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Purpose: To determine the loading, antioxidant activity protection and sustained-release effect of wheat starch on Ligustrum robustum (Rxob.) Blume extract (LRE) for the purpose of providing a theoretical basis for the high value added development and utilization of LRE in the food and biomedical industries. Methods: The major compounds in LRE were identified by mass spectroscopy (MS) and nuclear magnetic resonance (NMR) spectroscopy, and the in vitro antioxidant capacity of LRE was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and reducing power assays. The loading capacity and stability of starch for LRE were measured by cumulative release of total phenols. Besides, the protective effect of starch on the antioxidant activity of LRE was analyzed, and the sustained-release effect of starch on LRE during in vitro simulated digestion was investigated. Results: The major bioactive compounds in LRE were identified as ligurobustoside B (C31H44O13), ligurobustoside N (C35H46O18) and ligupurpuroside J (C35H46O19), and LRE had strong free radical scavenging capacity and reducing power. Furthermore, different concentrations of wheat starch could stably load LRE, delaying the attenuation of the free radical scavenging capacity and reducing power of LRE and inhibiting the release of LRE during in vitro simulated digestion to a certain extent.

Ligustrum robustum (Roxb.) Blume is utilized as a traditional Chinese herbal tea with various health benefits and protective effects. Streptococcus mutans is an important cariogenic oral bacteria species. The present study aimed to assess the influence of Ligustrum robustum extract (LRE) on the biofilm formation of S. mutans and the mechanism of its action, as well as to identify its chemical components. For chemical identification, HPLC‐MS and nuclear magnetic resonance were applied and four identified phytochemicals were reported (Ligurobustoside B, Ligurobustoside N, Ligurobustoside J, and Ligurobustoside C). The dose‐dependent (0.5 to 2.0 μg/μL) antimicrobial toxicity of LRE against S. mutans biofilm formation and exopolysaccharide (EPS) synthesis was evaluated by confocal laser scanning microscopy (CLSM), Crystal violet stain, and CFU counting. The microstructure of S. mutans biofilm treated with LRE was investigated both on glass coverslips and ex vivo bovine dental enamel by scanning electron microscopy (SEM). Moreover, LRE downregulated the expression of S. mutans glucosyltransferase‐encoding genes gtfB, gtfC, and gtfD, and the quorum sensing (QS) factors comD and comE, suggesting its toxic mechanism. In addition, the result of CCK‐8 test on human oral cells revealed an acceptable biocompatibility of LRE. These findings indicated the possible application of this daily consumed herbal tea for caries prevention. [ABSTRACT FROM AUTHOR]