Domínguez Díaz and colleagues characterized the ‘Rojo Brillante’ persimmons (
Diospyros kaki L.), Protected Designation of Origin (PDO) ‘Ribera del Xúquer’ with regard to the existence of fiber with a total content of 2.38–4.99 g/100 g FW (vaguely greater for soluble fiber); vitamin C in the range of 4.62–10.25 g/100 g FW (primarily as dehydroascorbic acid); carotenoids (with lycopene as primary, in 26.76–51.10 μg/100 g FW, followed by β-carotene, in 10.07–20.50 μg/100 g FW, and neoxanthin, violaxanthin and β-cryptoxanthin as minor compounds); and mineral elements (Ca, Cu, Fe, K, Mg, Mn, Na, and Zn). With this information in mind and taking into consideration the scientific results surrounding this fruit showing the richness of persimmon fruit in bioactive compounds such as carotenoids, fiber, and vitamin C, not to mention the micro- and macro-minerals with significant health-furthering properties, the authors propose that the use of persimmon fruit and its bioactive components may be a solid approach to improving the population’s health level globally. However, even though the consumption of persimmons brings important health benefits, to date, there are no specific health claims authorized for this fruit. As such, Domínguez Díaz and co-authors suggested that Persimon
® (the registered trademark for the ‘Rojo Brillante’ variety) fruit is in theory capable of demonstrating two nutrition allegations: “sodium-free or salt-free” and “source of fiber”. Persimon
® fruit ought to have 3 g at a minimum of total dietary fiber/100 g of edible portion or at least 1.5 g per 100 kcal for the use of the “source of fiber” nutrition assertion. Given that the total dietary fiber mean values of all analyzed batches (2017 and 2018 seasons) were greater than the necessity of 1.5 g of fiber/100 kcal, it could be feasible to present the nutrition assertion “source of fiber” for Persimon
® fruits. The nutrition claim “sodium-free or salt-free” might also be used for Persimon
® given that its sodium content is inferior to the requirement of 0.005 g of sodium. These results may prepare the conditions for considering natural food products as candidates for the use of approved nutrition claims such as those used for this or other persimmon varieties
[61], similarly to what has also been described for raspberry fruit (
Rubus idaeus L.)
[62]. It should also be noted that it has also been explained that the recommended daily intake of fresh persimmon should be around 100–150 g
[43].
3. Phenolic Compounds
Phenolic compounds (PCs) can be found in a variety of foods available to the human diet including vegetables, fruits, beverages, herbs, and spices, many of which have been used empirically by humanity for centuries, namely in traditional medicine
[63]. Fruits and vegetables, and their products, are among the foods richest in these compounds.
The persimmon is rich in phenolic compounds already identified as bioactive
[36][37][40]. Much like carotenoids, PCs are also more abundant in the peel when compared to the pulp
[64].
There is an interest in these compounds, which is mainly due to their antioxidant capacity (reaction with free radicals and chelation of metals) and possible beneficial implications for human health such as prevention and co-adjuvants in the treatment of various types of cancer, cardiovascular diseases, and other pathologies
[65][66][67]. In addition to their antioxidant capacity, phenolic compounds have many other characteristics such as anti-atherogenic, anti-tumor, and anti-inflammatory effects, which cannot be described based only on their antioxidant properties
[68].
Persimmons are rich in flavonoids, terpenoids, naphthoquinones, saponins, and condensed tannins
[69]. In addition to the low molecular weight phenols present in the edible part of the fruit, there are phenolic acids such as gallic acid and its glycoside and acyl derivatives, glycosides of p-coumaric and vanillic acid, caffeic, chlorogenic acids, and several different di-C-hexoxide flavones
[70]. It is worth noting that the following flavan-3-ol monomers were detected in persimmons: catechin, epicatechin, and epigallocatechin
[71]. It was also through the combination of several analytical techniques that it was possible to identify myricetin as the terminal unit of the most common flava-3-ois (catechin and epigallocatechin-3-
O-gall)
[72].
In their work, Chen, Fan, and colleagues determined the content of individual and total phenols (epigallocatechin, epicatechin, catechin, chlorogenic acid, gallic acid, and caffeic acid) and compared them with those of other fruits such as apples, grapes, and tomatoes. They then concluded that persimmon was the fruit with a higher content of total phenolic compounds (about 170 mg/100 g dry weight) when compared to grapes (about 100 mg/100 g dry weight), apple (about 40 mg/100 g dry weight), and tomato (about 20 mg/100 dry weight)
[15]. The content of total phenolic compounds in persimmons was eight times greater than that of tomatoes, which is in line with the high antioxidant capacity of the persimmon extract
[15]. Gorinstein and colleagues also obtained similar results, showing that the content of total phenolic compounds in persimmons was greater than that of apples
[8].
