甜菊多酚的抗氧化和抑菌作用

Antioxidant and antibacterial activities of stevia polyphenols

甜菊多酚(PPS)是甜菊糖苷生产过程中产生的副产物。本文以表没食子儿茶素没食子酸酯(EGCG)为对照,研究了PPS的抗氧化活性,及其对大肠杆菌、金黄色葡萄球菌、肺炎克雷伯菌、粪肠球菌、黑曲霉以及黄曲霉的抑菌活性。结果表明,PPS的抗氧化能力与其浓度呈正向依赖关系,其清除DPPH和ABTS自由基的IC50值分别为27.43和17.33μg/mL,对DPPH自由基清除能力略低于EGCG的;PPS的ABTS自由基清除能力和铁离子还原能力与EGCG无显著差异。此外,PPS具有优良的热稳定性,但在加工和储存过程中需注意过碱环境对其抗氧化稳定性的影响。PPS对所试4种细菌和2种霉菌均表现出一定的抑菌活性,在菌液浓度为106 CFU/mL时,最小抑菌浓度(MIC)均在2500μg/mL以下。PPS具有良好的抗氧化性能和对细菌、霉菌的抑制作用,是一种潜在的天然抑菌性抗氧化剂。

Stevia polyphenols(PPS)are a group of by-products of stevia production.In order to develop the application of PPS,a comparative study on the antioxidant activity of the PPS was characterized by measuring DPPH,ABTS free radical scavenging capacity,and iron ion reduction capacity.Meanwhile,the PPS’s antibacterial activities against Escherichia coli,Staphylococcus aureus,Klebsiella pneumoniae,Enterococcus faecalis,Aspergillus niger and Aspergillus flavus were investigated and compared with epigallocatechin galate(EGCG).The results indicated that the antioxidant activity of PPS was positively correlated with its concentration;the IC50 values of DPPH and ABTS radicals scavenging capacity of PPS were 27.43 and 17.33μg/mL,respectively;the DPPH free radicals scavenging capacity was lower than that of EGCG.There was no significant difference between EGCG and PPS on their iron ion reduction capacity or ABTS free radical scavenging capacity.In addition,PPS presented excellent thermal stability.However,during the processing and storage of PPS,it was necessary to pay attention to the influence of the overalkaline environment on its antioxidant stability.PPS showed certain antibacterial activity against four bacteria and two mold species,the minimum inhibitory concentration(MIC)was up to 2500μg/mL when bacteria concentration was 106 CFU/mL.The experiments showed that PPS had antioxidant properties and inhibitory effects on bacteria and molds,PPS has a potential to become a natural antibacterial antioxidant.