Background

Respiratory diseases share common pathological drivers - including chronic inflammation, oxidative stress, and metabolic dysregulation - that amplify airway injury, alveolar remodeling, and cardiopulmonary burden.

Patients with comorbid diabetes or metabolic syndrome often experience more severe outcomes due to postprandial hyperglycemia and insulin surges, which intensify systemic inflammatory and oxidative responses.

Objective

To evaluate mulberry leaf (Morus alba) as a nutritional pharmacological intervention for respiratory diseases, integrating its phytochemical basis, mechanistic pathways, and clinical evidence.

Bioactive Constituents

Mulberry leaf contains multiple bioactive compounds, including 1-deoxynojirimycin (DNJ, a natural α-glucosidase inhibitor), flavonoids (quercetin derivatives, rutin, and isoquercitrin), polyphenols (chlorogenic acid), polysaccharides, and phytosterols.

Mechanistic Pathways

- Metabolic regulation:

DNJ-mediated inhibition of α-glucosidase reduces postprandial glucose and insulin excursions, attenuating advanced glycation end-product (AGE) formation and limiting metabolic stress–induced activation of NF-κB.

- Anti-inflammatory activity:

Flavonoids and polyphenols suppress NF-κB and MAPK signaling, downregulating pro-inflammatory cytokines (IL-6, TNF-α, IL-1β) and reducing systemic inflammatory burden.

- Antioxidant defense:

Chlorogenic acid and polysaccharides enhance endogenous antioxidant enzymes (SOD, CAT, GSH-Px), lower malondialdehyde (MDA) levels, and mitigate oxidative epithelial and alveolar damage.

- Immunomodulation:

Polysaccharides restore Th1/Th2 balance, reduce mast cell–mediated allergic responses, and enhance antiviral defense.

- Vascular and cardiopulmonary protection:

Phytosterols improve lipid profiles (LDL-C reduction, HDL-C elevation) and endothelial function, lowering pulmonary circulatory pressure and supporting cardiopulmonary coupling.

Clinical Evidence

Randomized controlled trials in pre-diabetic, type 2 diabetes, and metabolic syndrome populations consistently show improvements in HbA1c, fasting glucose, lipid profiles, and inflammatory markers (CRP, IL-6, TNF-α), accompanied by increased antioxidant capacity.

Longer-term interventions demonstrate vascular benefits, including reduced carotid intima–media thickness and improved endothelial function, which have translational relevance for chronic obstructive pulmonary disease (COPD), asthma, and pulmonary fibrosis.

Conclusion

Mulberry leaf functions as a systemic “background modulator” of inflammation-oxidative stress-metabolic coupling.

Its integration into respiratory disease management, particularly in patients with metabolic comorbidities, may reduce acute exacerbation triggers, stabilize chronic inflammatory baselines, and enhance cardiopulmonary outcomes.

When combined with complementary nutrients (elderberry, quercetin, vitamin C, zinc, bromelain), mulberry leaf contributes to a multidimensional nutritional intervention framework for respiratory health.