Medlar—A Comprehensive and Integrative Review

Among fruit plants belonging to the Rosaceae family, medlar (Mespilus) can be classified as neglected or underutilized. It is a genus of two species of flowering plants: Mespilus germanica (common medlar) and Mespilus canescens. Appreciated for its specific taste and flavor, medlar also possesses biological properties (antioxidant and antimicrobial). Despite the special properties of medlar, there are few research papers on this subject. This review paper includes data not only on medlar fruits but also its leaves, bark, and bud flowers. The main identified components are presented, as well as several biological properties, morphological properties, ethnopharmacological uses, and molecular biology analyses emerging from the scientific papers published in this area.


Introduction
Over thousands of years, rosaceous plants from the temperate areas of the northern hemisphere have played an important role. The appreciated fruits of the Rosaceae family (e.g., apples, pears, cherries, apricots, peaches, nectarines, plums, quinces, etc.) are still an important part of the human diet. This plant family, which comprises over 100 genera and 3000 species, has been the third most economically important plant family in temperate regions in last decade [1]. The nutritional and sensory qualities of the edible rosaceous crops are well known. Moreover, the fruits of this family are extremely rich in compounds with strong antioxidant activities (e.g., L-ascorbic acid, phenolics, and flavonoids) and other phytochemicals with important effects on health. The obvious growing interest in almost "forgotten" fruit species as a source of important compounds and their pharmacological, antimicrobial, and gastronomic properties is due in part to the actual problem (of humanity) of the lack of food resources [2].
Among fruit-plants that belong to Rosaceae family, medlar (Mespilus) can be classified as neglected or underutilized [1]. It is a genus of two species of flowering plants in the subfamily Maloideae: Mespilus germanica L. (common medlar) and Mespilus canescens J.B.Phipps. The first one is a well-known native of Southwest Asia and also Southeastern Europe, while the second species was recently discovered in 1990 in North America [3,4]. The genus Eriobotrya (Eriobotrya japonica-loquats) is also related and sometimes called the "Japanese Medlar" [3,4].
The present review paper aims to present an almost complete image of the identified chemical compounds in different varieties/genotypes of the Mespilus germanica L., as well as their potential biological activities (antioxidant, antimicrobial, and pharmacological) and ethnopharmacological relevance, from scientific papers published in the past two decades. The selection of the articles included in the present review was performed by using the well known electronic databases (Web of Science, Scopus, ScienceDirect, EBSCO, PubMed, and Google Scholar), using specific keywords ("genetic identification," "chemical composition," "therapeutic," "uses," "anti*" (returning results for "antimicrobial"), "antifungal," etc.). The validation of the articles was performed by reading each article. In the present review, only articles with significant contributions to this field of research were considered.

Morphological Analysis
Medlars are hard to grow from seed (germination to seedling requires about 2 years), so most commercial varieties are grafted onto other root stock species in order to improve their performance in different soils, areas, and climates. The best results are achieved by grafting on generative rootstock of medlar (Mespilus germanica L.), sorb apple (Sorbus domestica L.), a whitethorn (Crataegus sp.), wild pear (Pyrus communis L.), and vegetative rootstock of pear and quince (Quince A, Quince C, and Ba 29) [4,61]. They are self-fertile; thus, they do not need another tree/plant for pollination: they will produce fruit by the second year [61].
In general, all medlar cultivars/genotypes analyzed in the present paper share some common characteristics. They are in a wild form or are commercial cultivars, are slow growing, and are large deciduous spiny shrubs or small trees growing up to 8 m tall (Figure 1a  The fruits are pomes and range from brown (when mature-ripe) to dark brown (overripe), with wide-spreading persistent sepals giving a "hollowed out" aspect to the fruit [4]; sometimes, the fruits are reddish coloured and pear-shaped or apple-shaped, with a diameter between 1.5 and 3 cm and weighing from 10 g to over 80 g (very small fruits-large fruits) [45] (Figure 1c,d,g,h). M. germanica fruits are very hard and acidic. The fruits become edible in the winter (among the few that do this) after being softened ("bletted") by frost or stored naturally for a long period of time. Starting with the softening phase, the skin rapidly acquires a wrinkled texture and turns dark color (chocolate brown); the inside of the fruit is transformed to the consistency and light-flavor of apple sauce. The flavor is described as rich, cidery, and wine-like, dried apples-like or quinces-like [20]. The cultivated plants have larger and sweeter fruits compared to the wild forms [38].
