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Abstract The archipelagic country of Indonesia is populated by the densest marine biodiversity in the world which has created strong global interest and is valued by both Indigenous and European settlements for different purposes. Nearly 1000 chemicals have been extracted and identified. In this review, a systematic data curation was employed to collate bioprospecting related manuscripts providing a comprehensive directory based on publications from 1988 to 2022. Findings with significant pharmacological activities are further discussed through a scoping data collection. This review discusses macroorganisms (Sponges, Ascidian, Gorgonians, Algae, Mangrove) and microorganism (Bacteria and Fungi) and highlights significant discoveries, including a potent microtubule stabilizer laulimalide from Hyattella sp., a prospective doxorubicin complement papuamine alkaloid from Neopetrosia cf exigua, potent antiplasmodial manzamine A from Acanthostrongylophora ingens, the highly potent anti trypanosomal manadoperoxide B from Plakortis cfr. Simplex, mRNA translation disrupter hippuristanol from Briareum sp, and the anti-HIV-1 (+)-8-hydroxymanzamine A isolated from Acanthostrongylophora sp. Further, some potent antibacterial extracts were also found from a limited biomass of bacteria cultures. Although there are currently no examples of commercial drugs from the Indonesian marine environment, this review shows the molecular diversity present and with the known understudied biodiversity, reveals great promise for future studies and outcomes. Graphical Abstract

The archipelagic country of Indonesia is populated by the densest marine biodiversity in the world which has created strong global interest and is valued by both Indigenous and European settlements for different purposes. Nearly 1000 chemicals have been extracted and identified. In this review, a systematic data curation was employed to collate bioprospecting related manuscripts providing a comprehensive directory based on publications from 1988 to 2022. Findings with significant pharmacological activities are further discussed through a scoping data collection. This review discusses macroorganisms (Sponges, Ascidian, Gorgonians, Algae, Mangrove) and microorganism (Bacteria and Fungi) and highlights significant discoveries, including a potent microtubule stabilizer laulimalide from Hyattella sp., a prospective doxorubicin complement papuamine alkaloid from Neopetrosia cf exigua, potent antiplasmodial manzamine A from Acanthostrongylophora ingens, the highly potent anti trypanosomal manadoperoxide B from Plakortis cfr. Simplex, mRNA translation disrupter hippuristanol from Briareum sp, and the anti-HIV-1 (+)-8-hydroxymanzamine A isolated from Acanthostrongylophora sp. Further, some potent antibacterial extracts were also found from a limited biomass of bacteria cultures. Although there are currently no examples of commercial drugs from the Indonesian marine environment, this review shows the molecular diversity present and with the known understudied biodiversity, reveals great promise for future studies and outcomes. [ABSTRACT FROM AUTHOR]

Several new 2-substituted allyl bromides were synthesized through cyclopropanol intermediates and were then involved in the Barbier allylation of (R)-2,3-O-isopropylideneglyceraldehyde in the presence of zinc in a mixture of tetrahydrofuran and saturated aqueous ammonium chloride to obtain the corresponding homoallylic alcohols with high diastereoselectivity. The possibility of using the latter as building blocks for macrocyclic antitumor agents (laulimalides) and their synthetic analogs was demonstrated. [ABSTRACT FROM AUTHOR]

Peloruside A (PLA) and Laulimalide (LAU) are novel microtubule-stabilizing agents with promising properties against different cancer types. These ligands share a non-taxoid binding site at the outer surface of β-tubulin and promote microtubule stabilization by bridging two adjacent αβ-tubulin dimers from parallel protofilaments. Recent site-directed mutagenesis experiments confirmed the existence of a unique β-tubulin site mutation (Gln293Met) that specifically increased the activity of PLA and caused resistance to LAU, without affecting the stability of microtubules in the absence of the ligands. In this work, fully atomistic molecular dynamics simulations were carried out to examine the PLA and LAU association with native and mutated αβ-tubulin in the search for structural and energetic evidence to explain the role of Gln293Met mutation on determining the activity of these ligands. Our results revealed that Gln293Met mutation induced the loss of relevant LAU-tubulin contacts but exerted negligible changes in the interaction networks responsible for PLA-tubulin association. Binding free energy calculations (MM/GBSA and MM/PBSA), and weak interaction analysis (aNCI) predicted an increased affinity for PLA, and a weakened association for LAU after mutation, thus suggesting that Gln293Met mutation exerts its action by a modulation of drug-tubulin interactions. These results are valuable to increase understanding about PLA and LAU activity and to assist the future design of novel agents targeting the PLA/LAU binding pocket. [ABSTRACT FROM AUTHOR]

