Cytotoxic and antiangiogenic paclitaxel solubilized and permeation-enhanced by natural product nanoparticles

Polymer-lipid hybrid microcarriers for oral codelivery of paclitaxel and tributyrin: development, optimization, and cytotoxicity in cells and spheroids of colorectal cancer

Colorectal cancer (CRC) is the third most frequent cancer worldwide. Despite advances in treatment, conventional chemotherapy suffers from severe side effects and limited drug selectivity, highlighting the importance of alternative therapies. In this study, a polymer-lipid hybrid microcarrier was developed for oral co-administration of paclitaxel (PTX) and tributyrin (TB) as a novel approach for CRC therapy. The microcarrier was designed with a pH-sensitive polymeric shell that encapsulates drug-loaded nanostructured lipid carriers (NLC); shell dissolution at intestinal pH enables localized release of the NLC. The methodological approach employed an emulsion of vegetable oil and NLC as a template for polymer deposition. Multiple parameters were optimized, including polymers ratios, NLC dilution, acid concentration, and sonication time. Spherical hybrid particles with smooth surface and mean size of 1000 nm were obtained; PTX encapsulation efficiency was 99.9 ± 0.2 %, with a production yield of 97.2 ± 0.08 %. Drug release followed the Korsmeyer-Peppas kinetic model. Cytotoxic evaluation in human colorectal adenocarcinoma HCT-116 monolayers showed that PTX encapsulation increased cytotoxicity, lowering IC50 to 83.7 nM compared to 199.5 nM for free PTX. The addition of TB further improved cytotoxicity, reducing the IC50 to 60.8 nM. A similar potentiation cytotoxicity was observed in spheroids. The microcarrier induced reductions in colony formation, alterations in cell cytoskeleton, and led to a significant reduction in P-glycoprotein expression compared to its free form, suggesting its potential to help to overcome drug resistance. These results point to the promising applicability of the hybrid microcarrier as an innovative delivery system for oral administration of cytotoxic agents.

Comparative Metabolome and Transcriptome Analysis Revealed the Accumulative Mechanism of Rubusoside in Chinese Sweet Tea

Terpenoids are important secondary metabolites in Rubus. Rubusoside is a relatively specific diterpenoid bioactive component in the leaves of Chinese Sweet Tea (Rubus suavissimus). However, the terpenoid anabolic pathway of Rubus and the molecular mechanism underlying the specific accumulation of rubusoside in R. suavissimus remain unclear. Here, metabolomics and transcriptomics analyses were performed on differences in terpenoid metabolism levels between R. suavissimus (sweet leaves) and Rubus chingii (bitter leaves). Steviol glycosides and goshonosides primarily accumulated in R. suavissimus and R. chingii, respectively. Three pairs of highly homologous glycosyltransferase genes (UGT85A57, UGT75L20, and UGT75T4) associated with rubusoside biosynthesis in the two Rubus species were identified. The three pairs of UGT proteins in both species could glycosylate steviol. Thus, the transcriptional regulation of UGTs in R. suavissimus appears to play a pivotal role in rubusoside accumulation. Our findings provide insights into the differences in terpenoid metabolism between R. suavissimus and R. chingii and reveal the molecular mechanism of rubusoside accumulation in R. suavissimus.

Engineering of layer-by-layer acetate-coated paclitaxel loaded poly(lactide-co-glycolide) acid nanoparticles for prostate cancer therapy- in vitro

It is hypothesized that layer-by-layer acetate-coated Paclitaxel-loaded PLGA nanoparticles (F2) can be engineered to potentiate the effectiveness of Paclitaxel (PTX) on LNCaP, a human prostate cancer cell line. The core of the layer-by-layer NPs is formed by nanoprecipitation, and the shell of the NPs is engineered using the sodium acetate's unique coating mechanism and surface-active properties. The resulting nanoformulation physicochemical properties are characterized by Fourier Transform Infra-Red (FTIR), Differential Scanning Calorimetry (DSC) Transmission Electron Microscopy (TEM), NanoSight NS300, spectrophotometry, Korsmeyer-Peppas model, respectively. The NP's cytotoxicity on LNCaP is assessed by MTS assay. The DSC and the FTIR confirm SA's coating of the NPs. The particle's mean diameters (PMD) are 89.4±2.3- to 114.4±7.6 nm. The TEM shows a unique multilayer and spherical nanoparticle. The encapsulation efficiency of commonly PTX-loaded PLGA NPs (F1) and F2 are 84.37±2.71% and 86.74±2.22, respectively. The drug transport mechanism of F1 and F2 is anomalous transport and case II, respectively. F2 follows a zero-order release mechanism. The cell viability is 45.08±2.18% and 60.17±4.72% when LNCaP is treated with 10 µg/mL of F2 and F1, respectively, after 48 hours of exposure. F2 and F1 cell growth inhibition are dose-dependent. This unique process of engineering the layer-by-layer NPs will provide new horizons for developing future innovative nanoparticles for targeted prostate cancer therapy.