Medlar trees require warm summers and mild winters and prefer sunny, dry locations with slightly acidic soil [4], but Gulcin et al. [45] considered that medlar grows poorly in frost-free areas and on rocks and in poor soils. It is well known that both biological factors (species/cultivar/genotype, age, or pests) and abiotic factors (weather, soil properties, irrigation, planting distance, etc.) have a significant influence on plant tree [18,23]. Thus, the phenological stages are closely related to morphological changes, and the characteristics of fruit trees, as an interannual variability, have been observed [18].
The foliage surface of trees is also influenced by the same factors mentioned above, but, in turn, it influences principal plant processes such as photosynthesis, transpiration, and absorption [23]. Moreover, leaf characteristics (dimensions and shape) can vary significantly between different genotypes within the same species [23], having an important role on plant growth and productivity. The leaves are elongated, lanceolate to obovate (like that of apple), entire or serrulate, dark green, 6-15 cm long, and 3-6 cm wide, and the leaves turn a special red when they acquire senescence (Figure 1d) [21,45] (Table 2). The plant has beautiful white-pink and hermaphrodite flowers in late spring [4] (Figure 1e,f). Flower buds are formed during May-June, and each bud has one flower. With a lifespan between 30 and 50 years, it is considered that M. germanica has a fairly short lifetime. [4]. However, there are 100 years old trees in UK [6]. Along with the rediscovery of Mespilus germanica L. plants, the medlar fruit has earned its place in human diet by its value. Thus, the fruit is a climacteric one, harvested in October and November and stored (in cold, dark, and aerated conditions, optionally in straw) until it becomes edible in the winter; the complex ripening process is genetically determined [4,39,45]. The green and hard flesh of the fruit softens and changes its color to light brown [53]. The result of this process includes major changes in texture, color, flavor, and aroma [39], resulting in brown (the pulp darkens), softened, and sweeter fruit. The inconveniences of this process include decreasing shelf-life and loss of marketable value [1,53]. Fruit shape may vary and generally include sub-globose or pyriform fruits crowned by foliaceous sepals [1,6]. The medlar shows better pest and climate resistance than most other fruit species of landscaping importance (apples, pears, apricots, peaches, cherries, etc.) [6]. The main characteristics of medlar fruits from research articles are listed in Table 3.
Several authors concluded that changes in structure, texture, color, aroma, and flavor of fruits are directly related to the stage of ripening process (usually presented as Days after full bloom = DAFB) [1,34,35,44]. Thus, at the final stage of the ripening process (207, 174, 187, and 206 DAFB), it was observed that the skin was completely brown, the pulp was whitish (50-60%)-brownish (40-50%) [34,44] or completely dark [1,35], and the fruit soft. The differences in the number of DAFB result from the starting date of the accounting days (10 May, 10 June, 8 May, and 10 May, respectively) [1,34,35,44]. Only Sulusoglu-Durul and Unver [53] did not use the same measure for the ripening stage. However, 25 days after harvest, they observed the same changes as other authors, meaning darkening, softening, dehydration, and flavor development of the fruits. Moreover, out of all the research papers, Sulusoglu-Durul and Unver [53] are the only ones that mentioned tree productivity, which ranged between 5.9 and 17.8 kg (province of Kocaeli, in Northwestern Turkey). As a result, from various research articles, the main morphometric characteristics of Mespilus germanica L. plant parts (fruits and stone) are presented in Table 4. The data indicate a high degree of fruit variability. The main difference between the genotypes is related to their average weight that ranged between 2.9± 0.1 g (at 39 DAFB, unripe stage) [36] and 40,80 g. Several authors [32,41,53] observed that even if there were important differences in fruit weight, diameter, and length (all these parameters being influenced by the genotype), there were no important differences by different years in measurement. Sulusoglu-Durul [53] observed that the fruit weight varied from 9.69 to 24.45 g and the seed numbers ranged from 1.7 to 4.7 among the genotypes. In addition, during the ripening period, some fruits lost their commercial value. In another research paper, Gruz et al. [44] presented the average fruit weight in ripe stage (between 191 and 206 DAFB) as 8.51 ± 0.26 g and 8.62 ± 0.83 g, concluding that fruit weight increase is slow and gradual during the natural ripening process.
