Phytochemicals Accumulation in Sanhua Plum ( Prunus salicina L.) during Fruit Development and Their Potential Use as Antioxidants

Phytochemical Compositions and Antioxidant Activities of Different Cultivars of Prunus salicina Lindl. in Southern China

There are representative Prunus salicina Lindl. (plum) cultivars in the different provinces of Southern China. However, little data are available on the physiochemical characteristics of those plums. In this study, the fruit weight and size, edible rate, rate of juice, color, moisture, total soluble solids, total acids, ascorbic acid (AA), reducing sugar, polysaccharide, total polyphenols, total tannins, total anthocyanins, antioxidant activity, and phenolic composition of 11 plum varieties in Southern China were analyzed. The results showed that the content of reducing sugar, AA, polysaccharide, total polyphenols, total tannins, and total anthocyanins in different cultivars was in the range of 3.09-10.48 g/100 g, 2.30-14.75 mg/100 g dry weight (DW), 0.78-2.20 g/100 g, 20.73-41.18 mg/g DW, 0.42-1.09 mg/g DW, and 1.80-8.95 mg/g DW, respectively. A total of 11 phenolic compounds were identified in plums by ultra high pressure liquid chromatography (UPLC)-QqQ-MS/MS. Cultivar "Da Pao" showed the highest level of total polyphenols, and ferric ion reducing antioxidant power values, whereas cultivar "San Hua" had the highest content of total anthocyanins, 1,1-diphenyl-2-picrylhydrazyl, and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt values. Principal component analysis separated cultivars according to their physiochemical characteristics. This study provides reference information for consumers and the further deep processing of those plums.

Polyphenols from Prunus salicina L. alleviate weight gain, obesity-related hyperlipidemia, hepatic steatosis, hyperglycemia, and modulate gut microbiota in mice fed a high-fat diet

Hyperlipidemia, hepatic steatosis, and hyperglycemia are prevalent metabolic disorders closely linked to obesity. The objective of this research was to examine the potential advantageous impacts of polyphenols extracted from Prunus salicina L. fruit (PSFP) on hyperlipidemia, hepatic steatosis, and hyperglycemia induced by a high-fat diet (HFD), as well as to elucidate the underlying mechanisms involved. Male C57BL/6J mice, free from specific pathogens, were assigned randomly into three groups. These groups were then subjected to a 14-week dietary intervention, including a low-fat diet, an HFD, or an HFD plus with PSFP via intragastric administration. The obesity-related biochemical indexes were evaluated. To assess alterations in gut microbiota resulting from PSFP treatment, 16S rRNA sequencing was performed. UPLC-ESI-MS/MS assay identified 162 distinct polyphenolic compounds in PSFP. The administration of PSFP significantly reduced both body weight gain and hyperlipidemia induced by HFD. In addition, PSFP ameliorated hepatic steatosis induced by HFD and enhanced liver function in mice. PSFP treatment also ameliorated HFD-induced insulin resistance and hyperglycemia, evidenced by the observed decrease in fasting serum concentrations of glucose and insulin, improved insulin sensitivity, and restored glucose tolerance. Moreover, PSFP modulated the composition and abundance of specific microbial genus, including Lachnospiraceae NK4A136 group, Akkermansia, Parabacteroides, Enterococcus, Adlercreutzia, and Roseburia. Correlation analysis indicated significant associations between gut microbiota and physiological indices associated with obesity. These findings suggested that PSFP supplementation ameliorated HFD-induced hyperlipidemia, hepatic steatosis, and hyperglycemia, potentially through modulating the gut microbiota composition and abundance of specific taxa.

