A Review on Fruit Metabolomics
Author(s) : Nesibe Ebru Kafkas 1 and Ilbilge Oguz 1
1 Faculty of Agriculture, Department of Horticulture , University of Cukurova , Turkey
J Agri Food Nutr
Article Type : Review Article
Fruits are produced and consumed not only because of their commercial and economic importance but also because they are essential and vital for human nutrition due to having their sugars, organic acids, pigments, volatiles and other nutraceutical compounds. They are a rich in bioactive metabolites, such as vitamins, minerals, and phenolic compounds, mainly anthocyanins. Numerous in vitro and in vivo studies indicated the health effects of fruits and their function as bioactive modulators of various cell functions associated with oxidative stress. So, fruits are play an important role and essential part of our diet and to grow nutrient-rich varieties with metabolite content is vital importance. Currently, hundreds of substances, including primary and secondary metabolites have been detected in fruits. Analysis of fruit metabolomics are not only important for growers, consumers are interests for food industry, also. In this paper, it was aimed to give information and discuss on advanced metabolomic analysis methodologies in fruits.
Keywords: Fruit; Metabolomic Analysis; Chromatography
Fruits are produced and consumed not only because of their commercial and economic importance but also because they are essential and vital for human nutrition due to having their sugars, organic acids, pigments, volatiles and other nutraceutical compounds. They are a rich in bioactive metabolites, such as vitamins, minerals, and phenolic compounds, mainly anthocyanins. Numerous in vitro and in vivo studies indicated the health effects of fruits and their function as bioactive modulators of various cell functions associated with oxidative stress. So, fruits are play an important role and essential part of our diet and to grow nutrient-rich varieties with metabolite content is vital importance. Currently, hundreds of substances, including primary and secondary metabolites have been detected in fruits. Analysis of fruit metabolomics are not only important for growers, consumers are interests for food industry, also. In this paper, it was aimed to give information and discuss on advanced metabolomic analysis methodologies in fruits. Keywords: Fruit; Metabolomic Analysis; Chromatography
Metabolomics has played a central role in various areas of plant sciences, offering new perspectives for the advancement of agriculture, drug discovery, chemical ecology and taxonomy. Plant metabolomics (identification and quantification) aims to understand the relationship between biological systems and genetic, pathological, and or environmental stimuli in terms of differential expression of the metabolism. In recent years, genomic, metabolomic and proteomic methods developed have been widely used for the diagnosis of plants. Fruit consumption is essential and vital for human health and nutrition due to its valuable composition such as primary and secondary metabolites, volatiles, and other nutraceutical compounds. Their valuable agronomic traits and metabolomic content are important for the producer, consumer, and fruit growers. Fruit is an essential part of our diet and the breeding to achieve nutrient-rich varieties requires a comprehensive analysis of metabolite content. Currently, hundreds of substances, including primary and secondary metabolites have been detected in the fruit. Anabolism, catabolism and amphibolism reactions occur simultaneously inside different cells of the plant. Primary metabolites are created first and are required for the survival of the live cell (fertilization and fruit set), while secondary metabolites are derived from primary metabolites. All the small molecules that can be found in a cell or a living being is called the metabolome, and the metabolome concentration is constantly changing as intracellular reactions occur every moment. With the analytical techniques used to investigate metabolomics, only the instantaneous content under certain conditions can be determined. Metabolomics studies have been widely used in many areas such as biomarker detection, enzyme-substrate relationship, bioactivity studies, and metabolic pathway analysis. Analyzes of small molecules in the metabolome are performed using high precision analytical techniques such as NMR (nuclear magnetic resonance), GC-MS (gas chromatography-mass spectrophotometry) and LC-MS (liquid chromatography-mass spectrophotometry). Additionally, metabolomics technologies have become increasingly important in systemically exploring the mechanisms of plant growth and development and the responses to biotic and abiotic stresses [1]. For example, during the ripening stage of the fruit, physiological changes such as changes in cell wall structure and tissue occur, as well as the formation of substances such as flavor compounds, sugars (to provide appealing taste and taste), and anti-pathogens such as phenolic compounds. While examining the genetic basis and developmental course of fruit development, mostly soft tissue fruiting species were emphasized [2,3]. In general, tomato and strawberry fruits were used in such studies. However, the ripening process of these strawberry and tomato fruits shows great differences. Tomato