Carboxylate Form Research Articles

Switching between CO2 Electroreduction Pathways

Electrochemical carbon dioxide reduction (CO2R) is a promising technology to use renewable electricity to convert CO2 into valuable carbon-based products (1-4). Of metal-based electrocatalysts, silver is one of the best known materials to produce CO in aqueous media, via two proton-coupled electron-transfer processes, with a high selectivity of near 100% Faradaic efficiency (FE) (5). Here, in this study, using density functional theory (DFT), we showed that hydronium (H3O+) is a key intermediate in the first oxygen hydrogenation step to form adsorbed carboxyl (*COOH), and lowers the activation energy barrier for CO formation. Removing the hydronium influence, we found that the activation energy barrier for oxygen hydrogenation and therefore adsorbed carboxyl formation increases significantly, while the activation energy barrier for carbon hydrogenation and consequently adsorbed formate (*HCOO) formation reduces. This mechanism suggests that formate formation pathway at lower concentration of hydronium is more favorable than CO formation pathway. Inspired by these DFT results, we designed experiments at highly concentrated KOH solution, to limit the hydronium availability in the aqueous electrolyte. Using a gas diffusion electrode in flow cell configuration enabled us to utilize a very basic electrolyte by separating it from the CO2 gas stream, and also to run experiments at a high current density of 300 mA/cm2. We found that, the CO2R pathways switches from entirely CO formation under neutral condition, to almost 60% FE for formate formation in 11 M KOH. Different in situ and ex situ materials characterization such as XAS, XPS, SEM and XRD, demonstrated that the electrocatalysts before and after the reactions were identical. In addition, control experiments excluded the applied potential effect, confirming that formate formation was a direct effect of alkaline media and lack of hydronium. Observing high selectivity for formate formation on silver in aqueous media and at high current density has never been reported before. We believe that selectivity shift provides new insights into the role of hydronium on CO2 electroreduction processes and the ability for electrolyte manipulation to directly influence transition state kinetics, altering favored CO2 reaction pathways. C.-T. Dinh et al., CO2 electroreduction to ethylene via hydroxide-mediated copper catalysis at an abrupt interface. Science 360, 783 (2018). T.-T. Zhuang et al., Steering post-C–C coupling selectivity enables high efficiency electroreduction of carbon dioxide to multi-carbon alcohols. Nature Catalysis 1, 421-428 (2018). Z.-Q. Liang et al., Copper-on-nitride enhances the stable electrosynthesis of multi-carbon products from CO2. Nat Commun 9, 3828 (2018). M. G. Kibria et al., A Surface Reconstruction Route to High Productivity and Selectivity in CO2 Electroreduction toward C2+ Hydrocarbons. Advanced Materials 30, 1804867 (2018). C. M. Gabardo et al., Combined high alkalinity and pressurization enable efficient CO2 electroreduction to CO. Energy & Environmental Science, (2018). Figure 1

Detection of Cigarette Smoke Using a Surface-Acoustic-Wave Gas Sensor with Non-Polymer-Based Oxidized Hollow Mesoporous Carbon Nanospheres.

The objective of this research was to develop a surface-acoustic-wave (SAW) sensor of cigarette smoke to prevent tobacco hazards and to detect cigarette smoke in real time through the adsorption of an ambient tobacco marker. The SAW sensor was coated with oxidized hollow mesoporous carbon nanospheres (O-HMC) as a sensing material of a new type, which replaced a polymer. O-HMC were fabricated using nitric acid to form carboxyl groups on carbon frameworks. The modified conditions of O-HMC were analyzed with Scanning Electron Microscopy (SEM), Fourier transform infrared spectrometry (FTIR), and X-ray diffraction (XRD). The appropriately modified O-HMC are more sensitive than polyacrylic acid and hollow mesoporous carbon nanospheres (PAA-HMC), which is proven by normalization. This increases the sensitivity of a standard tobacco marker (3-ethenylpyridine, 3-EP) from 37.8 to 51.2 Hz/ppm and prevents the drawbacks of a polymer-based sensing material. On filtering particles above 1 μm and using tar to prevent tar adhesion, the SAW sensor detects cigarette smoke with sufficient sensitivity and satisfactory repeatability. Tests, showing satisfactory selectivity to the cigarette smoke marker (3-EP) with interfering gases CH4, CO, and CO2, show that CO and CO2 have a negligible role during the detection of cigarette smoke.

Photoinitiated Intramolecular Proton Transfer in Deprotonated para-Coumaric Acid.

