Chemical Quality Profile and Bioactivities of “Hongyin” Tea, a Purple-budded Cultivar from Eastern Guangdong

‘Hongyin’ (HY) is a purple-budded Camellia sinensis cultivar from eastern Guangdong whose chemistry and bioactivities are not fully defined. We integrated sensory and compositional assays (catechins, caffeine, anthocyanins) with UPLC–MS/MS broad-targeted metabolomics, KEGG enrichment and network pharmacology, and evaluated bioactivity in high-fat-diet (HFD) mice with gut-microbiota (16S rRNA) profiling and microbiota–metabolite correlations. HY showed a distinctive chemical phenotype—low caffeine (most samples <1%), elevated gallocatechin gallate (GCG), anthocyanin enrichment, and predominance of linoleic/α-linolenic-acid (LA/ALA)–related unsaturated lipids; storage coincided with reduced astringency and orange-red liquor. Metabolomics annotated 2,105 metabolites, of which 1,311 differed from a green-tea control (GT), enriched in LA/ALA metabolism and unsaturated-fatty-acid biosynthesis. In HFD mice, HY from week 5 mitigated weight gain and fasting glycaemia, reduced hepatic lipid droplets and inflammatory infiltration, and improved intestinal morphology (higher villus/crypt ratio) and colonic histology. Microbiota analyses revealed recovery of α-diversity, β-diversity convergence toward normal diet, a lower Firmicutes/Bacteroidetes ratio, depletion of Proteobacteria/Enterobacteriaceae and Helicobacter, and enrichment of Akkermansia, Bacteroides, Faecalibacterium, Blautia, and Lactobacillus. Correlation heatmaps linked tea polyphenols (GCG, anthocyanins) and LA/ALA-axis lipids positively with these beneficial taxa and negatively with putative pro-inflammatory groups. Collectively, HY combines a low-caffeine, high-GCG/anthocyanin, UFA-enriched profile with multi-dimensional bioactivities—anti-obesity, hepatoprotective, anti-inflammatory and microbiota-modulating—supporting its quality evaluation and functional development as a regional tea resource.