A phytochemical study investigating the leaves of persimmon trees (Diospyros kaki) has revealed that seasonal climatic variation corresponds to pronounced shifts in major flavonoid chromatographic peaks and tannin fractions. Across multiple harvest periods evaluated in South Korea, researchers determined that major secondary metabolite profiles fluctuated considerably across the spring, summer, and autumn months, demonstrating distinctive seasonal peaks alongside significant inverse associations with recorded environmental factors such as temperature, precipitation, and relative humidity. In particular, the chromatographic peaks associated with flavonoids attained their highest relative levels in May, whereas non-polymeric tannin content reached its maximum in April and polymeric tannin content peaked during the cooler autumn conditions of October. Conversely, the lowest relative abundances across these chemical constituents coincided with the hottest, wettest, and most humid conditions recorded in August, indicating that seasonal environmental dynamics represent an essential consideration for the profiling, standardized sourcing, and commercial harvest scheduling of persimmon foliage across horticultural, beverage, cosmetic, and medicinal sectors.

Persimmon is cultivated globally as a major agricultural fruit crop, holding historical and ongoing prominence across East Asian nations including South Korea, Japan, and China. Beyond the commercial significance of the fresh fruit, the foliage of Diospyros kaki has traditionally been utilized for value-added products, serving as a popular ingredient in health-oriented beverages and topical cosmetic formulations. As an herbal infusion, persimmon leaves provide a distinctive flavor and supply notable quantities of vitamin C, historically serving as an alternative to citrus fruits. Furthermore, in Taiwanese cosmetic practices, the foliage has been referred to as beauty leaves due to documented reduction effects against hyperpigmentation disorders, highlighting commercial interest in its functional secondary metabolites. Phytochemical analyses identify flavonoids and terpenoids as the two predominant classes of bioactive constituents in persimmon foliage, with prior literature indicating that flavonoids constitute roughly a quarter of the leaf material while terpenoids account for thirty-nine percent, together comprising more than half of the total chemical constituents. Within the phenolic profile, specific flavonoid glycosides such as hyperoside, isoquercetin, and astragalin, alongside polymeric and non-polymeric tannins, have been linked to antioxidant activities and broader biological properties, making metabolite consistency a critical consideration for standardization.

Despite growing interest in persimmon foliage as a botanical raw material, previous investigations had left the relative influences of harvest timing, genetic lineage, cultivation conditions, and geographic origin insufficiently defined within a unified experimental framework. Secondary metabolite production in woody perennial plants is regulated by a complex interplay between intrinsic genetic programming and external environmental pressures such as ambient temperature, solar exposure, moisture, and rainfall. Prior germplasm evaluations noted that leaf catechin profiles and metabolite subgroups including flavones, flavanones, and flavonols differed among persimmon genotypes and varied across developmental leaf stages. However, agricultural producers and industrial processors faced limited empirical data regarding whether leaf phenolic variability is driven primarily by genotype, by the geographical origin of the parent stock, or by cultivation systems such as protected greenhouse environments compared to open-field orchard settings. Because unmonitored chemical fluctuations can compromise product potency, batch reproducibility, and functional extraction yields, the research team established an experimental program to quantify major chromatographic features and tannin accumulation across four genotypes, three South Korean geographic origins, greenhouse and open-field environments, and recurrent seasonal harvest intervals.

The experimental plant material was maintained and sampled at the Pear Research Center, operated by the National Institute of Horticultural and Herbal Science in Naju City, Jeollanam Province, South Korea. Each designated biological plant identity, or PlantID, was represented by a cohort of three approximately two-year-old trees. To evaluate temporal variation over consecutive growing seasons, preliminary seasonal tracking was performed from spring through autumn using PlantID 1, which represents Bansi, or genotype A, recognized as the most widespread persimmon cultivar in South Korea. Leaf tissue sampling was conducted across seven distinct dates spanning July 2023, October 2023, April 2024, May 2024, June 2024, August 2024, and October 2024. During this chronological period, the trees were initially cultivated under controlled greenhouse conditions before being relocated to open-field conditions in early April 2024. Consequently, the researchers noted that the preliminary seasonal timeline encompassed an environmental management transition, meaning temporal fluctuations reflected season-associated dynamics alongside physiological acclimation rather than completely isolated climatic effects. Foliage was harvested specifically from the midsection of the branches, sorted, dried at sixty degrees Celsius for forty-eight hours, pulverized into fine powder, and refrigerated at four degrees Celsius.

