A Comprehensive Review of the Nutritional, Pharmacological, and Industrial Value of Polyphenolic Antioxidants Found in Onions

Onions are an excellent source of a variety of essential antioxidants, polyphenols, and other phytonutrients. These onions were used to enhance the meal's flavour and aroma. Additionally, onions have long been recognised for their ability to change food texture, making it more pleasant for eating. Among the most significant phenolic compounds identified in onions was Quercetin, which has been proven to be very helpful for maintaining good health by reducing the risk of heart disease, cancer, and a number of other severe conditions. Polyphenol extraction is essential for the effective usage and research of these phytochemicals. Previously, the extraction process was complicated by a variety of traditional methods, but with the aid of contemporary technology, the procedure was simplified. Additionally, it was found that red onions had greater health benefits than yellow onions, which were the most commonly used kind at the time. Apart from their health benefits, polyphenols were well recognised for their industrial use in dyeing, polymer manufacturing, and resin synthesis.

Total Polyphenol Distribution and Extraction of Polyphenols from White Peel of Pomelo

Pomel has many polyphenol contents, the antioxidant compound group has many health benefits This study was conducted to investigate the distribution of total polyphenols in pomelo and the extraction condition of polyphenol, naringin, antioxidant capacity (DPPH) from the white peel of pomelo. The results of the study showed the fruit flesh had the highest percentage of weight at 48.6%; followed by the white peel accounting for 25.20%, the green peel accounted for 18.70% and the flesh membrane accounted for 7.5%. However, the distribution of mass and the distribution of total polyphenols is different; Specifically, the white peel accounted for a percentage of total polyphenols of 40.32%, the green peel accounted for 25.21%, the flesh accounted for 22.39% and the flesh membrane accounted for 12.15%. The white peel (a by-product of pomelo processing) selected as a polyphenol extraction material. The results also showed that the percentage of Pectinex Ultra SP-L supplementation, hydrolysis temperature and extraction time had a statistically significant effect (p <0.05) on the total polyphenol content, naringin content and antioxidation capacity. Using 50% ethanol extraction solvent with assisted enzyme; in which, the enzyme rate added 1%; hydrolyzed at 50 ℃ for 1 hour for the extract with the highest total polyphenol content, DPPH oxidation resistance, and highest naringin content of 19.48 mg GAE / g dry matter, 1.79 mg AAE / g dry matter and 5.85 mg NE / g dry matter.

Analytical Profile and Antioxidant and Anti-Inflammatory Activities of the Enriched Polyphenol Fractions Isolated from Bergamot Fruit and Leave

The aim of the study is to compare the qualitative and semi-quantitative profile of the polyphenol fraction purified from the leaf (BLPF) and fruit (BFPF) of bergamot (Citrus bergamia), and to evaluate their antioxidant and anti-inflammatory activity. The analytical qualitative profile was carried out by LC-ESI/MS using three different approaches: targeted (searching analytes already reported in bergamot extract), semi-targeted (a selective search of 3-hydroxy-3-methylglutarate [HMG] derivatives involved in the cholesterol reducing activity of BPF) and untargeted. A total number of 108 compounds were identified by using the three approaches, 100 of which are present in both the extracts thus demonstrating a good qualitative overlapping of polyphenols between the two extracts. The antioxidant activity was higher for BLPF in respect to BFPF but when normalized in respect to the polyphenol content they were almost overlapping. Both the extracts were found to dose dependently inhibit cell inflammation stimulated with IL-1α. In conclusion, the comparison of the qualitative and quantitative profile of polyphenols as well as of the antioxidant and anti-inflammatory activity of bergamot leaf and fruit well indicates that leaf is a valid source of bergamot polyphenol extraction and an even richer source of polyphenol in respect to the fruit.

Modification of Olive Leaves’ Surface by Ultrasound Cavitation. Correlation with Polyphenol Extraction Enhancement

We investigated the impact of ultrasound at 20 kHz on olive leaves to understand how acoustic cavitation could increase polyphenol extraction. Application of ultrasound to whole leaf from 5 to 60 min enabled us to increase extraction from 6.96 to 48.75 µg eq. oleuropein/mL of extract. These results were correlated with Environmental Scanning Electron Microscopy, allowing for leaf surface observation and optical microscopy of treated leaf cross sections to understand histochemical modifications. Our observations suggest that the effectiveness of ultrasound applied to extraction is highly dependent on plant structure and on how this material will react when subjected to acoustic cavitation. Ultrasound seems to impact the leaves by two mechanisms: cuticle erosion, and fragmentation of olive leaf surface protrusions (hairs), which are both polyphenol-rich structures.

Glycerol and Glycerol-Based Deep Eutectic Mixtures as Emerging Green Solvents for Polyphenol Extraction: The Evidence So Far

The acknowledgement that uncontrolled and excessive use of fossil resources has become a prime concern with regard to environmental deterioration, has shifted the orientation of economies towards the implementation of sustainable routes of production, through the valorization of biomass. Green chemistry plays a key role in this regard, defining the framework of processes that encompass eco-friendly methodologies, which aim at the development of highly efficient production of numerous bioderived chemicals, with minimum environmental aggravation. One of the major concerns of the chemical industry in establishing sustainable routes of production, is the replacement of fossil-derived, volatile solvents, with bio-based benign ones, with low vapor pressure, recyclability, low or no toxicity, availability and low cost. Glycerol is a natural substance, inexpensive and non-toxic, and it is a principal by-product of biodiesel industry resulting from the transesterification process. The ever-growing market of biodiesel has created a significant surplus of glycerol production, resulting in a concomitant drop of its price. Thus, glycerol has become a highly available, low-cost liquid, and over the past decade its use as an alternative solvent has been gaining unprecedented attention. This review summarizes the utilization of glycerol and glycerol-based deep eutectic mixtures as emerging solvents with outstanding prospect in bioactive polyphenol extraction.