Mulberry (Morus atropurpurea) has long been used to treat gastro-intestinal ailments; however, the functional basis of its therapeutic effects remains unclear. The aim of this study was to measure the effects of mulberry (administered by gavage) on diphenoxylate-induced constipation in mice and elucidate the mechanisms underlying these effects using constipation and physicochemical indexes, histological morphology and 16S rDNA amplicon analysis of fecal microbiota. Sixty Kunming mice were randomly divided into the following six groups (n = 10 per group): normal control, constipation model, positive control, and low-, mid- and high-dose mulberry groups. After 14 days of treatment, constipation was induced over 5 days and measurements were conducted. The results show that mulberry treatment prevented constipation by increasing the fecal water content, shortening the first red fecal defecation time, promoting gastric evacuation, and increasing the gastric-intestinal transit rate (P < 0.05). Compared with the constipation model group, the mulberry-treated groups showed decreased aquaporin gene expression (Aqp3, Aqp4, Aqp8 and Aqp9), decreased serum levels of inhibitory neurotransmitters (nitric oxide and vasoactive intestinal peptide) (P < 0.05), and increased serum levels of excitability neurotransmitters (acetyl choline, substance P, and motilin). The histological morphology of the colon showed that mulberry treatment increased the number of mucus cells (P < 0.05). Mulberry treatment also increased the concentrations of acetic, propionic, butyric, valeric and isovaleric acids (P < 0.05), increased the abundance of Lactobacillus and Bifidobacterium in feces, and decreased the abundance of Helicobacter and Prevotellaceae in feces. Our findings indicate that mulberry consumption effectively prevents constipation in mice and is a promising therapeutic candidate for constipation.

The antiobesity molecular mechanisms of mulberry leave components were analyzed based on intestinal micro-ecology and metabolomics. An obesity model was established by feeding rats with a high-calorie diet. Rats were divided into seven groups: the obesity model control (MC), positive control (PC), mulberry leaf powder (MLP), mulberry leaf fiber (MLF), mulberry leaf polyphenols (MLPS), mulberry leaf fiber and polyphenols mixture (MLM), and normal control (NC), and fed daily for 6 consecutive weeks. The results demonstrated that the MLM group had the best efficiency on weight loss, indicating synergistic interactions between MLPS and MLF. The reduction of Firmicutes abundance, and the downstream Clostridiales, Lachnespiraceae, was a key pathway for the antiobesity effects. The increased abundances of Lactobacillus vaginalis and Lactobacillus gasseri might result in lipid metabolism disorder. The test groups regulated the amino acid and oligopeptides metabolic disorder tents to normal levels compared with the MC and NC groups.

To elucidate the effects of cultivar and harvest month on the phenolic content and antioxidant activity of mulberry leaves, four major phenolics, including chlorogenic acid (ChA), benzoic acid (BeA), rutin (Rut) and astragalin (Ast), were quantified using an HPLC-UV method. Leaves from six mulberry cultivars, collected from April to October, were analyzed. The antioxidant activity of mulberry leaves was assessed by ferric reducing antioxidant power (FRAP), hydroxyl radical scavenging activity (HSA) and superoxide radical scavenging activity (SSA) assays. The results showed that the total values of the four phenolic compounds ranged from 2.3 dry weight (DW) to 4.2 mg/g DW, with ChA being the major compound. The mean total phenol (TP) content of the six cultivars ranged from 30.4 equivalents (GAE) mg/g DW to 44.7 GAE mg/g DW. Mulberry leaves harvested in May had the highest TP content. Moreover, the antioxidant activities of mulberry leaves harvested from April to October differed noticeably. In general, Kq 10 and May were considered to be a better cultivar and harvest month concerning phenolic content and antioxidant activity, respectively.

The present study attempted to evaluate the mechanism of action and bioactivity of mulberry leaf polyphenols (MLPs) in type-2 diabetes prevention via inhibition of disaccharidase and glucose transport. MLPs were purified with D101 resin and the main composition was determined as chlorogenic acid, rutin, benzoic acid and hyperoside. MLPs demonstrated a strong inhibitory effect on disaccharidases derived from both mouse and Caco-2 cells, and the order of IC₅₀ value was: murine sucrase (7.065 mg mL⁻¹) > murine maltase (4.037 mg mL⁻¹) > Caco-2 cell maltase (0.732 mg mL⁻¹) > Caco-2 cell sucrase (0.146 mg mL⁻¹). MLPs showed the strongest inhibitory effect on sucrase derived from Caco-2 cells and played a role in lowering postprandial glucose mainly by inhibiting sucrase activity. The Caco-2 monolayer cell model was established to simulate the glucose transport process in the human small intestine. We found that within the concentration range of 0.5–2 mg mL⁻¹, MLPs significantly inhibited glucose transport, and the inhibition rate increased with time and dose. The effect of phlorizin (SGLT1 inhibitor) in the control group showed a similar effect on glucose transport, revealing that MLPs may inhibit glucose transport mainly by inhibiting the SGLT1 transporter. RT-qPCR analysis confirmed that MLPs inhibited glucose absorption by suppressing the SGLT1–GLUT2 pathway via downregulation of the mRNA expression of phospholipase, protein kinase A and protein kinase C.