Solubilization of Paclitaxel with Natural Compound Rubusoside toward Improving Oral Bioavailability in a Rodent Model

Paclitaxel, which features low water solubility and permeability, is an efflux pump substrate. The current paclitaxel drugs are given intravenously after resolving the solubility issue. Yet, oral delivery to achieve therapeutic bioavailability is not effective due to low absorption. This study evaluated a natural compound, rubusoside, to improve oral bioavailability in an animal model. Free paclitaxel molecules were processed into nano-micelles formed in water with rubusoside. The particle size of the nano-micelles in water was determined using dynamic light scattering. The oral bioavailability of paclitaxel in nano-micelles was determined against Cremophor/alcohol-solubilized Taxol after oral and intravenous administration to pre-cannulated Sprague Dawley rats. When loaded into the rubusoside-formed nano-micelles, paclitaxel reached a supersaturated concentration of 6 mg/mL, 60,000-fold over its intrinsic saturation of 0.1 µg/mL. The mean particle size was 4.7 ± 0.7 nm in diameter. Compared with Taxol®, maximum blood concentration was increased by 1.5-fold; the time to reach maximum concentration shortened to 0.8 h from 1.7 h; and, relative oral bioavailability increased by 88%. Absolute oral bioavailability was 1.7% and 1.3% for the paclitaxel nano-micelles and Taxol®, respectively. Solubilizing paclitaxel with rubusoside was successful, but oral bioavailability remained low. Further inhibition of the efflux pump and/or first metabolism may allow more oral paclitaxel to enter systemic circulation.

Better together: nanoscale co-delivery systems of therapeutic agents for high-performance cancer therapy

Combination therapies can enhance the sensitivity of cancer to drugs, lower drug doses, and reduce side effects in cancer treatment. However, differences in the physicochemical properties and pharmacokinetics of different therapeutic agents limit their application. To avoid the above dilemma and achieve accurate control of the synergetic ratio, a nanoscale co-delivery system (NCDS) has emerged as a prospective tool for combined therapy in cancer treatment, which is increasingly being used to co-load different therapeutic agents. In this study, we have summarized the mechanisms of therapeutic agents in combination for cancer therapy, nanoscale carriers for co-delivery, drug-loading strategies, and controlled/targeted co-delivery systems, aiming to give a general picture of these powerful approaches for future NCDS research studies.

Development of α-Tocopherol Succinate-Based Nanostructured Lipid Carriers for Delivery of Paclitaxel

The management of retinoblastoma (RB) involves the use of invasive treatment regimens. Paclitaxel (PTX), an effective antineoplastic compound used in the treatment of a wide range of malignant tumors, poses treatment challenges due to systemic toxicity, rapid elimination, and development of resistance. The goal of this work was to develop PTX-loaded, α-tocopherol succinate (αTS)-based, nanostructured lipid carrier (NLCs; αTS-PTX-NLC) and PEGylated αTS-PTX-NLC (αTS-PTX-PEG-NLC) to improve ocular bioavailability. The hot homogenization method was used to prepare the NLCs, and repeated measures ANOVA analysis was used for formulation optimization. αTS-PTX-NLC and αTS-PTX-PEG-NLC had a mean particle size, polydispersity index and zeta potential of 186.2 ± 3.9 nm, 0.17 ± 0.03, −33.2 ± 1.3 mV and 96.2 ± 3.9 nm, 0.27 ± 0.03, −39.15 ± 3.2 mV, respectively. The assay and entrapment efficiency of both formulations was >95.0%. The NLC exhibited a spherical shape, as seen from TEM images. Sterilized (autoclaved) formulations were stable for up to 60 days (last time point checked) under refrigerated conditions. PTX-NLC formulations exhibited an initial burst release and 40% drug release, overall, in 48 h. The formulations exhibited desirable physicochemical properties and could lead to an effective therapeutic option in the management of RB.