Total phenolic content dosages in persimmons as reported by available literature differed extensively. Total phenolic compounds were registered to be in the range of 12.7 and 29.5 mg of GAE/100 g of fresh weight (FW)
[26]. Other researchers have registered soluble polyphenol concentrations to vary in the range of 1.3 mg to 1.550 mg/100 g FW of total phenolic compounds as well for the same astringent Triumph cultivar
[8][73]. As a matter of fact, if we consider the work done by Jang and co-authors performed on homogeneous samples of the non-astringent cultivar Fuyu, the smallest concentration of soluble polyphenols was 454 mg GAE/100 g FW with ethanol extraction, about half the maximum concentration determined through extraction with water (860 mg GAE/100 g FW)
[37]. Denev and colleagues determined 916.8 mg GAE/100 g FW
[74], and Direito and colleagues determined 641 ± 51.96 mg GAE/100 g FW
[75]. The inconsistency detected in these assays can be illuminated by considering the edaphoclimatic conditions, analysis of distinct opossum cultivars, and maturation phases, even when the fruit is more suitable for eating. Additionally, the various extraction methods that were used as well as the analytical methods of the protocols may have had an impact on the results
[43].
Through an improved extraction procedure, together with an ultraperformance liquid chromatography coupled with Q-TOF mass spectrometry (UPLC-Q-TOF-MS) platform, Esteban-Muñoz and colleagues characterized the PC composition of the two varieties of persimmon, Rojo Brillante and Triumph. The phenolic composition of the pulp of these two varieties was shown to have hydroxycinnamic and hydroxybenzoic acids, tyrosols, dihydrochalcones, hydroxybenzaldehydes, flavonols, flavanols, and flavanones. According to this team’s work, an overall amount of 31 compounds were detected, while 17 compounds were quantified. The prevalent phenolic compound observed in the Rojo Brillante type (0.953 mg/100 g fruit pulp) was gallic acid, while the concentration of p-hydroxybenzoic acid was greater in the Triumph variety (0.119 mg/100 g fruit pulp). The results demonstrated that the Rojo Brillante type had greater amounts of PCs than the Triumph type
[20]. The concentrations of the phenolic compounds (caffeic acid, catechin, chlorogenic acid, epicatechin, fisetin, ferulic acid, gallic acid, p-coumaric acid, and protocatechuic acid) were determined by the ultra-high performance liquid chromatography (UHPLC-DAD) method (
Table 2). In an aqueous persimmon fruit extract, gallic acid was found to be the most plentiful phenolic compound (2.794 ± 0.263 mg/100 g FW) detected
[75], which is also in accordance with Pu and colleagues who found a concentration of 2.789 mg/100 g FW in the variety
D. kaki var. silvestris M
[76]. Nevertheless, Veberic and co-authors reported 2.43 ± 0.215 mg/100 g FW
[26]. According to the work undertaken by Esteban-Muñoz et al., caffeic acid was the second most profuse hydroxycinnamic PC with 0.078 and 0.046 mg/100 g for the Triumph and Rojo Brillante varieties, respectively, levels that are consistent with those determined in other varieties of persimmon
[76][77]. The concentrations of the three hydroxycinnamic acids (caffeic acid, ferulic acid, and chlorogenic acid) in the study done by Direito and colleagues were below 0.1 mg/100 g FW, except for the chlorogenic acid content, as was illustrated by Pu and colleagues
[76]. The chlorogenic acid concentration in the work presented by these authors was 0.171 ± 0.016 mg/100 g FW
D. kaki extract
[75]. Published results of 0.274 mg/100 g FW in the variety of
D. kaki var. silvestris M and 0.145 mg/100 g FW in the variety of
D. kaki cv. Xingyangshuishi have also been found
[76]. These same authors were not able to discover p-coumaric acid in five out of the six genotypes that were evaluated. The only genotype where p-coumaric acid was found was in
D. kaki var. silvestris M, with a value of 0.048 ± 0.004 mg/100 g FW
[76], roughly less than twice the concentration reported by Direito and colleagues of 0.097 ± 0.004 mg/100 g FW
[75], in accordance with the concentration reported by Esteban-Muñoz and colleagues, where p-coumaric acid was the hydroxycinnamic acid with the greatest levels in both persimmon varieties (not statistically different) with ranges from 0.088 to 0.113 mg/100 g FW
[20]. According to these authors’ work, protocatechuic acid had a concentration of 0.013 ± 0.010 mg/100 g in the Rojo Brillante variety, which was greater than those attained for the Triumph sample (0.004 mg/100 g), which is in agreement with the concentration reported by Direito and colleagues (0.005 mg/100 g FW)
[75]. Greater concentrations were observed in various persimmon extracts acquired with various solvents
[77], but the use of a HPLC equipped with ECD (electron capture detector) detection might overemphasize the concentration, and lower concentrations have also been described
[75]. Esteban-Muñoz et al. identified ellagic acid for the first time in persimmon fruit in the Rojo Brillante variety (0.327 ± 0.173 mg/100 g fruit pulp), the variety of persimmons that had a greater concentration of ferulic acid than that found in the Triumph variety (0.011 vs. 0.008 mg/100 g). These concentrations are consistent with (or slightly lower than) those described for different persimmon varieties by other authors
[75][76][78].