Insights into tissue-specific anthocyanin accumulation in Japanese plum (Prunus salicina L.) fruits: A comparative study of three cultivars

In the present study, three matured Japanese plum cultivars with different colored peel and flesh were selected to mine the key transcription factors regulating anthocyanin formation in tissues. Results showed that PsMYB10 was correlated with structural genes C4H, F3H, and ANS. PsMYB6 could positively regulate C4H (r = 0.732) and accumulated anthocyanins in Sanhua plum's flesh. Sanhua plum has the highest phenolic and anthocyanin contents (10.24 ± 0.37 gallic acid equivalent mg g-1 dry weight (DW) and 68.95 ± 1.03 μg g-1 DW), resulting itself superior biological activity as 367.1 ± 42.9 Trolox equivalent mg g-1 DW in oxygen radical absorbance capacity value and 72.79 ± 4.34 quercetin equivalent mg g-1 DW in cellular antioxidant activity value. The present work provides new insights into the regulatory mechanism of tissue-specific anthocyanin biosynthesis, confirming the pivotal role of anthocyanins in the biological activity of plums, providing essential support for the development of horticultural products enriched with anthocyanins.

Genome-Wide Identification and Expression Profiling Analysis of SWEET Family Genes Involved in Fruit Development in Plum (Prunus salicina Lindl)

SWEETs (sugars will eventually be exported transporters) play a vital role in longer-distance sugar transportation, and thus control carbon flow and energy metabolism in plants. SWEET genes have been identified in various plant species, but their functions in fruit development remain uncharacterized. Here, we isolated 15 putative PsSWEETs from the Prunus salicina genome. For further analysis, comprehensive bioinformatics methods were applied to determine the gene structure, chromosome distribution, phylogeny, cis-acting regulatory elements, and expression profiles of PsSWEETs. qRT-PCR analysis suggested that these SWEETs might have diverse functions in the development of plum fruit. The relative expression levels of PsSWEET1 and PsSWEET9 were obviously higher in ripened fruit than the ones in other developmental stages, suggesting their possible roles in the transport and accumulation of sugars in plum fruit. Positive correlations were found between the expression level of PsSWEET3/10/13 and the content of sucrose, and the expression level of PsSWEET2 and the content of fructose, respectively, during the development of 'Furongli' fruit, suggesting their possible roles in the accumulation of sucrose and fructose. The current study investigated the initial genomic characterization and expression patterns of the SWEET gene family in plum, which could provide a foundation for the further understanding of the functional analysis of the SWEET gene family.

Free amino acids identification and process optimization in greengage wine fermentation and flavor formation

Greengage wine with low alcohol content is increasing in popularity owing to its fruity taste and rich nutrition. The key to wine aroma and taste is flavor substances like free amino acids (FAAs), volatile fatty acids, higher alcohols, and esters. Amino acid (AA) metabolisms in yeast are an important source of these secondary compounds, which vary with the fermentation conditions. This study explored and optimized the impact of different parameters (carbon source, inoculum, pH, temperature) on FAA contents and dynamics in greengage wine. The results demonstrated that total and essential amino acid (EAA) content rose with a higher proportion of glucose, less yeast inoculation, higher temperature, and higher initial pH. With the results obtained it was concluded that the condition of 22.4°C, pH 4.5, and 3% inoculation was optimum for a 14.9-fold increase of EAAs in fermented greengage wine. In the long run, the research will aid in the development of the greengage brewing industry.

Identification of Candidate Genes Associated with Pulp Color by Transcriptomic Analysis of 'Huaxiu' Plum (Prunus salicina Lindl.) during Fruit-Ripening