Whole-Cell Biocatalyst for Rubusoside Production in Saccharomyces cerevisiae

Rubusoside (Rub) is a highly sweet diterpene glycoside mainly isolated from the leaves of Rubus suavissimus (Rosaceae). It has been used as a low-calorie natural sweetener for decades and was recently found to be a potential drug lead. In this study, we designed a whole-cell biocatalyst to achieve the glycosylation of steviol to Rub in Saccharomyces cerevisiae. The sucrose synthases were applied to construct a uridine diphosphate glucose regeneration system, which were coupled with optimal combinations of different uridine diphosphate (UDP) glycosyltransferases from multiple plant species. After optimization of reaction conditions, the residues in SrUGT74G1 probably influencing glycosylation efficiency were subjected to site-directed mutagenesis. Double mutations of S84A/E87A reduced the accumulation of intermediates, finally glucosylating 1.27 g/L steviol to 0.45 ± 0.06 g/L steviolmonoside (conversion rate = 23.3%) and 1.92 ± 0.17 g/L Rub (conversion rate = 74.9%). A high efficiency of Rub biosynthesis could be achieved without supply of additional UDPG. This work provided the first example of multi-step glycosylation reactions in whole-cell biocatalysis, which laid a foundation of scalable production of the value-added diterpene sweetener in the future.

Balanced lipase interactions for degradation-controlled paclitaxel release from lipid cubic phase formulations

Lipid cubic phase (LCP) formulations enhance the intestinal solubility and bioavailability of hydrophobic drugs by reducing precipitation and facilitating their mass transport to the intestinal surface for absorption. LCPs with an ester linkage connecting the acyl chain to the glycerol backbone (monoacylglycerols), are susceptible to chemical digestion by several lipolytic enzymes including lipases, accelerating the release of hydrophobic agents from the lipid bilayers of the matrix. Unlike regular enzymes that transform soluble substrates, lipolytic enzymes act at the interface of water and insoluble lipid. Therefore, compounds that bind to this interface can enhance or inhibit the activity of enzymes to varying extent. Here, we explore how the lipolysis rate can be tuned by the interfacial interaction of porcine pancreatic lipase with monoolein LCPs containing a known lipase inhibitor, tetrahydrolipstatin. Release of the Biopharmaceutical Classification System (BCS) class IV drug, paclitaxel, from the inhibitor-modified LCP was examined in the presence of lipase and its effectors colipase and calcium. By combining experimental dynamic digestion studies, thermodynamic measurements and molecular dynamics simulations of the competitive inhibition of lipase by tetrahydrolipstatin, we reveal the role and mode of action of lipase effectors in creating a precisely-balanced degradation-controlled LCP release system for the poorly soluble paclitaxel drug.

Combination of metronomic administration and target delivery strategies to improve the anti-angiogenic and anti-tumor effects of triptolide

The metronomic administration of a low-dose cytotoxic agent with no prolonged drug-free breaks is an anti-angiogenic cancer treatment method. The use of nano-formulations in this manner enhances anti-tumor efficacy and reduces toxicity by inhibiting angiogenic activity, reduces adverse effects, and changes the biodistribution of TP in the body, steering TP away from potentially endangering healthy tissues. The present study uses liposomes and Asn-Gly-Arg (NGR) peptide conjugated aminopeptidase N(APN)-targeted liposomes for triptolide (TP), as a model for the investigation of targeted metronomic administration and subsequent effects on the toxicity profile and efficacy of the chemotherapeutic agent. Metronomic NGR-PEG-TP-LPs have been found to have enhanced anti-tumor activity, a phenomenon that is attributed to an increase in angiogenic inhibition properties. In vitro experiments demonstrate that the viability, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) are obviously suppressed in comparison with that of other treatment groups. In vivo experiments also demonstrate that the anti-tumor efficacy of targeted metronomic administration is superior to that of liposome-administered treatments given at maximum tolerated dose (MTD) schemes, as is evidenced by markedly decreased tumor volume, vessel density, and the volume of circulating endothelial progenitor cells (CEPCs) in serum. Moreover, we observed that the metronomic administration of NGR-PEG-TP-LPs could elevate thrombospondin-1 (TSP-1) expression in tumors, a finding that is consistent with the promotion of TSP-1 secretion specifically from HUVECs. Additionally, metronomic NGR-PEG-TP-LPs have minimal drug-associated toxicity (weight loss, hepatotoxicity and nephrotoxicity in mice). Our research demonstrates the significance of targeted metronomic administration using liposomes for anti-angiogenic cancer therapy.