To rigorously profile the secondary metabolites, the researchers employed two distinct analytical pathways targeting flavonoid-related peaks and tannin contents. For flavonoid profiling, powdered leaf samples underwent sonication in seventy percent ethanol for three hours, followed by filtration through zero-point-twenty-two micrometer polytetrafluoroethylene membranes. The extracts were separated on an Agilent Eclipse Plus C18 reversed-phase column using a Hitachi high-performance liquid chromatography system with a diode array detector, running a multi-step gradient of water with zero-point-one percent acetic acid and acetonitrile at a flow rate of one milliliter per minute with detection at two hundred and sixty-six nanometers. In parallel, total tannin indices were determined from dual extractions of powdered tissue sonicated in a solvent mixture of water, acetone, and methanol. Polymeric tannin content, or PTC, was isolated through bovine serum albumin protein-precipitation assays, reacted with ferric chloride, and quantified against tannic acid calibration curves at five hundred and ten nanometers, expressed as milligrams of tannic acid equivalents per gram of dried weight. Non-polymeric tannin content, or non-PTC, was quantified from the initial precipitation supernatant using vanillin-hydrochloric acid microplate assays measured against catechin standards at five hundred nanometers.

High-performance liquid chromatography profiling revealed a complex chromatographic landscape across monitored ultraviolet wavelengths, with chromatograms recorded at two hundred and sixty-six and three hundred and twenty nanometers displaying the most prominent analytical signals, particularly within retention windows spanning twenty-nine to forty minutes. By comparing retention times against authenticated reference standards, four of the nine major selected chromatographic peaks were tentatively identified as specific flavonoid glycosides, with peak one corresponding to hyperoside, peak two to isoquercetin, peak five to kaempferol 3-O-galactoside, and peak six to astragalin. The remaining five selected peaks lacked definitive structural identification and were tracked as reproducible, major UV-absorbing chromatographic features. Linear mixed-effects models applying Benjamini-Hochberg false discovery rate adjustments revealed statistically significant seasonal fluctuations across all nine monitored chromatographic peaks within the seasonal dataset. Relative peak abundances reached their highest standardized z-scores during May 2024, whereas the lowest values across all selected peaks were recorded during August 2024, demonstrating substantial temporal sensitivity in foliar flavonoid accumulation.

Tannin fractions exhibited equally pronounced seasonal shifts that corresponded closely with external meteorological records obtained from the Korea Meteorological Administration. Polymeric tannin content attained its highest concentration in October 2024, while non-polymeric tannin content peaked in early spring during April 2024, with both tannin metrics dropping to their lowest seasonal measurements during August 2024. Principal component analysis and partial least squares discriminant analysis confirmed strong inverse relationships between the accumulation of these polyphenolic compounds and prevailing climate parameters. In May 2024, when flavonoid peaks peaked, the local weather recorded a moderate average temperature of eighteen point fifty-five degrees Celsius, low relative humidity of seventy-four percent, and moderate precipitation totaling one hundred and one point eight millimeters. Conversely, August 2024 was characterized by the highest temperature, rainfall, and atmospheric humidity of the study period, coinciding with marked depressions in secondary metabolite abundance. These patterns align with biochemical hypotheses that elevated summer temperatures and excessive humidity may downregulate crucial phenylpropanoid enzymes, including phenylalanine ammonia-lyase and UDP-glucose: flavonoid 3-O-glucosyltransferase, or accelerate phenolic catabolism and turnover.

