| Sterculia nobilis Smith,a common cash crop,is widely distributed in Southern China,Japan and Southeast Asia.People are accustomed to using Sterculia nobilis Smith seeds for the food industries and pericarps are often underutilized.It has been found that Sterculia nobilis Smith pericarp contains multiple phenolics compounds,which has the potential to promote health.Thus,in this paper,the Sterculia nobilis Smith pericarp was taken to analyzes the composition of the active components,and to explores the antioxidant and anti-tumor cell proliferation activities of Sterculia nobilis Smith pericarp extract.The main conclusions and results of this work are as following(1)Sterculia nobilis Smith pericarp powders were extracted with 95%ethanol/water(v/v),and then the supernatant is filtered and taken as an ethanol extract(free phase).Then the extract was partitioned with various solvents and yielded(n-hexane fraction(HF),ethyl acetate fraction(EAF),n-butanol fraction(BF)and aqueous fraction(AqF).At the same time,the filter residue is extracted to obtain bound phase.Then the total phenolic content(TPC)and total flavonoid content(TFC)of the extracts of each phase were determined by the Folin-Ciocalteu and sodium borohydride/chloranil-based assay.The results showed that TPC and TFC of free phase in Sterculia nobilis Smith pericarp was higher than that in the bound phase.TPC of free phase was 468.2±14.0 mg GAE/100 g DW,and TFC of flavones was 2063.5±38.4 mg CE/100 g DW In the four-phase extracts with different polarities,the TPC of extracts followed the order:EAF>AqF>BF>HF,the TFC of extracts followed the order:EAF>HF>AqF>BF,and the EAF had the highest TPC(1044.9 ± 35.1 mg GAE/100 g DW)and TFC(10507.0 ± 201.4 mg CE/100 g DW).Seven phenolic compounds(quercetin,rutin,quercitrin,kaempferol,epicatechin,isoorientin,and myricetin)were identified in EAF using UHPLC-HR-TOFMS analysis.In addition,the in vitro hypoglycemic activity of the four-phase extract was measured by ?-glucosidase,it was found that the HF had the highest inhibition rate of ?-glucosidase.Nineteen chemical components of HF were identified by GC-MS.Among them,ethyl palmitate have the highest content,followed by pentadecanoic acid,ethyl linoleate,ethyl elaidate and ethyl heptadecanoate(2)Four fractions of Sterculia nobilis Smith pericarp were measured by five different antioxidant assays.It was found that EAF showed the best antioxidant activity among four fractions in oxygen radical absorbance capacity(ORAC),peroxyl radical scavenging capacity(PSC),DPPH radical scavenging activity and reducing power assays.The ORAC value of EAF was 228.2 ?mol TE/mg,the PSC value was 671.8 ?mol VCE/g,DPPH value was 18.1 ?mol VCE/mg,the VC equivalent of reducing power was 42.9 ?mol VCE/mg.In the ABTS experiment,the AqF showed the highest ABTS free radical scavenging ability,with a VC equivalent value of 154.5 ?mol VCE/mg;followed by EAF with a VC equivalent value of 45.0?mol VCE/mg.The TPC was significantly correlated with the results of the PSC assay(r=0.951,p<0.05)and the determination of reducing power(r=0.992,p<0.01).In addition,a significant correlation was found between the TFC and the results of DPPH assay(r=0.952,p<0.05)(3)Measure the anti-proliferative activity of EAF and explore its anti-proliferation mechanism.The results showed a significant dose-dependent inhibitory effect on the growth of HepG2,Caco-2,and A549 cells.The inhibitory effect of EAF on different cancer cells was followed the order:HepG2 cells>Caco-2 cells>A549 cells.The HepG2 cells were used as a model to study the antiproliferation mechanism of EAF.It was found that the EAF increased the ratio of cell cycle at the G0/G1 phase and the proportion of apoptotic cells.At the same time,it was found that EAF can inhibit ROS production in HepG2 cells at a high concentration(45-50 ?g/mL).Finally,according to the results of RT-PCR,it was found that the EAF may inhibit the proliferation of HepG2 cancer cells by inhibiting PI3K/AKT/mTOR signaling pathway. |
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