The plum (Prunus salicina Lindl.) is one of the traditional and economically important stone fruit trees in China. Anthocyanins are important pigments in plums. However, little is known about the molecular mechanisms underlying anthocyanin accumulation in plum fruits, which has hindered research on the molecular mechanism of its utilization. Our research shows that the chlorophyll content was gradually decreased and the contents of anthocyanin and flavonoid increased during the coloring process of the pulp in 'Huaxiu' plums (P. salicina). Then, the RNA-Seq technique was used to analyze the transcriptome of pulp color changes with three different stages (yellow, orange, and red) in the 'Huaxiu' plum (P. salicina). A total of 57,119 unigenes with a mean length of 953 bp were generated, and 61.6% of them were annotated to public databases. The Gene Ontology (GO) database assigned 21,438 unigenes with biological process, cellular components, and molecular function. In addition, 32,146 unigenes were clustered into 25 categories for functional classification by the COG database, and 7595 unigenes were mapped to 128 KEGG pathways by the KEGG pathway database. Of these, 1095 (YS-versus-OS), 4947 (YS-versus-RS), and 3414 (OS-versus-RS) genes were significantly expressed differentially between two coloration stages. The GO and KEGG pathway enrichment analysis revealed that 20 and 1 differentially expressed genes (DEG) are involved in flavonoid biosynthesis and anthocyanin biosynthesis, respectively. Finally, we mainly identified three structural genes as candidate genes. The transcriptome information in this study provide a basis for further studies of pulp colors in plum and contribute to our understanding of the molecular mechanisms underlying anthocyanin biosynthesis in pulp.

Comparative Analysis of Phytochemical Profiles and Antioxidant Activities between Sweet and Sour Wampee (Clausena lansium) Fruits

As a local medicine and food, wampee fruit, with abundant bioactive compounds, is loved by local residents in Southern China. Titratable acid (TA), total sugar (TS), and total phenolic and flavonoid contents were detected, and phytochemical profiles and cellular antioxidant activities were analyzed by the HPLC and CAA (cellular antioxidant activity) assay in five sweet wampee varieties and five sour wampee varieties. Results showed that the average TS/TA ratio of sweet wampee varieties was 29 times higher than sour wampee varieties, while TA content was 19 times lower than sour wampee varieties. There were much lower levels of total phenolics, flavonoids, and antioxidant activities in sweet wampee varieties than those in sour wampee varieties. Eight phytochemicals were detected in sour wampee varieties, including syringin, rutin, benzoic acid, 2-methoxycinnamic acid, kaempferol, hesperetin, nobiletin, and tangeretin, while just four of them were detected in sweet wampee varieties. Syringin was the only one that was detected in all the sour wampee varieties and was not detected in all sweet wampee varieties. Correlation analysis showed significant positive correlations between TA with phenolics, flavonoids, and total and cellular (PBS wash) antioxidant activities, while there were significant negative correlations between TS/TA with phenolic and cellular (no PBS wash) antioxidant activities. This suggested that the content of titratable acid in wampee fruit might have some relationship with the contents of phenolics and flavonoids. Sour wampee varieties should be paid much attention by breeders for their high phytochemical contents and antioxidant activities for cultivating germplasms with high health care efficacy.

Dynamic Changes in Anthocyanin Accumulation and Cellular Antioxidant Activities in Two Varieties of Grape Berries during Fruit Maturation under Different Climates

As popularly consumed fruit berries, grapes are widely planted and processed into products, such as raisins and wine. In order to identify the influences of different climatic conditions on grape coloring and quality formation, we selected two common varieties of grape berries, 'Red Globe' and 'Xin Yu', for investigation. Grapes were separately grown in different climates, such as a temperate continental arid climate and a temperate continental desert climate, in Urumqi and Turpan, China, for five developmental stages. As measured, the average daily temperature and light intensity were lower in Urumqi. Urumqi grape berries had a lower brightness value (L*) and a higher red-green value (a*) when compared to Turpan's. A RT-qPCR analysis revealed higher transcriptions of key genes related to anthocyanin biosynthesis in Urumqi grape berries, which was consistent with the more abundant phenolic substances, especially anthocyanins. The maximum antioxidant activity in vitro and cellular antioxidant activity of grape berries were also observed in Urumqi grape berries. These findings enclosed the influence of climate on anthocyanin accumulation and the antioxidant capacity of grapes, which might enlarge our knowledge on the quality formation of grape berries and might also be helpful for cultivating grapes with higher nutritional value.

