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Riccardin D-N (RD-N) is an aminomethylated derivative of the macrocyclic bisbibenzyl compound riccardin D (RD), which has shown stronger activity against cancer cells than RD. However, there has been no research on the metabolism of RD-N. The present study aimed to characterize the in vitro metabolism and metabolic stability of RD-N after incubation with mouse and human hepatic S9 fractions using high performance liquid chromatography-hybrid triple quadrupole/linear ion trap mass spectrometry (HPLC-Q-LIT-MS). Multiple ion monitoring (MIM) and multiple reaction monitoring (MRM)-information dependent acquisition-enhanced product ion (MIM/MRM-IDA-EPI) scans were used to identify the metabolites formed. MRM scans were also used to quantify the changes in the amount of RD-N and to semi-quantify the main metabolites. Twenty-eight metabolic products were detected and 25 structures were predicted. Hydroxylation, dehydrogenation, glucuronidation, and methylation were proposed to be the principle metabolic pathways in the in vitro incubation with human and mouse hepatic S9 fractions. There were differences in the number and abundance of RD-N metabolites between the human and mouse hepatic S9 fractions. RD-N was shown to have good metabolic stability. After 2 h of incubation, 44% of the original RD-N remained in the human hepatic S9 fraction compared with 22% in the mouse. The major metabolites of RD-N, M4, M8, M20 and M21, were monitored semi-quantitatively using the typical transitions. Finally, HPLC-Q-LIT-MS was used for the identification and quantitation of the metabolites of R D-N, which is a simple and efficient method to rapidly screen potential drug candidates., (Copyright © 2019 Elsevier B.V. All rights reserved.)

RD-N, an aminomethylated derivative of riccardin D, is a lysosomotropic agent that can trigger lysosomal membrane permeabilization followed by cathepsin B (CTSB)-dependent apoptosis in prostate cancer (PCa) cells, but the underlying mechanisms remain unknown. Here we show that RD-N treatment drives CTSB translocation from the lysosomes to the nucleus where it promotes DNA damage by suppression of the breast cancer 1 protein (BRCA1). Inhibition of CTSB activity with its specific inhibitors, or by CTSB-targeting siRNA or CTSB with enzyme-negative domain attenuated activation of BRCA1 and DNA damage induced by RD-N. Conversely, CTSB overexpression resulted in inhibition of BRCA1 and sensitized PCa cells to RD-N-induced cell death. Furthermore, RD-N-induced cell death was exacerbated in BRCA1-deficient cancer cells. We also demonstrated that CTSB/BRCA1-dependent DNA damage was critical for RD-N, but not for etoposide, reinforcing the importance of CTSB/BRCA1 in RD-N-mediated cell death. In addition, RD-N synergistically increased cell sensitivity to cisplatin, and this effect was more evidenced in BRCA1-deficient cancer cells. This study reveals a novel molecular mechanism that RD-N promotes CTSB-dependent DNA damage by the suppression of BRCA1 in PCa cells, leading to the identification of a potential compound that target lysosomes for cancer treatment., (© 2018 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.)

RDD648, a novel derivative of a natural molecule riccardin D, exhibited potent anticancer activity by targeting lysosomes in vitro and in vivo. Mechanistic studies revealed that RDD648 facilitated STAT3 to translocate into the nucleus, and this activity was involved in lysosome-mediated cell death as evidenced by our finding that inhibition of STAT3 alleviated lysosomal membrane permeabilization. Further investigation indicated that nuclear STAT3 directly interacted with transcription factor TFEB, leading to the partial loss of function of TFEB, which is essential for lysosome turnover. The present study first uncovers that STAT3 contributes to lysosomal-mediated cell death in RDD648-treated breast cancer cells though interacting with TFEB, and the findings may be significant in the design of treatments for breast cancers where STAT3 is constitutively expressed., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Multidrug resistance (MDR) is a major obstacle for successful chemotherapy treatment. Searching for effective MDR modulators and combining them with anticancer drug therapies has been a promising strategy against clinical MDR. In our previous study, we have found that DHA-E3, a synthetic derivative of DHA, has the ability to modulate the function of P-glycoprotein (P-gp) and reverse MDR in cancer cells. In this study, we further evaluated the reversal effect of DHA-E3 on MDR and explored its mechanism of action in vitro. Our findings showed that DHA-E3 significantly potentiated the cytotoxicity of vincristine(VCR) and adriamycin(ADR) in the P-gp over-expressing KB/VCR and A02 cells. The mechanistic study found that DHA-E3 increased the intracellular accumulation of ADR and rhodamine-123 by directly inhibiting the drug-transport activity of P-gp. In the present study, we found that DHA-E3 not only reversed MDR, but also induced autophagy in MDR cancer cells. To determine whether DHA-E3-induced autophagy is an adaptive survival response or contributes to cell death, we manipulated autophagic activity using autophagy inhibitor 3-MA or siRNA targeting Beclin1. We found that the reversal activity of DHA-E3 was significantly exacerbated in the presence of 3-MA or blocking the expression of Beclin1. These results suggest that DHA-E3 is capable of reversing MDR, induction of autophagy represents a defense mechanism and inhibiting this process may be an effective strategy to augment the reversal activity of reversal agents., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

