What Worth the Garlic Peel

Abstract

Plants have two types of reproduction: sexual, resulting in embryo production, and asexual, resulting in vegetative bodies commonly derived from stems and roots (e.g., bulb, tuber). Dead organs enclosing embryos (DOEEs, such as seed coat and pericarp) are emerging as central components of the dispersal unit acting to nurture the embryo and ensure its survival in the habitat. Here we wanted to investigate the properties of dead organs enclosing plant asexual reproductive bodies, focusing on the garlic (Allium sativum) bulb. We investigated the biochemical and biological properties of the outer peel enclosing the bulb and the inner peel enclosing the clove using various methodologies, including bioassays, proteomics, and metabolomics. The garlic peels differentially affected germination and post-germination growth, with the outer peel demonstrating a strong negative effect on seed germination of Sinapis alba and on post-germination growth of Brassica juncea. Proteome analysis showed that dead garlic peels possess 67 proteins, including chitinases and proteases, which retained their enzymatic activity. Among primary metabolites identified in garlic peels, the outer peel accumulated multiple sugars, including rhamnose, mannitol, sorbitol, and trehalose, as well as the modified amino acid 5-hydroxylysine, known as a major component of collagen, at a higher level compared to the clove and the inner peel. Growth of Escherichia coli and Staphylococcus aureus was promoted by garlic peel extracts but inhibited by clove extract. All extracts strongly inhibited spore germination of Fusarium oxysporum f.sp. melonis. Thus, the garlic peels not only provide physical protection to vegetative offspring but also appear to function as a refined arsenal of proteins and metabolites for enhancing growth and development, combating potential pathogens, and conferring tolerance to abiotic stresses.

Detailed analysis of agro-industrial byproducts/wastes to enable efficient sorting for various agro-industrial applications

“…The data presented here highlighted AIBWs, namely the WB and GSP as sustainable, rich sources for beneficial substances that can be exploited for use in agriculture as well as in the industry for various purposes including stimulating plant growth, protection against potential pathogen, combating weeds as well as in the food- and non-food industries. Notably, the WB analyzed in the present study mostly represent dead organs that enclosed the embryo, namely, pericarp, seed coat and endosperm contaminant but also live cells embedded within broken seeds, while GSP represent dry garlic residues (garlic straw) and the dead outer and inner garlic peels (Gp) enclosing the vegetative reproductive structure (Singiri et al 2022 ). The abovementioned organs undergo programed cell death (PCD) upon maturation, a process where macromolecules such as proteins, RNAs and DNAs undergo degradation by multiple hydrolytic enzymes (DNAses, RNases, proteases) and their constituents remobilized to other plant parts for supporting growth or storage.…”

“…Most garlic waste is disposed into landfills or burned, which negatively affecting the environment (Kallel and Ellouz Chaabouni 2017 ). Garlic waste can be used as a source for antimicrobial substances (Naqvi et al 2020 ; Singiri et al 2022 ), production of cellulose derivatives which can be used as nanofillers for polymer matrices (Moreno et al 2020 ; Kallel et al 2016 ), as well as for soil amendment and bioenergy (Kallel and Ellouz Chaabouni 2017 ; Ghani et al 2019 ). AIBWs in general can be used for extraction of bioactive substances some of which have beneficial effects on human health including amino acids, phenolics, vitamins, fibers as well as for generating biogas and bio-oil (Sadh et al 2018 ; Lopes and Ligabue-Braun 2021 ; Apprich et al 2014 ; Kuparinen et al 2023 ).…”

Characterization and Valorization of ‘Sulmona Red Garlic’ Peels and Small Bulbs

“…The multimethodological approach afforded a detailed fingerprint of the considered wastes allowing us to hypothesize their reuse in different applications. The presence of amino acids, polyphenols, organic acids, organosulphur compounds, lipids, and so on suggests potential employment in the cosmetic, pharmaceutic, and food supplements industries [ 45 , 46 ].…”

Turning Garlic into a Modern Crop: State of the Art and Perspectives

“…In this regard, the inner peels (enclosing each clove) and outer peels (enclosing the entire bulb) of garlic bulbs do have different metabolic composition: inner clove peels are rich in organic acids such as gluconic, gulonic acids and vanillic acid, whereas outer bulb peels are richer in carbohydrates (rhamnose, lyxose, glucose, xylobiose D and trehalose) along with sugar alcohols (mannitol, sorbitol and threitol), both differing greatly from clove metabolite composition. Some of these metabolites likely account for the allelopathic properties of onion bulb peels [ 96 ]. Liu and co-workers [ 97 ] analyzed the evolution of metabolites in different parts of the garlic plant (leaf, pseudostem, bulb peel wrapper, clover skin and clove) and identified 84 different compounds whose dynamics were highly correlated with the storage role of bulbs.…”