Cancer protective effects of plums: A systematic review

Plums is one of the most cultivated stone fruits due to its fast growing popularity. It has various traditionally recognized health benefits. There are two main commercial types of plums: the European plum (Prunus domestica) and the Japanese plum (Prunus salicina), each having many varieties. Researchers are gathering further evidence of pharmacological effects for plums by scientifically studying its anti-inflammatory, antioxidant properties. A systematic review analysing the literature related to the effects of plums on prevention and treatment of cancer is warranted. This is the first review examining the cancer-related effects of plums. Antioxidation properties of the active constituents of plum were also compared. Scopus, Google Scholar, PubMed, Medxriv and Cochrane Library databases, from their date of inception until July 2021 were utilized. The risk of bias was assessed using CONSORT checklist. A total of 6639 studies were screened and eventually only 54 studies were included. Full-text review of included studies revealed that plum extracts were rich in antioxidants. Overall, most of the studies that fulfilled the eligibility criteria were in vitro and a few clinical studies involving in vivo work. Therefore, it would be beneficial to perform more studies on animals or humans, to confirm that the result obtained from these in vitro studies are able to be extrapolated in a wider range of applications. Further clinical and in vivo studies are warranted to validate plums as a functional food for treatment and prevention of cancer.

Phenolic profiles, bioaccessibility and antioxidant activity of plum (Prunus Salicina Lindl)

Plum (Prunus Salicina Lindl) is a rich source of phenolic compounds. However, the bound phenolics and its bioaccessibility and antioxidant activity remain unclear. Hence, the purpose of this study was to determine: 1) phenolic profiles of plum, including both free and bound phenolic fractions, 2) bioaccessibility of phenolic compounds in plum during simulated gastrointestinal digestions, 3) their antioxidant properties. A total of 17 phenolic compounds were identified by UPLC-Q-Exactive Orbitrap/MS with most epicatechin, neochlorogenic acid and procyanidin B2 in the free phenolics fraction, while catechin and epicatechin was the main compounds in the bound phenolics fraction. After the gastrointestinal digestion phase, the most bioaccessible phenolics were quercetin-pentoside (61.64%), cyanidin-3-O-glucoside (43.26%), and naringenin-7-O-β-D-glucoside (42.04%). The antioxidant capacity of both undigested plum and its digested fractions showed a positive correlation with the total phenolics, and with specific individual phenolic compounds such as neochlorogenic acid, epicatechin and procyanidin B2 in undigested plum whereas catechin, neochlorogenic acid, and epicatechin in digested one. The results confirm that bound fraction of plum contribution to the total phenolic content must be taken into account in the assessment of the improving human health effects of plum.

Changes in Absolute Contents of Compounds Affecting the Taste and Nutritional Properties of the Flesh of Three Plum Species Throughout Development

The characteristics of plum fruits of three different species were investigated throughout their development (including over-ripening). The content of primary and secondary metabolites was expressed as amount per gram DW (dry weight) and per fruit in order to obtain information about the balance between their synthesis and dissimilation at different stages of fruit development. In all the plums, during the first stages of development, glucose was the most abundant sugar, whereas sucrose increased during ripening. There was no decrease in malate content per fruit before the commercial harvesting time of any of the plums, whereas a decrease was observed during over-ripening. In general, both the total phenol content and the contents of individual phenols in the flesh expressed on gram DW decreased throughout development, whereas their content per fruit increased, indicating that these decreases were due to a dilution effect arising from the expansion of the flesh. During the development of the flesh, the increase in the contents of the investigated metabolites per fruit shows that there was no net dissimilation of malate up to commercial harvest and of phenols throughout fruit development. Good correlations between the content of phenols to antioxidant activity were found. Shiro flesh, during the last part of fruit development, had lower total carbohydrate and polyphenol contents, lower antioxidant activities, and a higher malate content than the flesh of the other two genotypes.