Although Sebek et al. [6] indicated low variability between samples in terms of fruit weight, fruit width, fruit length, and petiole length based on genotypes, they observed an interesting aspect: The fruit weight of "Royal medlar" cultivar is three times greater than the fruit weight of medlar genotype "Pomoravka" (seedless variety from Bijelo Polje, Montenegro). A different conclusion from Haciseferogullari et al. [20], who assumed that changes in physical properties of fruits about the same size were probably due to environmental conditions.

Chemical Composition
Baird and Thieret [5] reviewed the medlar from almost all points of view, starting "from antiquity". They wrote about the origin (geographical, etymology, and existence history) of medlar, its chemical composition, morphology, and utilization. Edwards et al. [64], in a review on the chemistry of the Crataegus genus, mentioned the determination of total soluble sugars and phenolic acids in medlar fruits. Two years later, Acosta-Estrada et al. [65] also mentioned medlar in a review, emphasizing the bound phenolics in ripe medlar fruit. From various papers used in this review, the major components (as general composition) of medlar are summarized in Table 5. α-Tocopherol [45,55] Others Pentadecane, Tetradecane [48] The presented composition varies with a series of factors, such as the following: the cultivar/genotype, region of cultivation, and the degree of fruit maturity and ripeness. Among the reviewed research papers, several studies presented the chemical composition of Mespilus germanica L. fruits depending on several factors, and their relevant findings are presented in the following section.
The mineral composition of Mespilus germanica L. fruits, in terms of macro-elements and microelements, was analyzed by several authors (Table 6). By using inductively coupled plasma atomic emission spectrometer (ICP-AES), Haciseferogullari et al. [20] determined the mineral content of medlar fruit. The highest concentration was obtained for K (8052.91 mg/kg), followed by S, Ca, B, and p. Moreover, traces of Cr, Ti, and V were determined. In previous studies, Glew et al. [43] analyzed a series of minerals (Al, Ba, Ca, Cu, Co, Fe, K, Li, Mg, Mn, Na, Ni, P, Sr, Ti, and Zn) of medlar fruit and showed their high quantities of K (7370 µg/g dry wt), Ca (1780 µg/g dry wt), P (1080 µg/g dry wt), Mg (1661 µg/g dry wt), and Na (183 µg/g dry wt). The same researchers reported that the ripe medlar fruit is an important source of minerals and trace elements for the diet of populations in Western Asia (Turkey and Iran). They found significant differences in the levels of nutrients in medlar fruit related to different maturity stages [43]. In accordance with the studies of [20,43], Rop et al. [1] found that, at the ripe stage of medlar fruit of all the determined mineral compounds, the content of potassium was the highest (average 8320 ± 93 mg kg −1 ). Furthermore, they found some differences such as the following: a nine-fold higher accumulation of Mn, 3.5 times the amount of Ca, and 2.7 times that of P, 3.5-fold lower value for Fe. Accordingly, as previously mentioned, all of these differences in mineral composition can be caused by different growth, climate, and soil conditions or cultivation technique. Moreover, the ripening process has an influence on mineral composition, which tends to decrease these elements. The results from several research papers indicate that medlar fruits usually contain minor amounts of fatty acids (Table 7). These are considered important precursors (the fatty acid path produces esters and C6 compounds via lipoxygenase) for various odorous volatile compounds (e.g., benzaldehyde, pentadecane, and tetradecane) and contribute to characteristic aroma, flavor, and nutritional value of the fruit during ripening [35,36,39,42]. Thus, even if the content of fatty acids varies with genotype/cultivar, palmitic acid (C 16:0), linoleic acid (C 18:2n-6), linolenic acid (C 18:3n-3), oleic acid (C 18:1n-9), stearic acid (C 18:0), arachidic acid (C 20:0), and behenic acid (C 22:0) are the most predominant fatty acids [35,36,39,42] during development and senescence processes. Among these acids, the highest percentage was obtained for palmitic acid. Although Ayaz et al. [35] found capric acid (C 10:0) and tridecanoic acid (C 13:0) in all ripening stages (between 39-154 DAFB), Canbay et al. [39], Glew et al. [42], and Ayaz et al. [35] did not detect them. The authors [35,36,39,42] reported that the most important changes in fatty acids' composition of medlar fruit take place during medlar pulp softening. Glew et al. [42] considered that much of the potential benefit of fatty acids (C 18:2n-6 and C 18:3n-3) will be lost if the fruits are consumed 3-4 weeks after harvest. This idea confirms the findings of Ayaz et al. [35]: The level of linoleic acid and α-linolenic acid from the ripe hard fruits (60.0 and 13.5% of dry wt) decreased throughout ripening to a low of 28.7 and 5.6% of dry wt. Contrary to this, Ayaz et al. [35] emphasized a sudden increase in the content of some minor unsaturated fatty acids (palmitoleic acid, vaccenic acid, and erucic acid) at 187 DAF in the ripest, fully softened, and darkened pulp of medlar.  Where n.d. = not determined (depend on the ripening stage, not on the lack of determination); * = 3 weeks after harvest.
