Synergetic Inhibition of Human Colorectal Cancer Cells by Combining Polyyne-Enriched Fraction from Oplopanax elatus and Irinotecan

Bacterial polyynes uncovered: a journey through their bioactive properties, biosynthetic mechanisms, and sustainable production strategies

Covering: up to 2023Conjugated polyynes are natural compounds characterized by alternating single and triple carbon-carbon bonds, endowing them with distinct physicochemical traits and a range of biological activities. While traditionally sourced mainly from plants, recent investigations have revealed many compounds originating from bacterial strains. This review synthesizes current research on bacterial-derived conjugated polyynes, delving into their biosynthetic routes, underscoring the variety in their molecular structures, and examining their potential applications in biotechnology. Additionally, we outline future directions for metabolic and protein engineering to establish more robust and stable platforms for their production.

Effects of Structural Variations on Antibacterial Properties for Conjugated Diynes Generated through Glaser Hay Couplings

Antibiotic resistance is a growing problem facing global societies today. Many new antibiotics are derivatized versions of already existing antibiotics, which allows for antibiotic resistance to arise. To combat this issue, new antibiotics with different core structures need to be elucidated. Asymmetrical polyacetylenes have been isolated from natural products and they have previously been demonstrated to exhibit antimicrobial and antibacterial activity; however, their synthetic preparation has not made them easily amenable to rapid derivatization for SAR studies. Using a combination of solution and solid-supported chemistries, an array of diynes inspired by a known natural product were prepared and assessed for antibacterial activity. Ultimately, several compounds were identified with improved activity in bacterial viability assays. Moreover, some compounds were discovered that displayed a degree of specificity for E. coli over P. fluorescens and vice versa. These new compounds show promise, and further investigation is needed to pinpoint the specific structural components that elicit biological activity.

Falcarindiol and dichloromethane fraction are bioactive components in Oplopanax elatus: Colorectal cancer chemoprevention via induction of apoptosis and G2/M cell cycle arrest mediated by cyclin A upregulation

Oplopanax elatus (Nakai) Nakai has a long history of use as an ethnomedicine by the people living in eastern Asia. However, its bioactive constituents and cancer chemopreventive mechanisms are largely unknown. The aim of this study was to prepare O. elatus extracts, fractions, and single compounds and to investigate the herb's antiproliferative effects on colon cancer cells and the involved mechanisms of action. Two polyyne compounds were isolated from O. elatus, falcarindiol and oplopandiol. Based on our HPLC analysis, falcarindiol and oplopandiol are major constituents in the dichloromethane (CH₂Cl₂) fraction. For the HCT-116 cell line, the dichloromethane fraction showed significant effects. Furthermore, the IC50 for falcarindiol and oplopandiol was 1.7 μM and 15.5 μM, respectively. In the mechanistic study, after treatment with 5 μg/ml for 48 h, dichloromethane fraction induced cancer cell apoptosis by 36.5% (p < 0.01% vs. control of 3.9%). Under the same treatment condition, dichloromethane fraction caused cell cycle arrest at the G2/M phase by 32.6% (p < 0.01% vs. control of 23.4%), supported by upregulation of key cell cycle regulator cyclin A to 21.6% (p < 0.01% vs. control of 8.6%). Similar trends were observed by using cell line HT-29. Data from this study filled the gap between phytochemical components and the cancer chemoprevention of O. elatus. The dichloromethane fraction is a bioactive fraction, and falcarindiol is identified as an active constituent. The mechanisms involved in cancer chemoprevention by O. elatus were apoptosis induction and G2/M cell cycle arrest mediated by a key cell cycle regulator cyclin A.

Dimeric Artesunate-Phosphatidylcholine-Based Liposomes for Irinotecan Delivery as a Combination Therapy Approach

In this work, dimeric artesunate-phosphatidylcholine conjugate (dARTPC)-based liposomes encapsulated with irinotecan (Ir) were developed for anticancer combination therapy. First, dARTPC featured with unique amphipathic properties formed liposomes by classical thin-film methods. After that, Ir was encapsulated into dARTPC-based liposomes (Ir/dARTPC-LP) by the triethylammonium sucrose octasulfate gradient method. Physicochemical characterization indicated that Ir/dARTPC-LP had a mean size of around 140 nm and a negative ζ potential of approximately -30 mV. Most noticeably, liposomes displayed an encapsulation efficiency of greater than 98% with a controllable drug loading of 4-22%. The in vitro release of dihydroartemisinin (DHA) and Ir from Ir/dARTPC-LP was investigated by dialysis in different media. It was found that effective release of both DHA (65.42%) and Ir (77.28%) in a weakly acidic medium (pH 5.0) after 48 h was achieved in comparison to very slow release under a neutral environment (DHA 9.90% and Ir 8.72%), indicating the controllable release of both drugs. Confocal laser scanning microscopy confirmed the improved cellular internalization of Ir/dARTPC-LP. The cytotoxicity of Ir/dARTPC-LP was evaluated in the MCF-7, A549, and HepG2 cell lines. The results showed that Ir/dARTPC-LP had significant synergistic efficacy in the loss of cell growth. In vivo anticancer evaluation was performed using a 4T1 xenograft tumor model. Ir/dARTPC-LP had a high tumor inhibition rate of 62.7% without significant toxicity in comparison with the injection of Ir solution. Taken together, dARTPC encapsulated with Ir has great potential for anticancer combination therapy.

