Pomegranate peel (PP) is a by-product in the processing of pomegranate products, which is usually discarded as a waste. However, a large number of researches have shown that pomegranate peel extract (PPE) is rich in a variety of phenolic substances, among which ellagic acid (EA), as one of the main active components, has significant biological activities, such as anti-oxidation, anti-tumor, anti-inflammatory, neuroprotection, anti-viral, and anti-bacterial. We analyzed the mechanism of EA's biological activity, and discussed its application in the food industry, for instance, food preservation, food additives, and functional foods. Combined with the research status of PPE, we discussed the limitations and development potential of PPE, in order to provide theoretical reference and scientific basis for the development and utilization of pomegranate by-products. Practical applicationsPomegranate peel (PP), the inedible part of the fruit, is usually treated as waste. In recent years, researchers have been committed to exploring various bioactive ingredients in PP and exploring its potential benefits to human health, which has far-reaching significance. In this paper, the chemical constituents of polyphenols in PP were reviewed, mainly focusing on the biological activity and mechanism of ellagic acid (EA).We reviewed the applications and invention patents of pomegranate peel extract (PPE) in food field, including food preservation, food additive, and functional foods, providing reference for the recycling and reuse of PP.

A series of modified poly(ether ether ketone)s containing different content of benzene pendant group in the molecular chain have been successfully synthesized with 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bisphenol A and 4,4′-difluorobenzophenone by nucleophilic substitution. The inherent viscosities of obtained polymers were in the range of 0.261–0.889 dLg−1. They were found to have high glass transition temperatures (Tg) of 150–168°C and 148–169°C (examined by DSC and DMA, respectively), good thermal stability with 5% weight-loss temperature (T5%) of 439–469°C. The tensile strengths of the obtained polymers were 67.7–86.6 MPa, and the storage modulus was over 0.9 GPa at about 140°C. The modified poly(ether ether ketone)s showed the excellent solubility property, they could be processed by solution method. Additionally, the obtained polymers had good optical transmittance (>70%) at 400 nm, suggesting that they have potential to be applied to the heat-resistant optical films.

Two kinds of novel poly(arylene ether nitrile)s (CPDP-DCBN and CHDP-DCBN) containing pendant aliphtatic ring were synthesized by 4,4′-cyclopentane-1,1′-diyldiphenol (CPDP) or 4,4′-cyclohexane-1,1′-diyldiphenol (CHDP) and 2,6-dichlorobenzonitrile (DCBN) in this work. The inherent viscosities of poly(arylene ether nitrile)s (PENs) were in the range of 0.701–0.806 dL g−1. The polymers showed high glass transition temperatures ( T g) of 185.4–196.4°C and weight-loss temperatures ( T5%) of 447.8–454.3°C. The obtained CPDP-DCBN and CHDP-DCBN could be hot pressed into the films, which showed the tensile strengths of 82.6 MPa and 86.8 MPa, respectively. And the storage modulus of CPDP-DCBN and CHDP-DCBN were about 1.0 GPa and 1.5 GPa at 150°C, respectively. Additionally, the PENs could be dissolved in many solutions at room temperature, such as NMP and concentrated H2SO4, indicating that they had good solubility; they can be processed by the solution method. Meanwhile, the optical transmittance of CPDP-DCBN was 78.1% at 450 nm; it has potential to be applied to the heat-resistant optical film.