In addition to the determinations made, Canbay et al. [39] explained these major changes in the fatty acids' composition of medlar fruits as the following: During fruit ripening and senescence, cell disorganization is accompanied by enzymatic disruption of lipoproteins membranes resulting in variation in lipid composition. They also assumed that decreasing chemical components in fruits during the ripening process could be explained in two ways: the involvement of ethylene in the ripening (first stage of senescence) and senescence process or the involvement of degradative lipolytic enzymes that metabolize endogenous lipids in senescing membranes.
In the case of soluble proteins, Aydin and Kadioglu [38] observed that after a decrease during development, these compounds increased during ripening probably because of the ripening and senescence enzymes. This occurred for carbohydrates as well [38]; the level of glucose continuously increased during the development and ripening of medlar. This explains why the unripe medlar fruit has an astringent taste (high level of proanthocyanidin and low sugar content).
Most of the volatile components of fruits are mainly formed by esters, alcohols, acids, aldehydes, ketones, lactones, terpenoids, or apocarotenoids. These volatile aroma compounds appear during the ripening process through different metabolic pathways [49]. Among these constituents, organic acids are of increasing interest because of their role in the most important metabolic pathways of carbohydrates, lipids, and proteins [40]. Thus, several authors (Table 8) identified and quantified the main organic acids in fruits such as the following: ascorbic acid, citric acid, malic acid, oxalic acid, tartaric acid, fumaric acid, succinic acid, quinic acid, hexanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, and hexadecenoic acid. The data obtained in their studies confirm that medlar fruits represent a rich source of organic acids; their organic acid content per 100 g was greater than usual human daily consumption [40].
Selcuk et al. [66] indicated that malic acid was the most abundant organic acid, followed by succinic, quinic, oxalic, and citric acids in medlars, even in storage conditions. In general, a gradual decrease in malic acid content was observed during the entire storage period for both 1 MCP (1-Methylcyclopropene) treated fruit and control fruits. The fruit treated with 1-MCP also maintained high citric acid levels during storage, and this is probably due to the delay in the ripening process that results in decreasing organic acids levels.
Pourmortazavi et al. [48] and Velickovic et al. [49] studied the volatile compounds from medlar seeds by using supercritical fluid extraction followed by GC-MS analysis and from medlar fruits by using GC-MS analysis respectively. From medlar seeds, only three components were identified in the volatile oil: benzaldehyde, pentadecane, and tetradecane, the first one being the major component. In that study, the authors compared the supercritical fluid extraction method with hydro distillation and found an interesting result: supercritical fluid extraction products were markedly different from the corresponding hydrodistilled oil. Moreover, the authors considered that the supercritical fluid extraction method offers important advantages over hydro distillation (shorter extraction time, cost, and cleaner features) and contributes to the automation of the pharmaceutical industry [48]. On the other hand, Velickovic et al. [49] determined the changes in the volatile composition of medlar fruits during their two ripening stages: unripe and fully ripe stage. They found that the chemical compounds were aldehydes, alcohols, esters, acids, and terpenes, and C-6 aldehydes and alcohols were quantitatively dominant, among them.
Phenolic compounds represent a special and diverse class of plant secondary metabolites. Although they are known to be non-nutrient compounds, phenolics are reported to have multiple influences: tissue maturation processes, defense mechanisms, and sensory qualities of plant-derived food products (astringency, bitterness, and aroma) [44]. Several authors analyzed different medlar plant parts for antioxidant compounds (phenolics, flavonoids, carotenoids, etc.) and antioxidant capacity (Tables 9-11). The interest in phenolic acids comes from their potential protective role against oxidative damage, inflammation, cancer, cardiovascular diseases, and stroke. Researchers have found that phenolic compounds have strong antioxidant properties. Phenolic compounds are thought to contribute to the health effects of plant-derived products by scavenging free radical species, inhibiting free radical formation, and preventing oxidative damage to DNA [45].