Taxanes are microtubule-stabilizing agents used in the treatment of many solid tumors, but they often involve side effects affecting the peripheral nervous system. It has been proposed that this could be related to structural modifications on the filament upon drug binding. Alternatively, laulimalide and peloruside bind to a different site also inducing stabilization, but they have not been exploited in clinics. Here, we use a combination of the parental natural compounds and derived analogs to unravel the stabilization mechanism through this site. These drugs settle lateral interactions without engaging the M loop, which is part of the key and lock involved in the inter-protofilament contacts. Importantly, these drugs can modulate the angle between protofilaments, producing microtubules of different diameters. Among the compounds studied, we have found some showing low cytotoxicity and able to induce stabilization without compromising microtubule native structure. This opens the window of new applications for microtubule-stabilizing agents beyond cancer treatment. [Display omitted] • Chemotypes targeting the laulimalide site do not induce microtubule lattice expansion • Microtubule stabilization through the laulimalide site involves only lateral contacts • Variations of chemotypes targeting the laulimalide site alter inter-protofilament angle Microtubules are linked to cancer growth and are a chemotherapy target. Estévez-Gallego et al. provide insights into the mechanism of drugs targeting the stabilization pocket known as laulimalide site in microtubules. These findings will help to target microtubules also in other diseases and to unravel the relationship of microtubule structure and neurotoxicity. [ABSTRACT FROM AUTHOR]

Peloruside A (PLA) and laulimalide (LAU) are potent microtubule-stabilizing natural products that are effective against a broad spectrum of cancer cells. The interactions of PLA and LAU with tubulin have attracted a great deal of attention, mainly because they bind to β-tubulin at a site that is different from the classical taxoid site. Multiple βI-tubulin amino acid residues have been predicted by computer modelling studies and more recently by protein crystallography to participate in the binding of PLA and LAU to tubulin. The relevance of these residues in determining cellular sensitivity to the compounds, however, remains largely uncertain. To determine the role of four binding site residues, Q291, D295, V333, and N337 on PLA and LAU activity, we introduced single mutations to these sites by site-directed mutagenesis and transfected each mutant tubulin separately into HEK and/or HeLa cells. We found that a Q291M βI-tubulin mutation increased sensitivity of the cells to PLA, but not to LAU, paclitaxel (PTX), or vinblastine (VBL). In contrast, V333W and N337L mutations led to less stable microtubules, with the V333W causing resistance to PLA and PTX, but not LAU, and the N337L causing resistance to PLA, LAU, and PTX. Moreover, cells expressing either W333 or L337 were hypersensitive to the microtubule-destabilizing agent, VBL. The D295I mutation conferred resistance to both PLA and LAU without affecting microtubule stability or sensitivity to PTX or ixabepilone (IXB). This study identifies the first mammalian βI-tubulin mutation that specifically increases sensitivity to PLA, and reports mutations at PLA and LAU binding site residues that can either reduce microtubule stability or impair drug–tubulin binding, conferring resistance to these microtubule-stabilizing agents. This information provides insights on β-tubulin residues important for maintaining microtubule structural integrity and for sensitivity to microtubule-targeting agents, and suggests novel directions for rational structure-based design of new and more potent agents for cancer treatment that target the LAU/PLA site. [ABSTRACT FROM AUTHOR]

This review focuses on a relatively new class of microtubule stabilizers, the taccalonolides. The taccalonolides are highly oxygenated pentacyclic steroids isolated from plants of the genus Tacca . Originally identified in a cell-based phenotypic screen, the taccalonolides have many properties similar to other microtubule stabilizers. They increase the density of interphase microtubules, causing microtubule bundling, and form abnormal multi-polar mitotic spindles leading to mitotic arrest and, ultimately, apoptosis. However, the taccalonolides differ from other microtubule stabilizers in that they retain efficacy in taxane resistant cell lines and in vivo models. Binding studies with the newly identified, potent taccalonolide AJ demonstrated covalent binding to β-tubulin at or near the luminal and/or pore taxane binding site(s) which stabilizes microtubule protofilaments in a unique manner as compared to other microtubule stabilizers. The isolation and semi-synthesis of 21 taccalonolides helped to identify key structure activity relationships and the importance of multiple regions across the taccalonolide skeleton for optimal biological potency. [ABSTRACT FROM AUTHOR]

