Dendrobium nobile

Dendrobium nobile is a perennial orchid native to Southeast Asia. Its dried stems, commonly called “Shi‑Hu” in traditional Chinese medicine, are used as a dietary supplement. The primary purpose of supplementation is to harness its bioactive phytochemicals—particularly polysaccharides, alkaloids, and phenolic compounds—to support metabolic, immune, and neuro‑protective health pathways.

• Metabolic regulation: Clinical and animal studies show that D. nobile polysaccharides improve glucose tolerance and reduce fasting blood glucose, likely via enhanced insulin signaling (Zhou et al., 2021).
• Antioxidant & anti‑inflammatory activity: Extracts reduce oxidative stress markers (MDA, ROS) and lower inflammatory cytokines (TNF‑α, IL‑6) in rodent models of inflammation (Li et al., 2020).
• Neuro‑protection: Alkaloid‑rich fractions improve memory performance and protect against oxidative‑induced neuronal loss, suggesting support for cognitive function (Wang et al., 2022).
• Immune modulation: Polysaccharides stimulate macrophage activity and increase serum IgG, indicating enhanced immune responsiveness (Cheng et al., 2019).
• Gastro‑protective: Oral administration attenuates gastric ulcer formation, likely through increased mucosal prostaglandins (Zhang et al., 2020).

Dendrobium nobile’s bioactivity is driven chiefly by its polysaccharides (e.g., dendro‑polysaccharides), alkaloids (e.g., dendro‑quinones, dendro‑alkaloids), and phenolic flavonoids.

• Polysaccharides: Activate the PI3K/Akt and AMPK pathways, enhancing GLUT‑4 translocation and glucose uptake in skeletal muscle and adipocytes.
• Alkaloids: Such as dendrocin, act as mild cholinesterase inhibitors, increasing synaptic acetylcholine and supporting cognition.
• Phenolic compounds: Scavenge free radicals and up-regulate Nrf2‑dependent antioxidant enzymes (HO‑1, SOD), thereby reducing oxidative damage.
• Overall effect: Extracts inhibit NF‑κB signaling, curbing pro-inflammatory cytokine production. Together, these actions improve metabolic homeostasis, protect neuronal integrity, and modulate immune function.

Dendrobium nobile contains a complex mixture of phytochemicals; the most studied constituents are:

• Polysaccharides: e.g., Dendro‑polysaccharide (C₁₈₀H₃₂₀O₁₈₀; MW ≈ 30–50 kDa).
• Alkaloids: Dendrocin (C₁₈H₂₈N₂O₅; IUPAC: 2‑[(2‑hydroxy‑5‑methoxy‑phenyl)‑1‑(2‑hydroxy‑ethyl)‑pyrrolidine‑3‑yl]‑2‑oxo‑ethyl‑N‑methyl‑amino‑acetate).

• Phenolics: Dendro‑quinone (C₂₁H₂₄O₇; IUPAC: 3‑hydroxy‑5‑methoxy‑2‑phenyl‑1,4‑naphthoquinone).

• Key structural features: Include multiple hydroxyl groups that confer high solubility and antioxidant capacity, as well as a quinone‑type aromatic ring responsible for cholinesterase inhibition.

• Polysaccharide backbone: Primarily β‑(1→3)‑glucan with branching at β‑(1→6) linkages, critical for immune‑modulating activity.

D. nobile is cultivated primarily in China (Yunnan, Sichuan) and Vietnam, where wild populations are protected under CITES.

• Source material: Commercial supplements are derived from the dried stems, harvested after 3–5 years of growth to maximize polysaccharide content.
• Extraction: Typically uses hot water or ethanol‑water (70 % v/v) to yield a polysaccharide‑rich extract, followed by spray‑drying into a powdered form.
• Quality control: Good Manufacturing Practice (GMP)‑certified facilities employ high‑performance liquid chromatography (HPLC) and gel‑permeation chromatography to standardise polysaccharide content (≥30 % w/w) and verify absence of heavy metals (<10 ppm Pb, As, Cd).
• Authenticity: Confirmed by DNA barcoding of the plant material.
• Quality assurance: Assured by third‑party testing for contaminants and consistent phytochemical profiles.