## 4 Conclusions  
The current study presented a comparative study of the valorization of GF peels to obtain a single BCs (EO or polyphenol-rich extracts) or a multi-cascade BCs from the same by-product. A sustainable and integrated approach using Egyptian GF peel, a by-product from the juice industry, by producing consecutive GF-EO and polyphenol-rich extracts (GF-PE) using the same by-product was assessed. The method of extraction and pretreatment applied before the polyphenol extraction significantly influences the content of phenolic compounds and the biological activity of the final ingredient. The TPC and TFC increased 2-fold, while naringenin, narinutin, and hydroxycinamic acids increased by 6.2-, 1.9-, and 3.0-fold, respectively. However, the crude GF extract (GF-CE) exhibited a stronger free radical scavenging activity, mainly in DPPH (IC50 = 75.69 \(\pm\) 0.81 \(\mathrm{\SIUnitSymbolMicro}\)/mL), than the GF-PE (113.45 \(\pm\) 0.85 \(\mathrm{\SIUnitSymbolMicro}\)/mL). However, the GF-PE showed a higher anti-inflammatory activity than the GF-CE (0.67 \(\pm\) 0.058 \(\mathrm{\SIUnitSymbolMicro}\)/mL for COX1 and 0.7 \(\pm\) 0.1 \(\mathrm{\SIUnitSymbolMicro}\)/mL for COX2). Lastly, both the GF-CE and GF-PE showed antimicrobial activity (\(p\) > 0.05) against Gram\(-\) and Gram\(+\) bacteria; however, the GF-PE showed a better inhibitory capacity against _P. aeruginosa_ (7 mm) and _L. monocytogenes_ (7 mm). Nevertheless, the GF-EO demonstrated a higher antimicrobial activity than the polyphenol-rich extracts, mainly against Gram\(+\) bacteria compared to the reference standard (amoxicillin) and a strong activity against the yeast _Candida albicans_ (inhibition zone of 16 mm). The major compounds in the GF-EO included D-limonene (25%), nootkatone (24%), and \(\beta\)-pinene (8%). Although the GF-EO demonstrates anti-inflammatory capacity, its ability to inhibit COX 1 (0.97 \(\pm\) 0.1 \(\mathrm{\SIUnitSymbolMicro}\)/mL) is greater than that to inhibit COX 2 (3.9 \(\pm\) 0.1 \(\mathrm{\SIUnitSymbolMicro}\)/mL). This study highlights the potential of GF peels as a sustainable source of valuable ingredients/extracts for functional foods and their potential to establish synergies with the cosmetic and pharmaceutical industries. In addition, it proves the efficiency of the consecutive extraction of BCs from GF peels. By using these new upcycled ingredients, we can contribute to the achievement of the SDGs and zero waste, a set of principles focused on waste prevention that encourage finding new uses for resources instead of throwing them away. Conceptualization, F.M.I., R.S.M. and E.S.E.H. ; methodology, F.M.I., R.S.M., E.A. and W.E.S.A. ; software, R.S.M. ; validation, R.S.M. and F.M.I. ; formal analysis, F.M.I., R.S.M. and E.A. ; investigation, F.M.I., R.S.M., E.A. and W.E.S.A. ; resources, E.S.E.H. ; data curation, F.M.I. ; writing--original draft preparation, A.A.V.-B., F.M.I, R.S.M. and E.A. ; writing--review and editing, A.A.V.-B., F.M.I. and M.P. ; project administration, E.S.E.H. All authors have read and agreed to the published version of the manuscript. This research was financial supported by the Science, Technology and Innovation Funding Authority (STDF) from Egypt and PRIMA Program through the MEDISMART project--Mediterranean Citrus innovative soft-processing solutions for S.M.A.R.T (Sustainable, Mediterranean, Agronomically evolved nutritionally enriched Traditional) products (reference number: PRIMA-EU-2019-SECTION2; [[http://doi.org/10.54499/PRIMA/0014/2019](http://doi.org/10.54499/PRIMA/0014/2019)]([http://doi.org/10.54499/PRIMA/0014/2019](http://doi.org/10.54499/PRIMA/0014/2019))). Not applicable. Data Availability Statement: Data will be available upon request.