Deprotonated para-coumaric acid is commonly considered as a model for the chromophore in photoactive yellow protein, which undergoes E → Z isomerization following absorption of blue light. Here, tandem ion mobility mass spectrometry is coupled with laser excitation to study the photochemistry of deprotonated para-coumaric acid, to show that the E isomers of the phenoxide and carboxylate forms have distinct photochemical responses with maxima in their action spectra at 430 and 360 nm, respectively. The E isomer of the phenoxide anion undergoes efficient autodetachment upon excitation of its lowest ππ* transition. For the E isomer of the carboxylate deprotomer, a one-way photoinitiated proton transfer generates the phenoxide deprotomer through a mechanism postulated to involve an excited-state enol-keto tautomerism followed by a series of ground-state rearrangements including a second proton transfer. This mechanism is supported by experiments in which the relevant intermediate keto isomer is prepared and spectroscopically probed and through master equation modeling of possible ground-state isomerization processes. The Z isomer of the carboxylate deprotomer shows a weak Z → E photoisomerization response that occurs in competition with photodestruction (presumably electron detachment), demonstrating that the E and Z isomers undergo different processes in their excited states. The study highlights the utility of isomer-selective spectroscopy for characterizing the photochemistry of isolated anions possessing multiple deprotonation sites.

Effects of C-Terminal Carboxylation on α-Conotoxin LsIA Interactions with Human α7 Nicotinic Acetylcholine Receptor: Molecular Simulation Studies

α-Conotoxins selectively bind to nicotinic acetylcholine receptors (nAChRs), which are therapeutic targets due to their important role in signaling transmission in excitable cells. A previous experimental study has demonstrated that carboxylation of the C-terminal of α-conotoxin LsIA reduces its potency to inhibit human α7 nAChR relative to naturally amidated LsIA. However, little is known about the contribution of conformational changes in the receptor and interactions, induced by C-terminal amidation/carboxylation of conotoxins, to selective binding to nAChRs, since most conotoxins and some disulfide-rich peptides from other conotoxin subfamilies possess a naturally amidated C-terminal. In this study, we employ homology modeling and molecular dynamics (MD) simulations to propose the determinants for differential interactions between amidated and carboxylated LsIAs with α7 nAChR. Our findings indicate an overall increased number of contacts favored by binding of amidated LsIA versus its carboxylated counterpart. Toxin-receptor pairwise interactions, which may play a role in enhancing the potency of the former, include ARG10-TRP77, LEU141 and CYS17-GLN79 via persistent hydrogen bonds and cation-π interactions, which are weakened in the carboxylated form due to a strong intramolecular salt-bridge formed by ARG10 and carboxylated C-terminus. The binding of amidated LsIA also induces enhanced movements in loop C and the juxtamembrane Cys-loop that are closely associated with receptor function. Additionally, the impacts of binding of LsIA on the overall structure and inter-subunit contacts were examined using inter-residue network analysis, suggesting a clockwise tilting of the α7 C and F loops upon binding to carboxylated LsIA, which is absent for amidated LsIA binding. The predicted molecular mechanism of LsIA binding to the α7 receptor may provide new insights into the important role of the C-terminal in the binding potency of conotoxins at neuronal nAChRs for pharmacological purposes.

RELATIVE CHARACTERIZATION OF IMMOBILIZED BETA-GLUCOSIDASE ON CALCIUM-ALGINATE AND ACID FUNCTIONALIZED MULTIWALLED CARBON NANOTUBES

Natural polymeric gel such as alginate and carrageenan, and carbon nanomaterials, especially MWCNT and graphene are gaining increasing popularity as immobilization support owing to their biocompatibility. Thus, this study attempts to make a relative characterization of the immobilized β-glucosidase on alginate and multiwalled carbon nanotubes (MWCNT) to assess their relative merits as biocatalyst. Acid functionalization of MWCNT lead to the formation of carboxyl groups at the MWCNT surface which seemed to have role in the stable attachment of the enzyme on the MWCNT surface. The effectiveness of the immobilized enzyme was evaluated using hydrolysis of p-nitrophenyl-β-D-glucopyranoside to p-nitrophenol. The optimum immobilization conditions were found to be 17 mg MWCNT and 4 h incubation time for MWCNT, and 3.5 wt% sodium alginate solution and 2 h incubation time for the Ca-alginate beads. The immobilization yield on MWCNT was found to be 96% and that for the Ca-alginate beads was 86%. The residual activity of the enzyme at the third cycle of subsequent reuse was 85% for the enzyme-MWCNT and almost 50% for the enzyme-alginate beads. Both, Ca-alginate and MWCNT immobilized enzyme were found to follow Michaelis-Menten kinetics. The kinetic data were best represented by the Langmuir plot. The kinetic constants Vmax and Km for the MWCNT immobilized enzyme were obtained as 1.324 mM/min and 0.801 mM, respectively, while for the alginate immobilized enzyme, the constants predicted were 1.240 mM/min and 0.524 mM, respectively. Thus MWCNT immobilized β-glucosidase exhibited greater stability in terms of activity and reusability compared to Ca-alginate beads.