The main conclusion from the presented data is that the concentrations of phenolic compounds and antioxidative capacity are significantly influenced by the stage of medlar fruit maturation and genotype. Moreover, an important decrease in total phenolic com-pounds occurs during ripening stages of medlar fruits [1]. For example, at 134 DAFB (ripening phase), the total phenolics content was 170 ± 1 mg gallic acid equivalent for 100 g fresh matter, but at the 174 DAFB stage, the content of phenolics was of 54% of that value. This decrease in phenolic compounds is closely related to the increasing polyphenol oxidase activity [1]. During the last two ripening stages (193 and 214 DAFB), the phenolic compounds decreased no matter what solvent for extraction was used (acetone, methanol, ethanol 80% or water) [34]. Another interesting idea presented by Rop et al. [1] is that antioxidants operate through different pathways; one method alone is not sufficient for evaluating the antioxidant activity of fruits and does not represent the entire antioxidant capacity of pure compounds.
Due to the fact that polyphenols are reducing agents, they can react with Folin-Ciocalteu reagent exactly as vitamin C, vitamin E, and carotenoids do. Consequently, this determination method is considered to be inappropriate for the total phenolics content determination (Folin-Ciocalteu reagent reacts with several non-phenolic reducing compounds-organic acids, sugars, and amino acids). In this case, the results will include higher phenolic compound values than in reality [1].
Among phenolic compounds, several authors determined p-aminobenzoic acid, caffeic acid, chlorogenic acid, p-coumaric acid, gallic acid, quercetin, protocatechuic acid, rutin, and vanillin as major phenolic compounds and catechin, epicatechin, ferulic acid, quercitrin, and resveratrol as minor phenolic compounds [3,45]. The values obtained for these compounds are influenced by the genotype. Moreover, flavonoids (a class of polyphenolic compounds) act as antioxidants, antimicrobials, photoreceptors, visual attractants, feeding repellents, and light screening substances in plants [62]. Rop et al. [1] observed that during fruit maturation, quercetin and its glycosylated derivates (glucosides and rhamnosides), were the most abundant flavonols. They consider that the sensory qualities of medlar fruit are extremely complicated, and vanillin is considered an aroma quality parameter for these fruits. Resveratrol was also identified, and it is known as a in vivo strong antioxidant [3].
Another group of compounds with known antioxidant activity by scavenging oxygen radicals and reducing oxidative stress in the organism include carotenoids. They possess preventive activity against a wide range of diseases (cardiovascular disease, hepatic fibrogenesis, solar light induced erythema, human papillomavirus persistence, and some cancer types) [47]. For the extraction of carotenoids, several authors recommended a wide range of solvent mixtures such as the following: methanol/tetrahydrofuran (THF) (50:50 v/v), ethyl acetate (100%), ethanol/hexane, acetone/ethanol/hexane, ethyl acetate/hexane, or acetone/hexane.

Storage Conditions for Medlar
Generally speaking, the medlar fruit is a typical climacteric one, meaning that it reaches full consuming maturity in a few days after harvest. Medlar fruit is very perishable and susceptible to skin and flesh browning, fast softening, and water loss after harvest. The results of these postharvest processes include the decrease in its edible and commercial value [66]. In order to avoid fast softening and browning during postharvest handling and storage and to increase the shelf life of this fruit, several authors have tried to find methods to accomplish these aims by using a Palliflex storage system and 1-methylcyclopropene treatment [66]; Palliflex storage system with low O 2 and CO 2 atmosphere [62]; 28-homobrassinolide [63]; or modified atmosphere packaging and methyl jasmonate [67].
Palliflex storage system is used for short-term or long-term storage under specific conditions (the desired O 2 and CO 2 concentrations can be set for each individual pallet). It is also known that 1-methylcyclopropene inhibits ethylene, which facilitates softening and senescence of fruits. The results emphasized that the firmness values of all the variants decreased with storage time and the used dose of 1-MCp. Thus, in control and 0.2 µL/L 1-MCP treated fruit, the process was more pronounced than 0.4 and 0.6 µL/L 1-MCP treated fruit. The retention of firmness is very important for long term storage of medlars [66]. In another research paper, the same authors analyzed the influence of Palliflex storage system and modified atmosphere packaging on physiological properties, qualities, and storage period for some medlar cultivar [62]. The results showed that, for all the treatment variants, the contents of total phenolic, total flavonoid, total condensed tannin, ascorbic acid, antioxidant activity, and organic acids decreased during storage, while no significant changes were detected in the content of sugars. It was also shown that the softening and skin browning slowed.
