Purpose: To isolate and purify patchouli alcohol (PA), a tricyclic sesquiterpene constituent of Pogostemon cablin, and investigate its immunomodulatory potential in Kunming mice.

Methods: PA was prepared from an ethanol aqueous extract of P. cablin by silica gel column chromatography, and further purified by crystallization using n-hexane. Purity was assessed by analytical gas chromatography (GC) and confirmation of chemical structure performed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). The effect of PA from Pogostemon cablin on immunological function was studied by macrophage phagocytosis, immune organ index, serum immunoglobulin level and delayed type hypersensitivity (DTH) in mice that were administered orally doses of 20, 40 and 80 mg/kg. 

Results: The purity of PA was 99.3%. The oral administration of PA (40, or 80 mg/kg body weight) significantly increased the phagocytic index (p < 0.05), compared with prednisone acetate (PR) group. Administration of PA (80 mg/kg) boosted the production of circulating serum IgM (0.081 ± 0.010) and IgG (1.296 ± 0.120), while IgM and IgG in PR group was 0.069 ± 0.011 (p < 0.01) and 1.180 ± 0.070 (p < 0.01) respectively. However, PA (20 mg/kg) treatment elicited significant decrease in DTH induced by 2, 4-dinitro-chlorobenzene (DNCB) in mice (1.03 ± 0.40, p < 0.05), in comparison to DNCB-induced group (1.67 ± 0.84 mg).

Conclusion: These results suggest that PA has significant immunomodulatory properties which probably act by activating mononuclear phagocytic system, augmenting humoral immune response while suppressing cellular immune response.