Activation of glucose with Fenton’s reagent: chemical structures of activated products and their reaction efficacy toward cellulosic material

Abstract The release of harmful volatiles, such as formaldehyde, is a major issue of the chemical modification of wood that limits the utilization of the modified wood in indoor environment. In this study, glucose (Glc) was activated with Fenton’s reagent under various conditions and the chemical structure of the activated Glc was characterized. Also, the reactivity of the activated Glc toward filter paper as a wood model was evaluated. The results show that the H2O2 concentration controlled the activation ratio of Glc. Additionally, the Fe(II) concentration and activation temperature determined mainly the oxidation reaction rate. The Fenton reaction in an acidic solution resulted in higher activation efficacy of Glc and better fixation in the filter paper, compared to the reaction in an alkaline solution. The Glc cannot be fixed in the filter paper, but the activated Glc exhibited a fixation ratio of up to 48.2% due to the formation of carboxyl and aldehyde groups, as evidenced by Fourier-transform infrared (FTIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS). It was demonstrated that activation of Glc with the Fenton’s reagent is a feasible and eco-friendly approach and the activated products have a high potential for wood modification.

A study of synthesizing stable super-slip carbon nanotubes by grafting octadecylamine

A stable super-slip material with the electrical conductive property has been synthesized by chemical grafting. The multi-walled carbon nanotubes (MWCNTs) were chosen as the electrical conductive matrix. After the acidification of the mixed acid, the original MWCNTs were oxidized to form carboxyl groups on the surface. The octadecylamine (ODA) was bonded on the acidified MWCNTs with the amidation reaction. In order to obtain higher grafting rate, dicyclohexylcarbodiimide (DCC) was added into the reaction system. The MWCNTs with the ODA grifted had properties of superhydrophobic and super-slip. The modified MWCNTs properties of anti-icing, resistance of ultraviolet and acid-alkali were verified during the testing. The modified MWCNTs can be used as electrical conductors for special service, such as devices requiring hydrophobicity and super-slip.

Structural variations of cotton cellulose nanocrystals from deep eutectic solvent treatment: micro and nano scale

Solvents that produce cellulose nanocrystals (CNCs) and promote cellulose fibrillation are of current interest. In this work, CNCs were fabricated from cotton at 80 and 100 °C using deep eutectic solvents (DESs) having choline chloride/oxalic acid dihydrate (OA) ratios of 1:1, 1:2 and 1:3. To investigate the side effects of the fabrication, the crystal structure and morphology of micro-sized treated cellulose together with nano-sized CNCs were analyzed by X-ray diffraction, field emission scanning electron microscopy and atomic force microscopy. OA promoted the formation of carboxyl groups on the C6 positions of molecules on the hydrophilic (1–10) lattice planes, causing extensive fibrillation of cellulose and disruption of surface layers on (110) and (200) planes. Lower crystallinity and lamellar structures for CNCs with mild treatment were observed after mechanical disintegration and subsequent lyophilization, which was ascribed to van der Waals forces and hydrogen bonding between adjacent crystalline cellulose chains, accelerating the self-assembly into cellulose macrofibrils. This work is discussed in light of cellulose supramolecular structures that are modified from CNC fabrication via DES treatment, with a view to enhancing the efficacy of treatment by understanding the variations that arise in cellulose structure from a green solvent.

Correction: Statistical degradation modelling of Poly(D,L-lactide-co-glycolide) copolymers for bioscaffold applications.

[This corrects the article DOI: 10.1371/journal.pone.0204004.].

Statistical degradation modelling of Poly(D,L-lactide-co-glycolide) copolymers for bioscaffold applications.

