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Oleuropein was extracted from olive leaves by ultrasonic-assisted method and purified by silica gel column chromatography. The sample was identified as oleuropein by UV, infrared, mass spectroscopy and nuclear magnetic resonance spectroscopy analysis. Oleuropein and total phenolic contents over a year were determined by high-performance liquid chromatography and Folin-Ciocalteu methods. The results showed that 13.52% of pure oleuropein was found with a high purity of 96.54% and purification efficiency of 78.49%. Oleuropein and total phenolic contents of different olive varieties were quite different, but both had similar trends over the year. Five methods, including DPPH (2,2-diphenyl-1-picrylhydrazyl), ABST (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt), ferric reducing antioxidant power, total reducing power and nitrite-scavenging ability, were used to evaluate the antioxidant activities of oleuropein, and the IC50 were 34.54 ± 0.14 μg/mL, 18.79 ± 0.82 μg/mL, 75.32 ± 1.83 μg/mL, 13.80 ± 0.68 μg/mL and 1.00 ± 0.08 mg/mL, respectively. PRACTICAL APPLICATIONSThis study provides information on the changes in contents including oleuropein and total phenolics in a year to help understand the relationship between content of oleuropein and various influencing factors. Currently, the metabolic pathways of oleuropein are not clear. These results provide information for the study of the metabolism of phenolic compounds in olive and promote research at the molecular level. Oleuropein occupies a large proportion of total polyphenols in olive and can be to be purified by silica gel column chromatography with high purification efficiency for industrial production and laboratory production. In addition, the comprehensive evaluation of activity in vitro shows that oleuropein is more useful than BHT (2,6-di-tert-butyl-4-methylphenol) for the application in food and human health.

A semiconductor nano‐material was prepared, and its degradation efficiency of zearalenone (ZEN) was studied. The photocatalytic material graphitic carbon nitride (g‐C3N4) was synthesized by the traditional method of hot cracking. Its structure was characterized by X‐ray diffraction (XRD), Fourier‐transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The photocatalytic degradation experiment showed that under the irradiation of ultraviolet (UV) lamp (254 nm, including 185 nm), g‐C3N4 could induce photocatalytic effect, which provided a new method for the degradation of ZEN in real powder samples. The experimental conditions of photocatalytic degradation of the primary reference material of ZEN and ZEN in real powder samples were explored. And the degradation products of ZEN were analyzed after high‐performance liquid chromatography–mass spectrometry (HPLC–MS). Under each optimal experimental conditions, the degradation rate on primary reference material of ZEN and ZEN in real powder samples was 96.0% and 50.0%, respectively. The results in this work provide a theoretical reference and practical basis for the photocatalytic degradation of mycotoxin in real powder samples by g‐C3N4.

Reactive oxygen species (ROS) are usually produced in rice under aerobic environmental conditions, resulting in peroxidative changes in polyunsaturated fatty acids, and affecting the deterioration of rice during storage. In addition, as an important enzyme that participates in removing ROS, peroxidase is also present in rice, and takes part in protecting rice from attack by ROS. Moreover, loss of peroxidase activity may give rise to rice deterioration during storage. Therefore, measuring peroxidase activity makes it possible to ascertain the freshness of rice. In addition, peroxidase can also catalyze the luminol–hydrogen peroxide system. Based on this, in this work we established a new chemiluminescence (CL) method that was used to detect the freshness of stored rice. Under optimal experimental conditions, we showed that the freshness of rice can be measured using this CL method. This study is the first to detect the freshness of rice using a CL method, opening up a novel direction for the application of CL.