To isolate the specific contributions of genetic lineage, geographic origin, and cultivation settings without the confounding factor of harvest date, the team conducted a detailed investigation using an independent multi-plant dataset harvested in October 2024. This expanded cohort encompassed twenty distinct PlantIDs, split evenly between ten grown under open-field conditions and ten maintained within protected greenhouses, representing four genotypes originating from three distinct administrative regions of South Korea. Linear mixed-effects model evaluations demonstrated that genotype, geographical provenance, and cultivation setting exerted limited influence across the vast majority of individual flavonoid chromatographic peaks and polymeric tannins. Nevertheless, statistically significant, variable-specific effects emerged upon Benjamini-Hochberg correction. Most notably, non-polymeric tannin content displayed a significant geographic origin effect alongside a significant interaction between origin and genotype, demonstrating that non-polymeric condensed tannin accumulation differs among specific origin and genotype combinations. Furthermore, among individual chromatographic features, peak eight exhibited a statistically significant response to cultivation conditions, demonstrating that environmental sheltering exerts compound-specific rather than uniform influences.

When individual chromatographic peaks were compared between greenhouse and open-field orchards at identical harvest times using multiple t-tests with Holm-Šídák corrections, the differences for most isolated peaks were not statistically significant. However, evaluating temporal shifts between August and October 2024 revealed notable cultivation-associated differences when secondary metabolites were assessed as integrated traits. Open-field trees generally demonstrated a more pronounced proportional increase in the summed area under the curve for all nine flavonoid peaks and polymeric tannin content from August to October compared to greenhouse specimens, although individual exceptions occurred, such as PlantID 8 diverging from fellow open-field cultivars. In contrast, non-polymeric tannins exhibited greater variability, displaying more substantial increases across several greenhouse cohorts. These integrated trends suggest that protected structures alter the magnitude and responsiveness of seasonal metabolic adjustments, likely through microclimatic buffering such as the attenuation of ultraviolet radiation by greenhouse coverings, which can modulate ultraviolet photoreceptor signaling pathways and stress-related phytohormones like abscisic acid.

In their synthesis, the authors underscored key methodological boundaries and highlighted avenues for future horticultural and biochemical validation. Because the multi-season tracking was conducted predominantly using PlantID 1 and involved an early-spring relocation from greenhouse sheltering to the open field, the observed seasonal trajectories represent season-associated temporal patterns within this specific experimental design rather than absolute proof of genotype-independent seasonality. The general lack of broad divergence across the four evaluated genotypes may reflect shared adaptive mechanisms within the shared research orchard environment, limited genetic divergence among the selected cultivars, or the presence of genotype-specific markers outside the monitored chromatographic peaks. Future investigations utilizing untargeted ultra-high performance liquid chromatography coupled with tandem mass spectrometry, common-garden genotype-by-environment frameworks, and gene expression analyses will be vital to fully elucidate the molecular pathways governing persimmon foliage composition. Nonetheless, these findings offer valuable empirical baselines, indicating that harvest timing aligned with spring and autumn climactic conditions provides optimal opportunities for standardizing flavonoid and tannin yields in commercial persimmon leaf production.

Subject of Research: Phytochemical variation of flavonoid peaks and tannin indices in persimmon leaves across seasons, cultivation conditions, genotypes, and origins

Article Title: Seasonal climatic variation is associated with persimmon (Diospyros kaki) leaf flavonoid peaks and tannin indices

Article References: Haniffadli, A., Ban, Y., Choi, K.-O., Joyce, M., Happy, K., Gang, R., Rahmat, E., Im, S., Kang, C. H., & Kang, Y. (2026). Seasonal climatic variation is associated with persimmon (Diospyros kaki) leaf flavonoid peaks and tannin indices. Applied Biological Chemistry, 69(1), Article 64. https://doi.org/10.1186/s13765-026-01129-7

Image Credits: AI Generated

DOI: 10.1186/s13765-026-01129-7

Keywords: Diospyros kaki, persimmon leaves, flavonoids, polymeric tannins, seasonality, high-performance liquid chromatography, plant secondary metabolites, horticultural biochemistry, Seasonal, climatic, variation, associated