This methodology permits to simulate the performance of different Poly(D,L-lactide-co-glycolide) copolymer formulations (PDLGA) in the human body, to identify the more influencing variables on hydrolytic degradation and, thus, to estimate biopolymer degradation level. The PDLGA characteristic degradation trends, caused by hydrolysis processes, have been studied to define their future biomedical applications as dental scaffolds. For this purpose, the mass loss, pH, glass transition temperature (Tg) and absorbed water mass of the different biopolymers have been obtained from samples into a phosphate-buffered saline solution (PBS) with initial pH of 7.4, at 37°C (human body conditions). The mass loss has been defined as the variable that characterize the biopolymer degradation level. Its dependence relationship with respect to time, pH and biopolymer formulation has been modelled using statistical learning tools. Namely, generalized additive models (GAM) and nonlinear mixed-effects regression with logistic and asymptotic functions have been applied. GAM model provides information about the relevant variables and the parametric functions that relate mass loss, pH and time. Mixed effects are introduced to model and estimate the degradation properties, and to compare the PDLGA biopolymer populations. The degradation path for each polymer formulation has been estimated and compared with respect to the others for helping to use the proper polymer for each specific medical application, performing selection criteria. It was found that the mass loss differences in PDLGA copolymers are strongly related with the way the pH decay versus time, due to carboxylic acid groups formation. This may occur in those environments in which the degradation products remain relatively confined with the non degraded mass. This is the case emulated with the present experimental procedure. The results show that PDLGA polymers degradation degree, in terms of half life and degradation rate, is increasing when acid termination is included, when DL-lactide molar ratio is reduced, decreasing the midpoint viscosity, or when glycolide is not included.

High Performance Poly(methyl methacrylate-acrylic acid-divinylbenzene) Microcapsule Encapsulated Heat Storage Material for Thermoregulating Textiles

The preparation of high performance poly(methyl methacrylate-acrylic acid-divinylbenzene) (P(MMA-AADVB)) microcapsule encapsulating octadecane (OD) having carboxyl groups on the surface for textile application was studied. The P(MMA-methyl acrylate (MA)-DVB) microcapsule was previously prepared by microsuspension iodine transfer polymerization prior to hydrolysis of MA segment to obtain AA in the P(MMA-AA-DVB) shell. Using 30 wt% of MA and 20 wt% of DVB, the latent heats of melting and crystallization of the encapsulated OD were close to those of original OD (245 and 251 J/g-OD, respectively). After hydrolysis, the zeta potential value of the obtained P(MMA-AADVB) microcapsule surface was -33 mV representing the formation of carboxyl groups of PAA derived from PMA. The influences of nucleating agent amount and type on the reduction of supercooling were then investigated. Using 1-octadecanol at 10 wt% of OD provided the best result. Tc of the encapsulated OD increased and reached to that of original OD while the latent heats were maintained. The hydrolyzed P(MMA-AA-DVB) presented higher efficiency than P(MMA-MA-DVB) microcapsules for fabric coating without external binder which may due to the interaction of microcapsule surface functional group with fabric.

Synthesis and crystal structure of dinuclear based coordination polymer derived from N-6-[(4-pyridylmethylamino)carbonyl]-2-pyridinecarboxylic acid methyl ester

This study describes the facile synthesis and crystal structure of one dimensional coordination polymer which has been successfully obtained from reaction between semi rigid monoamide ligand namel N6-[(4-pyridylmethylamino)carbonyl]-2-pyridinecarboxylic acid methyl ester (L2) with copper perchlorate. The synthesized coordination polymer, with formula given by elemental analysis and X-ray crystallography as {[Cu3(L2-CH3)3(L2)2(H2O)2(CH3OH)](ClO4)3}n was crystallized in monoclinic crystal system and space group C2/c. The asymmetric unit of this complex consists of three copper atoms, three anionic carboxylate forms of ligand L2, two neutral forms of ligand L2 and four partially-occupied non-coordinated perchlorate anions. This asymmetric unit acts as the repeating fragment to form one-dimensional networks which was stabilized by intramolecular hydrogen bonds.

The Effect of Heat Treatment on the Chemical Composition of Ash Wood

Common ash (Fraxinus excelsior L.) wood was heat treated in an oven at temperatures of 160, 180, and 200 oC, and under atmospheric pressure in the presence of air for a duration of 3, 6, 9, and 12 h. The impact of heat treatment on the chemical composition of wood was studied. The extractives content initially increased up to 200 oC and 3 h. However, with extended treatment duration it decreased. Hemicellulosic monosaccharide (D-xylose) degraded under all treatment conditions and resulted in a decrease of holocellulose content. In the case of lignin, demethoxylation and the formation of more condensed structures were observed. This led to an increase in lignin content at temperatures of 180 and 200 oC. The oxidation process already began at 160 °C. This resulted in the formation of new carbonyl or carboxyl groups that contributed to color change, i.e., wood darkening. From the beginning the increase in the cellulose crystallinity was observed, and then it decreased. The maximum was reached at the temperatures of 160, and 180 °C for 9 h of treatment and at the temperature of 200 °C for 6 h.

