The Clinical Translation of α-humulene - A Scoping Review.

α-humulene, a sesquiterpene found in essential oils of various plant species, has garnered interest due to its potential therapeutic applications. This scoping review aims to consolidate α-humulene's evidence base, informing clinical translation, and guiding future research directions. A scoping review was conducted of EMBASE, MEDLINE, and PubMed databases up to 14th July 2023. All studies describing original research on α-humulene extraction, as well as pre-clinical and clinical research, were included for review. Three hundred and forty articles were analysed. α-humulene yields ranged from negligible to 60.90% across plant species. In vitro experiments demonstrated cytotoxicity against adenocarcinomas (such as colorectal, pulmonary, breast, prostatic, lung, and ovarian), with varying responses in other cell models. Mechanistic insights revealed its involvement in mitochondrial dysfunction, diminished intracellular glutathione levels, and the induction of oxidative stress. In rodent studies, oral administration of α-humulene at 50 mg/kg reduced inflammation markers in paw oedema and ovalbumin-induced airway inflammation. Intraperitoneal administration of α-humulene (50 - 200 mg/kg) exhibited cannabimimetic properties through cannabinoid 1 and adenosine A2a receptors. α-humulene also exhibited a multitude of properties with potential scope for therapeutic utilisation. However, there is a paucity of studies that have successfully translated this research into clinical populations with the associated disease. Potential barriers to clinical translation were identified, including yield variability, limited isolation studies, and challenges associated with terpene bioavailability. Consequently, rigorous pharmacokinetic studies and further mechanistic investigations are warranted to effectively uncover the potential of α-humulene.

GC-MS AND Chemometric Analysis of the Essential Oils Obtained from Mexican Commercial Chamomilla Recutita Teas.

The essential oils prepared by hydrodistillation of twenty-one brands of German chamomile (S1-S21) commercialized in Mexico were analyzed by GS-MS. Altogether, twenty-four different compounds were identified in the analyzed samples, varying from 77 to 100 % of the total composition. Multivariate analyses were applied to explore similarity/dissimilarity and correlation between all samples; the results revealed a strong correlation among samples S4, S5, and S7-S21 due to the presence of (Z)-en-yn-dicycloether [(Z)-tonghaosu], α-bisabolol, ß-farnesene, ß-eudesmol, and xanthoxylin. The samples S1-S3 and S6 were clustered separately. Samples S1, S3, and S6 were characterized by their higher content of bisabolol oxide A (38.78 %, 51.84 %, and 70.46 %, respectively) as most known chemotypes of German chamomile, but only S1 and S3 contained chamazulene. Finally, S2 differed from the others because of its high content of (E)-anethole (62.28 %), suggesting a case of adulteration or substitution of the crude drug employed for manufacturing the product.

Bisabolane-type sesquiterpenoids with potential anti-inflammatory and anti-HIV activities from the stems and leaves of Morinda citrifolia.

The phytochemical study on the stems and leaves of Morinda citrifolia L. resulted in the isolation of a new naturally occurring bisabolane-type sesquiterpenoid, morincitrinoid A (1), together with five known analogues (2-6). The chemical structure of 1 was elucidated by comprehensive spectral analyses. The known compounds 2-6 were identified by comparing their spectral data with those reported in the literature, which were isolated from M. citrifolia for the first time. In addition, the anti-inflammatory and anti-HIV activities of compounds 1-6 were evaluated in vitro. Compounds 1-6 displayed significant inhibitory activities on NO (nitric oxide) production induced by lipopolysaccharide in mouse macrophage RAW 264.7 cells with IC50 values ranging from 0.98 ± 0.07 to 6.32 ± 0.11 µM, which was comparable to hydrocortisone. Meanwhile, compounds 1-6 showed remarkable anti-HIV-1 reverse transcriptase (RT) effects with the EC50 values ranging from 0.16 to 6.29 µM.

Dolabellane Diterpenes and Elemane Alkaloids from the Soft Coral Clavularia inflata Collected in the South China Sea.

Five new dolabellane diterpenes, clavularinlides A-E (1-5), and four new racemic elemane alkaloids, clavulacylides A-D (7-10), together with one known compound (6), were isolated from the soft coral Clavularia inflata collected in the South China Sea. Their structures were elucidated by 1D and 2D NMR, HRESIMS, calculated ECD, and DP4+ probability analyses. Compounds 1-7 showed anti-inflammatory activity in the zebrafish assay.