Rubusoside alleviates the ovalbumin-induced mice allergic asthma by modulating the NF-κB activation

The anti-inflammatory and anti-asthmatic effects of rubusoside (Rbs) were investigated in the ovalbumin (OVA)-induced asthmatic mice, followed by effective attenuation of Rbs treatment on the airway hyperresponsiveness and reduction of inflammatory cells inside the bronchoalveolar lavage fluid (BALF). The mitigation of inflammatory infiltration as a result of Rbs treatment was histologically observed in these mice lungs. Rbs contributed to the decrease of inflammatory cytokines (TNF-α, IL-13, IL-6, IL-5, and IL-4) inside the BALF of mice with asthma. A decline of OVA-dependent IgE and IgG1 inside the serum was also noticed in these mice. Rbs was proved to enhance the mRNA level of Foxp3 inside the mice lung affected with asthma while decrease that of IL-17A, IL-23, and RORγt. NF-κB pathway activation elicited by OVA was suppressed by Rbs inside the pulmonary tissues. Rbs played significantly in the reduction of airway inflammation induced by OVA which with modulating NF-κB pathway activation. PRACTICAL APPLICATIONS: Simultaneous therapy with medicine and food is strategically significant for disease prevention and treatment in traditional Chinese medicine. Rbs is a diterpene glycoside isolated from Rubus suavissimus. The anti-inflammatory and anti-asthmatic mechanism dependent of Rbs need further study clinically. The goal of current investigation is to explore the anti-inflammatory as well as anti-asthmatic activity of Rbs in mouse models of OVA-induced experimental allergic asthma. Results of the present study are scientifically supportive for the use of Rbs as an adjunctive reagent for clinical treatment of allergic asthma.

Rubusoside-assisted solubilization of poorly soluble C6-Ceramide for a pilot pharmacokinetic study

Although C₆-Ceramide has attracted much attention as a possible tumor suppressor, the delivery of C₆-Ceramide is still challenging due to its inherent hydrophobicity and insolubility. In this study we explored the use of a natural compound rubusoside (RUB) as a solubilizer to enhance the solubility of a fluorescence-labeled C₆-Ceramide (NBD C₆-Ceramide) and to characterize its pharmacokinetics and tissue distribution in an animal model. RUB significantly enhanced the solubility of NBD C₆-Ceramide by forming nanomicelles, and efficiently delivered NBD C₆-Ceramide in rats by oral and intravenous administration. RUB loaded 1.96 % of NBD C₆-Ceramide in the nanomicelles and solubilized it to a concentration of 3.6 mg/mL in water. NBD C₆-Ceramide in nanomicelles remained stable in aqueous solutions, allowing intravenous administration without the use of any organic solvents or surfactants. After oral administration, NBD C₆-Ceramide rapidly rose to peak plasma concentrations within the first 90 min, distributed to tissues, and remained in vivo for more than 24 h. Tissular levels of NBD C₆-Ceramide from high to low were associated with heart, lung, cerebellum, testicle, spleen, liver, kidney, and brain. Altogether, our study demonstrated that RUB-assisted nanomicelles can serve as an efficient and convenient delivery system for short-chain C₆-Ceramide and enable in vivo evaluation of potential new cancer treatments.