Another experiment for increasing the postharvest life of medlars was made by Ekinci et al. [63]. They determined the effects of postharvest brassinosteroid treatment on the storage quality of medlar fruit and emphasized the influence of 28-homobrassinolide applications on the physical and chemical properties of medlar fruit stored for 60 days. Their conclusion was that treating medlar fruits with 5 µM 28-homobrassinolide after harvest retained higher quality over a longer period [63].
Ozturk et al. [67] analyzed the influence of modified atmosphere packaging and methyl-jasmonate on the quality and health promoting properties of medlar fruit during the storage period. The addition of methyl-jasmonate to the modified atmosphere packaging (already known to have a good influence in preserving the medlar fruits quality) was also found to be effective in slowing down the reduction in ascorbic acid (vitamin C), one of the most important vitamins for human nutrition.

Molecular Biology Analyses
There are only a few research articles regarding molecular biology analyses on Mespilus germanica L. These papers focus on the analyses of relationship between Mespilus and Crataegus genus or on analyses that emphasize the polymorphism between the apparent different Mespilus germanica L. genotypes/cultivars worldwide. Lo et al. [29] analyzed, in their research paper, the fact that Mespilus and Crataegus are two distinct genera and the relationship between M. canescens and other Mespilus or Crataegus taxa. They used ITS (Internal Transcribed Spacers) and LEAFY (intron2 of the floral homeotic gene), representative for the nuclear genome, and also trnS-trnG, psbA-trnH, trnH-rpl2, and rpl20-rps12-four noncoding (intergenic) chloroplast regions. Their research revealed that Mespilus comprises not only Mespilus germanica species (from Eurasia) but also Mespilus canescens (from USA). They concluded that molecular and morphological data indicate no clear genetic distinction between Crataegus and Mespilus. The best taxonomic solution (based on both the molecular phylogeny and the morphological data) is to include the genus Mespilus in Crataegus as a new monotypic section. This does not interfere with the actual nomenclature (see also [29]).
Schaefer et al. [30] made some analysis regarding the genetic diversity of medlar germplasm (10 M. germanica and 1 M. canescens samples) using microsatellite markers: 21 apple SSR (Simple Sequence Repeat) primer pairs and 2 pear SSR primer pairs, previously reported to be useful in the tribe Pyreae. They observed that SSRs from apples were successfully able to distinguish most of the accessions medlar samples. Moreover, they sustained the idea of diverse genetic backgrounds represented in the medlar samples collection and the necessity of additional SSRs in order to confirm genetic identity and relationships in all accessions in the medlar collection.
Another group of researchers, Zarei et al. [33], performed phylogenetic analysis among samples from fruit trees of the Rosaceae family by using RAPD (Random Amplified Polymorphic DNA) markers. It is well known that RAPD markers have been used to analyze genetic diversity, construction of genetic maps, population structures, phylogeny studies of supposed related species and genera, etc. In their analyses, all primers used in the experiments were highly polymorphic, producing 85 clear and reproducible bands. Even if these authors used another type of primer in their experiments, the results were similar to those obtained by Schaefer et al. [30] with microsatellite markers. Thus, Mespilus and Crataegus have the highest genetic similarity among the studied samples. At the same time, they have higher similarity with respect to members of Pyrus compared to the Malus genus. Moreover, different species from Crataegus were clearly separated and grouped together, and the Mespilus genus had some common genetic similarities with three other genera (in their study) and might represent the branching point for the development of different pome fruit trees.
The most recent study on phylogenetic position of Mespilus was conducted by Liu et al. [26]. Their study analyzed a high number of samples (131 chloroplast genomes representing 115 species from 31 genera). They concluded that three species of Amelanchier (from W North America), one species of A. ovalis (from Europe), and two species of A. sinica and A. asiatica (E Asia) form a strong clade that is sister to Malacomeles. At the same time, eight Amelanchier species (from E North America) formed a clade with Peraphyllum. These two major clades are sister to each other and are, together, sister to the Crataegus-Mespilus-Hesperomeles clade [26].

Antioxidant Properties
Several research papers provided valuable information on the antioxidant capacity of medlar plant parts (fruits, leaves, bud flowers, or stem bark). Antioxidants (phenolics and flavonoids) from fruits and vegetables have been associated with the decrease in incidences of heart disease, some cancers, or age-related degenerative diseases. Medlar plants were shown to be a forgotten rich source of polyphenolic and antioxidant compounds. Table 12 summarizes the main findings regarding the antioxidant potential of Mespilus germanica L., as well as the responsible classes of compounds (as presented by the authors).
