A Review on Apple Pomace Bioactives for Natural Functional Food and Cosmetic Products with Therapeutic Health-Promoting Properties

Abstract

Apples are consumed lavishly worldwide, while demand is increasing for the management of the huge apple-waste amounts that lead to significant disposal costs and ecological issues. Additionally, apples represent fruits with several bioactive constituents, which are key factors in a healthy, balanced diet. In the present study, an extensive review is presented regarding the bioactive compounds of an apple processing by-product, namely apple pomace, mentioning their significance as viable ingredients/substances in foods and cosmetics aiming at chronic disease prevention and health promotion. Apple pomace contains several constituents, such as polar lipids, phenolics, vitamins and dietary fibers, with potential antioxidant, anti-inflammatory, anti-thrombotic, anti-aging and skin-protecting properties, and thus, they may contribute to minimizing the risk of various health conditions. Additionally, the mechanisms of action of such functional bioactives from apple pomace exert health benefits that will be examined, while the potential synergistic effects will also be investigated. Moreover, we will present the methods and techniques needed for the utilization of apple pomace in the appropriate form, such as powder, extracts, essential oil and so on, and their several applications in the food and cosmeceutical industry sectors, which summarize that apple pomace represents an ideal alternative to synthetic bioactive compounds.

Keywords: anti-aging; anti-inflammatory; antioxidant; apple; apple pomace; cosmetics; functional foods; phenolics; polar lipids; unsaturated fatty acids.

Figure 1

The most characteristic phenolic and lipid bioactives associated with the diverse bio-functional health-promoting properties of apple pomace. (Abbreviations: FA = fatty acid; SFA = saturated fatty acid; UFA = unsaturated fatty acid; MUFA = monounsaturated fatty acid; PUFA = polyunsaturated fatty acid). The structures for each individual bioactive were obtained from https://molview.org; accessed on 8 July 2024.

Figure 2

The mechanisms of action of biofunctional polar lipids with UFA in their structures, derived from apple products and by-products, against thrombo-inflammatory signaling and associated inflammatory cell responses and manifestations. Red colors: the representative signaling of thrombo-inflammatory stimuli induced by the presence of several risk factors, such as those of PAF and thrombin, which, via the pathways shown, propagate the inflammatory cell responses. Blue colors: Apple pomace bioactive polar lipids (PLs) rich in UFA beneficially affect all these signaling pathways and transcription factors, and thus further inhibit the expression of thrombo-inflammatory genes and associated cell responses (The blue X represents an inhibitory effect on a pathway and/or an enzyme and/or a receptor and/or a transcription factor and/or the expression of thrombo-inflammatory genes by apple pomace bioactive polar lipids, as indicated by the blue arrows). Abbreviations: UFA = unsaturated fatty acid; MUFA = mono-unsaturated fatty acids; PUFA = poly unsaturated fatty acids; PAF = platelet-activating factor; GPCMR = G-protein-coupled membrane receptors; PAF-R = PAF receptor; PAR = protease-activated receptors for thrombin; PAF-CPT and LPCAT = the basic biosynthetic enzymes of the two distinct pathways of PAF synthesis, PAF-cholinephsphotransferase and lyso-phosphatidylcholine acetyltransferase 2, respectively; cPLA = cytoplasmic phospholipase A2; MAPK = Mitogen-activated protein kinase; IP3 = Inositol trisphosphate; OA = oleic acid; ALA = alpha-linolenic acid; COX = cycloxigenase; NF-kB = nuclear factor kappa beta; IKB = inhibitor of NF-kB; ROS = reactive oxygen species; PL = polar lipids; Ox-PL = oxidized phospholipids; ADP = adenosine diphosphate; PLC = phospholipase C. (the cell/nucleus membranes depicted were reproduced from https://mindthegraph.com/; accessed on 25 July 2024).

Figure 3

Representative mechanisms of the antioxidant and anti-inflammatory actions of phenolic bioactives from apple products and by-products against oxidative stress and thrombo-inflammatory signaling associated with aging and chronic disorders. Red colors: the signaling of oxidative stress and thrombo-inflammatory stimuli induced by aging-related risk factors, such as the induction of oxidative stress and the thrombotic and inflammatory pathways of PAF and thrombin that are associated with aging processes and chronic disorders. Blue colors: Apple pomace phenolic compounds affect all these signaling pathways related to oxidative stress, inflammation, aging and associated chronic disorders through the deactivation of ROS, the inhibition of oxidative damage to DNA, proteins and lipid molecules, and especially to the polar lipids in cellular and intracellular membranes, as well as through the inhibition of oxidized PLs, PAF- and thrombin-binding on their receptors, and thus through the reduction in their thrombo-inflammatory signaling and their aging-associated manifestations. (The blue X represents an inhibitory effect on a pathway and/or an enzyme and/or a receptor and/or a transcription factor and/or an expression of a gene related to oxidative stress and inflammation by apple pomace bioactive phenolics, as indicated by the blue arrows). Abbreviations: PAF = platelet-activating factor; GPCMR = G-protein-coupled membrane receptors; PAF-R = PAF receptor; PAR = protease-activated receptors for thrombin; PAF-CPT and LPCAT = the basic biosynthetic enzymes of the two distinct pathways of PAF synthesis, PAF-cholinephsphotransferase and lyso-phosphatidylcholine acetyltransferase 2, respectively; cPLA = cytoplasmic phospholipase A2; MAPK = mitogen-activated protein kinase; IP3 = inositol trisphosphate; OA = oleic acid; ALA = alpha-linolenic acid; COX = cycloxigenase; NF-kB = nuclear factor kappa beta; IKB = inhibitor of NF-kB; ROS = reactive oxygen species; PL = polar lipids; Ox-PL = oxidized phospholipids; ADP = adenosine diphosphate; PLC = phospholipase C. (the cell/nucleus membranes depicted were reproduced from https://mindthegraph.com/; accessed on 25 July 2024).