A stereoselective route to the C13-C28 subunit of (-)-laulimalide is described. L-Tartaric acid is the source of the hydroxy groups at C19 and C20. An α-chlorosulfide is employed as the key intermediate for the creation of the C17-C18 bond and the C16-C17 double bond was introduced using the Mislow-Braverman rearrangement and Hutchin's dexoxygenation with concomitant double bond transposition reaction. The C15 and C23 stereogenic centers were created using catalytic asymmetric reactions. The trisubstituted and trans-disubstituted alkenes were created stereoselectively by taking advantage of ring-closing metathesis and the Julia-Kocienski olefination reaction, respectively. [ABSTRACT FROM AUTHOR]

The investigational anticancer agents laulimalide and peloruside are known to exert an antimitotic effect on cells by binding to β-tubulin. The binding affinities of derivatives of laulimalide and peloruside to all known isoforms of human β-tubulin were calculated using molecular mechanical, molecular dynamical, and quantum mechanical methods. Several of the derivatives are predicted to have improved β-tubulin binding affinities compared to the parent structures. These results can form the starting point for developing laulimalide or peloruside derivatives with greater specificity for the particular β-tubulin isoforms, which are overexpressed in certain tumours. [ABSTRACT FROM AUTHOR]

Purpose: Acquired β-tubulin alterations in human ovarian carcinoma 1A9 cells were previously shown to confer resistance to the microtubule stabilizing agents peloruside A (PLA) and laulimalide (LAU). We examined the proteome of resistant cells to see what other protein changes occurred as a result of the acquired drug resistance. Methods: Two-dimensional differential in-gel electrophoresis was performed to explore differentially expressed proteins in the resistant 1A9-R1 (R1) and 1A9-L4 (L4) cells. The proteins on the gels were identified by MALDI-TOF MS, and altered protein abundance was confirmed by Western blotting and immunocytochemistry. Vimentin expression was restored in vimentin-deficient L4 cells by transfecting a full-length human vimentin cDNA, and sensitivity to PLA and LAU were tested using an MTT cell proliferation assay. Results: Proteomic analysis identified several proteins that were significantly altered in the resistant cells relative to the parental 1A9 cells. Using Western blotting and immunocytochemistry, a decreased vimentin abundance in the L4 cells was validated. Vimentin levels were unchanged in PLA-resistant R1 cells and paclitaxel/epothilone-resistant derivatives of 1A9 cells. Vimentin cDNA transfection into L4 cells partially restored PLA and LAU sensitivity. Conclusions: Downregulation of vimentin contributes to the resistance of 1A9 cells to the microtubule stabilizing agents, PLA and LAU. [ABSTRACT FROM AUTHOR]

This article reviews the recent findings regarding the binding sites, binding modes and binding affinities of three novel antimitotic drugs peloruside, laulimalide and noscapine with respect to tubulin as the target of their action. These natural compounds are shown to bind to β-tubulin and stabilize microtubules for the cases of peloruside A and laulimalide, and prolong the time spent in pause for noscapine. Particular attention is focused on β-tubulin isotypes as targets for new cancer chemotherapy agents and the amino acid differences in the binding site for these compounds between isotypes. We propose a new strategy for antimitotic drug design that exploits differential distributions of tubulin isotypes between normal and cancer cells and corresponding differential affinities between various drug molecules and tubulin isotypes. [ABSTRACT FROM AUTHOR]

Abstract: A simplified analogue of the C1–C11 fragment of peloruside A has been synthesised starting from a monoprotected 2,2-dimethylpropane-1,3-diol. Oxidation, asymmetric allylation and acryloylation provided a substrate for ring-closing metathesis to a δ-lactone. Reduction, acylation and homologation with trimethyl(vinyloxy)silane provided a protected C3–C11 analogue in a stereoisomer manner. Introduction of the C1–C2 fragment and incorporation of the 2,3-syn stereochemistry was achieved by a boron-mediated Evans aldol reaction. [Copyright &y& Elsevier]

