Essential oil and extract of clevenger’s waste of hymenocrater calycinus (boiss.) benth. as a non-toxicity option for cutaneous burns according to traditional use

Essential oils and their by-products extracted using distillation methods are a rich and diverse source of natural products with various therapeutic applications. Hymenocrater calycinus (Boiss.) Benth. is used in traditional Iranian medicine as an analgesic, antiallergic, and a remedy for treating cutaneous burns. The present study was conducted for the first time to compare the antimicrobial activity and cytotoxicity of the essential oil and the residual water extract after distillation of H. calycinus from the habitats of Kashan, Iran. The essential oil of this plant was extracted by hydro-distillation using a Clevenger apparatus, and the residual water extract in the Clevenger apparatus flask after separation from the plant waste was concentrated and converted into a dry extract. Chemical profiling of the essential oil was performed using GC-MS. Total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity were quantified using the Folin-Ciocalteu, quercetin equivalence, and DPPH assays, respectively. The antimicrobial activity of the essential oil and extract was determined by the agar diffusion method, and the lowest inhibitory and bactericidal concentrations were determined against eleven microorganisms (three Gram-positive bacteria, six Gram-negative bacteria, and one yeast strain). The MTT method was used to evaluate the cytotoxicity of the essential oil and extract on Human Dermal Fibroblast (HDF) cell lines. The results showed that the yield of H. calycinus essential oil was about 0.68% w/w, and heptacosane (48.06%), citronellol oleate (7.81%), and caryophyllene oxide (5.67%) were the dominant components of this essential oil. The IC50 value of the extract was 85.55 ± 5.31 µg/mL, and the total phenolic and flavonoid contents was 321.42 ± 8.04 and 30.6 ± 2.11 µg/mg, respectively. The results of antimicrobial activity showed that the lowest MIC value of the essential oil was against the Gram-negative Pseudomonas aeruginosa, with a value of 62.5 µg/mL. The results of cytotoxicity confirmed the non-toxicity of the extract at all concentrations and the non-toxicity of the essential oil at a concentration of 25 µg/mL. Therefore, the essential oil, and in particular the extract from Clevenger’s residual water (a waste and by-product), in vitro is a natural, inexpensive, and environmentally friendly option for combating skin infections and hospital-acquired burn complications caused by P. aeruginosa, which is in line with the use of this plant in traditional medicine for wound healing and burn care. Further clinical and in vivo trials are needed.