Melanin naturally exists in organisms and is synthetized by tyrosinase (TYR); however, its over-production may lead to aberrant pigmentation and skin conditions. Loquat (Eriobotrya japonica (Thunb.) Lindl.) flowers contain a variety of bioactive compounds, while studies on their suppressive capabilities against melanin synthesis are limited. Loquat flower isolate product (LFP) was obtained by ethanol extraction and resin purification, and its inhibitory efficiency against TYR activity was investigated by enzyme kinetics and multiple spectroscopy analyses. In addition, the impact of LFP on melanin synthesis-related proteins’ expression in mouse melanoma B16 cells was analyzed using Western blotting. HPLC-MS/MS analysis indicated that LFP was composed of 137 compounds, of which 12 compounds, including flavonoids (quercetin, isorhamnoin, p-coumaric acid, etc.) and cinnamic acid and its derivatives, as well as benzene and its derivatives, might have TYR inhibitory activities. LFP inhibited TYR activity in a concentration-dependent manner with its IC50 value being 2.8 mg/mL. The inhibition was an anti-competitive one through altering the enzyme’s conformation rather than chelating copper ions at the active center. LFP reduced the expression of TYR, tyrosinase-related protein (TRP) 1, and TRP2 in melanoma B16 cells, hence inhibiting the synthesis of melanin. The research suggested that LFP had the potential to reduce the risks of hyperpigmentation caused by tyrosinase and provided a foundation for the utilization of loquat flower as a natural resource in the development of beauty and aging-related functional products.

Melanin is extensively distributed in organisms and believed to be synthetized by tyrosinase (TYR), leading to aberrant coloring and skin conditions when over-produced. Loquat (Eriobotrya japonica (Thunb.) Lindl.) flowers contain large amounts of bioactive substances currently few studied on their suppressive capabilities to melanin synthesis. Its isolate product (LFP) was obtained by ethanol solution extraction and resin purification, of which the inhibitory mechanism on TYR activity was elaborated by enzyme kinetics and multi-spectroscopy determinations and the impact on related proteins’ expression in mouse melanoma B16 cells was analyzed with Western blotting. HPLC-MS analysis indicated that LFP was identified into 137 compounds, with 12 including flavonoids (quercetin, isorhamnoin, p-coumaric acid, etc.), cinnamic acid and its derivatives as well as benzene and its derivatives owning TYR inhibitory activities. LFP inhibited TYR activity in a concentration-dependent manner with its IC50 value being 2.8 mg/mL and an anti-competitive mechanism involved altering the enzyme's conformation. LFP reduced the expression of TYR, TRP1, and TRP2 in melanoma B16 cells, hence inhibiting the synthesis of melanin. Considered collectively, LFP would be a viable option for treating hyperpigmentation caused by tyrosinase, providing a theoretical basis for the value-added utilization of loquat flower resource in beauty and aging related functional products.

Background/Objectives: Chronic colitis presents a growing global health burden with rising incidence. This study investigated the ameliorative effect of Dendrobium officinale polysaccharide (DOP) against dextran sulfate sodium (DSS)-induced chronic colitis in mice, specifically examining its dual modulation of gut microbiota and metabolic pathways. Methods: DOP was extracted and purified from Dendrobium officinale stems and leaves. A chronic colitis model was established in male C57BL/6J mice via DSS induction. Eighty-four mice were randomized into seven groups: control, model, low/high-dose leaf-DOP, low/high-dose stem-DOP, and sulfasalazine positive control. We assessed body weight, disease activity index (DAI), colon length, splenic/thymic indices, inflammatory cytokines, and histopathology (Hematoxylin and Eosin/Alcian blue staining), with tight junction protein and tumor necrosis factor-alpha (TNF-α) expression quantified via immunofluorescence. 16S rRNA sequencing and untargeted metabolomics evaluated microbial and metabolic shifts. Results: DOP significantly attenuated colitis severity, restored colon histoarchitecture, elevated goblet cell counts, upregulated zonula occludens-1 (ZO-1) and occludin expression, and suppressed TNF-α. Crucially, DOP remodeled dysbiosis by enriching beneficial taxa (e.g., Candidatus_Saccharimonas, Lachnoclostridium) while reducing pathogens (Mucispirillum). Metabolomics further elucidated DOP-mediated regulation of purine and nicotinate/nicotinamide metabolism—pathways mechanistically linked to its anti-inflammatory and barrier-repair effects. Conclusions: DOP effectively alleviates symptoms of DSS-induced chronic colitis in mice, protects intestinal barrier integrity, and achieves therapeutic potential through simultaneous regulation of the gut microbiome and metabolome.

A potentially novel probiotic strain, YY-112, was previously isolated and identified as Lactiplantibacillus pentosus using 16S rDNA sequencing. The whole genome analysis showed that strain YY-112 has the potential to metabolize carbohydrates in the gastrointestinal environment and to regulate immunity. Further, comparative genomics analysis revealed that strain YY-112 was Lactiplantibacillus plantarum (L. plantarum) with more unique genes. The results of in vivo tests showed that L. plantarum YY-112 had no adverse effects and restored the damaged spleen and intestinal barrier of immunocompromised mice. L. plantarum YY-112 recovered the normal levels of lymphocytes, serum cytokines (Interferon-γ, tumor necrosis factor α, and interleukin-6), immunoglobulins (Ig) (IgA, IgM, and IgG) and lipids (albumin, cholesterol, triglyceride). Additionally, L. plantarum YY-112 might indirectly enhance the immune system by improving the intestinal microbiota structure. These results supported the potential of L. plantarum YY-112 as a probiotic to regulate the immune system of hosts.