Due to the fact that one method alone cannot be utilized to completely evaluate antioxidant activity, different antioxidant capacity tests with different approaches and mechanisms have been carried out [1,3,10,39,41,[44][45][46]55]. Gulcin et al. [45] demonstrated the antioxidant and radical scavenging mechanism of LEM (lyophilized extract of medlar) by using different in vitro bioanalytical methodologies: DPPH free radical scavenging, DMPD+ scavenging, total antioxidant activity (ferric thiocyanate method), reducing power using two methods (Fe 3+ -Fe 2+ transformation and Cuprac assays), superoxide anion radical scavenging generated, hydrogen peroxide scavenging, and metal chelating on ferrous ions (Fe 3+ ) activities. They found that LEM possessed powerful Fe 3+ reducing abilities with a Trolox equivalent (0.69 µg TE) (Table 12). Moreover, Rop et al. [1] presented the connection between the decrease in phenolic content and total antioxidant activity. Antioxidant activity measured using the ABTS test on medlar cultivars varied based on ascorbic acid equivalents from 100 to 180 AAE.
Unlike other authors, Nabavi et al. [46] and Isbilir et al. [55] studied the antioxidant capacity of different medlar plant parts and not only fruits but also leaves, stem bark, and flower bud. They found [46] that the radical-scavenging activities of all the extracts (methanol or water extracts) increased with increasing concentration. Thus, WB (water extract-bark stem) with the highest phenol content showed the highest activity (IC 50 = 10.7 ± 0.6 µg·ml −1 ), which is comparable with vitamin C and quercetin. There were no significant differences between stem bark and leaf extracts (aqueous and methanol) in terms of reducing power. Moreover, the fruit methanol extract exhibited better activity than other extracts (IC 50 = 247 ± 12.2 µg·ml −1 ). The main conclusion of their research was that stem bark extract (both aqueous and methanol) showed the most activity in nearly all tests.
On the other hand, Akbulut et al. [3] considered the genotype to influence the extent of antioxidant activity in medlar fruits at a statistically significant level (p < 0.05). Total antioxidant activity was the highest in genotype KRD-6 (187 mg AAE per 100 g fresh fruit sample) and lowest in genotype KRD-12 (124 mg AAE per 100 g fresh fruit).
As a general remark, it can be observed that most authors assign antioxidant potential to the total phenolic and total flavonoids content. They all consider medlar to be a valuable source of antioxidant compounds.

Antimicrobial Activity
Medicinal plants, especially the endemic and edible plants in certain locales, are particularly important for the development of new drugs due to their ability to produce compounds with antioxidant and antimicrobial activities and their importance in human health [10]. Thus, Mespilus germanica L. is a medicinal plant with therapeutic effects historically [5]. Despite the medical benefits and significant therapeutic effects of medlar, there are only a few scientific papers about the antimicrobial properties of this medicinal plant [10]. In this context, several authors evaluated the antibacterial effects of different extracts of medlar against microorganisms from various environments in last decade [10,46,[50][51][52]57] (Table 13). Thus, Niu et al. [52] analyzed the in vitro antibacterial effect of two medlar extracts (water extract and ethanol extract) on pathogenic bacteria Staphylococcus aureus and Klebsiella pneumonia. Their results showed that the medlar extract was moderately sensitive to Staphylococcus aureus, and its inhibiting effect on Klebsiella pneumoniae was particularly significant. In addition, the antibacterial effect of ethanol extract was greater than water extract.  Similar results were obtained by Ahmady-Asbchin et al. [50] who evaluated the antibacterial effects of methanolic and ethanolic medlar leaf extract against bacteria isolated from hospital environments (Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli). The results showed that the methanolic extract of medlar leaf (instead of ethanolic extract as previously studied) inhibited the growth of all Pseudomonas aeruginosa and Escherichia coli strains (except one) and four strains of Staphylococcus aureus. Moreover, the minimum inhibitory concentration (MIC) for all the strains was 125 mg/mL.