Antifungal mono- and dimeric nitrogenous bisabolene derivatives from a sponge in the order Bubarida from Futuna Islands.

An abundant sponge of the order Bubarida was selected for further chemical investigation following biological and chemical screening of sponges collected from Futuna Islands in the Indo-Pacific. Ten new nitrogenous bisabolene derivatives were isolated and identified: the monomeric theonellin formamide analogues named bubaridins A-F (1-6) with unusual oxidised linear chains, and the first isocyanide/formamide dimeric and cyclised bisabolenes 7-9. The structure elucidation of these nitrogenous bisabolenes involved HRESIMS, NMR, and ECD analyses, and the chiral compounds were found to be racemates. A biosynthetic hypothesis for the production of these metabolites is proposed and some chemotaxonomic considerations are discussed. Furthermore, the antimicrobial and antitumoral activity were evalutated and the trans-dimer theonellin isocyanide (7) was shown to exhibit potent and selective antifungal activity.

Role of Caryophyllane Sesquiterpenes in the Entourage Effect of Felina 32 Hemp Inflorescence Phytocomplex in Triple Negative MDA-MB-468 Breast Cancer Cells.

Cannabis sativa L. crops have been traditionally exploited as sources of fibers, nutrients, and bioactive phytochemicals of medical interest. In the present study, two terpene-rich organic extracts, namely FOJ and FOS, obtained from Felina 32 hemp inflorescences collected in June and September, respectively, have been studied for their in vitro anticancer properties. Particularly, their cytotoxicity was evaluated in different cancer cell lines, and the possible entourage effect between nonintoxicating phytocannabinoids (cannabidiol and cannabichromene) and caryophyllane sesquiterpenes (ß-caryophyllene, ß-caryophyllene oxide and α-humulene), as identified at GC/MS analysis, was characterized. Modulation of cannabinoid CB1 and CB2 receptors was studied as a mechanistic hypothesis. Results highlighted marked cytotoxic effects of FOJ, FOS, and pure compounds in triple negative breast cancer MDA-MB-468 cells, likely mediated by a CB2 receptor activation. Cannabidiol was the main cytotoxic constituent, although low levels of caryophyllane sesquiterpenes and cannabichromene induced potentiating effects; the presence in the extracts of unknown antagonistic compounds has been highlighted too. These results suggest an interest in Felina 32 hemp inflorescences as a source of bioactive phytocomplexes with anticancer properties and strengthen the importance of considering the possible involvement of minor terpenes, such as caryophyllane sesquiterpenes, in the entourage effect of hemp-based extracts.

Bisabolane, cadinane, and cyclonerane sesquiterpenes from an algicolous strain of Trichoderma asperelloides.

Ten new bisabolane derivatives, trichobisabolins Q-Z (1-10), one new cadinane derivative, cadin-4-en-11-ol (11), and three new cyclonerane derivatives, cycloner-3-en-7,11-diol (12), isoepicyclonerodiol oxide (13), and norepicyclonerodiol oxide (14), were isolated from the endophytic fungal strain RR-dl-6-11 of Trichoderma asperelloides that was obtained from a marine alga. Their structures along with relative configurations were established mainly by NMR and IR as well as MS techniques, and the absolute configurations of 10 and 11 were assigned by ECD and X-ray diffraction data, respectively. Sesquiterpenes from the fungus T. asperelloides are reported for the first time. It is interesting that half of the bisabolane derivatives are demethylated. Compound 12 represents the first the occurrence of cyclopentenyl-bearing cycloneranes, and 14 seems a cyclopentyl-degrading cyclonerane derivative. Several isolates feature potent inhibition of marine phytoplankton species.

Chemical Constituents of the Essential Oil from Ecuadorian Endemic Species Croton ferrugineus and Its Antimicrobial, Antioxidant and α-Glucosidase Inhibitory Activity.