Purpose: Microtubule-stabilizing agents are an important class of anticancer compounds. Peloruside A and laulimalide bind to a different site on the microtubule to taxoid site drugs such as paclitaxel (Taxol), docetaxel (Taxotere), ixabepilone (Ixempra), the epothilones, and discodermolide. The purpose of this study was to examine the synergistic interactions of these drugs when given in combination in relation to the differences in their binding sites on the microtubule. Methods: Human ovarian carcinoma cells (1A9 cells) and murine T cells were treated with different combinations of microtubule-stabilizing or destabilizing agents. The compounds were given individually and in combination, and the antiproliferative activity was assessed to calculate a combination index (CI) from the equation: CI = D/ Dx + D/ Dx in which D and D are the concentrations of drug 1 and drug 2 that when given together give the same response as drug 1 and 2 alone ( Dx and Dx). Thus, a CI value of less than 1.0 indicates a synergistic effect between the two drugs in which the response to the two drugs given together is greater than the additive response of the two drugs if given on their own. Results: As anticipated from previous in vitro studies, peloruside A and laulimalide did not synergize with each other. They also failed to synergize with the microtubule-destabilizing agents vinblastine and 2-methoxyestradiol. Peloruside A and laulimalide did, however, synergize with the epothilones, as had been previously shown, but not with docetaxel or discodermolide. Conclusions: Combining two microtubule-targeting agents with different binding sites does not guarantee a synergistic interaction in cells, and additional factors are likely to be involved. This study highlights the importance of preclinical testing of actual combinations of drugs before proceeding into clinical trials. [ABSTRACT FROM AUTHOR]

Abstract: An analogue of the paclitaxel-like antimicrotubule agent laulimalide with a phenyl in place of the dihydropyran has been synthesized. The fragments C1–C14 and C15–C28 were coupled via a stereoselective intermolecular allylboration. Ring closure was achieved using Yamaguchi’s protocol. [Copyright &y& Elsevier]

Abstract: The solution structures of the potent microtubule-stabilizing anti-cancer agent laulimalide and simplified analogues were determined by a combination of high field 1H NMR spectroscopic studies (J-based configuration analysis and NOESY) and constrained molecular dynamics simulations and discussed in relation to their antiproliferative activity. [Copyright &y& Elsevier]

Abstract: Novel, simplified analogues of the microtubule-stabilizing anticancer agent laulimalide, including the first derivatives with unnatural side chains, were designed by molecular modelling, synthesized by a late-stage diversification strategy, and evaluated in vitro for growth inhibition of human ovarian carcinoma cell lines (A2780, A2780/AD10). [Copyright &y& Elsevier]

Abstract: A stereoselective synthesis of the C3–C12 subunit of the tumor growth inhibitors laulimalide is disclosed. The key steps of the synthesis include asymmetric alkylation using Oppolzer’s protocol and an asymmetric hetero-Diels–Alder reaction using Jacobsen’s catalyst. Substrate controlled diastereoselective Luche reduction followed by Ferrier type reactions are other key steps. [Copyright &y& Elsevier]

Laulimalide (LA) is a microtubule-stabilizing agent, currently in preclinical studies. However, studying the binding of this species and successfully synthesizing potent analogues have been challenging. The LA binding site is located between tubulin protofilaments, and therefore LA is in contact with two adjacent [Formula: see text]-tubulin units. Here, an improved model of the binding mode of LA in microtubules is presented, using the newly available crystal structure pose and an extended tubulin heterodimer complex, as well as molecular dynamics simulations. With this model, a series of LA analogues developed by Mooberry and coworkers are also analyzed in order to establish important pharmacophores in LA binding and cytotoxicity. In the side chain, [Formula: see text]-[Formula: see text] interactions are important contributors to LA binding, as are water-mediated hydrogen bonds. An intramolecular hydrogen bond is correlated with high cytotoxicity, and is dependent on macrocycle conformation. Therefore, while the epoxide and olefin groups in the macrocycle do not engage in specific interactions with the protein, they are essential contributions to an active macrocycle conformation, and therefore potency. Calculations reveal that a balance in binding affinity is important for LA activity, where the more potent compounds have larger interactions with the adjacent tubulin unit than the less-active analogs. Several modifications are suggested for the rational design of LA analogues that should not disrupt the active macrocycle conformation.