Table 2. Main phenolic compounds from persimmon fruits quantified and identified.
Phenolic Compounds (PCs) |
Quantification and Reference |
Gallic acid (mg/100 g FW) |
0.953 ± 0.344 [20] |
2.794 ± 0.263 [75] |
2.789 ± 0.003 [76] |
2.43 ± 0.215 [26] |
Caffeic acid (mg/100 g FW) |
0.078 ± 0.001 [76][77] |
0.1 ± 0.001 [75][76] |
|
|
P-coumaric (mg/100 g FW) |
0.048 ± 0.004 [76] |
0.097 ± 0.004 [75] |
0.088 ± 0.046; 0.113 ± 0.055 [20] |
|
Ferulic acid (mg/100 g FW) |
0.1 ± 0.001 [75][76] |
0.008 ± 0.003 [20] |
|
|
Chlorogenic acid (mg/100 g FW) |
0.171 ± 0.016 [75] |
0.274 ± 0.003 [76] |
|
|
Protocatechuic acid (mg/100 g FW) |
0.013 ± 0.010; 0.004 ± 0.002 [20] |
0.005 ± 0.000 [75] |
|
|
Ellagic acid (mg/100 g FW) |
0.327 ± 0.173 [20] |
|
|
|
Quercetin (mg/100 g FW) |
0.224 ± 0.002;0.812 ± 0.006 [76] |
|
|
|
Proanthocyanins (mg/100 g FW) |
540.2 ± 0.000 [74] |
744 ± 8.6 [75] |
|
|
Identifications |
(Epi)catechin and (epi)gallocatechin |
[13][59][70][71][72][79] |
Quercetin 3--2′′-galloylglucoside), quercetin 3-O-glucoside and isomer and aglycone |
[59] |
Kaempferol-3-O-glucoside, kaempferol 3-(2′′-galloylglucoside) |
[59] |
2-Methoxy-1, 4-benzoquinone |
[59] |
Compared with hydroxycinnamic acids, the extent of hydroxybenzoic acids was higher
[20][75], but the (+)-catechin and (−)-epicatechin contents reported by Direito et al. were lower than previously reported values
[80][81]. The same situation occurred for the concentration of the flavone fisetin
[72]. Nevertheless, the various stages of maturation and the various cultivars may possibly lead to a variability in the results
[43]. The diversity of small phenols in pulp extracts reported to date is, however, surprisingly scarce, being normally restricted to three to ten components (derived mainly from cinnamic acid), depending on the variety being assayed
[43]. Thus, it can be concluded that the profile of low molecular weight phenols, for example, in the pulp of the persimmon, still remains to be determined
[20][70].
Catechins (flavan-3-ol) are the main flavonoids found in persimmons, which can offer potential benefits to human health, given that they are related to several physiological functions including a protective role against diseases associated with oxidative stress and have antimutagenic and anticarcinogenic capabilities
[71]. Persimmon extracts also showed apoptosis-inducing activity of Molt 4B leukemic cells
[82].
Procyanidins consisting of (epi)catechin and (epi)gallocatechin together with free phenolic acids in extracts of different varieties of Japanese persimmon have been reported in the literature
[71]. However, Sentandreu and colleagues found no evidence of their presence in their tested samples
[70]. Zang and colleagues described the presence of the precursor ion m/z 289, which may be -(−)epicatechin
[79] and with a fragmentation spectrum characteristic of this type of compound (m/z 109, 123, 125, 205, and 245)
[38]. Epicatechin and flavone di-C-hexoside were, however, identified by Maulidiani and colleagues
[59].