Croton ferrugineus Kunth is an endemic species of Ecuador used in traditional medicine both for wound healing and as an antiseptic. In this study, fresh Croton ferrugineus leaves were collected and subjected to hydrodistillation for extraction of the essential oil. The chemical composition of the essential oil was determined by gas chromatography equipped with a flame ionization detector and gas chromatography coupled to a mass spectrometer using a non-polar and a polar chromatographic column. The antibacterial activity was assayed against three Gram-positive bacteria, one Gram-negative bacterium and one dermatophyte fungus. The radical scavenging properties of the essential oil was evaluated by means of DPPH and ABTS assays. The chemical analysis allowed us to identify thirty-five compounds representing more than 99.95% of the total composition. Aliphatic sesquiterpene hydrocarbon trans-caryophyllene was the main constituent with 20.47 ± 1.25%. Other main compounds were myrcene (11.47 ± 1.56%), ß-phellandrene (10.55 ± 0.02%), germacrene D (7.60 ± 0.60%), and α-humulene (5.49 ± 0.38%). The essential oil from Croton ferrugineus presented moderate activity against Candida albicans (ATCC 10231) with an MIC of 1000 µg/mL, a scavenging capacity SC50 of 901 ± 20 µg/mL with the ABTS method, and very strong antiglucosidase activity with an IC50 of 146 ± 20 µg/mL.

Understanding and Engineering the Stereoselectivity of Humulene Synthase.

The non-canonical terpene cyclase AsR6 is responsible for the formation of 2E,6E,9E-humulene during the biosynthesis of the tropolone sesquiterpenoid (TS) xenovulene A. The structures of unliganded AsR6 and of AsR6 in complex with an in crystallo cyclized reaction product and thiolodiphosphate reveal a new farnesyl diphosphate binding motif that comprises a unique binuclear Mg2+ -cluster and an essential K289 residue that is conserved in all humulene synthases involved in TS formation. Structure-based site-directed mutagenesis of AsR6 and its homologue EupR3 identify a single residue, L285/M261, that controls the production of either 2E,6E,9E- or 2Z,6E,9E-humulene. A possible mechanism for the observed stereoselectivity was investigated using different isoprenoid precursors and results demonstrate that M261 has gatekeeping control over product formation.

Euphorboside A, a cytotoxic meroterpenoid glycoside with an unusual humulene-phloroglucinol skeleton from Euphorbia kansuensis.

Euphorboside A (1), an unusual meroterpenoid glycoside featuring the incorporation of an acylphloroglucinol moiety into a humulene skeleton to form a 6/6/11 ring system, was isolated from the roots of Euphorbia kansuensis. Its structure was elucidated by extensive spectroscopic analysis, chemical methods, and ECD calculations. Compound 1 was screened for the cytotoxicity against nine cancer cell lines, and 1 showed marked inhibitory activities against human colon cancer RKO and human breast cancer MDA-MB-231 cell lines with IC50 values of 3.70 and 4.15 µM, respectively.

The influence of ergosterol on the action of the hop oil and its major terpenes on model fungi membranes. Towards understanding the mechanism of action of phytocompounds for food and plant protection.

The aim of this work was to find the correlation between the content of ergosterol in fungi membrane and the action of the hop essential oil, myrcene and humulene on its properties. To reach this goal, the monolayers and bilayers composed of phosphatidylcholine, phosphatidyethanol amine and ergosterol, differing in the concentration of sterol, were used as model membrane systems. The impact of the essential oil and its major terpenes on one component ergosterol film was also investigated. It was found that pure isolated terpenes, in contrast to the hop oil being the mixture of them, do not incorporate into pure ergosterol membrane, however, they cause the loss of monolayer material from the interface. These results are in contrast to the effect of these terpenes on phospholipid films reported previously and they may suggest a strong effect of ergosterol on the behavior of terpenes in the mixed systems. Surprisingly, for model membranes, the effect of myrcene was qualitatively similar to the effect of the hop oil and ergosterol was found to regulate the incorporation of both these substances into the film. In contrast, very strong correlation between ergosterol content and the action of humulene was found. Namely, the ability of humulene to change model membrane properties was found to increase with ergosterol concentration. Additionally, the differentiating effect of ergosterol on humulene action in membranes was much more pronounced than for myrcene or the hop oil. Interestingly, at the highest ergosterol level the influence of humulene was even stronger than the effect of the hop oil. This is very important finding suggesting that ergosterol may regulate the sensitivity of particular membrane to the impact of humulene. Summarizing, ergosterol substantially differentiates the effect of the hop oil, myrcene and humulene on the lipid systems and it can be the molecule important for antifungal effect of the essential oil and terpenes.

