Lippia alnifolia essential oil induces relaxation on Guinea-pig trachea by multiple pathways

Tylophora indica (Burm. f.) Merr alleviates tracheal smooth muscle hyperresponsiveness in ovalbumin-induced allergic-asthma model in guinea-pigs: Evidences from ex vivo, in silico and in vivo studies

BACKGROUND

Tylophora indica (Burm. f.) Merr is a climbing perennial plant reported in Indian traditional system of medicine for its use in allergy and asthma. However, only few scientific studies have been performed in the past to validate its antiasthmatic potential.

OBJECTIVES

The present study deals with investigation of airway smooth muscle relaxant and antiasthmatic potential of extract and subsequent fractions prepared from T. indica.

METHODS

The most active fraction of T. indica leaves selected through bio-guided activity was subjected to liquid chromatography-mass spectrometry (LC-MS) analysis for chemical profiling. The binding affinity of identified compounds in fraction towards M3 and H1 receptors was determined by molecular docking study. F-2 (chloroform fraction prepared from methanolic extract of T. indica leaves) was examined for its smooth muscle relaxant properties using isolated trachea of guinea-pig. Further, F-2 was evaluated through in vivo studies employing ovalbumin-induced asthma model in guinea-pigs.

RESULTS

F-2 was found most effective in bioassay-guided fractionation. Characterization by LC-MS analysis revealed presence of five major bioactive compounds in F-2 that showed good docking interactions with M3 and H1 receptors. The ex vivo study demonstrated that F-2 could significantly relax tracheal rings via targeting multiple signalling pathways videlicet, namely, noncompetitive antagonism of the histamine and muscarinic receptors, β2-adrenergic stimulation and activation of soluble guanylyl cyclase. In in vivo studies, F-2 ameliorated airway hyperresponsiveness and decreased broncho alveolar lavage fluid (BALF) levels of inflammatory cytokines and immunoglobulin E (IgE).

CONCLUSION

These results confirm the traditional use of T. indica as an antiasthmatic agent which are evidenced through ex vivo, in silico and in vivo studies.

Rosa damascena Miller essential oil relaxes rat trachea via KV channels, KATP channels, and BKCa channels

AIM/OBJECTIVE

This study aimed to investigate the effects of Rosa damascena Miller essential oil on rat tracheal smooth muscle contractility and the hypothesis that voltage-gated potassium (K_V) channels, ATP-sensitive potassium (K_ATP) channels, and large-conductance calcium-activated potassium (BK_Ca) channels may have roles in these effects.

METHODS

Isometric contraction-relaxation responses of tracheal rings were measured with an isolated tissue bath model. The steady contraction was induced with both 10^-5 M ACh and 60 mM KCl, and then the concentration-dependent responses of rose oil (0.1-100 µg/mL) were examined. The time-matched control (double distilled water) group was also formed. To evaluate the role of K_V, K_ATP, and BK_Ca channels, tracheal rings were incubated with 4-AP (K_V channel blocker), glibenclamide (K_ATP channel blocker), TEA (BK_Ca channel blocker), and iberiotoxin (selective BK_Ca channel blocker). Also, a vehicle control group was formed for dimethyl sulfoxide (DMSO).

RESULTS

Rose oil exerted the relaxant effects in tracheal rings pre-contracted with both ACh and KCl at concentrations of 1, 10, and 100 µg/mL (p < 0.05). Besides, K_V channel blocker 4-AP, K_ATP channel blocker glibenclamide, and BK_Ca channel blockers TEA and iberiotoxin incubations significantly inhibited the rose oil-induced relaxation responses (p < 0.05). However, incubation of tissues with DMSO, glibenclamide solvent, for 10 min did not cause a significant change in the relaxation responses to rose oil (p > 0.05).

CONCLUSIONS

In conclusion, the first physiological findings were obtained regarding the functional relaxant effects of rose essential oil in rat trachea. The findings showed that rose oil induces bronchorelaxation in a concentration-dependent manner. Besides, this study is the first to report that rose oil-mediated bronchodilation responses are associated with the activity of K_V, K_ATP, and BK_Ca channels. These results suggest that rose oil might be a useful agent in the treatment of abnormal bronchoconstriction-related diseases such as asthma and chronic obstructive pulmonary disease.

Identification of Bioactive Compounds against Aedes aegypti (Diptera: Culicidae) by Bioassays and in Silico Assays

Most of the hematophagous insects act as disease vectors, including Aedes aegypti, responsible for transmitting some of the most critical arboviruses globally, such as Dengue. The use of repellents based on natural products is a promising alternative for personal protection compared to industrial chemical repellents. In this study, the repellent effect of essential oils extracted from Lippia thymoides, Lippia alba, Cymbopogon winterianus, and Eucalyptus globulus leaves was evaluated. Essential oils used showed repellent activity against Ae. aegypti in laboratory bioassays, obtaining protection rates above 70 % from 3.75 mg/mL and higher concentration for all analyzed oils. GC/MS identified 57 constituents, which were used in the ligand-based pharmacophore model to expose compounds with requirements for repellents that modulate mosquitoes behavior through odorant-binding protein 1 Ae. aegypti. Ligand-based pharmacophore model approach results suggested that repellent activity from C. winterianus, L. alba, and L. thymoides essential oils' metabolites is related to Citronelal (QFIT=26.77), Citronelol (QFIT=11.29), Citronelol acetate (QFIT=52.22) and Geranil acetate (QFIT=10.28) with synergistic or individual activity. E. globulus essential oil's repellent activity is associated with Ledol (0.94 %; QFIT=41.95). Molecular docking was applied to understand the binding mode and affinity of the essential oils' data set at the protein binding site. According to molecular docking, Citronelol (ChemPLP=60.98) and geranyl acetate (ChemPLP=60.55) were the best-classified compounds compared to the others and they can be explored to develop new repellents.