by TCM has a wealth of clinical experience and theoretical basis, and a large number of effective clinical prescriptions have been accumulated. In recent years a large number of studies have shown that TCM prescription and its active ingredient can improve cerebral ischemic injury in experimental animal [20,21]. Ginsenoside Rb1 and Rg1, for example, improved spatial learning and increase hippocampal synaptophysin level in mice [22]. Curcumin had been demonstrated to stimulate developmental and adult hippocampal neurogenesis, and a biological activity that may enhance neural plasticity and repair [23]. A recent report has shown that NeuroAid (MLC601 and MLC901), a Traditional Chinese Medicine is used in China for patients after stroke, reduced the increase in escape latency and in swim distance induced by ischemia [24]. With an extensive clinical experience, there are ample opportunities to discover natural compounds that effectively promote the proliferation of NSPCs and neurogenesis from TCM. Sal B was discovered in an in vitro screening assay for searching the NSPCs proliferation-inducing natural molecules. It is one of the major ingredients in the water-soluble extracts of S. miltiorrhiza Bunge which has been reported to reduce cerebrovascular disease [25–27]. As a well-known Chinese herbal medicine, Danshen (Salvia miltiorrhiza) has been widely used in traditional Chinese medicinal preparation for the treatment of ischemic disease, and the medicinal properties of this plant have been extensively studied [28,29]. Several studies have demonstrated the effect of salvianolic acids on preventing brain injury [27,30]. Importantly, Sal B was reported to be capable of improving the recovery of motor function after cerebral ischemia in rats [31,32]. However, research on the mechanism of Sal B in treatment of stroke, and the molecular mechanisms responsible for the reported beneficial Salvianolic Acid B Promote Neurogenesis cerebrovascular effects of Sal B are fairly rare. Meanwhile, the effect of delayed treatment with Sal B after ischemic stroke is still unclear. Therefore, the effect of chronic Sal B treatment beginning seven days after ischemic stroke on neurological deficits and pathophysiology after the transient cerebral ischemic model in rats were studied in our research. Considering the significance of neurogenesis-related brain recovery, the present study was undertaken to examine the promotive effects of Sal B on NSPCs proliferation and neurogenesis. We provide evidence that Sal B increasing the proliferation of NSPCs in vitro and in vivo. These actions are at least in part mediated by altering the PI3K/Akt signaling pathway. Additionally, delayed post-ischemic administration of Sal B had beneficial effects on the recovery of cognitive function. The stimulative effects of Sal B on NSPCs self-renew and neurogenesis might be associated with a favorable outcome for stroke and other neurological disease. Results Salvianolic acid B induced the proliferation of cultured NSPCs in vitro Forty-five herbal compounds, which are extensively used clinically for treating stroke in China, were screened in an in vitro proliferation assay to identify compounds that could induce proliferation of NSPCs. As shown in Fig. 1, among these natural compounds screened, berberine and Sal B displayed marked activity promoting NSPCs proliferation. In the following study, the proliferative effect of berberine and Sal B were systematically investigated but the action of berberine was proved to be an Figure 1. Screening for NSPCs proliferation-inducing natural materials. The proliferation-inducing activities on NSPCs of a total of 45 natural compounds, which were from medicinal materials extensively used in China to treat stroke clinically, were tested using a MTS assay, and the results are expressed in fold change relative to the corresponding controls. The proliferation-inducing effect of the most potent compound, Sal B (A) and berberine (B), were indicated by the arrow and its structure is shown in the inset. Data represent the mean 6 S.D. from three independent experiments. **Significant difference from the control group at P,0.01. doi:10.1371/journal.pone.0035636.g001 PLoS ONE | www.plosone.org 2 April 2012 | Volume 7 | Issue 4 | e35636