Lysosomes are important targets for anticancer drug discovery. Our previous study showed that Riccardin D-N (RD-N), a natural macrocylic bisbibenzyl derivative produced by Mannich reaction, induced cell death by accumulating in lysosomes. Experiments were performed on human lung squamous cell carcinoma tissue from left inferior lobar bronchus of patient xenografts and H460 cells. RD-N was administrated for 25days. The specimens of xenografts in Balb/c athymic (nu+/nu+) male mice were removed for immunohistochemistry, subcellular fractionation, enzyme activities and Western blotting analysis. mRFP-GFP-LC3 reporter was used to examine autophagy in H460 cells. Sphingomyelin assay was evaluated by thin-layer chromatography and assay kit. Lysosomal membrane permeabilization (LMP) caused by acid sphingomyelinase (ASM) inhibition and subsequent changes of sphingomyelin (SM) metabolism selectively destabilized the cancer cell lysosomes in RD-N-treated H460 cells in vitro and tumor xenograft model in vivo. The destabilized lysosomes induced the release of cathepsins from the lysosomes into the cytosol and further triggered cell death. These results explain the underlying mechanism of RD-N induced LMP. It can be concluded that a more lysosomotropic derivative was synthesized by introduction of an amine group, which could have more potential applications in cancer therapy., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Candida albicans, which is the most common human fungal pathogen, causes high mortality among immunocompromised patients. Antifungal drug resistance becomes a major challenge for the management of Candida infection. Diorcinol D (DD), a diphenyl ether derivative isolated from an endolichenic fungus, exerted fungicidal action against Candida species. In this study, we investigated the possible mechanism of its antifungal activity. The change of membrane dynamics and permeability suggested that the cell membrane was disrupted by the treatment of DD. This was further supported by the evidences of intracellular glycerol accumulation, alteration of cell ultrastructure, and down-regulation of genes involved in cell membrane synthesis. In addition, the treatment of C. albicans with DD resulted in the elevation of reactive oxygen species (ROS), which caused the dysfunction of mitochondria. These altogether suggested that DD exerted its antifungal activity through cytoplasmic membrane destruction and ROS accumulation. This finding is helpful to uncover the underlying mechanisms for the diphenyl ether derivatives and provides a potential application in fighting clinical fungal infections.

