A murine in vitro model of allergic contact dermatitis to sesquiterpene alpha-methylene-gamma-butyrolactones

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

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.

Ethnopharmacology, phytochemistry, agrotechnology, and conservation of Inula racemosa Hook f. - A critically endangered medicinal plant of the western Himalaya

ETHNOPHARMACOLOGICAL RELEVANCE

Inula racemosa Hook. f., is a critically endangered perennial herb distributed throughout the Himalaya; commercially useful in pharmaceutical products mainly because of its expectorant, antispasmodic, hypotensive, anti-inflammatory, carminative, thermogenic, digestive, cardiotonic, acrid, alexipharmic, anodyne, aphrodisiac, febrifuge, and antiseptic properties. The roots including rhizomes of the plant were used in the treatment of various ailments like chest pain, liver dysfunction, dyspnoea, and cardiovascular diseases by the ethenic Himalayan residents.

AIM OF THE REVIEW

Even though there are plentiful studies involving I. racemosa for pharmacological properties, but there is gap or few records available on production technologies and patents. The purpose of review is to provide large unmanageable information in systematic form for researchers, health care contributors, and policy makers so that they efficiently integrate the existing information and provide balanced decision making.

MATERIALS AND METHODS

Relevant data search was completed through systematic searches using various scientific databases including e-resources viz., Scopus, Google Scholar, Science Direct, ACS, Springer Link, Taylor and Francis, Scifinder, PubMed, PubChem, Web of Science, LibGen, Wiley, and China National Knowledge Infrastructure (CNKI). The list of literature cited in this review are dated from 1959 to 2021.

RESULTS

Till date variety of ethnobotanical and pharmacological properties of essential oil including crude extract of I. racemosa have been documented. The shortlisted records revealed that the herb has a potential to treat stomach ulcer, respiratory tract infections including chronic obstructive pulmonary disease (COPD). Alantolactone and isoalloalantolactone were reported as the major bioactive constituents along with few fatty acids, phytosterols, and glycosides characterized by GC, GC/MS, HPLC, HPTLC and qNMR techniques.

CONCLUSIONS

Based on a detailed literature survey on the plant, evidences were found fascinating for biological, traditional, and pharmacological effects, whilst there are no genomic resources available for this medicinal herb. Thus, molecular studies are critical for unravelling the production process of bioactive metabolites inside herb, which will underlay a path for improving these metabolites at commercial scale. Moreover, the association and role of particular phytoconstituent in its biological properties still needs to be validated. In addition, there are no reports on measures on its conservation and mechanism of toxicity research, which also needs more attention. We hope this review can provide a basis for further studies concerning the protected and efficient utilization of I. racemosa.

Impact of sesquiterpene lactones on the skin and skin-related cells? A systematic review of in vitro and in vivo evidence

Although anti-inflammatory properties are attributed to sesquiterpene lactones (SL), cutaneous hypersensitivity reactions are proposed as limitations for SL-based therapies. Thus, the impact of SL on the skin and skin-related cells was systematically reviewed. Studies indexed in electronic databases were screened from the PRISMA strategy. The risk of bias in all studies was verified from the SYRCLE's tool. Thirty original studies were recovered and analyzed. Mice and guinea pig, keratinocytes and fibroblasts were predominantly investigated from in vivo and in vitro studies, respectively. In vivo studies indicated that most SL induced contact dermatitis associated with edema, erythema, and inflammatory infiltrate. Conversely, in vitro evidence was consistent with a dose-dependent anti-inflammatory effect of SL in response to reduced cytokines, 5-LOX, and COX-2 levels or activity in keratinocytes, fibroblasts, macrophages and dendritic cells; which are events potentially triggered by downregulation of gene expression and/or inhibition of the NF-κB signaling pathway. In vivo studies presented uncertain to high-risk of bias mainly associated with underreporting of randomization and experimental blinding. The current evidence supports potent cutaneous immunomodulatory properties of SL. Although in vitro and in vivo studies indicate opposite anti- or proinflammatory effects, this contradiction exhibits a dose-dependent component. In addition, the anti-inflammatory pathways activated by SL are better understood from in vitro evidence. However, additional studies are required to elucidating specific anti-inflammatory and proinflammatory mechanisms triggered by SL in vivo. Thus, controlling the sources of bias described in this review can contribute to improving the quality of the evidence in further investigations.

Helenin from Stevia lucida. The first report of this natural eudesmanolide mixture in Eupatorieae tribe

From aerial parts of Stevia lucida Lagasca was isolated the natural mixture of isomeric eudesmanolides helenin. The identification and quantification of the constituents of helenin (alantolactone 1 and isoalantolactone 2, ratio 3:7) was performed through the quantitative analysis of its 1D and 2D NMR spectra.