Fabrication of pore-selective carboxyl group functionalized polyimide honeycomb-patterned porous films using KOH humidity

Carboxyl group functionalization in honeycomb-patterned porous (HCP) films was obtained by breath figure process using polyimide (PI) which can react with KOH humidity at the polymer solution/aqueous alkali droplet interface to form carboxyl groups. PI containing CO-NR2 imide ring group reacts with KOH for imide ring-cleavage reaction by interfacial reaction. In order to obtain pore-selective carboxyl group functionalized PI HCP films, we have suggested a new strategy introducing KOH humidity with time interval after using initial water humidity during breath figuring process. The carboxyl group functionalized pores can be applied to obtain ordered microarray of biological and inorganic materials, which have potential applications in biosensors, separations, medical biology, etc.

Topotecan effect on the structure of normal and cancer plasma membrane lipid models: A multi-model approach

Topotecan is a relatively large, planar, asymmetric and polar molecule with a lactone moiety. In neutral or basic aqueous solutions, this ring opens forming the carboxylate form of Topotecan that is biologically inactive and uncapable of passively cross membranes. Nevertheless, despite this inability to cross membranes at this form, Topotecan may still be able to interact with phospholipid bilayers, disturbing them. In this context, phospholipid models, mimicking normal (DMPC at pH 7.4) and cancer cell lipid membranes (DMPC:DMPS (5:1) at pH 6.5), were used to assess structural modifications upon interaction with Topotecan. Langmuir isotherms of monolayers coupled with Brewster angle microscopy, differential scanning calorimetry of liposomes and X-ray scattering of small and wide angle of stacked multilayers were used as complementary techniques. The overall results show that the interaction of Topotecan with lipid membranes is deeply conditioned by their composition and that Topotecan seems to have a preferential interaction with the glycerol backbone of phosphatidylcholine phospholipids.

Ni(cyclam)]2+ and [Ni(R,S-Me6cyclam)]2+ as Linkers or Counterions In Uranyl–Organic Species with cis- and trans-1,2-Cyclohexanedicarboxylate Ligands

The macrocyclic species [Ni(cyclam)]2+ and [Ni(R,S-Me6cyclam)]2+ were used as additional cations in the solvo-hydrothermal synthesis of five uranyl ion complexes with cis- or trans-1,2-cyclohexanedicarboxylic acids (c-1,2-chdcH2 and t-1,2-chdcH2). In the complex [UO2(c-chdc)2Ni(cyclam)(H2O)] (1), dimeric uranyl dicarboxylate subunits are assembled into a two-dimensional (2D) network through axial coordination of NiII to carboxylate groups. Although they involve different isomers, the complexes [(UO2)2(c-chdc)2(c-chdcH)2Ni(cyclam)] (2) and [(UO2)2(t-chdc)2(t-chdcH)2Ni(cyclam)] (3) are very similar, both containing uranyl-based one-dimensional (1D) subunits which are assembled into 2D networks by bridging [Ni(cyclam)]2+ groups. The orientation of the uncoordinated carboxylic group is different in 2 and 3, the layers in 2 being hydrogen bonded to each other through carboxylic acid dimer formation. Using the pure (1R,2R) enantiomer of t-1,2-chdcH2 gives the complex [Ni(cyclam)][(UO2)5(R-t-chdc)3(R-t-chdcH)(O)...

Hyperspectral FTIR imaging of olive fruit for understanding ripening processes

A combination of micro-FTIR hyperspectral imaging and chemometrics is proposed to better understand biochemical changes in olive fruit during the ripening process without the need for fractionation and related analytical methods. Principal component analysis was used for the study of the spatial distribution of vibrational spectroscopic signatures in flesh, hypodermis and epidermis tissues. Partial least squares discriminant analysis was then employed to highlight the main spectral changes related to ripening. Modifications in cell wall polysaccharides were identified as the major processes taking place during ripening in both the flesh and the hypodermis whereas olive oil accumulation was characteristic in the flesh of the fruit. Evidence of solubilization and depolymerization of cell wall polysaccharides as well as demethylation with the subsequent formation of carboxylate groups were found. Spectral features attributed to polyphenols and sugars also change during the ripening process. No clear temporal trends were observed in the epidermal tissues.