Anti-Tumor Drug Discovery Based on Natural Product ß-Elemene: Anti-Tumor Mechanisms and Structural Modification.

Natural products are important sources for drug discovery, especially anti-tumor drugs. ß-Elemene, the prominent active ingredient extract from the rhizome of Curcuma wenyujin, is a representative natural product with broad anti-tumor activities. The main molecular mechanism of ß-elemene is to inhibit tumor growth and proliferation, induce apoptosis, inhibit tumor cell invasion and metastasis, enhance the sensitivity of chemoradiotherapy, regulate the immune system, and reverse multidrug resistance (MDR). Elemene oral emulsion and elemene injection were approved by the China Food and Drug Administration (CFDA) for the treatment of various cancers and bone metastasis in 1994. However, the lipophilicity and low bioavailability limit its application. To discover better ß-elemene-derived anti-tumor drugs with satisfying drug-like properties, researchers have modified its structure under the premise of not damaging the basic scaffold structure. In this review, we comprehensively discuss and summarize the potential anti-tumor mechanisms and the progress of structural modifications of ß-elemene.

Total Synthesis and Computational Investigations of Sesquiterpene-Tropolones Ameliorate Stereochemical Inconsistencies and Resolve an Ambiguous Biosynthetic Relationship.

The sesquiterpene-tropolones belong to a distinctive structural class of meroterpene natural products with impressive biological activities, including anticancer, antifungal, antimalarial, and antibacterial. In this article, we describe a concise, modular, and cycloaddition-based approach to a series of sesquiterpene mono- and bistropolones, including (-)-epolone B, (+)-isoepolone B, (±)-dehydroxypycnidione, and (-)-10-epi-pycnidione. Alongside the development of a general strategy to access this unique family of metabolites were computational modeling studies that justified the diastereoselectivity observed during key cycloadditions. Ultimately, these studies prompted stereochemical reassignments of the pycnidione subclass and shed additional light on the biosynthesis of these remarkable natural products.

Boronic Acid-Catalyzed Final-Stage Site-Selective Acylation for the Total Syntheses of O-3'-Acyl Bisabolol ß-D-Fucopyranoside Natural Products and Their Analogues.

The first concise total syntheses of O-3'-senecioyl α-bisabolol ß-D-fucopyranoside (4a) and O-3'-isovaleroyl α-bisabolol ß-D-fucopyranoside (4b) were achieved through final-stage site-selective acylation via the activation of cis-vicinal diols by imidazole-containing boronic acid catalysts as a key step. This synthetic method was also effective for the syntheses of unnatural analogues with modified acyl side chains or carbohydrate moiety.

Phenolic bisabolane and cuparene sesquiterpenoids with anti-inflammatory activities from the deep-sea-derived Aspergillus sydowii MCCC 3A00324 fungus.

Seventeen undescribed sesquiterpenoids including 14 phenolic bisabolanes, namely asperbisabolanes A-N (1-14), and 3 cuparenes (aspercuparenes A-C, 15-17), together with 10 known bisabolane analogues (18-27) were isolated from the EtOAc extract of fermented cultures of the deep sea sediment-derived fungus Aspergillus sydowii MCCC 3A00324. The new structures were established on the basis of extensive NMR and HRESIMS spectroscopic data analyses, while their absolute configurations were assigned by comparison of the experimental ECD spectra with those of the TDDFT-ECD calculated spectra or reported data in literature. Asperbisabolanes A (1) and B (2) are the first examples of bisabolane sesquiterpenoids featuring a 6/6/6 tricyclic nucleus. Compound 3 possessed a novel seco-bisabolane skeleton with a rare dioxolane ring moiety, while asperbisabolane K (11) represents the first case of bisabolanes bearing a rare methylsulfonyl group. All the isolated compounds (1-27) were evaluated their activities against NO secretion in LPS-activated BV-2 microglia cells. As a result, 6, 12, 16, and 25-27 exhibited the inhibition rate over 45% at a concentration of 10 µM. Moreover, 12 exerted the anti-inflammatory activity by inhibiting the NF-κB-activated pathway in dose-dependent manner.

Putative Biomimetic Route to 8-Oxabicyclo[3.2.1]octane Motif from a Humulene Sesquiterpenoid Zerumbone.

