In vitro study of the tocolytic effect of oroxylin A from Scutellaria baicalensis root

After pregnancy, the endocrinology of the body of pregnant women obviously changes, including uterine contraction agonist receptors (such as oxytocin receptor, prostaglandin receptor, β-adrenergic receptor, and corticotrophin releasing hormone receptor), and ion channel proteins which determine the resting membrane potential and excitability of myocytes [1]. Dysfunctional uterine contractions can lead to premature delivery. Spontaneous preterm labo and delivery accounts for approximately one-third of preterm births, which is the predominant cause of prenatal mortality and morbidity. The wide range of tocolytic agents in use is testament to the fact that we still do not have an ideal drug available [2]. Therefore, development of new safe and effective tocolytic agents is an important research topic.The Chinese herbs, Huang-Chi, Scutellaria baicalensis, has been widely used to treat several diseases such as inflammation, hypertension, suppressive dermatitis, diarrhea, and pyrogenic infections [3]. Oroxylin A (5,7-dihydroxy-6-methoxyflavone) is a flavonoid that is an active component isolated from the root of S. baicalensis. Several previous reports suggested that oroxylin A is a potential anti-inflammatory agent [4]. It has suppressive effects on superoxide and nitric oxide (NO) generation [5] and an inhibitory effect on diclofenac 4-hydroxylation (CYP2C9) activity [6]. In addition, it inhibits lipopolysaccharide-induced inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 gene expression by suppressing nuclear factor-κB (NF-κB) activation [7,8], and it has also been reported to suppress lymphocyte blastogenesis [9,10]. However, the effect of oroxylin A on the uterus is still unknown. The tocolytic effect of oroxylin A is demonstrated in the present study.Oxytocin, acetylcholine (Ach), (S)-(-) propranolol hydrochloride, dimethyl sulfoxide (DMSO), papaverine HCl, tetraethylammonium (TEA), 4-aminopyridine (4-AP), glipizide, and N-nitro-L-arginine (LNNA) were obtained