Quercetin was measured in comparable quantities in the Triumph and Rojo Brillante varieties in the range of 0.005–0.007 mg/100 g fruit pulp. Even though these values are lower than those described for other varieties of persimmon
[76], some authors did not find any quercetin in persimmons
[78]. Maulidiani and colleagues identified quercetin and kaempferol derivatives as the major flavonoids in persimmon where the four derivatives of quercetin including quercetin 3-(2′′-galloylglucoside), quercetin 3-
O-glucoside and its isomer and quercetin aglycone were also identified. Kaempferol-3-
O-glucoside and its isomer, kaempferol aglycone and kaempferol 3-(2′′-galloylglucoside) were likewise also identified
[59].
Persimmons accumulate a large amount of condensed tannins (or proanthocyanidins, PACs) in vacuoles of specific cells called “tannin cells” during the development of the fruits, which are responsible for the astringency, which is a sensation of dryness or “tie the mouth” due to the clotting of oral proteins
[83]. As maturation progresses, tannin content decreases and the risk of bitter taste of astringent varieties also decreases
[84]. However, the greater or lesser astringency of all cultivars decreases during ripening, not only because of the decrease in tannin content, but because the soluble tannins turn into insoluble forms
[85]. Astringent cultivars continue to have a significant amount of soluble tannins even when ripe
[51].
Gu and colleagues used the HPLC method coupled with electrospray ionization mass spectrometry (ESI-MS) to determine the fractions of condensed tannins of high molecular weight that constitute the persimmon, which permitted them to verify that the antioxidant activity of high molecular weight tannin fractions was significantly higher than that of low molecular weight tannins and that of proanthocyanidins in grape seeds. This led the author to consider that condensed high molecular weight tannins were the largest antioxidant present in persimmon pulp
[13]. As studied by Suzuki and colleagues, the highest proanthocyanidin content was found in astringent varieties
[71]. Proanthocyanins diminished proportionately throughout maturation from 540.2 mg CE/100 g FW to 90.2 mg CE/100 g FW
[74]. In the study by Direito and colleagues, proanthocyanidin content was 744 ± 8.6 mg CE/100 g FW
[54].
In the study of the structure of the proanthocyanidins present in the persimmon, it was found that they consist essentially of (epi)gallocatechin-3-
O-gallate, (epi)catechin-3-
O-gallate, and epicatechin
[13][72]. The molecular weight distribution of the condensed tannins of high molecular weight was determined as being in an interval between 1.16 × 10
4 Da and 1.54 × 10
4 Da
[13], and Li and colleagues described between 7 and 20 kDa (degree of polymerization 19–47), but sizes estimated by gel permeation chromatography were 50–70% smaller
[72].
Tyrosol was found at similar levels in both varieties of persimmon (Rojo Brillante and Triumph), 0.020 ± 0.017 mg/100 g fruit pulp for Triumph and 0.038 ± 0.021 mg/100 g fruit pulp for Rojo Brillante studied by Esteban-Muñoz and colleagues, but no other studies discussing tyrosol have been found to date
[20].
Triterpene and fatty acids are detected in different amounts in all cultivars: Fuyu, Triumph, Krembo, Jiro, Romang, and Taishu. Spathodic acid, a pentacyclic triterpenoid, rotungenic acid, and oleanolic acid were identified based on the molecular ion at m/z 455.3532
[59]. Spathodic, barbinervic, and rotungenic acids, which were only found in Krembo, can be considered as the chemical markers of the Krembo cultivar. L-malic and citric acids were also found in all cultivars. Interestingly, pantothenic acid was only detected in the Krembo persimmon. According to analyses, monogalloyl-hexoside was only found in Krembo and Triumph, while gallic acid was found in Krembo, Triumph, and Jiro cultivars. Quercetin and kaempferol were found in the Fu and Ji varieties, while its glycosidic forms were mostly found in Fuyu, Krembo, Triumph, and Jiro. Fructose was found in all cultivars, while glucuronic acid was found in the Krembo variety and had 23 unique compounds, while Fuyu and Taishu varieties had only eight and two unique compounds, respectively. All three cultivars shared the same 15 compounds, which were mostly sugars, amino acids, and fatty acids
[59].
Two benzoquinone derivatives were also identified based on their molecular ions at m/z 137.0233 and 293.1760, the 2-methoxy-1, 4-benzoquinone, and embelin, respectively. Embelin is a dihydroxy-1,4-benzoquinone that has an undecyl group substitution at position C3
[59].