Danielski, Renan (2024) Unconventional fruits and their by-products as sources of phenolic compounds: effect of microencapsulation on biological activities and bioefficiency. Doctoral (PhD) thesis, Memorial University of Newfoundland.
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Abstract
Nutraceuticals are capable of providing health benefits beyond basic nutrition and are used in the medicinal form. This product category has played a pivotal role in health promotion, being associated with a reduced incidence of metabolic syndrome conditions such as obesity, type 2 diabetes, some types of cancers, and cardiovascular ailments. Typically, bioactive compounds serve as the foundational elements of nutraceutical development due to their ability to positively modulate human physiology. Among the widely explored bioactive classes, phenolic compounds stand out as a heterogeneous group with several subclassifications and varying degrees of complexity. Recognized as potent free radical scavengers, their antioxidant mechanisms allow these molecules to mitigate oxidative stress and protect vital biomolecules, including lipids (e.g., LDL-cholesterol) and nucleic acids (e.g., DNA). Phenolic compounds can also form complexes with proteins, granting them the ability to inhibit metabolic enzymes such as a-glucosidase and pancreatic lipase, which are highly active in people living with type 2 diabetes and obesity, respectively. Due to their potential impact on human health, novel phenolic sources have been procured for the development of nutraceuticals and functional food ingredients. Phenolics are abundant in plant material and are part of food linked with health promotion, including fruits and vegetables, cereals and grains, legumes, nuts, herbs and spices. Among phenolic-rich fruits, several types remain unexplored and could hold great potential for commercialization if their nutraceutical potential is confirmed. Examples include tropical fruits like guava, butiá, and jerivá, as well as sea buckthorn, a berry recently introduced to some locations in North America, including Newfoundland. Besides the edible portions of these fruits, their by-products (e.g., seeds, skins) could also serve as sources of phenolic compounds, opening new possibilities for the upcycling of these usually discarded fractions. In this study, the phenolic composition of guava, jerivá, butiá, Newfoundland’s sea buckthorn, and their by-products was assessed. All studied fruits, along with their residual portions, proved to be rich sources of phenolics, distributed in the free, esterified, and insoluble-bound fractions. Guava pulp and its processing discards (a homogenous fraction composed of peels, seeds, and residual pulp) were abundant in ellagic and gallic acid derivatives, similar to jerivá and butiá pomace and seeds. Sea buckthorn pomace and seeds were also high in ellagitannins and the seeds containing a substantial amount of (+)-catechin. Phenolic extracts from these fruits demonstrated strong antiradical activity and ferric reducing capacity, which was positively reflected in their in vitro ability to inhibit oxidative damage to human LDL-cholesterol and supercoiled plasmid DNA, as well as to hamper the activity of a-glucosidase and pancreatic lipase. However, these bioactivities were significantly affected when powdered samples of the studied fruits and their residues underwent in vitro gastrointestinal digestion, simulating the oral, gastric, small and large intestinal phases. After small intestinal digestion, most samples exhibited low phenolic bioaccessibility, meaning that their phenolic concentration was considerably diminished, consequently reducing their effectiveness in protecting key biological markers. To address this, phenolic extracts from the studied fruits and their by-products were microencapsulated by freeze-drying using maltodextrin as a wall material. The microencapsulated extracts were subjected to in vitro digestion, revealing a considerable increase in intestinal phenolic bioaccessibility compared to their unencapsulated counterparts. This increase was coupled with higher protection against LDL-cholesterol and DNA oxidative damage, as well as higher inhibitory activity toward a-glucosidase and pancreatic lipase in most cases. Microencapsulation also proved beneficial to the cellular antioxidant activity (CAA) of differentiated human adenocarcinoma (Caco-2) cells promoted by phenolic extracts, showing greater stability of CAA levels than unencapsulated extracts across tested extract concentrations. On the other hand, microencapsulated phenolic extracts demonstrated an augmented prooxidative effect and cytotoxicity toward cervical cancer (HeLa) cells compared to their unencapsulated versions, suggesting a potential anticancer effect. Thus, the microencapsulation of phenolic extracts obtained from guava (pulp and processing waste), butiá, jerivá, and sea buckthorn (pomace and seeds) potentiated the nutraceutical prospects of these underutilized sources of bioactive compounds. These findings support further exploration of unconventional fruits for therapeutic purposes, and future work needs to test microencapsulated phenolic extracts in vivo while studying the underlying mechanisms through which phenolic compounds exert their health-promoting effects.
| Item Type: | Thesis (Doctoral (PhD)) |
|---|---|
| URI: | http://research.library.mun.ca/id/eprint/16445 |
| Item ID: | 16445 |
| Additional Information: | Includes bibliographical references (pages 319-338) -- Restricted until April 11, 2025 |
| Keywords: | polyphenols, nutraceuticals, antioxidants, functional foods, biological activity |
| Department(s): | Science, Faculty of > Biochemistry |
| Date: | February 2024 |
| Date Type: | Submission |
| Library of Congress Subject Heading: | Polyphenols; Functional foods; Antioxidants; Phenols; Health promotion; Sea buckthorn--Newfoundland and Labrador |
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