Synthesis and Characterization of Nanofiber of Oxidized Cellulose from Nata De Coco

Oxidized cellulose (OC) nanofiber was successfully prepared from the dry sheet of Nata De Coco (DNDC) using the mixture system of HNO3/H3PO4–NaNO2for the first time. The carboxyl content of the OC was investigated at different conditions (HNO3/H3PO4ratios, reaction times, and reaction temperatures). The results revealed that the carboxyl content of the OC increased along with the reaction time, which yielded 0.6, 14.8, 17.5, 20.9, 21.0, and 21.0% after 0, 6, 12, 36, and 48 hours, respectively. The reaction yields of the OC ranged between 79% and 85% when using HNO3/H3PO4ratio of 1 : 3, 1.4% wt of NaNO2at 30°C at different reaction times. From the structural analysis, the OC products showed a nanofibrous structure with a diameter of about 58.3–65.4 nm. The Fourier transform infrared spectra suggested the formation of carboxyl groups in the OC after oxidation reaction. The crystallinity and crystalline index decreased with an increase of reaction time. The decrease of crystallinity from oxidation process agreed with the decrease of degree of polymerization from the hydrolysis ofβ-1,4-glycosidic linkages in the cellulose structure. The thermal gravimetric analysis results revealed that the OC products were less thermally stable than the raw material of DNDC. In addition, the OC products showed blood agglutinating property by dropping blood on the sample along with excellent antibacterial activity.

Acid-Triggered Polymer Backbone Degradation and Disassembly to Achieve Release of Camptothecin from Functional Polyphosphoramidate Nanoparticles.

Camptothecin (CPT) is a promising anticancer drug, yet its therapeutic potential has been limited by poor water solubility and facile hydrolysis of the lactone form into an inactive carboxylate form at neutral pH. In this work, a fundamental synthetic methodology was advanced to allow for the preparation of well-defined functional polyphosphoramidate (PPA)-based block copolymers that coassembled with CPT into nanoparticles, which underwent coincident acid-triggered polymer backbone degradation, nanoparticle disassembly, and CPT release. Encapsulation of CPT by the PPA polymer inhibited premature hydrolysis of CPT at pH 7.4 and enabled accelerated CPT release at pH 5.0 (ca. 4× faster than at pH 7.4). Two degradable oxazaphospholidine monomers, with one carrying an alkyne group, were synthesized to access well-defined block PPAs (dispersity, Đ<1.2) via sequential organobase-catalyzed ring-opening polymerizations (ROP). The resulting amphiphilic block copolymers (PEOMP-b-PBYOMP) were physically loaded with CPT to achieve well-dispersed nanotherapeutics, which allowed the aqueous suspension of CPT at concentrations up to 3.2 mg/mL, significantly exceeding the aqueous solubility of the drug (<2.0 μg/mL at 37 °C). Cytotoxicity studies revealed enhanced efficacy of the CPT-loaded nanoparticles over free CPT in cancer cells and similar toxicity in normal cells.

Mechanism of Resistance to Camptothecin, a Cytotoxic Plant Secondary Metabolite, by Lymantria sp. Larvae.

Camptothecin (CPT), a monoterpene indole alkaloid, is a potent inhibitor of eukaryotic topoisomerase I (Top 1). Because of this property, several derivatives of CPT are widely used as chemotherapeutic agents. The compound is produced by several plant species, including Nothapodytes nimmoniana (Family: Icacinaceae) presumably as a deterrent to insect pests. Here, we report, a lepidopteran larva, Lymantria sp. of Lymantriidae family which feeds voraciously on the leaves of N. nimmoniana, without any adverse consequences. Larval body weight and molting period were unaffected despite captive feeding of the larva with CPT enriched leaves. Mass spectrometric analysis indicated that nearly 46% of the ingested CPT was excreted while the rest was sequestered predominantly in the exuviae and setae (~35%). Although most of the CPT was in the parental form as found in the plant, traces of inactive, sulfated forms of CPT were recovered from the larva. Compared to that in plant, there were no critical mutations at the CPT binding domain of the insect's Top 1. The gut pH of the larva was alkaline (pH10.0). The alkaline gut environment converts CPT from its active, lactone form to inactive, carboxylate form. It is likely that such conversion might help the larva to reduce the overall burden of CPT in its gut. We discuss the results in the context of the mechanisms of resistance adapted by insects to plant toxins.