Phloretin

The peel of apple.

Phloretin is a dihydrochalcone, a type of natural phenols which can be found in apple tree leaves and Manchurian apricot. Phloretin inhibits the active transport of glucose into cells via sodium-glucose linked transporter (SGLT) 1 and 2 with IC50 value of 49±12 μM [2].

SGLTs are a family of glucose transporter which is found in the small intestine mucosa (SGLT 1) and nephron proximal tubule (SGLT 2). They contribute to the renal glucose reabsorption.

After treatment of phloretin, differentiated 3T3-L1 cells exhibited significantly enhanced glycerol and the inhibition of adipogenesis-related transcription factor that were regulated by SGLTs. Additionally, phloretin promoted phosphorylation of AMP-activated protein kinase and increased activity of adipose triglyceride lipase and hormone-sensitive lipase [1]. When RAW 263.7 cells were cultured from differentiated 3T3-L1 cell media, PT suppressed the SGLT-associated nuclear transcription factor kappaB and mitogen-activated protein kinase pathways [1].

In streptozotocin-induced rat model of diabetes type I, oral administration of phloridzin (5/10/20/40 mg/kg/day) resulted in significant reduction of blood glucose levels and improved dyslipidemia. Additionally, Administration of phloridzin reduced urine volume and water intake in a dose-dependent manner [3].

References:
[1] Huang W C et al. , Phloretin and phlorizin promote lipolysis and inhibit inflammation in mouse 3T3-L1 cells and in macrophage-adipocyte co-cultures. Mol Nutr Food Res. 2013, 57: 1807-1817.
[2] Kasahara T, Kasahara M.  Expression of the rat GLUT1 glucose transporter in the yeast Saccharomyces cerevisiae. Biochem J. 1996, 315 ( Pt 1):177-182.
[3] Najafian M, Jahromi M Z, Nowroznejhad M J, Phloridzin reduces blood glucose levels and improves lipids metabolism in streptozotocin-induced diabetic rats.  Mol Biol Rep. 2012, 39(5): 5299-306.

Phloretin promotes osteoclast apoptosis in murine macrophages and inhibits estrogen deficiency-induced osteoporosis in mice.[Pubmed:24932975]

Phytomedicine. 2014 Sep 15;21(10):1208-15.

Bone-remodeling imbalance induced by increased osteoclast formation and bone resorption is known to cause skeletal diseases such as osteoporosis. The reduction of estrogen levels at menopause is one of the strongest risk factors developing postmenopausal osteoporosis. This study investigated osteoprotective effects of the dihydrochalcone Phloretin found in apple tree leaves on bone loss in ovariectomized (OVX) C57BL/6 female mice as a model for postmenopausal osteoporosis. OVX demoted bone mineral density (BMD) of mouse femurs, reduced serum 17beta-estradiol level and enhanced serum receptor activator of NF-kappaB ligand (RANKL)/osteoprotegerin ratio with uterine atrophy. Oral administration of 10 mg/kg Phloretin to OVX mice for 8 weeks improved such effects, compared to sham-operated mice. Phloretin attenuated TRAP activity and cellular expression of beta3 integrin and carbonic anhydrase II augmented in femoral bone tissues of OVX mice. This study further examined that osteogenic activity of Phloretin in RANKL-differentiated Raw 264.7 macrophages into mature osteoclasts. Phloretin at 1-20 muM stimulated Smac expression and capase-3 activation concurrently with nuclear fragmentation of multi-nucleated osteoclasts, indicating that this compound promoted osteoclast apoptosis. Consistently, Phloretin enhanced bcl-2 induction but diminished bax expression. Furthermore, Phloretin activated ASK-1-diverged JNK and p38 MAPK signaling pathways in mature osteoclasts, whereas it dose-dependently inhibited the RANKL-stimulated activation of ERK. Therefore, Phloretin manipulated ASK-1-MAPK signal transduction leading to transcription of apoptotic genes. Phloretin was effective in preventing estrogen deficiency-induced osteoclastogenic resorption.

Immunomodulation of phloretin by impairing dendritic cell activation and function.[Pubmed:24651121]

Food Funct. 2014 May;5(5):997-1006.

Dietary compounds in fruits and vegetables have been shown to exert many biological activities. In addition to antioxidant effects, a number of flavonoids are able to modulate inflammatory responses. Here, we demonstrated that Phloretin (PT), a natural dihydrochalcone found in many fruits, suppressed the activation and function of mouse dendritic cells (DCs). Phloretin disturbed the multiple intracellular signaling pathways in DCs induced by the Toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS), including ROS, MAPKs (ERK, JNK, p38 MAPK), and NF-kappaB, and thereby reducing the production of inflammatory cytokines and chemokines. Phloretin also effectively suppressed the activation of DCs treated with different dosages of LPS or various TLR agonists. The LPS-induced DC maturation was attenuated by Phloretin because the expression levels of the MHC class II and the co-stimulatory molecules were down-regulated, which then inhibited the LPS-stimulating DCs and the subsequent naive T cell activation in a mixed lymphocyte reaction. Moreover, in vivo administration of Phloretin suppressed the phenotypic maturation of the LPS-challenged splenic DCs and decreased the IFN-gamma production from the activated CD4 T cells. Thus, we suggest that Phloretin may potentially be an immunomodulator by impairing the activation and function of DCs and Phloretin-contained fruits may be helpful in the improvement of inflammation and autoimmune diseases.

Biochemical and antimicrobial activity of phloretin and its glycosilated derivatives present in apple and kumquat.[Pubmed:24799241]

Food Chem. 2014 Oct 1;160:292-7.

Phloretin and its glycosylated derivatives (phlorizin and Phloretin 3',5'-di-C-glucoside) are dihydrochalcones that have many interesting biological properties. The results obtained showed that the dihydrochalcones are able to inhibit growth of Gram positive bacteria, in particular Staphylococcus aureus ATCC 6538, Listeria monocytogenes ATCC 13932 and methicillin-resistant S. aureus clinical strains. Moreover, Phloretin is active also against the Gram negative bacteria Salmonella typhimurium ATCC 13311. The determination of the enzymatic activity of key metabolic enzymes allowed us to shed some light on the biochemical mechanism of aglycon cell growth inhibition, showing as it remarkably influences the energetic metabolism of S. aureus. In addition, structure/activity determinations highlighted that the presence of a glycosyl moiety bound to the chalcone structure dramatically decreases the antimicrobial activity of Phloretin.

Phloretin (NSC 407292; RJC 02792) is a flavonoid extracted from Prunus mandshurica, has anti-inflammatory activities. Phloridzin is a specific, competitive and orally active inhibitor of sodium/glucose cotransporters in the intestine (SGLT1) and kidney (SGLT2). Phloretin inhibits Yeast-made GLUT1 as well as Human erythrocyte GLUT1 with IC50values of 49 μM and 61 μM, respectively.Phloretin has the potential for the treatment of rheumatoid arthritis (RA) and allergic airway inflammation.

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