Sesquiterpenes and monoterpenes from the bark of Inula macrophylla

Constituents of Pulicaria inuloides and Cytotoxic Activities of Two Methoxylated Flavonols

Plants of the genus Pulicaria are known for providing traditional medicines, spices, herbal teas, and insect deterrents. Pulicaria inuloides (Poir.). DC. is one of the less chemically studied species within the genus. Hydroalcoholic extracts from roots and aerial parts of P. inuloides were analyzed using the UHPLC-PAD-MSn technique and revealed the presence of six caffeoylquinic and eleven caffeoylhexaric conjugates together with hydroxykaempferol dimethyl ether and quercetagetin trimethyl ether. Moreover, constituents of chloroform extract from the whole P. inuloides plants were isolated and identified by spectroscopic methods. One new and four known caryophyllene derivatives, three thymol derivatives, and four polymethoxylated flavonols were found in the analyzed extract. The structure of the new compound was established by spectroscopic methods (HRESIMS, 1H NMR, 13C NMR, COSY, HSQC, HMBC, NOESY). The cytotoxicity of 6-Hydroxykaempferol 3,7-dimethyl ether and quercetagetin 3,7,3’-trimethyl ether (chrysosplenol C), which are major flavonols isolated from the plant, were tested on prostate epithelial cells (PNT2), prostate cancer cells (DU145 and PC3), human keratinocytes (HaCaT), and melanoma cells (HTB140 and A375). Both flavonols demonstrated moderate cytotoxic activity against PC3 cells (IC50 = 59.5 µM and 46.6 µM, respectively). The remaining cell lines were less affected (IC50 > 150 µM).

High-Content Screening Pipeline for Natural Products Targeting Oncogenic Signaling in Melanoma

The incidence of melanoma, the most fatal dermatological cancer, has dramatically increased over the last few decades. Modern targeted therapy with kinase inhibitors induces potent clinical responses, but drug resistance quickly develops. Combination therapy improves treatment outcomes. Therefore, novel inhibitors targeting aberrant proliferative signaling in melanoma via the MAPK/ERK and PI3K/AKT pathways are urgently needed. Biosensors were combined that report on ERK/AKT activity with image-based high-content screening and HPLC-based activity profiling. An in-house library of 2576 plant extracts was screened on two melanoma cell lines with different oncogenic mutations leading to pathological ERK/AKT activity. Out of 140 plant extract hits, 44 were selected for HPLC activity profiling. Active thymol derivatives and piperamides from Arnica montana and Piper nigrum were identified that inhibited pathological ERK and/or AKT activity. The pipeline used enabled an efficient identification of natural products targeting oncogenic signaling in melanoma.

Natural soluble epoxide hydrolase inhibitors from Inula helenium and their interactions with soluble epoxide hydrolase

The inhibition of soluble epoxide hydrolase (sEH) is regarded as a promising therapeutic approach to treat inflammation and its related disorders. In present work, we investigated inhibitory effects of forty-nine kinds of traditional Chinese medicines against sEH. Inula helenium showed significant inhibitory effect against sEH, and the extract of I. helenium were isolated to obtain eight compounds, including 4H-tomentosin (1), xanthalongin (2), and linoleic acid (3), 8-hydroxy-9-isobutyryloxy-10(2)-methylbutyrylthymol (4), dehydrocostus lactone (5), alantolactone (6), costunolide (7), and isoalantolactone (8). Among them, 4H-tomentosin (1), xanthalongin (2), and linoleic acid (3) showed significantly inhibitory activities on sEH with half maximal inhibitory concentration (IC50) from 5.88 ± 0.97 μM to 11.63 ± 0.58 μM. The inhibition kinetics suggested that 4H-tomentosin (1) and xanthalongin (2) were mixed-competitive type inhibitors with inhibition constant (Ki) values of 7.02 and 6.57 μM, respectively, and linoleic acid (3) was a competitive type inhibitor with a Ki values of 3.52 μM. The potential interactions of 4H-tomentosin (1), xanthalongin (2), and linoleic acid (3) with sEH were analyzed by molecular docking, which indicated that these bioactive compounds had interactions with key amino acid residues Tyr343, Ile363, Tyr383, and His524.

Inula sesquiterpenoids: structural diversity, cytotoxicity and anti-tumor activity

INTRODUCTION

The plants of the genus Inula (Asteraceae) are widely distributed throughout Europe, Africa and Asia, and many of these plants have long been used in folk medicine. This genus is a rich source of sesquiterpenoids, which exhibit a wide range of biological activities. Recently, a series of bioactive sesquiterpenoid dimers, with unusual carbon skeletons, have been reported and these have gathered considerable interest.

AREAS COVERED

This article systematically reviews sesquiterpenoids isolated from the genus Inula that have appeared in literature up to August 2013, critically highlighting their anti-tumoral activities and relevant mechanistic insights. The authors also discuss the initial structure-activity relationships for the cytotoxic and anti-tumoral activities of the Inula sesquiterpenoids. Finally, the authors discuss the challenges and potential applications of these sesquiterpenoids in the future.

