Investigation into the mechanism of action of essential oil of Pistacia integerrima for its antiasthmatic activity.

ETHNOPHARMACOLOGICAL RELEVANCE: Pistacia integerrima J.L. Stewart ex Brandis locally known as Karkatashringi is an important medicinal plant whose galls are valued in traditional medicine used in India for the treatment of asthma, chronic bronchitis, phthisis, diarrhea, fever, other ailments for the respiratory tract, and as antispasmodic, carminative, antiamoebic and anthelmintic. However, in vitro and in vivo investigations providing new insights into its pharmacological properties have not been thoroughly investigated yet. The present investigation aimed to elucidate the probable mechanism of antiasthmatic action of essential oil of Pistacia integerrima J.L. Stewart ex Brandis galls (EOPI).

METHODS: EOPI was tested using in vitro studies such as antioxidant activity, mast cell degranulation, angiogenesis, isolated guinea pig ileum preparation and soyabean lipoxidase enzyme activity. In vivo studies included lipopolysaccharide-induced bronchial inflammation in rats and airway hyperresponsiveness in ovalbumin in sensitized guinea pigs using spirometry.

RESULTS: EOPI (5-30 µg/ml) inhibits 5-lipoxidase enzyme activity with IC50 of 19.71 µg/ml and DPPH scavenging activity up to 100 µg/ml with maximum inhibition of 44.93 ± 2.53% at 100 µg/ml. Pre-treatment with EOPI inhibited erythropoietin-induced angiogenesis. It showed dose dependent (10, 30 and 100 µg/ml) anti-allergic activity by inhibiting compound 48/80 induced mast cell degranulation to an extent 19.08 ± 0.47%. The finding that essential oil induced inhibition of transient contraction of acetylcholine in calcium free medium, and relaxation of S-(-)-Bay 8644-precontracted isolated guinea pig ileum jointly suggests that the L-subtype Cav channel is involved in spasmolytic action of EOPI. Treatment with EOPI dose dependently (7.5, 15 and 30mg/kg i.p.) inhibited lipopolysaccharide-induced increase in total cell count, neutrophil count, nitrate-nitrite, total protein, albumin levels in bronchoalveolar fluid and myeloperoxidase levels in lung homogenates. Roflumilast was used as a standard. EOPI reduced the respiratory flow due to gasping in ovalbumin sensitized guinea pigs.

CONCLUSION: The study demonstrates the effectiveness of essential oil of Pistacia integerrima J.L. Stewart ex Brandis galls in bronchial asthma possibly related to its ability to inhibit L-subtype Cav channel, mast cell stabilization, antioxidant, angiostatic and through inhibition of 5-lipoxygenase enzyme.