Phytochemical profiling of Costus (Saussurea lappa Clarke) root essential oil, and its antimicrobial and toxicological effects

Purpose: To carry out gas chromatography-mass spectrometry (GC-MS) analysis of the phytochemical content of the root essential oil of Saussurea lappa Clarke Asteraceae (Costus, SLEO), and to evaluate its physicochemical, antimicrobial and cytoxic properties. Methods: The oil was extracted from the plant’s roots by steam distillation using a Clevenger system. Various physicochemical parameters for the oil including refractive index, color, acid value, saponification number, ester and peroxide values were measured. Flavonoid content was assessed using thin layer chromatography (TLC). Thermoscientific trace ultra gas chromatograph equipped with a Thermoscientific capillary TR-5MS column was utilized to determine the volatile components of SLEO. Antimicrobial activity of SLEO was performed against various Gram (+ve) and Gram (-ve) microorganisms, viz, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans, while cytotoxic effect was monitored using Artemia salina (brine shrimp) lethality assay. Results: Essential oil yield was good (3 %). Concentration-dependent antimicrobial effects were observed on all test microorganisms and no marked difference in lethality levels was observed among the tested SLEO concentrations on brine shrimp (p < 0.05). The main component of SLEO was costunolide or eudesma-5,11(13)-dien-8,12-olide (52.01 %). Conclusion: The results indicate the promising therapeutic properties of S. lappa. However, further phytochemical and biological investigations are required to establish the mechanism of action and toxicological the extract.

Encapsulation of Carlina acaulis essential oil and carlina oxide to develop long-lasting mosquito larvicides: microemulsions versus nanoemulsions

Carlina acaulis root essential oil (EO) is one of the most potent mosquito larvicides (LC50 < 2 ppm). This EO is mainly composed of carlina oxide (> 90%). Poor water solubility and rapid degradation from UV light and oxygen in the environment limit the real-world use of this EO. Herein, we developed nanocarrier-based formulations, namely micro- and nanoemulsions (ME and NE, respectively) containing C. acaulis EO or carlina oxide (both at 0.5%) as active ingredients (a.i.). The larvicidal activity of ME and NE was evaluated against Culex quinquefasciatus. The highest larvicidal activity was achieved by the ME containing 0.5% of the EO (M1); its LC50(90) was 579.1 (791.3) µL L−1. Sublethal effects of this ME and its a.i. were assessed testing both at the LC16, LC30, LC50 and LC90 on mosquito larvae exposed to each product for 1–7 h, and then monitoring mortality for 18 days. At variance with the EO, ME application, even at LC16, led to 100% mortality at 18 days. The EO and its encapsulated form were scarcely toxic to human keratinocytes (HaCaT) and human fibroblast (NHF A12) cell lines. The acute toxicity of C. acaulis EO and its ME (M1) was also evaluated in Wistar rats through oral administration; EO LD50 was 1098 mg kg−1 bw, whereas its ME, even at 5000 mg kg−1 bw (considered the upper testing limit to establish safety to mammals), was not toxic. This study highlights the outstanding efficacy of C. acaulis EO ME for developing long-lasting and safe larvicides against Cx. quinquefasciatus.

Root essential oil of Chrysopogon zizanioides relaxes rat isolated thoracic aorta – an ex vivo approach

Root of Chrysopogon zizanioides (L.) Roberty has been used in Siddha system of medicine to treat hypertension. The present study was therefore to investigate the vasorelaxation effect of root essential oil of C. zizanioides using rat isolated thoracic aortic rings. Chemical characterization of root essential oil was carried out using Gas Chromatography–Flame Ionization Detector (GC–FID) and Gas Chromatography–Mass Spectrometry (GC–MS). Essential oil nanoemulsion (EONE) was prepared and characterized. Vasorelaxant effect of EONE in endothelium-intact aortic rings precontracted with phenylephrine (PE) (1 µM) or KCl (80 mM) was investigated. Role of Ca2+, nitric oxide and K+ channels in precontracted aortic rings were investigated to elucidate the mechanism of action of the essential oil. Further, the role of muscarinic and prostacyclin receptors in EONE induced relaxation was studied. The EONE significantly induced relaxation (Emax 77.1 ± 4.87%) in PE precontracted aortic rings. The nitric oxide synthase, and cyclooxygenase inhibitors and potassium channel blockers have not significantly inhibited the vasorelaxation induced by EONE. However, EONE induced relaxation in precontracted endothelium-intact aortic rings was significantly inhibited by muscarinic receptor and calcium channel. The root essential oil of C. zizanioides possesses vasorelaxant effect through muscarinic pathway as well as acts as calcium channel blocker.