EXPERT OPINION

Cytotoxic and anti-tumor activities of Inula sesquiterpenoids have been extensively studied since the 1970s. One promising compound, Japonicone A, a dimeric sesquiterpene lactone from traditional herb Inula japonica, has displayed potent in vitro and in vivo anti-tumor activity against Burkitt's lymphoma. Additionally, acetylbritannilactone is thought to be capable of suppressing the abnormal vascular smooth muscle cell proliferation, with the induction of apoptosis in vivo and in vitro. In this regard, it may be worthwhile further investigating acetylbritannilactone in patients with vascular restenosis. Furthermore, given the anti-inflammatory property of britanin, clinical studies on chronic bronchitis and asthma, using the ethanol extract of I. japonica, are currently underway in South Korea. However, despite demonstrating good therapeutic effects, additional pharmacological and toxicological studies are still needed.

Pseudoguaianolides and guaianolides from Inula hupehensis as potential anti-inflammatory agents

Eight new pseudoguaianolides (1-8), two new guaianolides (9 and 10), and 14 known sesquiterpenes were isolated from the aerial parts of Inula hupehensis. The structures were elucidated using spectroscopic methods and circular dichroism analysis. All compounds were tested for inhibitory activities against LPS-induced nitric oxide production in RAW264.7 macrophages. Compounds 13 and 22 were found to inhibit nitric oxide production potently, with IC50 values of 0.9 and 0.6 μM, respectively. Preliminary structure-activity relationships for these compounds are proposed.

Two new eudesmanolides from Inula racemosa

Two new eudesmane-type sesquiterpene lactones were isolated from the roots of Inula racemosa and their structures were elucidated as 3β-hydroxy-11α,13-dihydroalantolactone (1) and 11α-hydroxy-eudesm-5-en-8β,12-olide (2). Their cytotoxic activities against five human cancer cell lines had been tested and compound 2 exhibited weak cytotoxic activity against BEL-7402 and HCT-8 cell lines. The anti-inflammatory activities were also tested, but neither of them showed any activities.

Four new glucosides from the aerial parts of Mediasia macrophylla

As part of our chemical studies on the medical plants in Uzbekistan aimed at searching for new drug leads, we have examined the aerial parts of Mediasia macrophylla. This has resulted in the isolation of four new glucosides, together with 30 known compounds. The structures of new compounds were elucidated as (1'S)-(4-hydroxyphenyl) ethane-1',2'-diol 2'-O-β-glucopyranoside (1), 3-(4'-methoxyphenyl)-propanol 1-O-β-glucopyranoside (2), 2-methoxy-3-hydroxy-5-(E)-propenyl-phenol 1-O-β-glucopyranoside (3), 1-O-angeloyl-β-glucopyranose (4), on the basis of spectral analysis.

A C14-polyacetylenic glucoside with an alpha-pyrone moiety and four C10-polyacetylenic glucosides from Mediasia macrophylla

Polyacetylenic glucosides (1-5) were isolated from the MeOH extract of Mediasia macrophylla, and their structures were established by spectroscopic analyses. Compounds 2-4 were the first examples of C(10)-polyacetylenic glucosides found in the family Umbelliferae, while compound 1 was a unique polyacetylenic glucoside possessing an alpha-pyrone moiety.

Thymol derivatives from hairy roots of Arnica montana

Five known thymol derivatives were isolated from roots of Arnica montana transformed with Agrobacterium rhizogenes LBA 9402. The compounds were characterized by spectral methods. The pattern of thymol derivatives in light-grown hairy roots was slightly different from that in dark-grown ones. This is the first report on the presence of thymol derivatives in hairy roots of the plant.

Eudesmane sesquiterpenoids from the Asteraceae family

This review covers the structures and biological activities of eudesmane-type sesquiterpenoids from the plants of the Asteraceae family. Biosynthetic studies or chemical syntheses leading to the revision of structures or stereochemistries have also been included, and 593 references are cited.

Novel antioxidants isolated from plants of the genera Ferula, Inula, Prangos and Rheum collected in Uzbekistan

We examined the effects of 48 compounds isolated from Ferula pallida, F. penninervis, Inula macrophylla, Prangos pabularia, P. tschimganica and Rheum maximowiczii collected in Uzbekistan on ADP/Fe2+-induced lipid peroxidation of egg yolk phosphatidylcholine liposomes. Of those compounds, 23 inhibited ADP/Fe2+-induced lipid peroxidation and nine showed especially strong inhibition of lipid peroxidation. Most compounds that inhibited peroxidation scavenged the 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical, indicating that the inhibition was due to radical scavenging. However, some compounds did not scavenge DPPH but inhibited lipid peroxidation significantly, suggesting that their inhibitory effect was not due to radical scavenging but to some other mechanism, such as prevention of Fe2+ function. Thus, we found various new antioxidants, some of which had a unique mechanism of action, in Ferula, Inula, Prangos and Rheum plants collected in Uzbekistan as seeds used in medicine.

Antiproliferative sesquiterpene lactones from the roots of Inula helenium

The MeOH extract of the roots of Inula helenium showed a high inhibitory activity for cell growth against MK-1, HeLa and B16F10 cell lines. Significant activity was found in the hexane-soluble fraction. From the hexane-soluble fraction, seven sesquiterpenes, namely, one germacrane (4beta,5alpha-epoxy-1(10),11(13)-germacradiene-8,12-olide), one elemane (igalane), and five eudesmanes (alantolactone, isoalantolactone, 11alpha,13-dihydroalantolactone, 11alpha,13-dihydro-isoalantolactone, 5-epoxyalantolactone) were isolated. In vitro antiproliferative activities of the isolates against MK-1, HeLa and B16F10 cells are reported.