Formation of delayed bitterness is an intractable problem in the processing of citrus juice. This study analyzed the distribution of main bitter-causing substances in sweet orange and the effect of heat treatment, storage temperature, clarification, and homogenization on the limonin content in sweet orange juice. The segment membrane accounted for 34–42% of limonin in the fruit and 21–45% of limonoate A-ring lactone (LARL). Heat treatment accelerated the formation of limonin in juice. Pectinase treatment appeared to facilitate the formation of limonin by reducing the pH of juice. In addition, refrigeration at 4 °C was found to restrain the formation of limonin in juice by inhibiting the activity of limonin D-ring lactone hydrolase (LDLH). In conclusion, segment membrane may have a great contribution to the delayed bitterness of sweet orange juice due to its abundant LARL. These results may provide some guidance for citrus processing and bitterness removal.
Penicillium italicum, the cause of citrus blue mold, is a pathogenic fungus that seriously affects the postharvest quality of citrus fruit and causes serious economic loss. In this study, a eugenol nanoemulsion containing limonin, an antimicrobial component from citrus seeds, was prepared using a high-pressure microfluidizer and the antifungal activity of the nanoemulsions againstP. italicumwas evaluated based on the conidial germination rate, mycelial growth, and scanning electron microscopy analysis. The results showed that the minimum inhibitory concentration and the inhibition rate of limonin-loaded eugenol nanoemulsion was 160 μg/mL and 59.21%, respectively, which was more potent than that of the limonin-free eugenol emulsion. After treatment with the nanoemulsions, the integrity of theP. italicumcell membrane was disrupted, the cell morphology was abnormal, and the leakage of nucleic acid and protein was observed. In addition, the challenge test on citrus fruits revealed that the limonin-loaded eugenol emulsion inhibited citrus infection for longer periods, with an infection rate of 29.2% after 5 days. The current research shows that nanoemulsions containing limonin and eugenol have effective antifungal activity againstP. italicum, and may be used as a substitute for inhibiting blue mold in citrus fruits.Keywords:eugenol nanoemulsion;citrus blue mold;limonin;Penicillium Italicum;antifungal activity
Aihua Zhang,Huiyu Wang,Hui Sun,Yue Zhang,Na An,Guangli Yan,Xiangcai Meng,Xijun Wang
Limonin has been found to possess significant anti-inflammatory properties in animal tests and with, human cells, however, its precise metabolism mechanism has not been well explored. The aim of this study was to investigate the anti-inflammatory effects of limonin in a nonbacterial prostatitis (NBP) animal model. Global metabolite profiling was performed by ultra-high-performance liquid chromatography combined with time-of-flight mass spectrometry (UPLC/ESI-TOFMS) and in conjunction with multivariate data analysis and pathway analysis which were integrated to explore differentiating metabolites and clarify the mechanism of limonin against capsaicin-induced NBP. Limonin has a potential protective function revealed by the metabolic profiling of limonin-treated rats located closer to the normal group. Twenty potential biomarker candidates and several key metabolic pathways contributing to the treatment of NBP were discovered and identified. Among the pathways, the related glycine, serine and threonine metabolism, glycerophospholipid metabolism were acutely perturbed. The changes in metabolites were restored to their base-line levels after limonin treatment, which might be through regulating the perturbed pathways to the normal state. The results indicate that changed biomarkers and pathways may provide evidence and insight into limonin action mechanisms and enable us to increase research productivity toward metabolomics in therapeutical assessment and drug discovery.
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