Anti-asthmatic activity of phenolic compounds from the roots of Gastrodia elata Bl

We previously reported that 4-hydroxy-3-methoxybenzaldehyde has the most potent anti-inflammatory and analgesic activity of eight phenolic compounds obtained from the dried roots of Gastrodiaelata (GE) Blume (Orchidaceae); its activity may be related to inhibition of cyclooxygenase activities and oxidation. In the present study, the effects of nine phenolic compounds from GE on immediate-phase (IAR) and late-phase (LAR) asthmatic responses after aerosolized-ovalbumin (OA) challenge were evaluated by determining the specific airway resistance (sRaw) using a double-chambered plethysmograph in conscious guinea pigs with IgE-mediated asthma. Furthermore, recruitment of leukocytes, histamine release, and eosinophil peroxidase (EPO) and phospholipase A2 (PLA2) activities were determined in bronchoalveolar lavage fluids (BALF) 24 h after the antigen challenge. 4-Hydroxy-3-methoxybenzyl alcohol (12.5 mg/kg) significantly (p < 0.05) inhibited sRaw in IAR and in LAR by 51.97 ± 4.96% and 39.93 ± 3.46%, respectively, compared to that of the controls. Further, hydroxy-3-methoxybenzyl alcohol significantly (p < 0.05) inhibited recruitment of leukocytes in accordance with amelioration of eosinophilia and neutrophilia, histamine (30.66 ± 5.20%), EPO activity (21.58 ± 2.02%), and specific PLA2 activity (16.60 ± 2.52%) in BALF compared with the control. In addition, bis-(4-hydroxyphenyl) methane, 4-hydroxy-3-methoxybenzoic acid, and 4-hydroxy-3-methoxybenzaldehyde (12.5 mg/kg) significantly (p < 0.05) inhibited sRaw, while bis-(4-hydroxyphenyl) methane, benzyl alcohol, and 4-hydroxybenzaldehyde at 12.5 mg/kg significantly (p < 0.05) inhibited leukocytes, histamine, EPO and PLA2 activities in BALF compared with the controls. The phenolic glycoside, parishin had less activity compared to aglycones, 4-hydroxybenzyl compounds. These results suggest that the C4 hydroxy and C3 methoxy radicals in benzyl alcohols and aldehydes play important roles in mediating the anti-asthmatic activities of these compounds.