Ceramide-Rubusoside Nanomicelles, a Potential Therapeutic Approach to Target Cancers Carrying p53 Missense Mutations

Ceramide (Cer) is an active cellular sphingolipid that can induce apoptosis or proliferation-arrest of cancer cells. Nanoparticle-based delivery offers an effective approach for overcoming bioavailability and biopharmaceutics issues attributable to the pronounced hydrophobicity of Cer. Missense mutations of the protein p53, which have been detected in approximately 42% of cancer cases, not only lose the tumor suppression activity of wild-type p53, but also gain oncogenic functions promoting tumor progression and drug resistance. Our previous works showed that cellular Cer can eradicate cancer cells that carry a p53 deletion-mutation by modulating alternative pre-mRNA splicing, restoring wild-type p53 protein expression. Here, we report that new ceramide-rubusoside (Cer-RUB) nanomicelles considerably enhance Cer in vivo bioavailability and restore p53-dependent tumor suppression in cancer cells carrying a p53 missense mutation. Natural RUB encapsulated short-chain C₆-Cer so as to form Cer-RUB nanomicelles (∼32 nm in diameter) that substantially enhanced Cer solubility and its levels in tissues and tumors of mice dosed intraperitoneally. Intriguingly, Cer-RUB nanomicelle treatments restored p53-dependent tumor suppression and sensitivity to cisplatin in OVCAR-3 ovarian cancer cells and xenograft tumors carrying p53 R248Q mutation. Moreover, Cer-RUB nanomicelles showed no signs of significant nonspecific toxicity to noncancerous cells or normal tissues, including bone marrow. Furthermore, Cer-RUB nanomicelles restored p53 phosphorylated protein and downstream function to wild-type levels in p53 R172H^/+ transgenic mice. Altogether, this study, for the first time, indicates that natural Cer-RUB nanomicelles offer a feasible approach for efficaciously and safely targeting cancers carrying p53 missense mutations.

Enzymatic Production of Steviol Glucosides Using β-Glucosidase and Their Applications

Sweet leaf, Stevia rebaudiana Bertoni, is a perennial plant species widely known for its sweet-tastingent-kaurene type diterpenoid glycosides (steviol glucosides). Steviol glucosides include rubusoside (Ru), stevioside (Ste), and rebaudioside (Reb), which have immunomodulatory capability and protective effects against hyperglycemia, hypertension, inflammation, tumors, and diarrhea. In addition, they can enhance the solubility of epotoside, liquiritin, paclitaxel, curcuminoids, quercetin, and wheat bran flavonoids, thus increasing their permeability. The hydrolysis of three glucosyl groups at positions C13 and C19 of Ste will produce steviolbioside, steviol, isosteviol, steviol mono-glucoside, or Ru. S. rebaudiana contains these hydrolyzed products in trace amounts. This chapter describes recent advances in the preparation of various steviol glycosides from Ste by using different β-glycosidases, with particular focus on their potential industrial applications as natural solubilizers of insoluble compounds. Furthermore, the reaction mechanism of β-glycosidases and their kinetic properties are summarized.

Cytotoxicity Enhancement of Paclitaxel by Loading on Stearate-g-dextran Micelles on Breast Cancer Cell Line MCF-7

Objective:

Paclitaxel (PTX) is a chemotherapeutic agent used for treating breast cancer. The study aimed to prepare PTX loaded dextran stearate (Dex-SA) and evaluate its efficacy against human breast cancer cell line MCF-7.

Methods:

Dex-SA/PTX micelles were prepared by dialysis method. The micelles size, zeta potential and particle size distribution were measured by dynamic laser light scattering method. Amount of loaded PTX on the polymer measured by HPLC. Release profiles of the drug from the micelles were obtained in buffer (phosphate pH=7.4). Then the cytotoxicity of blank micelles, Dex-SA/PTX micelles and free PTX were evaluated in the MCF-7 cells by MTT method.

Result:

Loading efficiency of PTX on the Dex-SA was measured about 84.24±9.07%. The smallest particles size was about 193.9±7.1 nm but the other formulation with larger particle size had better zeta potential (-33.5±6.74 mV). The drug release from the micelles was slowly and reached steady state after about 12 hours. The cytotoxicity experiment showed that Dex-SA/PTX micelles have more cytotoxicity compared to free PTX against MCF7 cell lines.

Conclusions:

Dex-SA polymeric micelle is a suitable carrier for hydrophobic cytotoxic drugs such as PTX.