An approach to expand the diversity of terpenes to novel polycyclic skeletons with contiguous stereogenic centers is described. An unprecedented 8-oxabicyclo[3.2.1]octane motif was obtained in quantitative yield by photoirradiation of zerumbone in the presence of a catalytic amount of Lewis acid. The vital role of light in the isomerization of double bonds in zerumbone, which ensued cyclization via tertiary carbocation intermediate, emulates a biosynthetic route. Synthetic diversification of the phototransformed product afforded epoxy derivatives with up to seven contiguous stereogenic centers and eight-member ring fused tricyclic motifs. The present work sheds light on the possible role of UV irradiation in the biosynthesis of oxo-bridged tricyclic structures from polyene terpenes.

The characteristic smell emitted from two scale insects, Ceroplastes japonicus and Ceroplastes rubens.

The volatile components emitted from two scale insects, Ceroplastes japonicus and Ceroplastes rubens, were identified using GC-MS analysis. The major volatile components of the solvent extract from C. japonicus were α-humulene (35.8%) and δ-cadinene (17.0%), while those of C. rubens were ß-selinene (10.3%) and ß-elemene (5.1%). In GC/olfactometry, linalool, butyric acid, 3-methylbutyric acid, 2-methylbutyric acid, and vanillin were identified as the odor-active components of the extract from C. japonicus, in addition to trace amounts of trans-4,5-epoxy-(2E)-decenal, 4-methyl-(3E)-hexenoic acid, and phenylacetic acid. With regard to C. rubens, trans-4,5-epoxy-(2E)-decenal, 3-methylbutyric acid, and phenylacetic acid were identified as the odor-active components. Besides, decan-1,4-olide (γ-decalactone) with milky cherry-like note and 3-hydroxy-4,5-dimethylfuran-2(5H)-one (sotolone) with brown sugar-like note were also detected as the characteristic cherry-like sweet-and-sour note of these two scale insects. ABBREVIATIONS: GC: Gas chromatography; GC/O: gas chromatography/olfactometry.

Isolation, Characterization, and Possible Anti-Alzheimer's Disease Activities of Bisabolane-Type Sesquiterpenoid Derivatives and Phenolics from the Rhizomes of Curcuma longa.

One new bisabolane-type sesquiterpenoid, together with four known bisabolane-type sesquiterpenoid derivatives and seven phenolics, was isolated from the rhizomes of Curcuma longa. Their structures were elucidated by extensive spectroscopic (IR, HR-ESI-MS, and NMR) data analysis. The possible anti-Alzheimer's disease (AD) activities of the isolated compounds were also evaluated using Caenorhabditis elegans AD pathological model, and 1ß-hydroxybisabola-2,10-dien-4-one had the highest possible anti-AD activity.

Deciphering the anti-apoptotic potential of α-bisabolol loaded solid lipid nanoparticles against Aß induced neurotoxicity in Neuro-2a cells.

Nanoparticles based drug delivery system offers an alternative strategy to overcome several therapeutic limitations of various human ailments, particularly in age-linked Alzheimer's disease. Results of our previous cell-free studies indicated that α-bisabolol loaded solid lipid nanoparticles (ABS) significantly inhibited the aggregation of Aß25-35. The present study intended to evaluate the neuroprotective effect of ABS against Aß25-35 induced toxicity in Neuro-2a cell lines. The results of in vitro cell line study revealed that pretreatment of Neuro-2a cell lines with ABS (5 & 10 µg/ml) significantly suppressed the production of free radicals such as reactive oxygen species (ROS)/reactive nitrogen species (RNS), and also augmented the ROS mediated macromolecular damages and loss of mitochondrial membrane potential induced by toxic Aß peptide when compared to the standard drug donepezil (50 µg/ml). Moreover, reduced ß-secretase, caspase-3, and cholinesterase activities were observed in the cells pretreated with ABS, which clearly evidenced the neuroprotective effect of ABS. Reduced expression of Bax and induced expression of Bcl-2 proteins observed through western blot analysis and live/dead cell viability analysis of Neuro-2a cells through confocal microscope further validated that ABS protects the cells from Aß induced apoptosis. Taken together, the outcome of the present study signifies the neuroprotective effect of ABS against the Aß induced toxicity in in vitro model of Neuro-2a cells.