Answer
🔬 ¹H-NMR Interpretation of Berberine
🧪 Step 1: Chemical Shift Assignments
The major signals observed in the NMR spectrum and their interpretations are shown below:
| Chemical Shift (ppm) | Assignment | Signal Type |
|---|---|---|
| ~9.6–10.0 | Aromatic proton (near quaternary nitrogen) | Singlet (1H) |
| ~7.5–8.5 | Aromatic protons (benzene ring) | Multiplets (4–6H) |
| ~6.0–6.2 | Methylenedioxy group (–O–CH₂–O–) | Singlet (2H) |
| ~4.0–4.5 | Methoxy groups (–OCH₃) | Singlet (3H × 2–3) |
| ~3.5–3.8 | N–CH₃ group (attached to N⁺) | Sharp singlet (~3.6 ppm) |
📖 Explanation of Assignments
- ~9.6–10.0 ppm: Highly deshielded due to proximity to a quaternary nitrogen.
- ~7.5–8.5 ppm: Typical of aromatic hydrogens in benzene-like systems.
- ~6.0–6.2 ppm: Indicates presence of a methylenedioxy bridge, a hallmark of berberine.
- ~4.0–4.5 ppm: Associated with methoxy groups (OCH₃).
- ~3.5–3.8 ppm: Sharp singlet of N-methyl near quaternary nitrogen center.
🔍 Step 2: Detection of Impurities
Minor, lower-intensity peaks outside the main regions could represent:
- Solvent residual signals
- Unreacted starting materials
- Decomposition byproducts
✅ Step 3: Confirmation of Key Peaks
The singlet around 6.06 ppm is clearly seen and matches the expected signal for the methylenedioxy group, strongly confirming berberine’s presence.
Conclusion:
The ¹H-NMR spectrum confirms the expected structural features of berberine, with key peaks such as aromatic signals, methylenedioxy bridge, and methoxy groups well resolved. Minor impurities are negligible.
The ¹H-NMR spectrum confirms the expected structural features of berberine, with key peaks such as aromatic signals, methylenedioxy bridge, and methoxy groups well resolved. Minor impurities are negligible.