A Novel Solubility-Enhanced Rubusoside-Based Micelles for Increased Cancer Therapy

Many anti-cancer drugs have a common problem of poor solubility. Increasing the solubility of the drugs is very important for its clinical applications. In the present study, we revealed that the solubility of insoluble drugs was significantly enhanced by adding rubusoside (RUB). Further, it was demonstrated that RUB could form micelles, which was well characterized by Langmuir monolayer investigation, transmission electron microscopy, atomic-force microscopy, and cryogenic transmission electron microscopy. The RUB micelles were ellipsoid with the horizontal distance of ~25 nm and vertical distance of ~1.2 nm. Insoluble synergistic anti-cancer drugs including curcumin and resveratrol were loaded in RUB to form anti-cancer micelles RUB/CUR + RES. MTT assay showed that RUB/CUR + RES micelles had more significant toxicity on MCF-7 cells compared to RUB/CUR micelles + RUB/RES micelles. More importantly, it was confirmed that RUB could load other two insoluble drugs together for remarkably enhanced anti-cancer effect compared to that of RUB/one drug + RUB/another drug. Overall, we concluded that RUB-based micelles could efficiently load insoluble drugs for enhanced anti-cancer effect.

Phage-derived protein-mediated targeted chemotherapy of pancreatic cancer

Pancreatic cancer has been a life-threatening illness associated with high incidence and mortality rates. Paclitaxel (PCT) that causes mitotic arrest in cancer cells disrupting microtubule function is used for pancreatic cancer treatment. Nausea, anorexia and abdominal pain are some of the typical dose-limiting toxicity associated gastrointestinal side effects of the drug. Here, we present the use of polymeric mixed micelles to enable a targeted delivery of PCT and to provide additional advantages such as enhanced drug solubility, bioavailability and minimal dose-limiting toxicity. Also, these micelles self-assemble with pancreatic cancer cells-specific phage proteins P38, L1 and with the hydrophobic drug PCT resolving the issue of complex chemistry efforts normally needed for any conjugation. Our cytotoxicity and binding experiment results in vitro in 2 D and 3 D models suggested that the phage protein-targeted drug-loaded micelles bind and exhibit higher cell killing over the non-targeted ones.

Study on orally delivered paclitaxel nanocrystals: modification, characterization and activity in the gastrointestinal tract

Drug nanocrystals (NCs) can improve the solubility and bioavailability of insoluble drugs for oral administration. However, the biocompatibility and mechanisms of transmittance of drug NCs through the intestinal epithelial tissue are still not well understood. In this work, the physico-chemical properties and interactions with biomolecules in oral delivery pathways, as well as the transmittance through mimical intestinal epithelial cells, of NCs of paclitaxel (PTX) are investigated. PTX was previously demonstrated to be an effective anti-cancer drug. It is found that maximum 1% (w/v) poly(styrenesulfonate) is sufficient to keep PTX NCs monodisperse in varied biological environments and presents no significant interaction with extracellular biomolecules for at least 24 h. The concentration of PTX NCs is kept carefully controlled to avoid serious toxicity to cells (10 µg ml^-1 in our experiments but this also depends on NC size). The transmittance of PTX NCs through mimical intestinal epithelial reached 25% in 6 h, demonstrating its comparatively high oral bioavailability in the human body. This work demonstrates the great potential of PTX NC treated in oral delivery.

Xanthoceraside hollow gold nanoparticles, green pharmaceutics preparation for poorly water-soluble natural anti-AD medicine

In order to increase the solubility of poorly water-soluble natural product, xanthoceraside, an effective anti-AD compound from Xanthoceras sorbifolia Bunge, and maintain its natural property, the xanthoceraside hollow gold nanoparticles were successively prepared by green ultrasonic method with silica spheres as templates and HF solution as selective etching solvent. Hollow gold nanoparticles and drug-loaded hollow gold nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The solubilities of xanthoceraside loaded on hollow gold nanoparticles were increased obviously from 3.0μg/ml and 2.5μg/ml to 12.7μg/ml and 10.7μg/ml at 25°C and 37°C, respectively. The results of XRD and DSC indicated that the reason for this increase was mainly due to the amorphous state of xanthoceraside loaded on the hollow gold nanoparticles. In summary, the method of loading xanthoceraside onto hollow gold nanoparticles was a green and useful strategy to improve the solubility and dissolution of poorly water-soluble natural products and worth to applying to other natural products.

Towards taxane analogues synthesis by dienyne ring closing metathesis

The synthesis of highly functionalized 16,17,18-trinortaxane analogues based on a dienyne cyclization is described.