From Monographs to Chromatograms: The Antimicrobial Potential of Inula helenium L. (Elecampane) Naturalised in Ireland

Abstract

With antimicrobial resistance rising globally, the exploration of alternative sources of candidate molecules is critical to safeguard effective chemotherapeutics worldwide. Plant natural products are accessible, structurally diverse compounds with antimicrobial potential. The pharmacological applications of plants in medicine can be guided by the attestation of traditional use, as demonstrated in this study. In Irish ethnomedical literature, Inula helenium L. (elecampane) is often indicated for respiratory and dermal ailments. This is the first assessment of antimicrobial sesquiterpene lactones from the roots of elecampane, naturalised in Ireland. Traditional hydro-ethanolic extracts were prepared from multi-origin elecampane roots. A novel clean-up strategy facilitated the bioactivity-guided fractionation of a subset of anti-staphylococcal fractions (the compositions of which were investigated using HPLC-DAD, supported by 1H NMR). The natural products attributing to the antimicrobial activity, observed in vitro, were identified as alantolactone (1), isoalantolactone (2), igalan (3), and an unseparated mixture of dugesialactone (4) and alloalantolactone (5), as major compounds. The findings suggest that the geographical origin of the plant does not influence the anti-bacterial potency nor the chemical composition of traditional elecampane root. Considering the prevalence of staphylococci-associated infections and associated broad spectrum resistance in Irish hospitals, currently, further research is warranted into the usage of the identified compounds as potential candidates in the control of staphylococcal carriage and infection.

Biological Activities and Chemical Profile of Gentiana asclepiadea and Inula helenium Ethanolic Extracts

“…The in vitro anti- Staphylococcus aureus efficacy against both antibiotic-resistant and susceptible clinical isolates was documented for a hydroethanolic extract obtained from the rhizome and roots at concentrations between 0.9 and 9.0 mg/mL [ 50 ]. Similar in vitro anti-staphylococcal activity was reported for (hydro)ethanolic root extracts of I. helenium L. (elecampane) naturalized in Ireland supporting their traditional usage [ 20 ]. Additionally, these products demonstrated efficacy against other Gram-positive bacteria such as Group-A Streptococcus pyogenes , Group-B Streptococcus agalactiae , Listeria monocytogenes , and also Gram-negative Escherichia faecalis ATCC 29212 and Escherichia coli , as well as Mycobacterium tuberculosis H37Ra (ATCC 25177) [ 20 ].…”

“…Similar in vitro anti-staphylococcal activity was reported for (hydro)ethanolic root extracts of I. helenium L. (elecampane) naturalized in Ireland supporting their traditional usage [ 20 ]. Additionally, these products demonstrated efficacy against other Gram-positive bacteria such as Group-A Streptococcus pyogenes , Group-B Streptococcus agalactiae , Listeria monocytogenes , and also Gram-negative Escherichia faecalis ATCC 29212 and Escherichia coli , as well as Mycobacterium tuberculosis H37Ra (ATCC 25177) [ 20 ]. In vitro antibacterial ( Staphylococcus aureus , Enterococcus faecalis , Escherichia coli , Pseudomonas aeruginosa ) and antifungal ( Candida albicans and Candida tropicalis ) properties were demonstrated by the agar dilution method in case of methanolic extracts obtained from three Inula species, I. viscosa , I. helenium ssp.…”

“…Previous studies documented the in vitro antimicrobial efficacy of G. asclepiadea - [ 2 , 48 , 49 ] and I. helenium -derived products [ 18 , 19 , 20 , 43 , 50 ], tested alone or in combination with different compounds.…”

“…Currently, oral administration of I. helenium root tea is recommended in herbal medicine for the alleviation of respiratory symptoms, as a digestive tonic, choleretic, and vermifuge agent; as a topical application, this species is indicated in bacterial and fungal dermatitis and for skin disorders characterized by dry and itchy skin [ 16 , 17 ]. Recent studies have reported that roots of I. helenium exhibit in vitro anti-inflammatory, antioxidant, anti-proliferative, antimicrobial, antibacterial, anticandidal, prebiotic, and anthelmintic effects [ 4 , 18 , 19 , 20 , 21 ]. These proprieties could be attributed to its main secondary metabolites, such as sesquiterpene lactones (alantolactone and isoalantolactone), phenolic acids (gallic acid, caffeic acid, cinnamic acid, coumaric acid), and flavonoids (quercetin, myricetin, kaempferol, catechin) [ 16 , 22 ].…”

Optimization of inulin extraction from Inula helenium L. using response surface methodology followed by its MALDI-TOF and TLC-FLD based characterization

“…Inula helenium L. belongs to the Asteraceae family which is distributed in Europa, Asia, and Africa. The root of this plant has medicinal applications from ancient times and includes coumarin, flavonoids, polysaccharides (inulin 9-12 %), Fatty acid, and saponin [2][3][4].…”