The phenolic acids from Oplopanax elatus Nakai stems and their potential photo-damage prevention activity

25 phenolic acids, including four new isolates, eurylophenosides A-D (1-4) and 21 known ones (5-25) were isolated and identified from the stems of Oplopanax elatus Nakai. Among the known compounds 5-9, 11-13, 16, 18-25 were isolated from the genus for the first time; 17 was first obtained from the plant; and the NMR data of 22 was reported here first. Meanwhile, the UVB-induced photodamage model of HaCaT cells was used to study the prevent-photodamage abilities of compounds 1-2, 4-8, 11-13 and 15-25 with a nontoxic concentration at 50 μM. Moreover, a dose-dependent experiment was conducted for active compounds at the concentration of 10, 25, and 50 µM, respectively. Consequently, pretreatment with compounds 1, 16, 17, 19, 20, 22, 24 and 25 could suppress the cell viability decreasing induced by UVB irradiation in a concentration-dependent manner. These results indicated that phenolic acids were one kind of material basis with prevent-photodamage activity of O. elatus.

Redox responsive 7-ethyl-10-hydroxycamptothecin (SN38) lysophospholipid conjugate: synthesis, assembly and anticancer evaluation

7-Ethyl-10-hydroxycamptothecin (SN38), a potent camptothecin derivative specifically targeting DNA topoisomerase I cleavage complexes, has shown great potential in the treatment of solid tumors. Because of its poor solubility and chemical and metabolic stability, the clinical application of SN38 is highly limited. To address these problems, a novel redox-responsive SN38 conjugate based liposomal formulation is developed in this report. First, SN38 was conjugated with lysophospholipid by using a cleavable disulfide bond linker. After that, the conjugate (SN38-SS-PC) was assembled into liposomes by thin film method. Dynamic lightscattering(DLS) characterization indicated that SN38-SS-PC liposomes possessed a narrow size distribution (172.8 ± 10.5 nm) and negative charged zeta potential (-8.9 ± 0.3 mV). The results of storage and physiological stabilities showed that SN38-SS-PC liposomes was stable under different conditions. More importantly, a reduction responsive release of parent drug SN38 was observed in the medium containing glutathione (GSH). In addition, SN38-SS-PC liposomes had a much more rapid cellular uptake behavior against cancer cells. The enhanced anti-cancer efficacy of SN38-SS-PC liposomes was further demonstrated by in vitro cytotoxicity assay against MCF-7 and A549 cells. Under in vivo evaluation in 4 T1 xenograft tumor model, SN38-SS-PC liposomes were observed to have lower systemic toxicity and higher tumor inhibition rate of 53.3% compared with the commercialized SN38 prodrug Irinotecan (Ir). In summary, SN38-SS-PC liposomes could be a promising redox responsive delivery system of SN38 for cancer therapy.

Chemo-Preventive Potential of Falcarindiol-Enriched Fraction from Oplopanax elatus on Colorectal Cancer Interfered by Human Gut Microbiota

Oplopanax elatus (Nakai) Nakai is an oriental herb, the polyyne-enriched fraction of which (PEFO) showed anticolorectal cancer (anti-CRC) effects. Other concomitant components, which are inevitably bio-transformed by gut microbiota after oral administration, might be interfere with the pharmacodynamics of polyynes. However, the influence of human gut microbiota on molecules from O. elatus possessing anticancer activity are yet unknown. In this study, the compounds in PEFO and PEFO incubated with human gut microbiota were analyzed and tentatively identified by HPLC-DAD-QTOF-MS. Two main polyynes ((3[Formula: see text]8[Formula: see text]-falcarindiol and oplopandiol) were not significantly decomposed, but some new unknown molecules were discovered during incubation. However, the antiproliferative effects of PEFO incubated with human gut microbiota for 72 h (PEFO I) were much lower than that of PEFO on HCT-116, SW-480, and HT-29 cells. Furthermore, PEFO possessed better anti-CRC activity in vivo, and significantly induced apoptosis of the CRC cells, which was associated with activation of caspase-3 according to the Western-blot results ([Formula: see text]). These results suggest anticolorectal cancer activity of polyynes might be antagonized by some bio-converted metabolites after incubation with human gut microbiota. Therefore, it might be better for CRC prevention if the polyynes could be orally administrated as purified compounds.