The genus Inula and their metabolites: from ethnopharmacological to medicinal uses

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Inula comprises more than one hundred species widespread in temperate regions of Europe and Asia. Uses of this genus as herbal medicines have been first recorded by the Greek and Roman ancient physicians. In the Chinese Pharmacopoeia, from the 20 Inula spp. distributed in China, three are used as Traditional Chinese medicines, named Tumuxiang, Xuanfuhua and Jinfeicao. These medicines are used as expectorants, antitussives, diaphoretics, antiemetics, and bactericides. Moreover, Inula helenium L. which is mentioned in Minoan, Mycenaean, Egyptian/Assyrian pharmacotherapy and Chilandar Medical Codex, is good to treat neoplasm, wound, freckles and dandruff. Many other Inula spp. are used in Ayurvedic and Tibetan traditional medicinal systems for the treatment of diseases such as bronchitis, diabetes, fever, hypertension and several types of inflammation. This review is a critical evaluation of the published data on the more relevant ethnopharmacological and medicinal uses of Inula spp. and on their metabolites biological activities. This study allows the identification of the ethnopharmacological knowledge of this genus and will provide insight into the emerging pharmacological applications of Inula spp. facilitating the prioritirization of future investigations. The corroboration of the ethnopharmacological applications described in the literature with proved biological activities of Inula spp. secondary metabolites will also be explored.

MATERIALS AND METHODS

The major scientific databases including ScienceDirect, Medline, Scopus and Web of Science were queried for information on the genus Inula using various keyword combinations, more than 180 papers and patents related to the genus Inula were consulted. The International Plant Name Index was also used to confirm the species names.

RESULTS

Although the benefits of Inula spp. are known for centuries, there are insufficient scientific studies to certify it. Most of the patents are registered by Chinese researchers, proving the traditional use of these plants in their country. Although a total of sixteen Inula species were reported in the literature to have ethnopharmacological applications, the species Inula cappa (Buch.-Ham. ex D.Don) DC., Inula racemosa Hook.f., Inula viscosa (L.) Aiton [actually the accepted name is Dittrichia viscosa (L.) Greuter], Inula helenium, Inula britannica L. and Inula japonica Thunb. are the most frequently cited ones since their ethnopharmacological applications are vast. They are used to treat a large spectrum of disorders, mainly respiratory, digestive, inflammatory, dermatological, cancer and microbial diseases. Fifteen Inula spp. crude extracts were investigated and showed interesting biological activities. From these, only 7 involved extracts of the reported spp. used in traditional medicine and 6 of these were studied to isolate the bioactive compounds. Furthermore, 90 bioactive compounds were isolated from 16 Inula spp. The characteristic compounds of the genus, sesquiterpene lactones, are involved in a network of biological effects, and in consequence, the majority of the experimental studies are focused on these products, especially on their cytotoxic and anti-inflammatory activities. The review shows the chemical composition of the genus Inula and presents the pharmacological effects proved by in vitro and in vivo experiments, namely the cytotoxic, anti-inflammatory (with focus on nitric oxide, arachidonic acid and NF-κB pathways), antimicrobial, antidiabetic and insecticidal activities.

CONCLUSIONS

Although there are ca. 100 species in the genus Inula, only a few species have been investigated so far. Eight of the sixteen Inula spp. with ethnopharmacological application had been subjected to biological evaluations and/or phytochemical studies. Despite Inula royleana DC. and Inula obtusifolia A. Kerner are being used in traditional medicine, as far as we are aware, these species were not subjected to phytochemical or pharmacological studies. The biological activities exhibited by the compounds isolated from Inula spp., mainly anti-inflammatory and cytotoxic, support some of the described ethnopharmacological applications. Sesquiterpene lactone derivatives were identified as the most studied class, being britannilactone derivatives the most active ones and present high potential as anti-inflammatory drugs, although, their pharmacological effects, dose-response relationship and toxicological investigations to assess potential for acute or chronic adverse effects should be further investigated. The experimental results are promising, but the precise mechanism of action, the compound or extract toxicity, and the dose to be administrated for an optimal effect need to be investigated. Also human trials (some preclinical studies proved to be remarkable) should be further investigated. The genus Inula comprises species useful not only in medicine but also in other domains which makes it a high value-added plant.

Optimization of the mouse ear swelling test for in vivo and in vitro studies of weak contact sensitizers

Murine models for the assessment of the contact sensitizing properties of chemicals rely on mouse ear swelling tests (Mest), which are not sensitive enough to detect weak sensitizers. The aim of the present study was to develop in mice an adjuvant-free Mest appropriate for in vivo detection of any type of sensitizer (weak to strong), and useful for in vitro assessment of contact sensitivity (CS). 3 haptens were tested: dinitrochlorobenzene (DNCB), para-phenylenediamine (pPD) and isoeugenol. We compared various protocols for induction of the CS reaction, differing by the site of induction, the number of applications and the concentrations of the 3 haptens. Comparison of the induction site for optimal CS reaction showed that, in Balb/c mice, the back was a better site of induction than the abdomen. Detection of the sensitizing properties of weak sensitizers (pPD, isoeugenol) was possible using an adjuvant-free protocol, provided that the induction phase comprised hapten applications on 3 consecutive days on the backs of animals. For DNCB, one application was sufficient to obtain optimal CS reaction. For all 3 haptens, a secondary response in vitro was obtained using semi-purified lymph node T cells from animals sensitized 5 days before with the optimized Mest. These results demonstrate that the Mest could be a useful experimental model for the study of all types of contact sensitizers.