METHODS: In the present study, an aqueous two-phase system (ATPS) of polyethylene glycol (PEG)-(NH4)2SO4 was used to extract Arctium lappa L. polysaccharides (ALPs) from the Arctium lappa L. roots, the optimal extraction conditions of crude ALPs were optimized by using the single-factor experiment and response surface methodology. The structure and composition of ALPs were determined by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and high-performance liquid chromatography (HPLC). At the same time, the antioxidant activity of ALPs was investigated by in vitro antioxidant experiment.
RESULTS: The optimized extraction parameters for extraction ALPs were as follows: the PEG relative molecular weight of 6,000, a quality fraction of PEG 25%, a quality fraction of (NH4)2SO4 18%, and an extraction temperature of 80°C. Under these conditions, the extraction rate of ALPs could reach 28.83%. FTIR, SEM and HPLC results showed that ALPs were typical acidic heteropolysaccharides and had uneven particle size distribution, an irregular shape, and a rough surface. The ALPs were chiefly composed of glucose, rhamnose, arabinose, and galactose with a molar ratio of 70.19:10.95:11.16:6.90. In addition, the ALPs had intense antioxidant activity in vitro with IC50 values in the ·OH radical (1.732 mg/ml), DPPH radical (0.29 mg/ml), and superoxide anion (0.15 mg/ml) scavenging abilities.
DISCUSSION: The results showed that ATPS was an efficient method to extract polysaccharides and could be used for the extraction of other polysaccharides. These results indicated that ALPs had great prospects as a functional food and could be exploited in multiple fields.
METHODS: A comprehensive systematic search was carried out in PubMed/MEDLINE, Web of Science, SCOPUS and Embase from inception until June 2019. Weighted mean difference (WMD) with the 95 % CI were applied for estimating the effects of metformin on serum IGF-1 levels.
RESULTS: 11 studies involving a total of 569 individuals reported changes in IGF-1 plasma concentrations as an outcome measure. Pooled results demonstrated an overall non-significant decline in IGF-1 following metformin intake (WMD: -8.292 ng/ml, 95 % CI: -20.248, 3.664, p = 0.174) with heterogeneity among (p = 0.000,I2 = 87.1 %). The subgroup analyses displayed that intervention duration <12 weeks on children (WMD:-55.402 ng/ml, 95 % CI: -79.845, -30.960, I2 = 0.0 %) significantly reduced IGF-1. Moreover, in age 18 < years older metformin intake (WMD: 15.125 ng/ml, 95 % CI: 5.522, 24.729, I2 = 92.5 %) significantly increased IGF-1 than 18 ≤ years older (WMD:-1.038 ng/ml, 95 % CI: -3.578,1.502,I2 = 78.0 %). Following dose-response evaluation, metformin intake reduced IGF-1 (coefficient for dose-response analysis= -13.14, P = 0.041 and coefficient for liner analysis= -0.066, P = 0.038) significantly based on treatment duration.
CONCLUSION: We found in children, intervention duration <12 weeks yielded significant reductions in IGF-1, whilst paradoxically, in participants >18 years old, metformin intake significantly increased IGF-1. We suggest that caution be taken when interpreting the findings of this review, particularly given the discordant supplementation practices between children and adults.