The analysis of dihydroptychantol (DHA) and its chemically synthesized macrocyclic bisbibenzyl derivatives (DHA1, 2 and 3) led to the selection of DHA2 as a potential drug candidate for ovarian cancer. The exposure of ovarian cancer SKOV3 cells to DHA2 resulted in the downregulation of the anti-apoptotic X-linked inhibitor of apoptosis protein (XIAP) and Bcl-2 and led to caspase-independent cell death. The overexpression of XIAP reversed DHA2-induced cell death, and the depletion of XIAP had the opposite effect. DHA2 could induce autophagy, as evidenced by increases in the formation of acidic vesicular organelles and the processing of LC3B-I to LC3B-II. Pretreatment with autophagy inhibitors potentiated DHA2-mediated cell death. We showed that typical PI3K/Akt signaling was involved in DHA2-mediated cell death. The overexpression of Akt almost completely reversed DHA2-induced cell death, and the inactivation of Akt significantly facilitated DHA2-induced cell death. The administration of DHA2 to xenograft mice reduced tumor growth by causing Akt inactivation, the conversion of LC3B and proliferation inhibition. Our study demonstrates that the inhibition of XIAP and the inactivation of Akt/mTOR facilitate the efficacy of DHA2 in ovarian cancer cells., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Purpose: Our previous studies had shown that Riccardin D (RD) exhibited cytotoxic effects by induction of apoptosis and inhibition of angiogenesis and topoisomerase II. Here, we reported that apoptosis is not the sole mechanism by which RD inhibits tumor cell growth because low concentrations of RD caused cellular senescence in prostate cancer (PCa) cells., Methods: Low concentrations of RD were used to treat PCa cells in vitro and in vivo, and senescence-associated β-galactosidase activity, DNA damage response markers, and/or colony-forming ability, cell cycle were analyzed, respectively. We then used siRNA knockdown to identify key factor in RD-triggered cellular senescence., Results: RD treatment caused growth arrest at G0/G1 phase with features of cellular senescence phenotype such as enlarged and flattened morphology, increased senescence-associated-beta-galactosidase staining cells, and decreased cell proliferation in PCa cells. Induction of cellular senescence by RD occurred through activation of DNA damage response including increases in the phosphor-H2AX, inactivation of Chk1/2, and suppression of repair-related Ku70/86 and phosphor-BRCA1 in PCa cells in vitro and in vivo. Analysis of expression levels of p53, p21(CIP1), p16(INK4a), p27(KIP1), pRb and E2F1 and genetic knockdown of p21(CIP1) demonstrated an important role of p21(CIP1) in RD-triggered cellular senescence., Conclusions: Involvement of the DNA damage response and p21(CIP1) defines a novel mechanism of RD action and indicates that RD could be further developed as a promising anticancer agent for cancer therapy.

We recently reported that Riccardin D (RD) was able to induce apoptosis by targeting Topo II. Here, we found that RD induced cell cycle arrest in G2/M phase in PC-3 cells, and caused remarkable DNA damage as evidenced by induction of γH2AX foci, micronuclei, and DNA fragmentation in Comet assay. Time kinetic and dose-dependent studies showed that ATM/Chk2 and ATR/Chk1 signaling pathways were sequentially activated in response to RD. Blockage of ATM/ATR signaling led to the attenuation of RD-induced γH2AX, and to the partial recovery of cell proliferation. Furthermore, RD exposure resulted in the inactivation of BRCA1, suppression of HR and NHEJ repair activity, and downregulation of the expressions and DNA-end binding activities of Ku70/86. Consistent with the observations, microarray data displayed that RD triggered the changes in genes responsible for cell proliferation, cell cycle, DNA damage and repair, and apoptosis. Administration of RD to xenograft mice reduced tumor growth, and coordinately caused alterations in the expression of genes involved in DNA damage and repair, along with cell apoptosis. Thus, this finding identified a novel mechanism by which RD affects DNA repair and acts as a DNA damage agent in prostate cancer.

Macrocyclic bisbibenzyls, characteristic components derived from liverworts, have various biological activities. Riccardin D (RD), a liverwort-derived naturally occurring macrocyclic bisbibenzyl, has been found to exert anticancer effects in multiple cancer cell types through apoptosis induction. However, the underlying mechanisms of such effects remain undefined. In addition, whether RD induces other forms of cell death such as autophagy is unknown. In this study, we found that the arrest of RD-caused U2OS (p53 wild) and Saos-2 (p53 null) cells in G1 phase was associated with the induction of p53 and p21(WAF1) in U2OS cells. RD-mediated cell cycle arrest was accompanied with apoptosis promotion as indicated by changes in nuclear morphology and expression of apoptosis-related proteins. Further studies revealed that the antiproliferation of RD was unaffected in the presence of p53 inhibitor but was partially reversed by a pan-inhibitor of caspases, suggesting that p53 was not required in RD-mediated apoptosis and that caspase-independent mechanisms were involved in RD-mediated cell death. Except for apoptosis, RD-induced autophagy occurred as evidenced by the accumulation of microtubule-associated protein-1 light chain-3B-II, formation of AVOs, punctate dots, and increased autophagic flux. Pharmacological blockade of autophagy activation markedly attenuated RD-mediated cell death. RD-induced cell death was significantly restored by the combination of autophagy and caspase inhibitors in osteosarcoma cells. Overall, our study revealed RD-induced caspase-dependent apoptosis and autophagy in cancer cells, as well as highlighted the importance of continued investigation on the use of RD as a potential anticancer candidate., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

