of the development of the diagnostic procedures and methods.In recent years,with the promotion of head-up tilt test and drug-provocated head-up tilt test,the hemodynamic classification of neurally-mediated syncope gets continually refined.In recent years,with the effort of clinicians,an appropriate diagnostic protocol for children with syncope has been established.The initial evaluation consists of history taking,physical examination,standing test and standard electrocardiography.After the initial evaluation,some patients could be diagnosed definitely,such as postural tachycardia syndrome,orthostatic hypotension,and situational syncope.Those with a specific entity causing syncope need selective clinical and laboratory investigations.Patients for whom the cause of syncope remained undetermined should undergo head-up tilt test.The precise pathogenesis of neurally-mediated syncope is not entirely clear.In recent years,studies have shown that neurally-mediated syncope may be related to several factors,including hypovolemia,high catecholamine status,abnormal local vascular tension,decreased skeletal muscle pump activity and abnormal neurohumoral factors.Currently based on the possible pathogenesis,the individualized treatment of neurally-mediated syncope has also been studied in-depth.Generally,the management of neurallymediated syncope includes non-pharmacological and pharmacological interventions.Patient education is the fundamental part above all.In addition to exercise training,the first-line treatments mainly include oral rehydration salts,beta adrenoreceptor blockers,and alpha adrenoreceptor agonists.By analyzing the patient's physiological indexes and biomarkers before treatment,the efficacy of medication could be well predicted.The individualized treatment will become the main direction in the future researches.