fruit is a climacteric fruit since it’s ripening depends on ethylene. Moreover, climacteric fruits such as tomatoes, bananas, apples, and avocados produce ethylene biosynthesis emissions due to increased respiration during ripening. On the other hand, non-climacteric strawberries and a few citrus fruits do not have respiration and autocatalytic ethylene formation. Ethylene is responsible for the coordination and completion of ripening in climacteric fruits. Although these links are not yet obvious in the development history of non-climacteric fruits, they can be explained by ethylene production [3,4]. Besides, in the secondary metabolism of the fruit formation stage of the two fruit species (tomato and strawberry), aroma and aromatic volatiles as well as an intense color formation and color transformation seem to be effective. Also, ethylene is required for the coordination and completion of ripening in climacteric fruit, whereas it is not yet associated in the developmental program of non-climacteric fruit, although they may respond to ethylene as well [4]. Therefore, for example, in tomatoes, the chloroplast membranes are disrupted during the transition from chloroplast to chromoplast and helping the synthesis of carotenoids, including lycopene and b-carotene. As a result of the accumulation of anthocyanins in strawberries, the intense red color of the strawberry fruit is occurred [3]. As it is known, the growth and maturation of strawberry fruit includes many complex physiological development events. In addition, with the increase of phenolic and other antioxidant components in the last stage of fruit development and ripening; conversion of starch to sugar and biosynthesis pigments into anthocyanins are observed and biochemical and physiological changes occur in the sense of taste and the contents of volatile aromatic compounds [5,6]. During the development of strawberry fruit, the transformation of sucrose from photosynthetic tissue into ripe fruit, which forms a complex network of primary and secondary specific metabolism, is a very important event [7]. The content of sugar, organic acids, and fatty acids as well as the consumption of amino acids during fruit development in many berries, especially in strawberries, are important indicators in forming the metabolic profile of the fruit. Moreover, it is known that the ratio of sugar, organic acids and amino acids in fruits plays an important role on the taste of the fruit, as well as other water-soluble compounds [8-10]. As it is known, metabolomics are biotechnological profiles of metabolites emerging from lipids, carbohydrates, vitamins, hormones and other cell components in fruit tissues, cells and physiological fluids in a certain time period. For this reason, the metabolomic method is used in more comprehensive chemical metabolome analyzes that help to identify structural changes in fruit biochemical composition and metabolism during fruit development pre- and post-harvest. These natural changes can be determined by analyzing using metabolic methods, such as Nuclear Magnetic Resonance (NMR) or Mass spectrometry (MS)-based fingerprinting, profiling or imaging strategies, and their possible combination with each other (e.g. antioxidant metabolites). It is remarkably known that fruit quality is closely related to their biochemical composition in terms of organoleptic and nutritional properties, especially low molecular weight organic compounds (metabolites, including sugars, organic acids, amino acids, phenolic compounds, isoprenoids, alkaloids), starch, minerals, and cell walls. It is attempted to make such chemical components appealing by culturing the fruits first and then by breeding and cultural practices. However, these chemical compositions are still likely to be affected by environmental factors. Briefly, the biochemical composition of the ripe fruit is the result of complex metabolic changes during fruit development. For decades, assays targeting specific biochemical features have been used to make detailed measurements of metabolites during fruit development. Recently, non-targeted metabolomic approaches based on proton nuclear magnetic resonance (1H NMR) or mass spectrometry (MS) have been widely used in the analysis of metabolites [11-13]. Model fruit metabolomics have become increasingly popular in recent years for a variety of agriculturally important fruit species, such as tomatoes [11,14]. In a study conducted by Hanhineva and Aharoni [3], evaluated the outputs corresponding to the application of metabolomics and identification of genomic regions associated with metabolite traits to study metabolism in transgenic plants, mutants or populations. Tohge and Fernie have stated that many metabolomic analyzes are successful in tomatoes and strawberries, and successful results can be obtained in other fruits as well. Also, they conducted a study on the determination of tomato metabolomics at different developmental stages, different environmental conditions, or following the genetic degradation and they described how the effect of primary metabolism on fruit and development growth can contribute to a better understanding of metabolomics depending on the evolution and nature of specific metabolic pathways. In a study conducted by Tsugawa [15] on the correct use and development of MS-based spectral