Mango rejects and mango waste: Characterization and quantification of phenolic compounds and their antioxidant potential

Valorization of Fruit Waste for Bioactive Compounds and Their Applications in the Food Industry

The fruit production and processing sectors produce tremendous amounts of by-products and waste that cause significant economic losses and an undesirable impact on the environment. The effective utilization of these fruit wastes can help to reduce the carbon footprint and greenhouse gas emissions, thereby achieving sustainable development goals. These by-products contain a variety of bioactive compounds, such as dietary fiber, flavonoids, phenolic compounds, antioxidants, polysaccharides, and several other health-promoting nutrients and phytochemicals. These bioactive compounds can be extracted and used as value-added products in different industrial applications. The bioactive components extracted can be used in developing nutraceutical products, functional foods, or food additives. This review provides a comprehensive review of the recent developments in fruit waste valorization techniques and their application in food industries. The various extraction techniques, including conventional and emerging methods, have been discussed. The antioxidant and antimicrobial activities of the active compounds extracted and isolated from fruit waste have been described. The most important food industrial application of bioactive compounds extracted from fruit waste (FW) has been provided. Finally, challenges, future direction, and concluding remarks on the topic are summarized.

LC-ESI-QTOF-MS/MS Characterization and Estimation of the Antioxidant Potential of Phenolic Compounds from Different Parts of the Lotus (Nelumbo nucifera) Seed and Rhizome

Edible lotus (Nelumbo nucifera G.) is widely consumed in Asian countries and treated as a functional food and traditional medicinal herb due to its abundant bioactive compounds. Lotus rhizome peels, rhizome knots, and seed embryos are important byproducts and processing waste of edible lotus (Nelumbo nucifera G.) with commercial significance. Nevertheless, the comprehensive phenolic profiling of different parts of lotus is still scarce. Thus, this study aimed to review the phenolic contents and antioxidant potential in lotus seeds (embryo and cotyledon) and rhizomes (peel, knot, and pulp) grown in Australia. In the phenolic content and antioxidant potential estimation assays by comparing to the corresponding reference standards, the lotus seed embryo exhibited the highest total phenolic content (10.77 ± 0.66 mg GAE/g_f.w.), total flavonoid content (1.61 ± 0.03 mg QE/g_f.w.), 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity (9.66 ± 0.10 mg AAE/g_f.w.), 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) scavenging activity (14.35 ± 0.20 mg AAE/g_f.w.), and total antioxidant capacity (6.46 ± 0.30 mg AAE/g), while the highest value of ferric ion reducing antioxidant power (FRAP) activity and total tannin content was present in the lotus rhizome knot (2.30 ± 0.13 mg AAE/g_f.w.). A total of 86 phenolic compounds were identified in five parts of lotus by liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS/MS), including phenolic acids (20), flavonoids (51), lignans (3), stilbenes (2), and other polyphenols (10). The most phenolic compounds, reaching up to 68%, were present in the lotus seed embryo (59). Furthermore, the lotus rhizome peel and lotus seed embryo exhibit significantly higher contents of selected polyphenols than other lotus parts according to high-performance liquid chromatography (HPLC) quantification analysis. The results highlighted that byproducts and processing waste of edible lotus are rich sources of phenolic compounds, which may be good candidates for further exploitation and utilization in food, animal feeding, and pharmaceutical industries.

Determination and Characterization of Phenolic Compounds from Australia-Grown Sweet Cherries (Prunus avium L.) and Their Potential Antioxidant Properties

Sweet cherries (Prunus avium L.) are popular fruits around the world with a high nutritional value and abundant phenolic compounds. Phenolic compounds of cherries contribute to positive health benefits. This study aimed at determining the phenolic content and antioxidant activities in four Australian-grown sweet cherry cultivars, including Bing, Ron's, Merchant, and Lapins, as well as the identification of individual phenolic compounds with liquid chromatography-electrospray ionization-quantum time-of-flight-mass spectrometry (LC-ESI-QTOF-MS²). Lapins exhibits the highest total phenolic content (TPC) value (1.73 ± 0.90 mg gallic acid equivalents (GAE)/g) while Ron's exhibits the highest total flavonoid content (TFC) value (0.51 ± 0.02 mg QE/g). In 2,2'-azinobis-(3-ethylbenzo-thiazoline-6-sulfonic acid) (ABTS), reducing power assay (RPA), and total antioxidant content (TAC) assays, Merchant exhibited the highest values (0.51 ± 0.07, 1.74 ± 0.04, and 2.79 ± 0.09 mg AAE/g, respectively) and almost showed the highest antioxidant activity. Ron's presented the highest value (1.21 ± 0.09 mg EDTA/g) in ferrous ion-chelating activity (FICA) assay and exhibits the strongest metal chelating ability. The correlation between phenolic contents and antioxidant assays was observed. In the LC-ESI-QTOF-MS² analysis, a total of 43 phenolic compounds has been detected in four sweet cherry cultivars, including 11 phenolic acids, 25 flavonoids, 5 other phenolic compounds, 1 lignan, and 1 stilbene. Venn graph showed that Lapins has the greatest number of unique compounds. Our study shows the presence of phenolic acids and provides information to be utilized as an ingredient in food, pharmaceutical, and nutraceutical industries.