Safari et al. [10] evaluated different standard (ATCC) bacterial strains that include Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Enterococcus faecalis, Salmonella typhi, Salmonella paratyphi, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Yersinia enterocolitica, Serratia marcescens, Shigella dysenteriae, and Citrobacter freundii. They tested different concentrations of methanolic extract of medlar leaves in order to emphasize antibacterial activity against both Grampositive and Gram-negative bacteria. Higher inhibition activity was observed against S. aureus (one of the most common causes of several diseases and responsible for food poisoning). The experiments showed interesting results, meaning that the methanolic extracts of medlar leaves emphasized relatively higher antibacterial activity against Gram-positive than against Gram-negative bacteria. Moreover, the antibacterial effect of this extract against S. aureus, S. epidermis, and E. coli was stronger than that of gentamicin [10].
In previous studies, there are several mentions about two antibiotics produced by the medlar plant [8,14]. In 1964, two antibiotic cyclopentoid monoterpenes were isolated and identified as genipic acid and genipinic acid (its carbomethoxyl derivative). Another group of researchers tested the effect of ethanolic extract of medlar on cutaneous leishmaniasis [57]. This group of infectious diseases is caused by species of the genus Leishmania and is a significant cause of morbidity and mortality in several countries. At present, Leishmania affects 6 million people in 98 countries. Due to the fact that there is no effective antileishmania cure, the researchers attempted to find new plant constituents as the source of new chemotherapeutic compounds. As previously mentioned, plants are rich in a wide variety of secondary metabolites (tannins, terpenoids, alkaloids, and flavonoids) and are found to have in vitro antimicrobial properties [10,46,[50][51][52]. Since this severe disease has a long treatment period, used for over 55 years with parental drug administration and several toxic side effects (pentavalent antimonials), it was necessary to find alternative solutions [57]. Thus, the use of ethanolic Mespilus germanica L. extracts in laboratory experiments reduces both lesion size and the number of parasites. During treatment, 40% concentration (leaves ethanolic extract) had the maximum effect on cured scar diameters (compared to 60% and 80% variants). The authors suggested that these ethanolic extracts had potential for topical wound healing, representing motivation for further exploration of anti-leishmania agents.

Usage of Medlar
As a medicinal plant, forgotten, neglected, and abandoned Mespilus germanica L. represents a suitable source of a wide range of secondary (and primary) metabolites: essential oils, antimicrobials, vitamins, antioxidants, minerals, etc. Based on some reports from World Health Organization, almost 80% of the world's people use traditional medicine for their primary health care needs [4]. Medicinal plants have several advantages: fewer side effects, effectiveness, and relatively low-cost production. The most common uses of medlar plants and the articles that we analyzed for this paper are presented in Table 14.
The diversity of recipes with medlar is amazing, especially in countries with a tradition of the cultivation or presence of medlar plants.  Diabetes Leaves Leaves decoction [21] Leaves infusion [55] Tuberculosis boiled and administered orally Bark of the branches [21] Abdominal pain n.m.

Conclusions
Mespilus germanica L. represents a forgotten and abandoned species of fruit tree that is becoming more and more interesting and attractive due to the special properties of its fruits. The current study aimed to present a complete picture of the currently known morphology, composition, biological properties, usage, and storage conditions for medlar.
It is used (fruits, leaves, bark, and bud flowers) in traditional medicine in a variety of diseases or medical conditions, as well as in gastronomic areas, and in a wide range of recipes (traditional/local recipes).
The chemical composition of Mespilus germanica L. fruits, leaves, bark, or bud flowers revealed high concentrations in antioxidant compounds (polyphenols and flavonoids), carotenoids, vitamins, minerals, etc. Highlighting the composition and properties of the medlar fruits is a very important aspect in order to rediscover this valuable fruit tree and to stimulate its cultivation and consumption.
The literature study revealed a lack of information (only few related studies exist) on molecular biology analysis for identifying the polymorphism between cultivars from different countries and for identifying different genes that encode for special properties. Moreover, although medlar trees are present in many places than is presented in research papers, no information (scientific literature) from other countries was found.
Future research directions should include, as the industrial perspective, the possibility of using the biocompounds from Mespilus germanica L. in the pharmacology industry or food industry. The content in microelements, polyphenols, and vitamins render these fruits excellent raw materials for obtaining natural bioproducts that are standardized, with a role in maintaining the health of the human body. Moreover, an important advantage of this fruit tree is the period of ripening in fruits-late autumn-which renders it an important source of fruits for the winter (food supply when other fruits are missing from the market). Regarding the valorification of medlar fruits, it should be used in small entrepreneurial business development.