databases in computational techniques and data processing, it was reported that the desired result could not be achieved in the identification of metabolites. Metabolic studies on fruit set or early fruit development (stage of cell division) are less common compared to the studies on later stages of development, especially ripening [16]. In a study on stenospermocarpy in grapes, it was reported that metabolic analyzes provided information about the regulation of sugar and hormone-mediated pathways and suppression of special metabolism in grapes, and the details of molecular events occurring during flowering and fruit set [17]. Moreover, it has been reported that vegetative growth regulators play a very important role in the ripening of fruits during the growth period of tomatoes and citrus fruits [18,19]. Although, the quality and the quantity of fruit quality parameters may differ from one variety to another depending on the maturity stage and storage conditions [20]. Climatic conditions and cultivation methodologies specifically fertigation, irrigation and pruning methodologies also play an important role on the fruit quality [21]. Indeed, extraction these parameters is the first step for the qualitative and quantitative analysis of the metabolomites. This crucial step significantly affects the yield as well as the quality of the molecules. The measurement of fruit metabolomics can be identified and quantified by reliable, replicable and advanced technologies such as Nuclear Magnetic Resonance (NMR) or Gas- and Liquid-Chromatography coupled with Mass Spectrometry (GC-MS and LC-MS) and other chromatography techniques. In addition, High Resolution Mass Spectrometry analyses, allows us to detect and measure chemical substances in infinitesimal amounts (Tandem LC/MS) [22]. Fruit flavor is the product of the complex interactions between the chemical composition of a fruit and the taste, olfaction, and psychology of the consumer [23,24]. Extraction of a flavor fraction is one of the most important and preliminary issue for detecting exact and accurate chemical compounds. There are several extraction methodologies depending on the detection limitations and volatile types since chemesthetic compounds may be volatile, semi-volatile and non-volatile characteristics. Fruit flavors can be analyzed using Gas Chromatography (GC) and High-Performance Liquid Chromatography (HPLC) techniques. It can be also evaluated by consumer sensory panels or individually by the breeders. However, according to the previous results field evaluations can provide mostly non-objective or subjective results and typically consist of the sensory preferences of one or few individuals. However, the advantage of field evaluation is that many varieties can be evaluated on a given day. In contrast, population-based sensory panels are more objective, accurate, and well-established, but they can be costly, time-consuming, and difficult to scale to a large breeding program. Difficulties with accurate flavor phenotyping have contributed to the lack of fruit flavor selection and thereby to the widespread consumer belief that commercial fruit flavor is declined [25,26]. Fruits contain a diverse array of sugars, acids, and volatiles whose concentrations are driven by genetic and environmental effects. Sugars and acids are largely perceived by taste receptors on the tongue and the volatiles by receptors located in the olfactory epithelium [14].
As a result, plant metabolomics plays important roles in both basic and applied studies regarding all aspects of plant development and stress responses. In addition, it is known that the complex gene, protein and metabolite network in the fruit varies greatly during the development of the fruit. The use of metabolomic methods with the ability to study a large number of metabolite analyzes, rather than making a single or several analyzes in the content analysis of fruits, creates the opportunity to examine the development metabolism in fruits in detail and provides important conveniences in terms of obtaining accurate and fast results in breeding. As it is known, it has been proven by many studies that the metabolomics method provides remarkable convenience in the effective detection of multiple chemical components in cell layers in a tissue or, for example, in a single cell. In addition, the metabolomic method has been widely used in many life science disciplines in recent years. Moreover, metabolomics can also be used in plant breeding to monitor metabolism in transgenic plants, mutants and populations of introgression lines. Recent studies have shown that metabolic quality characteristics of fruits are a very important parameter in the identification of genomic regions. In general, the metabolomic analysis method is used for tomato and strawberry plants. However, it is expected that the metabolomic analysis will be applied more to many other fruit species in the following years. Therefore, we believe that this study will shed light on more comprehensive studies in the future.
Corresponding author: Nesibe Ebru Kafkas, Faculty of Agriculture, Department of Horticulture, University of Çukurova, Turkey. Copyright: © 2022 All copyrights are reserved by Nesibe Ebru Kafkas, published by Coalesce Research Group. This work is licensed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