In the present study, the effect of a novel derivative of riccardin D (RD-N) against cancer cell lines was investigated in vitro and in vivo. We found that RD-N accumulated in the lysosomes associated with lysosomal swelling. As a result, the destabilized lysosomes induced cathepsins to release from the lysosomes into the cytosol and induced cell death which displayed features characteristic to both apoptosis and necrosis. In vivo tumor xenograft model indicated treatment of RD-N significantly reduced size and weight of the tumor compared with vehicles. These findings suggest RD-N could be a promising candidate for treatment of cancer., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Riccardin D (RD) is a novel compound extracted from Chinese liverwort Marchantia polymorpha L. It exhibits various anticancer activities and can be used during lung cancer treatment. However, the compound's low solubility hinders its development. Recently nanosuspension has been developed as one of the most promising formulations for poorly water-soluble drugs. In order to understand the dissolution behavior of riccardin D in vitro and in vivo, two nanosuspensions of riccardin D with markedly different sizes were prepared. The particle size of nanosuspension A prepared by bottom-up method was 184.1±3.15 nm, while that of nanosuspension B prepared by top-down method was 815.4±9.65 nm. The main purpose of this study was to investigate the effects of particle size on pharmacokinetics and tissue distribution after intravenous administration. Riccardin D dissolving in organic solution was studied as control group. In pharmacokinetics study in Wistar rats, nanosuspension A showed properties similar to the control group, while nanosuspension B exhibited rather different properties. In tissue distribution research on Kunming strain mice, nanosuspension A had a multi-peak phenomenon because of reticulate endothelial system (RES) while nanosuspension B showed a high uptake in RES organs that passively target to the lungs. In conclusion, particle size of riccardin D nanosuspensions had obvious effects on pharmacokinetics and tissue distribution., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Objectives: This study aimed to examine the effects of marchantin C and fucoidan on angiogenesis induced by glioma cells and monocytes, and to elucidate the role of sFlt-1 in this process., Methods: T98G glioma cells and THP1 monocytes were pretreated with marchantin C or fucoidan, respectively. Conditioned media were used for endothelial cell tube formation assay and detection of sFlt-1 by ELISA. Depletion of sFlt-1 was achieved by a neutralizing antibody to assess its role in the process., Key Findings: Marchantin C inhibited angiogenesis induced by T98G cells while fucoidan inhibited both T98G and THP1 cell-induced angiogenesis. In all three groups in which angiogenesis was inhibited, sFlt-1 level in the supernatants was elevated. Pretreatment of the conditioned media with sFlt-1 antibody restored the inhibited angiogenesis to a certain degree., Conclusions: This study suggested for the first time that marchantin C and fucoidan could significantly inhibit angiogenesis induced by glioma cells or monocytes. Up-regulation of sFlt-1 played an important role in this process., (© 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.)

Riccardin D is a new compound extracted from liverwort Marchantia polymorpha L. It has been proved to be useful in antifungal therapy and reversing the resistance of Candida albicans against fluconazole. However, the poor solubility leads to the poor bioavailability and limits its development. In this study, nanocrystals were prepared in the evaporative precipitation into aqueous solution (EPAS) and the microfluidisation process. The characterizations of nanocrystals were compared by transmission electron microscope, size distribution, and zeta potential. In the EPAS method, the drug was dissolved in the organic phase and F68, HPMC, PVP K30 were dissolved in water with the mass ratio of 2:1:2:1. In the microfluidisation process, two key factors - pressure and number of cycles were screened and 8 cycles at 2000 bar was the most efficient parameter. The nanocrystals made in EPAS process were smaller, more uniform and had a narrower distribution than the microfluidisation nanocrystals. Differential scanning calorimetry (DSC) and X-ray diffraction confirmed the crystalline states that were both reserved. The solubility was greatly improved by the two methods and the EPAS nanocrystals were more soluble due to the smaller size. An enhanced dissolution was obvious in vitro. And the stable nanocrystals were successfully achieved by the two methods., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Riccardin D, a macrocyclic bisbibenzyl isolated from Chinese liverwort Dumortiera hirsute, has been proved to have inhibitory effect on biofilms formation of Candida albicans in in vitro study. Our present study aims to investigate the in vivo effect and mechanisms of riccardin D against C. albicans biofilms when used alone or in combination with clinical using antifungal agent fluconazole. XTT reduction assay revealed riccardin D had both prophylactic and therapeutic effect against C. albicans biofilms formation in a dose-dependent manner when using a central venous catheter related infective animal model. Scanning electron microscope and laser confocal scanning microscope showed that the morphology of biofilms was altered remarkably after riccardin D treatment, especially hypha growth inhibition. To uncover the underlying molecular mechanisms, quantitative real-time RT-PCR was performed to observe the variation of related genes. The downregulation of hypha-specific genes such as ALS1, ALS3, ECE1, EFG1, HWP1 and CDC35 following riccardin D treatment suggested riccardin D inhibited the Ras-cAMP-Efg pathway to retard the hypha formation, then leading to the defect of biofilms maturation. Moreover, riccardin D displayed an increased antifungal activity when administered in combination with fluconazole. Our study provides a potential clinical application to eliminate the biofilms of relevant pathogens.

Dihydroptychantol A (DHA), a novel macrocyclic bisbibenzyl compound extracted from liverwort Asterella angusta, has antifungal and multi-drug resistance reversal properties. Here, the chemically synthesized DHA was employed to test its anti-cancer activities in human osteosarcoma U2OS cells. Our results demonstrated that DHA induced autophagy followed by apoptotic cell death accompanied with G₂/M-phase cell cycle arrest in U2OS cells. DHA-induced autophagy was morphologically characterized by the formation of double membrane-bound autophagic vacuoles recognizable at the ultrastructural level. DHA also increased the levels of LC3-II, a marker of autophagy. Surprisingly, DHA-mediated apoptotic cell death was potentiated by the autophagy inhibitor 3-methyladenine, suggesting that autophagy may play a protective role that impedes the eventual cell death. Furthermore, p53 was shown to be involved in DHA-mediated autophagy and apoptosis. In this connection, DHA increased nuclear expression of p53, induced p53 phosphorylation, and upregulated p53 target gene p21(Waf1/Cip1). In contrast, cytoplasmic p53 was reduced by DHA, which contributed to the stimulation of autophagy. In relation to the cell cycle, DHA decreased the expression of cyclin B₁, a cyclin required for progression through the G₂/M phase. Taken together, DHA induces G₂/M-phase cell cycle arrest and apoptosis in U2OS cells. DHA-induced apoptosis was preceded by the induction of protective autophagy. DHA-mediated autophagy and apoptosis are associated with the cytoplasmic and nuclear functions of p53., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Cancer cell migration is a leading cause of tumor recurrence and treatment failure. Previously, we reported that marchantin C exhibited promising antitumor activity by inducing microtubule depolymerization and apoptosis. In the present study, we investigated the effect of marchantin C on inhibition of migration in T98G and U87 cells. The scratch-induced migration, Boyden chamber and cell invasion assays were applied to determine that the migrating capacity and invasiveness of these glioma cell lines were inhibited when exposed to marchantin C at a low concentration. There are no obvious signs of apoptosis with this dose. Western blot analyses confirmed that MMP-2, a key role in cancer cell migration, was reduced after incubation with marchantin C in both glioma cell lines. In addition, signaling pathway investigations demonstrated that ERK/MAPK might be involved in MMP-2 downregulation, rather than the AKT/PI3K or JAK/STAT3 pathways. Moreover, marchantin C potently suppressed angiogenesis activity in vivo by CAM assay. This is the first study to demonstrate that marchantin C can inhibit glioma cell migration and invasiveness.

Biofilm formation plays a key role in the life cycles and subsistence of many microorganisms. The human fungal pathogen Candida albicans has a high propensity to develop biofilms and resulted resistant to traditional antifungal agents. Biofilms are composed of a mixture of cell types, including yeast, pseudohyphal and hyphal cells, and hyphae are a prominent feature of biofilms. Riccardin D is a macrocyclic bisbibenzyl isolated from the liverwort Dumortiera hirsute in our laboratory. In the present investigation, the XTT [2,3-bis(2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5-carboxanilide] reduction assay and live/dead cell staining were employed for evaluating the effects of riccardin D on C. albicans biofilms. The results demonstrated that riccardin D can interfere with the biofilm formation. To investigate whether this effect was due to the inhibition of hyphae formation, morphological observation and real-time reverse transcriptase polymerase chain reaction (RT-PCR) were employed for evaluating the effects of riccardin D on the hyphae formation and the expression of hyphae specific genes. The results showed that the hyphae formation was strongly inhibited and the mRNA expression levels of hyphae specific genes were downregulated after riccardin D treatment. We concluded that riccardin D interfered with the biofilm formation of C. albicans through downregulating the expression of hyphae specific genes and inhibiting the formation of hyphae.